Pin Drive Width Front Setups? [Archive]

Todd Buttrick

07-17-2014, 03:29 PM

For those of you who are running pin-drive fronts, I'm attempting to zero in on the best setup for a base setting of near zero bump-steer on a MKI. Tire size is somewhat irreverent but.. I had been running a FR rack with an inch of extensions total side to side. (half inch each side) this placed the inside tie rod pivot well inside the upper and lower CA pivot plane. It was acceptable but still some bump-steer. SAI Mod helped tremendously. I just installed a new Unisteer 3.7 with 1" extenders per side which brings the inner pivot more inline (outward) with inside upper and lower CA points and bump-steer is worse. Trying to get a conscious on best starting point if you have the details. Looking for detail and your overall impression of bump steer with your setup:

MK1,2,3: ?
Ride height: ?
Spindle type: ?
SAI Mod ?
Caster: ?
Rack type: ?
Rod End type: ?
Extenders: ?
Rod end orientation top/bottom: ?

CraigS

07-18-2014, 06:28 AM

Todd, can you post a pic of your bump steer curve so we can see what is going on. Then maybe we can help decide what needs to be done.

Todd Buttrick

07-18-2014, 07:38 AM

Todd, can you post a pic of your bump steer curve so we can see what is going on. Then maybe we can help decide what needs to be done.

I'll do the best I can here from memory. This is pretty darn close to what's going on. I did the laser on the wall thing while moving through the suspension.

First here is with the heim joint rod end mounted on top of the spindle arm with 1/8" spacer to eliminate any binding. As you can see from the curve, this can produce some scary steering at speed. If I move out of my path too quickly and unweight the opposite wheel, the toe out wants to take me back the other way and fast. Very spooky. At slow speeds, the car handles amazingly as you could imagine. There's no binding here.

http://www.ffcars.com/photopost/data/500/Top_Spindle.jpg

Second here is with the rod-end heim joint still mounted on the top but with 1/2" spacer added. Very spooky handling still so I moved to the bottom and I'll take another profile tonight and post. My best guess is that the 1" spacer per side is amplifying everything with the tie rod being so short with pin drive. I think a longer tie would produce a more gradual arc to the outside. None of these components ideally line up as they should with respect to inside and outside upper and lower control arm pivots so I'll never get to zero bump.

http://www.ffcars.com/photopost/data/500/bottom_spindle.jpg

Settings are:

+3 caster
-1 camber
1/8" toe in

skullandbones

07-18-2014, 02:37 PM

Hi Todd,

Does the pin drive width change the geometry of the steering that much? I suppose you are trying to get "apples to apples" type comparisons but I'm not sure if the difference would be significant related to bump steer. I could be wrong. Thanks, WEK.

Todd Buttrick

07-18-2014, 07:28 PM

I don't think pin drive width changes the geometry so much but with the addition of the SAI mod and rack extenders, I've bungled things up. I thought that getting the extenders closer to the inner pivot planes would be better but I think I'm wrong. I've tried to diagram this best to my knowledge. I'm sure the perspective isn't quite right so don't be hatin me. Ideally, planes ABS and DEF should be in line but that aint happening. I've got the blue plus the red. Adding pin drive makes the angles AD, BE, CF steeper given the same ride height.

http://www.ffcars.com/photopost/data/500/SAI_Pindrive.jpg

skullandbones

07-19-2014, 01:13 AM

CraigS

07-19-2014, 07:03 AM

Couple of questions. 1-Is your ride height that high so that both control arms angle down so the ball joints are lower than the pivot points? 2-Do you have the solid offset rack mounts? If so you can change rack height by rotating 180 degrees. I haven't worked on a pin drive car so bear w/ me. I was thinking about your thought that the rack spacer makes the tierods shorter but can't remember-are the LCA and UCA shorter w/ pin drive?

