Koni Shock Spring Rates

[33fromSD]

Hey All

Still dialing in the 33. When cruising around town, I get a solid sounding thump somewhere in the front, not sure where, I don't feel it in the steering wheel so I don't think it's control arms or steering rack. This thing is stiff as a board and I almost feels like I'm not getting a lot of dampening from the front shocks.

In the pics I show the car so you get an idea of the set up (full fenders / running board) and I show a shot of the front & rear shocks.

On the front, you'll see that I have my shocks inverted for easy adjustment so I know I'm opening up a can of worms with that discussion but it is what it is. You'll also notice I have the adjustment collar about 1/3" of the way up on the threads. With full fenders this gives me about 2.5" of clearance between the fender and the tire. I've never had tire rub on the front so maybe I'm too aggressive on my setting.

My "theory" on the front is with the 400# spring in the front, and my adjustment on the spring collar to prevent possible tire rub and my lighter engine (SBF 302), I'm thinking my "thump" I'm hearing in the front may be that I'm just too stiff (I have not tried backing off the spring adjustment yet), or the other theory of course is by inverting the shocks they are just not working.

On the rear, you'll see in the pic that I am almost up to the top of the adjustment collar. Anything lower than that I get serious tire rub, especially with a passenger. Even as it is, on huge bumps in the road or potholes I still get minor tire rub even with this adjustment.

As far as rims / tires I'm running FFR's Bonneville wheel / tire package they offer (Front = 245/40R18; Rear = 305/35R20)

Questions:
1) What are folk's thoughts on the front? Am I causing my own issue with my adjustments? Or possibly the shocks being inverted?
2) Since I'm only running a SBF 302, and it seems like I need a little more lift in the rear, should I swap the 250# springs from the rear to the front and move the 400# springs to the rear?

151916 151917 151918

Thanks

Jim

[NAZ]

FFR puts way too stiff spring rates on their HR kit. And the Koni shocks are low end of the scale when compared to performance shocks. Doesn't matter if you're racing or simply driving your car on the street, good shocks and the right spring rates make all the difference in ride quality and handling. I suggest you bite the bullet and get some double adjustable shocks that you can dial in for your particular car and the roads you run it on. QA1 makes double adjustable shocks that are a direct fit and can be run in any orientation you choose. I run my QA1 Proma Star shocks inverted on the front and can get to the pre-load adjusters and both compression and rebound adjustments. I run 8" 250 lb/in springs on the front (just a little stiff, 225# would be better) and 10" 150 lb/in on the rear but my rear suspension is different than yours. On the front I run extended spring caps to keep the springs separated when running the shocks inverted.

I would suspect that that "thump" you hear and feel on the front is the shock topping out on rebound from lack of damping control. That 400# spring on the front requires a lot of damping and if those Koni shocks are not designed to run inverted, your damping has been compromised. If you want to solve this problem and get a better ride you are going to have to replace the front shocks (or perhaps mount them body down) and go to a much much softer spring than what you have now.
151921151922

If you want to keep the tires from contacting the fenders, the correct way to do that is with limiting the suspension travel in bump. Cranking up the spring force will negatively affect traction, handling and ride quality and will not guarantee the tire and fenders won't rub.

[Brave Salmon]

Jim, those silver bodied Konis are not approved for body up usage. See the sticky note on list of posts.
My 33 runs bike fenders with the sbf like you. I settled on QA1 single adjustable shocks with 9" 220# springs and extended caps to invert the fronts. On the rear I am running 10" 200# springs in body down config. Major improvement over the Konis. Only change I would do is perhaps an even lighter spring in the rear like 150-175 like HAZ is using. Mine is not a race car and I built it to drive nicely, not road race harsh.

[33fromSD]

FFR puts way too stiff spring rates on their HR kit. And the Koni shocks are low end of the scale when compared to performance shocks. Doesn't matter if you're racing or simply driving your car on the street, good shocks and the right spring rates make all the difference in ride quality and handling. I suggest you bite the bullet and get some double adjustable shocks that you can dial in for your particular car and the roads you run it on. QA1 makes double adjustable shocks that are a direct fit and can be run in any orientation you choose. I run my QA1 Proma Star shocks inverted on the front and can get to the pre-load adjusters and both compression and rebound adjustments. I run 8" 250 lb/in springs on the front (just a little stiff, 225# would be better) and 10" 150 lb/in on the rear but my rear suspension is different than yours. On the front I run extended spring caps to keep the springs separated when running the shocks inverted.

I would suspect that that "thump" you hear and feel on the front is the shock topping out on rebound from lack of damping control. That 400# spring on the front requires a lot of damping and if those Koni shocks are not designed to run inverted, your damping has been compromised. If you want to solve this problem and get a better ride you are going to have to replace the front shocks (or perhaps mount them body down) and go to a much much softer spring than what you have now.
151921151922

If you want to keep the tires from contacting the fenders, the correct way to do that is with limiting the suspension travel in bump. Cranking up the spring force will negatively affect traction, handling and ride quality and will not guarantee the tire and fenders won't rub.

Thanks NAZ...no issues spending the money, would you happen to recall the front & rear QA1 part numbers for the shocks/

Jim

[33fromSD]

Jim, those silver bodied Konis are not approved for body up usage. See the sticky note on list of posts.
My 33 runs bike fenders with the sbf like you. I settled on QA1 single adjustable shocks with 9" 220# springs and extended caps to invert the fronts. On the rear I am running 10" 200# springs in body down config. Major improvement over the Konis. Only change I would do is perhaps an even lighter spring in the rear like 150-175 like HAZ is using. Mine is not a race car and I built it to drive nicely, not road race harsh.


Thanks Brave, I guess same question to you, what is the front & rear QA1 p/n you went with on your single adjust shocks?

Thanks for the advice.

Jim

[FF33rod]

Jim
For what it's worth, I got the FFR double adjustable upgrade package and have the IRS rear end.
When I first got the car on the road back in October it was stiff as a board, not comfortable at all.
I changed the fronts to 220 and am very happy with it. The rears, I believe, are 400 and I've left those for the time being.
It handles well in street driving so I won't make further adjustments until I do something else with it like autocross.


Steve

[NAZ]

I will recommend you go double adjustable on the front as you'll want much more rebound damping than compression up front; probably just the opposite in the rear but I can't say that for sure on your car but if so, DA on the rear will allow you to adjust bump and rebound independently.