Todd Buttrick

07-19-2014, 08:56 AM

Todd,

I don't know if you saw this thread but it explains how I changed my front suspension to get as close to the MKIV setup as I could with the MKIII structure and components I had compiled for my build. I fabbed an SAI adaptor which I used on the SN95 spindle I had (2000 Mustang). You have the real one so that's good. I flipped my Moog rod ends on top of the steering arm. I have not positioned the rack optimally yet but I have the Breeze adaptors to do that. I also have not done the procedure to measure my bump steer yet. I was able to leave the UCA length long by switching the UCA bracket to the bottom of the frame bracket and adding a wedge to change the bracket angle. It resulted in decreasing the angle of the front and rear mounting positions. Coincidently, FFR did a very similar change to the UCA brackets on the spec racers and also to the MKIV. I liked being able to keep the stock length of the UCAs. Just had to lengthen the adjustment arms to accommodate the changes on the frame bracket and the spindle. Also, on mine I added lots of castor since I'm running PS. Like you I know I improved my SAI very much. Also, I think I improved the geometry of the front end. I have some shots of the arms and rod ends if you would like to see them. WEK.

Changing MKIII Front Steering to Resemble MKIV Level (http://thefactoryfiveforum.com/showthread.php?10889-Changing-MKIII-Front-Steering-to-Resemble-MKIV-Level&highlight=similar+mkiv)

Eurekha! No I haven't seen this and I think this is the direction I need to go. Was thinking last nigh that I might revert back to the stock upper CA location but hadn't even considered that the mount could be repositioned underneath it's original location. I really think this is playing a big part in my bump steer issues. Is this (http://www.summitracing.com/parts/rex-re1468) the wedge you purchased? Yikes.. $32!? Are they made of gold? :rolleyes:

http://static.summitracing.com/global/images/prod/large/REX-RE1468.jpg

Couple of questions. 1-Is your ride height that high so that both control arms angle down so the ball joints are lower than the pivot points? 2-Do you have the solid offset rack mounts? If so you can change rack height by rotating 180 degrees. I haven't worked on a pin drive car so bear w/ me. I was thinking about your thought that the rack spacer makes the tierods shorter but can't remember-are the LCA and UCA shorter w/ pin drive?

Craig,

No, my ride height is not actually that high. Just did that pic from memory so I'm sure it's not a true picture. I have the offset bushings but not solid and rack is mounted low. Yes, the upper and lower CAs are shorter than standard width and frame side mounting points don't change when going with pin drive width (at least on a MK1). The biggest departure from stock seems to be the upper CA inner mounting point by adding the SAI mod.

REALLY appreciate the help guys. If I can get zero bump steer, I might just drive this car for another 12 years. :cool:

skullandbones

07-19-2014, 10:56 AM

Here is the item I got from Summit. It was $18 plus shipping. I only used one of them.

DJM Suspension ACC-6PSK - DJM Suspension Pinion Angle Shims

BTW: I did not have to modify the frame 3/4 inch rail as in the Breeze video by using this piece. You can see that I had a piece of paper placed between the UCA and the frame rail to show the clearance in one of the pics. It was close but still not touching. Also, the thick washers (brass colored) I installed on the mounting bolts are shaved to an angle that matches the slight angle change when mounting the bolts with the pinion shim. This allows everything to lay flat when torqueing the bolts down. Small detail but important if you didn't notice.

Good luck with your project,

WEK.

Todd Buttrick

07-19-2014, 02:57 PM

Thanks WEK. I lowered the ride height a bit and added some caster to raise the steering arm end with tie rod on the bottom of the arm. Much improvement but I'm going ahead with your mod as I think it will allow me to zero in on close-to-zero bump.

Thanks again.

Todd

CraigS

07-20-2014, 04:47 PM

Double checking w/ you again. Since your car is a MkI, have you upgraded to SN95 spindles? Do you have 15 or 17 inch wheels? Since the SN95 spindle is shorter it has a big effect on which mounting point for the UCA you use. Keep in mind, as you look into changes, the SAI mod was designed for SN95 spindles and 17 inch wheels. So using it on any other combination, including pin drive, you are kind of on your own. I am enjoying this very interesting thread.

Todd Buttrick

07-20-2014, 05:20 PM

Yes, SN95 spindles and 15" wheels. I sort of pioneered the SAI on pin drive and 15" wheels so I'm flying blind. Don't get me wrong, I'm enjoying this and learning much. The MK1s had a slot for upper CAs so they can be moved. They've never budged from where I put them so long as I spot-torque them with lock washers. Moving the upper CA back and underneath it's original location will bring plane ABC in line with the 1 inch rack extenders but still keep the SAI geo. The steering arm seems to be a bit outside plane DF still as in my diagram but I have a future plan for that as well. I have a welder now and dangerous.