Below is what I used except I substituted a 225# spring.

Front:
https://www.summitracing.com/parts/qa1-dd403
https://www.summitracing.com/parts/qa1-9018-113
https://www.summitracing.com/search/part-type/coilover-springs/coilover-spring-inside-diameter-in/2-500-in/coilover-spring-length-in/8-000-in?N=filter-options%3Ain-stock%2Bcoilover-spring-rate-lbs-in%3A225-lbs-in&SortBy=BestKeywordMatch&SortOrder=Ascending&keyword=qa1%20springs
https://www.summitracing.com/search/part-type/frame-bump-stops?fr=part-type&SortBy=BestKeywordMatch&SortOrder=Ascending&keyword=qa1-bc02 I used the shorter bump stop on the front.

I designed my rear suspension so that I could use the same shocks as the front so I can't help you with part numbers there. While I can't remember the motion ratio on the FFR rear three-link, it's probably not too different than mine. Therefore, you could likely use just a slightly stiffer rear spring than I'm using, say maybe 50# more but I suggest you copy Brave Salmon's set-up in the rear if you both have the same suspension system. Also, I suggest you add bump stops to the rear in whatever amount necessary to prevent the tire from contacting the fender. You can stack bump stops.

[33fromSD]

I will recommend you go double adjustable on the front as you'll want much more rebound damping than compression up front; probably just the opposite in the rear but I can't say that for sure on your car. Here's what I used:

Front --
https://www.summitracing.com/parts/qa1-dd403
https://www.summitracing.com/parts/qa1-9018-113
https://www.summitracing.com/search/part-type/coilover-springs/coilover-spring-inside-diameter-in/2-500-in/coilover-spring-length-in/8-000-in?N=filter-options%3Ain-stock%2Bcoilover-spring-rate-lbs-in%3A225-lbs-in&SortBy=BestKeywordMatch&SortOrder=Ascending&keyword=qa1%20springs
https://www.summitracing.com/search/part-type/frame-bump-stops?fr=part-type&SortBy=BestKeywordMatch&SortOrder=Ascending&keyword=qa1-bc02

I designed my rear suspension so that I could use the same shocks as the front so I can't help you with part numbers there. While I can't remember thee motion ratio on the FFR rear three-link, it's probably not too different than mine which is .957. Therefore, you could likely use just a slightly stiffer rear spring than I'm using, say maybe 50# more but I suggest you copy Brave Salmon's set-up in the rear if you both have the same suspension system. Also, I suggest you add bump stops to the rear in whatever amount necessary to prevent the tire from contacting the fender. You can stack bump stops.

Thanks for the info on the front Naz.

Should have clarified on the rear I'm running 4-Link suspension. I currently have the 17.5" Koni w/ 250# springs.

[NAZ]

Thanks for the info on the front Naz.

Should have clarified on the rear I'm running 4-Link suspension. I currently have the 17.5" Koni w/ 250# springs.

If it were my car, I'd reduce the spring rate on the rear maybe 75# and adjust from there. These cars are not cookie-cutter builds so expect that some experimentation will be required. Even the best engineers and experienced crew chiefs use an iterative process in adjusting the suspension so don't expect "ideal" with the first change. I also understand you don't want to make an expensive science project out of this and that's why I'm saying reduce the rear by 75#, it's a moderate aggressive change that should get you closer than your current. Body roll may increase a bit on the autocross course but so will traction and ride quality will improve even more with the correct damping.

[cob427sc]

Has anyone considered the upper A-arm hitting the tube frame when the suspension moves upward? I checked the amount of movement and it doesn't allow the wheel to raise much at all before the arm contacts the frame. I don't think I've bottomed mine out yet, but with the horrible roads here in Mass I'm sure it's bound to happen.

[33fromSD]

If it were my car, I'd reduce the spring rate on the rear maybe 75# and adjust from there. These cars are not cookie-cutter builds so expect that some experimentation will be required. Even the best engineers and experienced crew chiefs use an iterative process in adjusting the suspension so don't expect "ideal" with the first change. I also understand you don't want to make an expensive science project out of this and that's why I'm saying reduce the rear by 75#, it's a moderate aggressive change that should get you closer than your current. Body roll may increase a bit on the autocross course but so will traction and ride quality will improve even more with the correct damping.

Game Plan:

For the front I ordered NAZ's suggestion for the QA1 Double Adjustable Proma Star Shocks from SummitRacing per NAZ's list

https://www.summitracing.com/parts/qa1-dd403
https://www.summitracing.com/parts/qa1-9018-113
https://www.summitracing.com/search/...=qa1%20springs
https://www.summitracing.com/search/...yword=qa1-bc02

For the rear I'm going to start with installing 175# 10" long QA1 springs (2.5" dia) on the existing Koni Shock. I figure if I still do not like it, then I'll order QA1 single adjustable shocks and reuse the 175# 10" long springs.

I also have a set of 12" long 175#-350# QA1 springs (2.5" dia) I could try on the rear Koni shocks too that I must have bought for another project (Maybe my 55 F100, can't remember).

Thanks for all the help.

Jim

[NAZ]

Jim, sounds like a good plan. Let us know how it works.

[NAZ]

Jim, I forgot to mention that you'll want to get some spanner wrenches for adjusting your QA1 coilovers, the Koni spanners won't fit. You'll want to get a set of the traditional long handle spanners and for the front, these will come in very handy:https://www.summitracing.com/parts/qa1-t115w They work great in tight spaces such as on the front of your HR.

[33fromSD]

Jim, I forgot to mention that you'll want to get some spanner wrenches for adjusting your QA1 coilovers, the Koni spanners won't fit. You'll want to get a set of the traditional long handle spanners and for the front, these will come in very handy:https://www.summitracing.com/parts/qa1-t115w They work great in tight spaces such as on the front of your HR.

Awesome, appreciate it NAZ

Jim

[33fromSD]

I installed the QA1 Proma Star double adjustable shocks in the front today as well as swapped the 250# 8" Koni springs in the rear for some 12" 175#-350# incremental QA1 springs. All I can say is Wow, Wow, Wow, what an amazing transformation in the ride. I still need to tweak the slightest bit yet in the front, but it is so nice to ride around feeling like the shocks are working and having a smooth comfortable ride verses feeling like I my suspensions is a brick. In the springtime, I may also swap out the rear Koni shocks with QA1 shock too, but for now with the new springs they are much better..

I still need to do the alignment since the car is sitting much lower now due to the koi shocks in front being inverted and I had to movementment in them what so ever.

Some observations doing this:
* What a PITA swapping front shock with the hood, side covers & full fenders on. I got it done, but I did a lot of reaching / stretching to get in there.
* I'm not sure how you guys without lifts build these cars. I have a 4 post lift which i used for my whole build however today, I just told myself "it's just shocks, how bad can it be?, I'll doing this with the car on the garage floor".....Holy crap, also having the belly pan underneath and trying to first see to figure out where to jack the car up front, and then to get the car high enough to actually work under there, and then the constant up and down...wow, I can't do that anymore, getting too old for that stuff. My wife is wondering if I'll be able to move tomorrow. Kudos to all who build these without lifts.

Thanks for all the advice / help everyone (especially NAZ), I greatly appreciate it.

Jim

[NAZ]

Jim, I know what you mean about how important my lift is now that I'm old.

[peterh226]

Hi guys
I’m debating on the whole shock/spring situation as well. I had only a small clearance between fender and tire so I took the front end apart and adjusted the springs and put it back together.
I’m at the extreme end of the adjustment and probably have too mush preload in the front end as well. Here’s what it looks like. 152109

Now i have some clearance above the tire, maybe more than in need with this spring rate.
The spring perch is 4 in up on the adjustment collar. At the front of the flat part of the frame, I’ve got just a bit over 5 in. Once I drive it a bit, I expect it will settle.
Any comments?

[NAZ]

First a few questions. Front ride height measured at the bottom of the tubing directly below the firewall? How much tire to fender clearance do you have at full bump? What front spring rate and no-load spring length are you working with? Were these shocks supplied in your kit?

[peterh226]

First a few questions. Front ride height measured at the bottom of the tubing directly below the firewall? How much tire to fender clearance do you have at full bump? What front spring rate and no-load spring length are you working with? Were these shocks supplied in your kit?

Yes for ride height.
I don’t know at full bump. Not sure how to compress the suspension enough. I think I might put some foam under the fender to see if it makes contact while driving. I’ve got a couple of inches above the tire now.
I’ve got the stock 400# springs. Not sure the length.
Stock shocks.

[33fromSD]

If you're going to eventually end up coating your inside of the fenders with a protecting (bed liner, rubber coating, etc.) then for now just spray a light coat of white paint (rattle can) on the inner fender in the general area of the tire. If it makes contact you'll see scuff marks.

Jim.

[NAZ]

What do you set your front ride height to (inches of clearance between the bottom of the tubing to the ground)?

To determine the tire to fender clearance at full bump requires you to install the shocks without the springs and carefully lower the jack until the car's weight is fully on the shocks at full bump travel. Carefully so you don't allow the weight of the car to be supported by the front fenders if they should contact the tire. If the tire hits the fender before full travel is reached, measure the shaft travel left so you can determine the amout of bump stop to install. You'll want to turn the wheels lock to lock when checking clearance.

Once the springs are off you can measure their free length. I would also encourage you to consider installing softer springs unless you like the ride of a Conestoga wagon.

[33fromSD]

NAZ, quick question for you

On my QA! Proma Star double adjustable shocks, I just noticed that the shocks at rest are compressed on the bump stops, seems odd to me.

The good news is the bump stops you suggested keep the tires from hitting the front fenders but any idea why this is?

My settings:
C = 10 clicks
R = 4 clicks
225# springs

I wouldn't think a 302 would be that heavy.

See attached pic
152201

Jim

[NAZ]

The softer springs require more preload for the same ride height as the originals. You will have to adjust the preload to meet your ride height needs. If you know your weights and how much droop you want I can calculate it or since your car is similar to Brave Salmon you can use his preload adjustment as a starting point.

I suggest you start the compression and rebound settings at zero and adjust from there. You'll need sections of roads that have sharp bumps (like speed bumps) and large rolling bumps that really exercise the suspension so you can fine tune the damping. I like to start with rebound as since it is driven from the spring is a constant. Run over speed bumps and adjust a couple clicks at a time until you no longer feel the clunk when the shock tops out, then fine tune from there for the ride you like. Generally speaking about the only time you will notice too little compression damping is on a g-out (bump so big that the suspension bottoms out). But too much compression damping will make for a very hard ride so start with zero compression damping and adjust from there. It really shouldn't take much compression damping.

[33fromSD]

The softer springs require more preload for the same ride height as the originals. You will have to adjust the preload to meet your ride height needs. If you know your weights and how much droop you want I can calculate it or since your car is similar to Brave Salmon you can use his preload adjustment as a starting point.

I suggest you start the compression and rebound settings at zero and adjust from there. You'll need sections of roads that have sharp bumps (like speed bumps) and large rolling bumps that really exercise the suspension so you can fine tune the damping. I like to start with rebound as since it is driven from the spring is a constant. Run over speed bumps and adjust a couple clicks at a time until you no longer feel the clunk when the shock tops out, then fine tune from there for the ride you like. Generally speaking about the only time you will notice too little compression damping is on a g-out (bump so big that the suspension bottoms out). But too much compression damping will make for a very hard ride so start with zero compression damping and adjust from there. It really shouldn't take much compression damping.


The interesting thing is I did preload the springs and set my ride height at 6.5" (1" above the suggested manual height to give myself a bit more clearance), after driving it and sitting for the last couple of days the ride height settled lower.

Because of that, I'm starting to wonder if the QA1 225# 8" springs for my application is right. If I think about various weights on my application, it looks like this:

* 302 SBF = ~460 lbs fully dressed
* Radiator / fan / Grill set up = ~30 lbs
* Full fenders, hood, side covers & belly pan = ~ 50 lbs
* steering rack, Suspension parts / frame in front = guessing ~75 lbs (maybe more)

Total weight from above = ~615 lbs.

The two QA1 225# springs support 500 lbs max so unless I'm thinking about this wrong it seems like I'm ~150 lbs light. I'm wondering when FFR spec'd the 400# springs in front if they were looking at worst case scenario meaning hood, side covers, full fenders and belly pan on top of 400-600 lbs for eng plus the other weight I mention above

The funny thing is the manual suggests ride height at 5.5" for full fender cars and I set my ride height at 6.5" as noted above and now after a couple of days I'm right at 5.5" with my suspension fully compresses against the bump stop. It does look kind of cool (see pics) and it doesn't rub on the tires and I can turn lock to lock without the tire hitting the fender so the 1" or so high bump stops I sourced (from NAZ's p/n) work fine.