Todd Buttrick

07-21-2014, 02:28 PM

I ordered the 6deg wedge and AFCO 5" 5/8-18 steel sleeves. I have the silver with black sleeve control arms which I just rebuilt.

CraigS

07-22-2014, 07:46 AM

Seems you are making progress. Can you snap a couple of pics. If you don't have hoses attached a pic through the brake duct opening w/ it all together and on the ground would be very interesting.

Todd Buttrick

07-22-2014, 10:37 AM

Seems you are making progress. Can you snap a couple of pics. If you don't have hoses attached a pic through the brake duct opening w/ it all together and on the ground would be very interesting.

Can do. I have a four post so it's easy. I'll snap some before pics tonight and should have parts by the weekend.

skullandbones

07-22-2014, 11:02 AM

Todd,

What are your final alignment goals? Also, what are you using the car for besides driving on the roads? I know you were attempting to get the SAI to the standard (9 degrees). I wanted to do that also. I think getting the geometry close to a good baseline, will help in any future changes you make. Personally, I was trying to get close to the MKIV geometry without changing to the new spindles. I don't know any of the specific specs on the MKIV with all the new components. That would be good data to have for comparison for any of the MKs.

Todd Buttrick

07-22-2014, 12:11 PM

I'd just like to get as close to zero bump as I can. I drive all street and drive a ton (96,000 miles now) I also have a slight vibration at 65MPH that I can drive through and would REALLY like to rid myself of this as well. I've replaced rack (last month), spindles, rotors, wheels, tires, etc. and have the wheels balanced on a Hunter at Moroso. I'd like to find a on-the-car-balancer service but that has proved impossible. I bought a bubble balancer and ready to rip the weights off and give it go myself. Bump steer amplifies this a bit so I might be good if I can get close to zero.

David Hodgkins

07-22-2014, 12:34 PM

Todd Buttrick

07-22-2014, 03:46 PM

Todd,

GREAT thread. I have pin drive as well but I'm using fox spindles, that support my Levy Wilwoods. Sorry for the lame question, but can I use the suggestions here to improve the bumpsteer in my MKIII, can I use a variation thereof or do I have to do something completely different?

Also, just for clarification: When you say SN95, do you have the straight arm or '94 dogleg spindles?

:)

I have the dogleg type. WEK's mod duplicates the geometry that is shipping with the MKIV with their new hubs. To go there from what you have you would have to buy SN95 spindles, SAI mod, rack extenders and then mount the upper CA cross mount underneath as he described. From what I understand, you can't use the new FFR spindle with pin drive. Don't know why but that's what I think I've read.

More good reading here;

SAI and the MK4 (http://www.ffcars.com/forums/17-factory-five-roadsters/295019-sai-mk4.html)
SAI on a MKII..... (http://www.ffcars.com/forums/17-factory-five-roadsters/299818-sai-mkii.html)

Todd Buttrick

07-22-2014, 04:59 PM

Here's a before mods pic.

SAI Mod
SN95 Spindles
Pin Drive CAs
AFCO Steel swaged tubes
8" x 450lb Eibach springs
Unisteer 3.7 rack
bump steer with heim ends
15" Vintage Wheel pin drive knock offs
Cooper Cobra 245/60/15 sneakers

- 1 Camber
+3 Caster
1/8 toe in

http://www.ffcars.com/photopost/data/770/front_before_mods.jpg

CraigS

07-23-2014, 07:07 AM

The pic looks pretty standard doesn't it. 2 thoughts for you. 1- safety measure. next time you have the bolt out of the rodend at the steering arm put a larger diameter washer under the head of the bolt. Idea is that, if the rodend were pulled apart in an accident, the housing wouldn't be able to slip over the head of the bolt. 2- from my post in a thread on the other forum about a steering vibration
"Well I tried for 20 minutes to see if this or similar is available on manual racks w/ no luck. So I will pass on what I know about this problem w/ PS racks.
http://i3.photobucket.com/albums/y91/craig-s/psrack_zps0fe57641.png
See the big nut in between the two tubes in center left part of pic. that is a big jam nut (maybe 2 inches) w/ a smaller bolt head (3/4 inch) in the center. The bolt head is used to adjust friction in the rack. There is a rubbing block that contacts the rack and a spring on that w/ the other end of the spring contacting the bottom of the adjuster bolt. The idea is that the rack needs a little bit of friction to damp out vibrations like you are feeling. There is usually a torque spec for the bolt in a few inch pounds. My technique for adjusting is to drive at parking lot speed, yank the steering wheel about a 1/4 turn and let it go. At that speed, the wheel probably won't return fully to center. At 30 mph, a slight (much less than a 1/4 turn) yank should have the wheel return fully to center. I hope there is something here that translates to a manual rack. We ran into this problem at Lexus when, on one model, they replaced the rubbing block w/ a roller. Spent a year dealing w/ this w/ new tires, super careful balancing etc. The answer was to go back to a rubbing block."
__________________

Todd Buttrick

07-23-2014, 07:32 AM

Thanks Craig. Never thought about the heim joint pulling a part. I used a smaller washer so that I'd get max travel of the heim. I have the same washer on the other side for the same reason. A larger washer will limit the travel but probably not as much as I think. You can see its already pretty close between the top of the heim and the larger diameter bottom of the steering arm.

I tried adjusting the Flamming River Rack as you suggest before I replaced it with the Unisteer I have now. Very little noticeable change.

skullandbones

07-23-2014, 01:21 PM

Todd,
I couldn't duplicate the MKIV geometry since I don't really know what it is specifically and since I have different components (some same) the best I could do was to try to get a similar result. I haven't even addressed the bump steer directly but I have not experienced any issues with it as described by other resources. The real benefits for my application were the improved SAI and static roll center (baseline suspension geometry). I know I've improved both those numbers to what you might call a standard (SAI for sure but roll center only estimate). Also, and I know this is anecdotal, but it looks more normal! It looks more like just about every race car suspension I've seen and studied. Even straight axles have a proper SAI so it blew me away when I found mine to be around 18 to 20 degrees. Anyway, here are some pics of mine after changes. The big difference between ours is that I am using 17x9 wheels. My upper ball joint and adjustment arm ends are inside the wheel offset with very little clearance but enough. It didn't look that way on yours and I don't know what further changes will cause with yours. Good luck,

BTW: you said your Eibach springs were 250#. Is that a typo. I haven't heard of running that low of a spring on the front. Mine are FFR 450#.

WEK.

Todd Buttrick

07-23-2014, 04:57 PM

WEK,

I use the term "duplicate" loosely. :o Yes, typo and fixed. I'm running 450#, 8" springs. Theoretically, the only change I'll be making is moving the upper control arm inboard pivot inside and down which will allow the inner tie rod pivot to be in the same plane as the upper and lower CA inner pivots with the 1" extensions installed on my rack. I should also gain from a lower instant center. SAI and scrub will remain same as I already have the SAI mod installed assuming same camber setting. It looks as though my sweet spot for near zero bump is right in the middle of the steering arm so I'm going to dial in more pos caster to raise the arm a bit. (at +3 now so have plenty of room). A bit surprised that your tie rod end is on top of the arm. I was getting some wild and scary oversteer at speed when mounted that way but would have been kick *** for autocross. My first bump profile posted was that way. I'm pretty confident that this will make for some positive changes.

skullandbones

07-23-2014, 05:54 PM

Hi Todd,

Another big difference in our setups is the spindle. I have the late model without the dog leg. That's why the rod end is on top for now. I wish I had yours. I think I would be in better shape but that's the way it goes. I'll be interested to see how you get your bump steer solved. Would love to learn something new. Thanks, WEK.

CraigS

07-24-2014, 06:32 AM

You may need a longer bolt. Use a big washer right under the head of the bolt and your small OD spacer under that. On the rack, I was just hoping there might be some help for you. I have done the adjustment many, many times on a power rack and only assumed there must be something similar on a manual rack. Don't forget that you can move the rack up and down w/ the offset mounting bushings. IE raising the rack has the same effect as lowering the tie rod end. You might come up w/ a better combination of rack position and tierod on top or bottom of the steering arm. A caution though, you might need to change the length of the lower steering shaft when you move it.
http://www.breezeautomotive.com/details.php?prod_id=720&cat_id=12

Todd Buttrick

07-24-2014, 06:49 AM

Thanks Craig. My rack is as low as it goes without major mods and I need to raise the rod end. I think I have plenty adjustment to get to that sweet spot by adding caster. I'll need a longer bolt to add another washer as you suggest so I'm waiting to this with the other mods. AFCO sleeves should be here Friday and I will wait for the next rainy day to start the mods. Too many car events this weekend to take it off the road if it's nice out.

rlampman

07-25-2014, 01:57 PM

I have a MKII with pin drive LCA's, Pole Position UCA's, Pro Shocks, and I am planning to install the SAI kit. Bolting the UCA to the bottom of the frame mount sounded like a great solution as that allows clearance from my shock spring as well as keeping a longer arm. As Todd has already done the SAI mod shorter springs are an option using the standard SAI relocation bracket.