I'm just wondering if my shocks being bottomed out on the bump stops are a result of too light of springs for my particular application.

Thoughts on my thinking or am I looking at this wrong.

152215 152216

Jim

[NAZ]

Jim, a few things to keep in mind:

1. Spring rates are per inch so each 220# spring at 2" of preload will have a force of 440 lbs or 880 lbs for the pair. So let's say you let the car down off the jack and roll it several feet forward and back to check your ride height and the springs settle 1.5" under the weight of the car, that combined force is now 1,540 lb.
2. Preload must be set with the springs fully extended and no weight being supported on the tires to avoid damaging the preload adjusters.
3. If you make a preload adjustment then simply lower the jack without rolling the car fore and aft, the ride height will be higher as the A-Arms swing on an arc and the tire will resist the movement and bind the suspension. You MUST roll the car for and aft some amount (several feet) to ensure you have no suspension bind before checking the ride height.

Let's take my car as an example. My front tires support 1,233 lbs with me in the car and ready to race. I have 8" 250 lb/in springs with 6.95" preload length which means I have 1.05" of preload and that gives me ~5" ride height. I check ride height after every race and after almost three-years now have never seen the springs "settle".

So with your car on a jack and the front wheels off the ground, measure the length of your 8" springs and subtract that number from 8" to determine your preload. That preload amount times 220 will give you the amount of force each spring has in stored energy before you lower the car to the ground.

Don't give up just yet, you'll get it worked out.

[J R Jones]

Interesting thread for me even though I am encumbered by a different and needing chassis.
Too much spring rate, just right, or too little = relevance. I think I see a rocker arm ratio on the UCA so wheel rate is not the same as spring rate but it is proportional.

To my surprise the chassis I am developing has significant bump steer making me (more) skeptical. Have you Hot Rod guys measured bump steer?
My Hot Rod photo review suggests a bit of camber gain on compression. Have you measured that?
jim

[33fromSD]

Jim, a few things to keep in mind:

1. Spring rates are per inch so each 220# spring at 2" of preload will have a force of 440 lbs or 880 lbs for the pair. So let's say you let the car down off the jack and roll it several feet forward and back to check your ride height and the springs settle 1.5" under the weight of the car, that combined force is now 1,540 lb.
2. Preload must be set with the springs fully extended and no weight being supported on the tires to avoid damaging the preload adjusters.
3. If you make a preload adjustment then simply lower the jack without rolling the car fore and aft, the ride height will be higher as the A-Arms swing on an arc and the tire will resist the movement and bind the suspension. You MUST roll the car for and aft some amount (several feet) to ensure you have no suspension bind before checking the ride height.

Let's take my car as an example. My front tires support 1,233 lbs with me in the car and ready to race. I have 8" 250 lb/in springs with 6.95" preload length which means I have 1.05" of preload and that gives me ~5" ride height. I check ride height after every race and after almost three-years now have never seen the springs "settle".

So with your car on a jack and the front wheels off the ground, measure the length of your 8" springs and subtract that number from 8" to determine your preload. That preload amount times 220 will give you the amount of force each spring has in stored energy before you lower the car to the ground.

Don't give up just yet, you'll get it worked out.

Hey NAZ

#1) - Okay, now I understand, Thanks as always for clarifying
#2) - Agree, this is how I did mine
#3) - Agree, this is how I did mine

No giving up, you're teaching me some really valuable stuff here and I do appreciate you taking the time to do that.. I'll get my car jacked up in the next few days to measure my preload (high school soccer starting today so I will be running around a bit these next few nights).

Thanks

Jim

[NAZ]

JR, the front motion ratio on the Gen-1 cantilevered upper arms is ~1.37:1. Interesting that I did not record the camber gain or my bump steer before and after as I'm anal about data. I did have to adjust the bump steer and to facilitate that I started with a bump steer kit (for a Mustang if memory serves) and customized that with a few parts to install a Pinto taper threaded pin to adapt the rod ends and stack my spacers & shims. The original kit used thru-bolts which I didn't like. If I remember I was able to get bump steer down to just a few thousands over a range of of four inches (+/- 2" higher and lower than ride height). That was checked at straight ahead and at 20-deg left & right.

[J R Jones]

Naz, Your bump steer correction is excellent.
I was looking at Roadracer's autocross photos, and it looks to me like positive camber in turns, with body roll. Not many options to correct other than a static setting to compensate.
I heard the HR castor spec is 8* I never experienced that. I assume steering effort is high.
BTW, when you pull out all the stops, what is your ET?
jim

[NAZ]

JR, I haven't run this combo yet but on paper it should run mid eights with a 300-shot of nitrous on a full pass at Wild Horse Pass on a winter night when the DA is only ~2500'. I hope to see mid nines on the engine only but we'll see. With the other combo it would run nines but at the end of the 2019 race season I pulled the 500 HP street engine and built a bigger "nitrous" engine dedicated to drag racing (compression ratio is too high for pump gas). Also put in a new narrowed axle with 3.90:1 gears and a spool. The gear ratio with my small tires should wake up the car as I was running 3.55:1. But Covid preempted the 2020 racing season and the first half of this year so in JAN I started building another race car, this time for desert racing. That's kept me so busy I haven't even cleaned the dust off the hot rod this year. And I was going to run the street racing event in Kingman this OCT but I likely won't be ready now. This is a legal street racing event where the city closes down a stretch of highway so you run an unprepared track heads-up for fun and whatever side bet you want to wager. Several racers in my car club have gone to this event.

[J R Jones]

NAZ I reconditioned/repaired a 1923 Studebaker for a collector and sold it to a guy in Kingman. He was a large PIA. Wooden wheel car with (rear) outside-drum brakes.
That event sounds like fun, and the kind of thing that resolves BS.
I assume you will do your best to not break-out of the 8.5 class.

I integrated Lexus IS300 powertrain and suspension into my Series I Excalibur which is the 1953 vintage Studebaker chassis, kingpins, trunnion pins and bell crank steering.
The bump steer was complicated by the 50's style swept-back control arms. Lexus tapers are not SAE or QA1, so I used straight pins on the steering and re-tapered the ball joints.
I fabricated a drag link for the too wide rack/pinion, which gave me options for the tie rods. A lot of Speedway parts in that.
That car is a replica of a 1929 Mercedes SSK now.
jim

152245

[33fromSD]

Finally getting back to this. Odd stuff going on, I'm missing something. I also turned both the compression & rebound knobs full clockwise before starting anything to get a base line.

NAZ, here is the info
* 1st pic; With the car jacked up (wheels off the ground), my spring height is 7.5" so structracting that from 8", I have a .5" preload times 225# gives me a 112.5# each spring has in stored energy before lowering the car
* 2nd pic is actually the first pic I took with the car sitting at ride height. The springs are compressed down to 5" at ride which seems odd / extreme to me.

I'm a little more confused now than before, I'm not sure why the 225# springs are both compressed to 5" at ride height and the shocks are bottomed out on the bump stops.

Pic 1 (wheels off ground; .5" preload):
152411

Pic 2 (car @ ride height - driven around block before taking pic with "C" and "R" knobs at full counter clockwise):
152410

The other thing I don't understand, is even with only .5" preload, I'm 2/3 of the way through the threads on the QA1 shocks already.

Something is off. There are no markings on the QA1 springs that I see so maybe Summit sent me the springs, the box did say 225# though.

I'll keep digging. My next step is going to be to remove the QA1, remove the springs, reinstall the shocks and see if the shocks bottomed out on the stop gives me the clearance I am seeing now (with springs) attached of it it will sit lower yet / hit the fenders. If it's the same height, then something is either messed up on the shock or the springs are wrong.

The instructions for the QA1 DD403 shock recommend 10" springs, I have some 175# 10" springs I guess I could try.
152412

Jim

[J R Jones]

Jim, I too am interested in the NAZ take on this.
Shocks and damping have nothing to do with ride height, they just limit stroke speed.
Your 225lb springs at 3" compression are at 1350lb spring compression and 985lb wheel compression based on NAZ rocker ratio of 1.37. Seems right and seems light.
jim

[33fromSD]

Jim, I too am interested in the NAZ take on this.
Shocks and damping have nothing to do with ride height, they just limit stroke speed.
Your 225lb springs at 3" compression are at 1350lb spring compression and 985lb wheel compression based on NAZ rocker ratio of 1.37. Seems right and seems light.
jim

Agree on they "seem" light but I could very well be missing something. I learning a ton of stuff from everyone and I love the education, just feels like I'm overlooking something from my lack of knowledge or 225# springs are indeed too light..


Jim

[33fromSD]

Just found this on-line, pretty interesting stuff, obviously not being an engineer by trade I never thought about half of this stuff when I think of a what to me is a simple coil spring. Guess it's not.

https://www.qa1.net/assets/uploads/documents/general/Spring-Rate-Chart-Vehicle-Weights.pdf

In the PDF it talks about 25-30% max compression for springs, since I'm using an 8" spring and my springs are compressed to 5", that is ~37% compression.

Jim

[NAZ]

Jim, it will take much more preload that what you’ve dialed in to keep the front at an acceptable ride height. If you know the front-end weight, I can calculate the preload required for whatever droop you need for your desired ride height. If you don’t know the weight you can dial in a couple inches of preload and see what ride height you end up with and we can calculate how much to adjust from there.


Also, if you have or can borrow a dial caliper and get me your spring wire size I can calculate the coil bind height. Also helpful is if you can get an accurate measurement of the distance between the center of the upper arm pivot (chassis attachment point) and the center of the hole you have your shock mounted in. I just want to check if your Gen-2 has the same motion ratio as the Gen-1.


Remember, this is an iterative process as every car is built different. Of course if we know the actual weight of the front it makes it easier to get to the goal line.

[33fromSD]

Jim, it will take much more preload that what you’ve dialed in to keep the front at an acceptable ride height. If you know the front-end weight, I can calculate the preload required for whatever droop you need for your desired ride height. If you don’t know the weight you can dial in a couple inches of preload and see what ride height you end up with and we can calculate how much to adjust from there.


Also, if you have or can borrow a dial caliper and get me your spring wire size I can calculate the coil bind height. Also helpful is if you can get an accurate measurement of the distance between the center of the upper arm pivot (chassis attachment point) and the center of the hole you have your shock mounted in. I just want to check if your Gen-2 has the same motion ratio as the Gen-1.


Remember, this is an iterative process as every car is built different. Of course if we know the actual weight of the front it makes it easier to get to the goal line.

Thanks NAZ, I have a calipers at my other garage so I will grab that tomorrow. I will gather this info (try to get the weight) and respond in a day or so.

I assume on this --> "if you can get an accurate measurement of the distance between the center of the upper arm pivot (chassis attachment point) and the center of the hole you have your shock mounted in" you want the upper shock mount hole right since I am measuring the upper arm pivot point?

This is fascinating stuff.

Jim

[NAZ]

Yes, Jim -- I'm assuming that the distance from the upper pivot to the ball joint on the Gen-2 hasn't changed as that would also change the front end geometry which would create a lot of work for FFR. The distance from the pivot to the shock mount on the Gen-1 is 7.75" and if yours is the same then I expect the motion ratio and shock angles to be the same on yours. These all are baked into the calculations to determine how much spring rate you car needs (as well as some others suspension stuff). It's all black magic to most but really makes sense once you understand it.

[33fromSD]

Yes, Jim -- I'm assuming that the distance from the upper pivot to the ball joint on the Gen-2 hasn't changed as that would also change the front end geometry which would create a lot of work for FFR. The distance from the pivot to the shock mount on the Gen-1 is 7.75" and if yours is the same then I expect the motion ratio and shock angles to be the same on yours. These all are baked into the calculations to determine how much spring rate you car needs (as well as some others suspension stuff). It's all black magic to most but really makes sense once you understand it.

Got it, Thank You NAZ

Jim

[33fromSD]

Did some playing this weekend on the QA1 double adjust Proma Star shocks, got really efficient at removing shocks / swapping springs upfront.