I don't have the SAI kit yet but I did some mock up today. If I install the UCA to the bottom of the frame mount the rear of the UCA will be right in the middle of the 3/4" support tube. I think even with the SAI relocation bracket moving it outboard I will still have an interference problem. I know WEK said he was close but cleared. There is no way mine will clear mounted below the frame mount (or at least without frame modification/relocation). Is this a difference MKII to MKIII? Todd, looks like you haven't started the install of the wedges but did you check for this clearance yet? Also, did you have a problem when you did the initial SAI kit using the UCA relocation bracket?

I will be following to see how it works out for you..
Rod

Todd Buttrick

07-25-2014, 04:11 PM

I haven't mocked up relocating the cross beam for the UCA yet but I've been concerned about the clearance of the butt end with respect to any inconsistencies from frame to frame. We shall see. Just back from a long week on the road and will take a look tomorrow. I had no issues with the stock SAI mod bracket location. You're seeing an issue with this as well? Not sure of the differences between MKs. The shorter springs work just fine. We could schedule a time to facetime and I can show you what I got live and discuss but if it's not raining, I'll either be driving or fishing. :cool:

rlampman

07-25-2014, 10:44 PM

I don't have the SAI kit yet but I unbolted the UCA and held it up. I am only holding the UCA up where I "think" it will go based on hole dimensions I have seen here. Unless the frame bracket brings the UCA about 1/4" - 1/2" away from the frame I will need to clearance the 3/4" frame brace where butt end of the UCA is. Doable for me but I didn't think anyone else had to do this. This also means in order to locate the UCA below the frame mount I would need to relocate the 3/4" brace.

I got tied up with work too but I am available any time now.

CraigS

07-26-2014, 03:22 PM

On my MkII there is no way to put the UCA cross shaft below the usual position w/o cutting the 3/4x3/4 which I will not do. The standard SAI angle iron bracket moves the cross shaft outward enough to clear the 3/4x3/4. I have a few friends w/ MkIs, MkIIs, and MkIIIs who have done the SAI mod and none have mentioned cutting the tube. As backround, the SAI mod was designed for SN95 spindles and 17 in wheels. People had started using SN95 spindles, which are shorter than the Fox spindles, and made no changes to the UCA location. Then David Borden got into working out the SAI problem w/ a Cad program. He could have just fixed the SAI w/ the new adapter but realized there were other geometry problems that could be dealt with too. That led to the frame mount adapter which made some geometry improvements and had the side benefit of allowing the use of the same UCA and no longer sleeves needed (unless one is going for more caster too). I say all this so people reading this thread can see how it all works together and also, how parts can be done but may not give the full benefit of the complete mod. IE, on my MkII, I still have Fox spindles and stock UCA location. I asked Whitby's to machine the adapter so the UCA ball joint would sink 5/16 further into the adapter. That allows me to do a partial SAI w/ my 17 inch Bullit wheels. I will do the frame mod part when I finally swap to SN95 spindles.

rlampman

07-28-2014, 01:36 PM

Craig, Good to know that I should be able to get the SAI mod to fit the UCA bracket without modification.

Todd, Great talking to you today.

I am still undecided on whether I will modify the 3/4" tube or just use the standard SAI bracket. If I do modify the 3/4 tube I think it would be best to make a Y out of it and have a support above and below the UCA. That way it keeps the strength of the forward stringer and still clears the UCA. Then whether to change to upper frame mount or use a wedge like WEK did.

Below is pictures of my UCA mounted in the standard location. There is no shock installed and the suspension is at full droop. Mine is a MKII and there is obviously a change from what WEK has (I think MKIII) to mine and talking with Todd maybe different from a MKI

From the side
http://i1349.photobucket.com/albums/p751/rlampman/Cobra/20140728_112248_zpsiqir0qjn.jpg (http://s1349.photobucket.com/user/rlampman/media/Cobra/20140728_112248_zpsiqir0qjn.jpg.html)

From above
http://i1349.photobucket.com/albums/p751/rlampman/Cobra/20140728_105947_zps3y9qy4yw.jpg (http://s1349.photobucket.com/user/rlampman/media/Cobra/20140728_105947_zps3y9qy4yw.jpg.html)

skullandbones

07-28-2014, 02:27 PM

Mine is definitely and MKIII. So was the Breeze roadster in the video. I went back to look at the measurements closely. The closest I can tell is the 3/4 tube to the bottom of the bracket is 1 3/4 close to the 2x2 vertical. When you measure at the back of the bracket down to the 3/4 inch tube it's 1 5/16 inch. So they are converging making that area very tight for the modification. I measured app. 1.5 mm (10 paper thicknesses) using the paper as a feeler gauge between the 3/4 tube and my rear attachment point on the UCA. It's very close. As a matter of fact, I had a hard time just mocking it up with the clearance I had. I wasn't sure it was going to work until 30 minutes into the fitting. I believe I had to put bolts in in a certain order and hold my mouth a certain way (ha). Honestly, if I had not been able to get it to work without modifying the 3/4 inch tube, I don't think I would have done it. On the positive side, it goes to show that we can make several combinations of changes to improve the geometry without having to use everything. I think I would have gone with the SAI angle piece on the chassis with the shorter adjustment arms without a second thought. That still gets you some of the improvements done on the new Spec Racers and MKIVs. Sorry if I confused the situation.

Good luck guys,

WEK.

rlampman

07-29-2014, 01:20 AM

WEK,
Thanks for the measurements! I measured mine and I have the same

The closest I can tell is the 3/4 tube to the bottom of the bracket is 1 3/4 close to the 2x2 vertical. When you measure at the back of the bracket down to the 3/4 inch tube it's 1 5/16 inch.
That makes sense because of the other parts that would have to be changed if they where different. If you can check a few other measurements so I can see what we have the same or different. I measured from the center of the rear mounting bolt to the rear of the UCA (not including the zerk fitting) and I have 3-3/8". The center of the same bolt forward to the vertical 2x3 is 1" measured at the bottom of the UCA frame mount. BTW, the UCA has 5" center to center bolts and is centered over the same vertical 2x3".

Either my UCA is different and extends further back or I just need to hold my mouth in the right position (I do this too). I will try and set the UCA in the lower position tomorrow and see where I end up. Maybe I'm not as far as I thought. I appreciate any help as I would rather use the wedge like you have done and mount under the mount without modification to the frame. (see "I have to stop changing things or I will never finish").
Rod

skullandbones

07-29-2014, 11:40 AM

Todd: step in if I'm "stepping on your thread". Don't like to do that. But I thought this would help you, too.

Rlampman: You have different UCAs than I if you check the link for my thread on the MKIII changes. It looks like the upgraded ones that people have been talking about in another thread. The measurement on yours was 3 3/8 and mine was 2 7/8 for same measure. The brackets are on 5 inch center. Center of rear bolt to vertical is also 1 inch on mine. So the new UCA pivot arm would not even begin to fit as mine just barely fit in that space. Sorry. BTW: I am considering using a spherical rod end on the forward pivot point on my "old" UCAs. Even though the ones I have are functioning properly, I don't like the bad misalignment of the end (carrying a lot of castor), so it will function better with a rod end like on the Levy suspension arms as an example.

Good luck you guys,

WEK.

Todd Buttrick

07-30-2014, 05:08 PM

Todd: step in if I'm "stepping on your thread". Don't like to do that. But I thought this would help you, too..

Not at all WEK. The more experience, the better for all.

Rod,

Great to talk to you as well. It looks as though those are the same UCAs that I had when I got my kit in 2001 and it seems as though FFR has reverted back to the same. I have the same as WEK which have billet ends and came with the black anodized aluminum sleeves. I just got the AFCO sleeves and wedges so I'm ready to rock and waiting for a rainy day. I start into convolutions when its nice out and my car is disassembled. This is great info here guys. I have much work ahead of me with my paying job so may not get to this quickly. Just have to wait until the planets align.

rlampman

07-31-2014, 01:15 AM

Well, I mocked up the UCA today. I ended up bolting it above the frame mount with shims to simulate the 3 degree shim angle. Measuring from that setup with my older UCA I would need to make clearance into the 3/4" tube about half way and then some for spacing to mount below. I could do this with another 3/4" tube welded below for support. I will have to debate this to see if it's worth it and I'm not ready to weld anything until my body is back off anyway.
I also measured and the SAI mod frame bracket should work out fine without any modification. As it should but I wasn't sure by just eyeballing before.