What I found is any combination of spring height or weight under 250# causes the QA1 Proma Star shocks to bottom out on the bump stop (no shock travel at all). Nothing changed no matter how much preload I put on the springs. On 250# springs it "starts" to keep the shock from bottoming out but not still not great. The combinations i tried were as follows:

* 175# 10 spring; 1" preload --> shocks bottom out on bump stop, no shock shaft seen, 5.5" ride height (tires ~3/4" from fender, doesn't bottom out due to bump stop, but no shock travel)
* 175# 10 spring; 2" preload --> shocks bottom out on bump stop, no shock shaft seen, 5.5" ride height (tires ~3/4" from fender, doesn't bottom out due to bump stop, but no shock travel)
* 175# 10 spring; 3" preload --> shocks bottom out on bump stop, no shock shaft seen, 5.5" ride height (tires ~3/4" from fender, doesn't bottom out due to bump stop, but no shock travel)
* 225# 8" spring; 1" preload --> shocks bottom out on bump stop, no shock shaft seen, 5.5" ride height (tires ~3/4" from fender, doesn't bottom out due to bump stop, but no shock travel)
* 225# 8" spring; 2" preload --> shocks bottom out on bump stop, no shock shaft seen, 5.5" ride height (tires ~3/4" from fender, doesn't bottom out due to bump stop, but no shock travel)
* 250# 8" spring; 1" preload --> shocks are about 1/4" from bottoming out on bump stop, 5.75" ride height (tires ~1" from fender, doesn't bottom out but very little shock travel)
* 250# 8" spring; 2" preload --> shocks are about 1/4" from bottoming out on bump stop, 5.75" ride height (tires ~1" from fender, doesn't bottom out but very little shock travel)

All preload was done with wheels off ground, then adjusted coil, then lowered car, then rolled car back and forth 5-6 feet several times.

For s**ts & giggles I then removed the 400# 8" springs from the koni shocks that came with the kit and installed them on the QA1 Proma Star shocks to see what happens, here are the results

* 400# 8" spring; .5" preload --> no bottoming out on bump stop; ~1.5" of shock shaft still seen, ride height 7" (tires ~2.5" from fender, too much clearance)
* 400# 8" spring; 1" preload --> no bottoming out on bump stop; ~1.5" of shock shaft still seen, ride height 7.25" (tires ~2.75" from fender, too much clearance)

Now, not sure why the above is from a calculation standpoint, but I have physical trial an error data. So, 400# springs definitely keep the shocks from bottoming out on the bump stops, I have actual shock travel which in my opinion is important to be able to adjust the QA1 shocks, but the car sits too high. The 250# springs are not quite enough, clearance between tire & fender is still too low, very very little shock travel. Feels like the sweet spot will be 300# springs. I ordered a set of 300# 9" springs (this way I can get 1.5" - 2.0" of preload if needed), I think this will put me in a good spot for the front and I can then adjust the compression & rebound knobs on the QA1 shocks from there.

The feel of the ride with the 400# springs and the QA1 shocks set to 6 on "C" and 10 on "R" was comfortable (not too stiff)

I also ordered single adjust Proma Start (DS601) shocks for the rear. With the Koni's, I have tried 250# 8" springs, 175# 10" springs, and no matter how much preload I put on the springs to increase the ride height the tires smack the fenders hard on bad bumps. I also ordered some longer bump stops (I know from above the bump stop is what keeps the tired from hitting the fender). I then ordered some 300# 12" springs for the rear shocks.

I think between the combination of adjustability on the QA1 shocks with a little more spring I will end up pretty good. Ride may be a little more stiff but I'm actually okay with that.

Naz -

I still owe you one measurement on the dia. of the 225# coil, I just didn't get to my other garage this weekend to grab my calipers to do that.

On the distance between the center of the upper arm pivot (chassis attachment point) and the center of the hole you have your shock mounted in --> Mine Gen2 frame is 7.0" (due to full fenders, I'm using the lower mounting hole in the upper control arm)

Regarding the weight, I don't have scales to do individual wheels so I can't get per wheel weight, but when I had the car weighed for regisstration it was 2,512 lbs. if I use a 55/45 rule (I'm told that will get me in the ball park), that puts me at 1,381 lbs upfront, 1,131 lbs in the rear so 690 lbs per corner upfront and 565 lbs per corner in the rear.

Jim

[NAZ]

Jim, the Gen-2 has a significant increase in motion ratio which is why you can't use the 225# springs others have and achieve the same result. So based on your guestimated weight and using 250# springs, if you were shooting for a 2" droop you would use 2.9" of preload. Not knowing your spring wire diameter I can't calculate your spring bind height but 2.9" of preload might have spring bind (not a good thing). A 300# spring would need 2.2" of preload to get 2" of droop. 275# spring would need 2.5" of preload for a 2" droop. I'm just using 2" droop as a SWAG but can calculate any droop you want.

Let us know how you make out with the 300# springs and if you give me the spring wire diameters I can calculate spring bind height. You want to avoid spring bind.

[33fromSD]

Jim, the Gen-2 has a significant increase in motion ratio which is why you can't use the 225# springs others have and achieve the same result. So based on your guestimated weight and using 250# springs, if you were shooting for a 2" droop you would use 2.9" of preload. Not knowing your spring wire diameter I can't calculate your spring bind height but 2.9" of preload might have spring bind (not a good thing). A 300# spring would need 2.2" of preload to get 2" of droop. 275# spring would need 2.5" of preload for a 2" droop. I'm just using 2" droop as a SWAG but can calculate any droop you want.

Let us know how you make out with the 300# springs and if you give me the spring wire diameters I can calculate spring bind height. You want to avoid spring bind.


Will do, Thanks NAZ

[33fromSD]

Hi Naz

The QA1 300# (9" Length) springs arrived yesterday for the front end. For the preload calculation, the wire diameter of the 300# spring is .4435". These are powered coated so I have no clue the thickness of the powder coating is compared to the bare wire dia. (not sure if it really matters in the scheme of things).

Let's shoot for about 1.5" droop.

Thanks for all the help.

Jim

[Jim Schenck]

Naz,

The Hot Rod motion ratio didn't change from Gen1 to Gen2, there was a second set of holes added to the arms for height adjustment but at the same radial distance from the pivot point. The Gen2 cars do have the steering rack moved for better bump-steer but that was the only geometry change other than adding the second set of ride height holes.


My only thing to add to the conversation here is that there have been changes over the course of production to both the standard and optional shocks as well as spring rates and steering geometry. The change to the nickel plated twin tube shocks and lower rates was a very significant one so just for anyone building a new car I would say finish it and drive it before deciding it has to be changed just from what others have done to earlier cars.

Jim

[33fromSD]

Naz,

The Hot Rod motion ratio didn't change from Gen1 to Gen2, there was a second set of holes added to the arms for height adjustment but at the same radial distance from the pivot point. The Gen2 cars do have the steering rack moved for better bump-steer but that was the only geometry change other than adding the second set of ride height holes.


My only thing to add to the conversation here is that there have been changes over the course of production to both the standard and optional shocks as well as spring rates and steering geometry. The change to the nickel plated twin tube shocks and lower rates was a very significant one so just for anyone building a new car I would say finish it and drive it before deciding it has to be changed just from what others have done to earlier cars.

Jim

Thanks for the input Jim

I think FFR needs to review / verify the suggested ride height in the manual for 33s running the full fender / running board package. I am running full fenders / running board and using the supplied standard Koni Shock, and the supplied 400# coil springs, even with zero pre-load on the coil spring I cannot achieve the suggested 5.5" ride height (even after driving the car and letting the springs settle). I'm at 6.75" for ride height with zero preload. I'm also using the lower set of holes as suggested in the manual for full fender 33s.

As you suggested I have driven the Koni package awhile and I agree the supplied standard Koni shock / 400# spring package is "not bad" and most folks will probably be okay with it, but it's a little too stiff for my taste and I switch to the QA1s for a little more adjustability, as well as I switched to a QA1 9" long 300# spring to get a little lower ride height (closer to the manual suggested 5.5" height for full fender cars".

Jim

[33fromSD]

NAZ

See the attached pic, these are the added holes in the upper Contro Arm Jim S from FFR is referring to. Basically it raises the suspension 1" if you're running full fenders / running boards. But it's still 7" CTC on both the lower & upper set of holes.

152722

Jim

[J R Jones]

Jim, As you know, those are the high ride height settings. You could experiment with the three low options. With your new springs you might find the sweet spot. It just takes time.
jim

[33fromSD]

Jim, As you know, those are the high ride height settings. You could experiment with the three low options. With your new springs you might find the sweet spot. It just takes time.
jim

yup, I know. Thanks

Jim

[NAZ]

OK Jim, base on Jim Schenck's confirmation that your G-2 motion ratio is the same as my G-1, we can calculate the preload but need the front end weight to do so.

Thanks for the wire diameter info but my bad, I forgot to ask you for the number of full coils.

[33fromSD]

OK Jim, base on Jim Schenck's confirmation that your G-2 motion ratio is the same as my G-1, we can calculate the preload but need the front end weight to do so.

Thanks for the wire diameter info but my bad, I forgot to ask you for the number of full coils.

7 full coils NAZ unless you count the outside coils too which have the flattened spots for the spring sets then it's 9 full coils

Jim

[NAZ]

Jim, I'll give you the theoretical preload for three different front end weights to achieve 1.5" of droop:

1250lbs needs 1.8" of preload
1300lbs needs 1.9" of preload
1350lbs needs 2.0" of preload

All these preloads will allow full shock travel without coil bind.

[33fromSD]

Jim, I'll give you the theoretical preload for three different front end weights to achieve 1.5" of droop:

1250lbs needs 1.8" of preload
1300lbs needs 1.9" of preload
1350lbs needs 2.0" of preload

All these preloads will allow full shock travel without coil bind.

Perfect, Thanks NAZ

Jim

[33fromSD]

Lot of work into the suspension with many hours on my back on the floor removing and reinstalling shocks with different spring combos. I still quite honestly don't know how you guys build your whole car without a lift, doesn't help I'm in my mid-50s and the ground is no longer my friend but still, kudos to you all.

Also, a lot of extra $$ tied up in the QA1 shocks, but more so the various spring sets I purchased (if anyone is interest in some sets let me know) but in the end I'm going to call this suspension issue closed as I believe I now have the right shock / spring combo on my car. I still have some fine adjustments on the knobs for all the QA1 shocks but the major work is now done.

Here is the combo that feels best to me for my 33:

* Front = QA1 DD403 Proma Star Double Adjustable coil over shocks with 9" long 300# springs
* Rear = QA1 DS601 Proma Star single Adjustable coil over shocks with 12" long 300# springs

With the longer springs in the back I needed to do the modification to the shock mounts where to take a 2-1/2" hole saw and cut slightly more than 1/2 a hole of the material away so the spring clears the mount, but I knew that coming into this. No biggie there, just a heads up to anyone else swapping to 12" springs.

The beauty of the rear shock / spring set up, is this is the first time since I completed the car and started driving it, that I have not bottomed out on all the really bad bumps and dips I know of in the city. Certain tweaks I made with the Koni Shocks / 250# spring with the kit kept me from bottoming out on some of the lesser severe bumps / dips but not 100%. This morning when I took out the car when I finished the new set up, I purposely looked for and drive over every really bad bump, dip, gap, seam or pot hole I came across verses avoiding them and not once did I bottom out....FINALLY!! Still need to do the same route with a passenger in the car but I'm fairly confident it will be fine.

Someone mentioned it above (can't find who now) and they are 100% correct, each of these 33s are unique regarding build / set up, so my taste / setup in shock / spring combo may not be to the liking of someone else but it this is why we tweak on our own rides and make them our own. It was a great learning experience, I learned a ton from them with the wealth of information everyone provided (especially NAZ).

Thank You everyone!!

Jim

[RoadRacer]

I suspect I'll need longer rear springs.. or stiffer. My car is almost through the 'glass above the tire now. But I'm waiting to final fix more when I have my sway bar on (next weekend) and larger tires (not sure when). Also may add more bumpstops.. so a lot up in the air.

[NAZ]

James, if the tire hits the fender over bumps you have too much suspension bump travel for your fender clearance. The fix is not stiffer springs, that doesn't guarantee the tire won't rub -- it just requires a bigger bump to make contact. And stiffen the springs on the rear enough and it will lead to your car handling like a drift car and longer stopping distances as traction diminishes at the rear.

A bump stop is the cheap and easy fix. Bump stops come in extra lengths that you can cut to the size needed or you can stack bump stops to get the length you need.