You guys have some great information. Looking forward to seeing what you come up with Todd. Thanks for all the help and I hope I didn't side track your thread either.
Rod

Todd Buttrick

08-15-2014, 04:11 PM

Well I'm back to square one on this. I put it all back to the way it was after seeing the UCA couldn't be mount underneath it's stock location. No way, no how with out cutting the 3/4 tube Back to SAI mod with bracket, 1 inch rack extenders and heim tie rod ends at the bottom of the steering arm with 95 spindles. I dialed in more caster to raise the steering arm but had little effect. I could go 96 spindles with the straight arm but I don't want to go out the 8mm more than I am. The most dramatic effect on bump steer has been putting the tie rod end on top of the steering arm wich almost eliminated bump steer but real spooky handling when unweighting either side of the front suspension as you can see in this profile. Downright scary but making headway.

http://www.ffcars.com/photopost/data/500/Top_Spindle.jpg

Think I'll give Gordon Levy a call to discuss my set up. I think his kit may just do the trick but need to see what effect the SAI mod and pin drive CAs might have. This is his kit:

http://www.ffcars.com/photopost/data/500/levy_bmp_steer.jpg

Todd Buttrick

09-11-2014, 06:09 PM

Well after much experimenting with bump steer, it was pretty obvious that changing the relationship between the tie rod end and the steering arm has the most effect on bump steer. Changing caster would have to change pretty drastically to have any significant impact and even then, you still need to keep within reasonable geometry of all the moving parts. With my existing setup, the 95 spindle put it's off-set steering arm smack in the middle of where my tie rod end needed to be for minimum bump steer. Putting the tie rod end on the top or bottom of the steering arm was having opposite and extreme results. I purchased a set of 96 spindles whose steering arms are straight and EUREKA! Best bump steer this car has ever seen.

I knew by eyeballing the inner UCA and LCA pivots that the inner tie rod pivot was right in plane with the upper and lower CA pivots with 1" extenders installed. (I have SAI mod with the inside bracket piece that lowers and shortens that pivot point) This is key to the start of good suspension geometry so the inside plane I have now was solid. Changing out the spindle from 95 to 96 is time consuming but is it's quality time spent with my love and the garage frig is always full of brew and Pink Floyd is blasting on the stereo. Life is good.

My new 96 spindles were without hub so I had to R&R from existing 95 hubs. That is one TOUGH nut. Impact wrench took it off with little struggle. I had Mike Forte's bump steer kit already installed but decided to get a new set and more of an excuse to go visit Mike while I was doing biz in Boston. Man, he has no idea how many cool parts I stuffed in my car while he wasn't looking! :cool: That place is a candy store for the gear head. Anyway, just a note on Mike's bump steer kit.. it's unique in that the tie rod end of the sleeve is right hand thread and the heim joint steering arm end is left hand thread. If you muck around with your front suspension enough, you'll know that this is absolute heaven when you have to adjust toe. You can simply twist up Mike's sleeve to adjust toe rather than twisting the tie rod itself.(I have a new rack and the tie rods are a bear to move even with vise-grips) I set the rod end on top with a 1/2” spacer.

http://www.ffcars.com/photopost/data/500/medium/2014-09-10_20_18_20.jpg

First, I set ride height and zeroed the center hub for the same. I put a laser parallel to the rotor and pointed it forward to the front wall and marked a spot on the wall so I could get the new spindle back to straight forward toe when I needed to get back to that point in the future for reference. I used the same laser attached and perpendicular to the rotor to measure bump steer. I took my magnetic caster/camber gauge and slapped it on the rotor with the laser pointer mounted on top with some clay and locked the rotor with two clamps on either side of the caliper.