[sread]

Bump stops are a versatile method to fine tune suspension travel - they come in all sizes and hardness (durometer). GM 1/2 ton suvs of the early 2000 vintage have bump stops that that are in contact at normal ride height. They are made of a dense foam type material and when they age they will start to crumble and deteriorate. When you go to the GM parts catalog for replacements they are actually called "auxiliary springs"

[NAZ]

Elastomers can be used as springs. I've designed punch press tooling stations using polymers for short throw springs. They outlasted steel springs and are not as susceptible to harmonics from the sudden and repeated impacts over millions of strokes like steel springs. At 400 strokes per minute, 24/7 punch press tooling takes a real beating.

[J R Jones]

As long as this thread has "mission creeped" a bit: I have a fondness for air suspension. Back in the 60s air shocks for trailer towing made the unloaded suspension rough. Air Lift air bags inside coil springs were great. Operating pressures (5-20) were much more comfortable and the ultimate spring rate seemed progressive. I never measured the actual boosted spring rate. I see that Air Lift is making an "Airover" shock unit currently, but I have not tried it. One can tune the spring rate and ride height with air pressure.

In the seventies I was doing interstate service work with occasional heavy loads in my mid-size Chevy wagon. I put (used) Air Lift bags in the rear coils. Late one night on the interstate in NW WI I was carrying a load at speed passing 18 wheelers in the left lane. A loud report came from the rear, I assumed it was a tire, the car sagged, but was stable. One of the bargain bags blew but I did not use the system lines for service, I serviced them individually. I moved the load over the good bag and moved-on.
Seems to me not interconnecting the Airovers would provide the ability to balance weight.
jim

[NAZ]

Jim, my hauler is a F550 I ordered new with all the bells that fit my needs. They only come as a cab and chassis so you have to finish the vehicle. When it arrived at the dealer I drove it straight to my shop to start modifying it for my particular use and the first item on the agenda was pull all the steel springs and install an air ride suspension including a four-link rear. I set it up with auto leveling in the rear and have a dump valve that makes it squat when attaching one of my trailers or even offloading by hand so it's easier to reach the load. I love air ride on a truck and it rides twice as good as the OEM springs. The auto leveling adjusts the air pressure based on load so the truck doesn't ride like an old farm wagon when not loaded.

The next thing was fabricate a lightweight aluminum bed which looks better than store bought. I love that truck but I think it'll be the last Class-5 truck I purchase, the annual insurance and license fees are more than all my other seven road driven vehicles combined. I think the next truck will be a 1-Ton, they're way less expensive to operate.

[J R Jones]

NAZ, One has to assume there is something behind (high) insurance rates; it is not obvious to me.
In the old days air shocks lifted the chassis to inappropriate height and loaded shock mounts with spring load, also inappropriate. The air bags did not lift to an extreme, but would lift overloads to original ride height.
The Air Overs are an odd configuration with the air chamber around the shock body. Quite different from bag in coil. Seems like an opportunity for innovation, especially for the Hot Rod, like a mono-bag in front. "Soft Nose" TM.
I have been visualizing a unique front anti roll device as well.
jim

[RoadRacer]

Jim, (33fromSD) I sent you a PM about some spring questions when you have a chance. Thanks.

[33fromSD]

Jim, (33fromSD) I sent you a PM about some spring questions when you have a chance. Thanks.

Just responded, sorry about the late response, trying to pack some of the toys away for the upcoming down turn in weather so I've been off line a bit.

Jim

[5mspeed]

Took your advice on QA 1 took 3 months to get but what a great ride now thanks Gary

[33fromSD]

Took your advice on QA 1 took 3 months to get but what a great ride now thanks Gary

Awesome!! Yes, the ride is night & day between Koni & QA1. Little spendy, but worth it in my opinion. I also like the adjustability of QA1.

Jim

[RoadRacer]

JR, the front motion ratio on the Gen-1 cantilevered upper arms is ~1.37:1.

I know NAZ is no longer around unfortunately, but I've been thinking about the spring rates a lot since starting autocross. I keep getting a little more serious about making my car faster :)

So, I want to make sure I'm thinking about this cantilever the right way. Many folks (roadster, coupe) run high spring rates, i.e. 700-800lbs front. I'm at 650, btw, but I think the cantilever is working against me? Can anyone confirm.. given that the inner arm is ~7" and the outer arm ~10", the 650 spring is the equivalent of a ~475lb (650/1.37) spring in a cobra? I can't believe it works the other way, i.e. equivalent to a 650x1.37 = 890lb spring?

If this is the case, it would explain a lot.. cos 450lb would seem to be awful light for a competitive autocross car.

[33fromSD]

I know NAZ is no longer around unfortunately, but I've been thinking about the spring rates a lot since starting autocross. I keep getting a little more serious about making my car faster :)

So, I want to make sure I'm thinking about this cantilever the right way. Many folks (roadster, coupe) run high spring rates, i.e. 700-800lbs front. I'm at 650, btw, but I think the cantilever is working against me? Can anyone confirm.. given that the inner arm is ~7" and the outer arm ~10", the 650 spring is the equivalent of a ~475lb (650/1.37) spring in a cobra? I can't believe it works the other way, i.e. equivalent to a 650x1.37 = 890lb spring?

If this is the case, it would explain a lot.. cos 450lb would seem to be awful light for a competitive autocross car.

I don't autocross James but I'm only run-in 300# springs in the front with dual adjustable shocks.

Jim

[RoadRacer]

Yeah I get it Jim, sounds crazy I know. :) different animals!

My point being though that compared to other cars without the cantilever, the extra 1.37 leverage means that your car is like a normal car with 220lb springs :)

* actually very simplistic because all cars have some leverage and we’d have to measure their distance on the lower a-arm to determine theirs. It’s not 1:1 for a roadster..

[Dgc333]

I have read through this thread and find the info to be very informative. I do have one question:

Why would you want to use a spring that is shorter than what the longest length the shock can accommodate?

Assuming the same spring rate a longer spring will minimize the chances of coil bind.

[RoadRacer]

I have read through this thread and find the info to be very informative. I do have one question:

Why would you want to use a spring that is shorter than what the longest length the shock can accommodate?

Assuming the same spring rate a longer spring will minimize the chances of coil bind.

Agree at the back.. but at the front of a 33 the longer springs can touch and interfere with each other. I only use 7” springs on the front now.