http://www.ffcars.com/photopost/data/500/medium/2014-09-10_20_20_59.jpg

I pointed the laser at the wall graph which is 4 feet away with a leveled graph. (lift is leveled as well) Checked ride height and zero spindle height with no spring tension and checked toe (moved the mark on the front wall 5/16 outward to make up the difference in spindle width from 95 to 96). I pointed the laser to the graph and marked zero and then moved the suspension through it's travel +1” and -1”. The video shows the suspension travel falling from +1 to -1 inch. Remember, this is four feet away so the movement is amplified.

http://youtu.be/enUUDp1vtj8

My Setup

MK1
Pin Drive Width Lower CA
SAI Mod
Unisteer 3.7 Manual Rack
1" Rack Extenders
96 Mustang Spindles
95 Mustang Calipers
Fortes Bump Steer kit
15" Vintage Wheels knock off Halibrands 3.5" BS
Poly offset rack bushings

rlampman

09-11-2014, 07:34 PM

Looking good Todd. You had a chance to drive it yet? How did the extra 8mm work out with your tires?
Rod

Todd Buttrick

09-11-2014, 07:53 PM

Rod,

I still have to mirror this to the other side so another evening in the garage tomorrow. Like anything, it should take half the time now that I know what the hell I'm doing. Neither upper or lower CA was changed so all should be same with caster/camber, just have to check toe due to the extra 8mm width but I'll check caster/camber for sh!ts and giggles and report back. I was more concerned about the extra 8mm width than anything else. I cannot see any difference whatsoever in the stance as it relates to the fender and trust me, I'm anal when comes to that stuff. Not an issue at all.

Todd Buttrick

09-16-2014, 06:26 AM

I got this mod completed and over 300 miles this past weekend. Amazing difference and dramatic reduction in bump steer. I haven't checked the opposite passenger side bump steer to see if it's the same as I simply used the same spacers and setup as the drivers side. This is a better perspective of what my current front geometry looks like.

http://www.ffcars.com/photopost/data/500/SAI_Pindrive_Final.png

skullandbones

09-16-2014, 10:25 AM

Hi Todd,

Your geometry really got better, didn't it. It looks like your static roll center is significantly lowered. That's what happened with mine even though we did different things. I'm surprised you ended up with the tie rod ends on top but it works according to your video. Are you still going to adjust your rack with the Breeze offset bushings? I haven't done that yet but did do the real measurements on my pickup points by using a friend's 4 post lift. It was so much easier than crawling under the car and trying to "guestimate" the correct points. From looking at the measurements on a full scale cardboard mockup, it looks similar to yours in that the SAI is good and the UCA is angled down. My rack is too high I think but the offset bushing should allow enough adjustment. I took a long curvy trip this last weekend and the car handled like a dream even at speed. I didn't feel any bump steer during that time but I also didn't hit any pot holes. There were some dips though and cattle gratings.

Did you lower your ride height to cause the LCA to change from the original position? I didn't catch anything that you would have done to cause that to go to a parallel position with the ground. Anyway it looks good. Your hard work paid off! WEK.

Todd Buttrick

09-16-2014, 05:37 PM

Hey WEK.

The first drawing I'd done was not really accurate with respect to geometry. It was really only intended to show differences in SAI vs no-SAI and the angle of the CAs where a bit of a guess. I did however lower the ride height from 4.5" to 4" which makes the lower CA more parallel. The second pic is more accurate and still a guess as you can't see from dead on with the body on. When you think about it, changing from standard to pin drive width steepens all the CA angles if all else doesn't change like the segments below. I went from standard to pin drive and added SAI which shortens the upper CA even more. That could be good or it could be bad unless you account for the changes. In this case it lowers the instant center nicely and as you mentioned ealier, it looks more like any racecar suspension you see.

The MK1 had built in bump steer issues out of the chute so my car has NEVER felt this good. Like you say, handles like a dream and even at speed. Can't even begin to tell you how delighted I am and learned much from this.

http://www.ffcars.com/photopost/data/500/medium/Sai_vs_standard.png

CraigS

09-17-2014, 06:38 AM

Todd, I am glad to see you got the bump steer worked out. My tierod is also on the top of the steering arm. Mine is a MkII w/ a partial SAI mod and the Ackerman mod. When I moved the rack back for the Ackerman, I had to use the offset bushings to raise the rack. It is close to the square tubes of the "X" frame so even with raising it I had to notch the tube a little. I think this is why I had to put my tierods on top of the steering arm. I got similar bump steer results to yours. This is also why I always recommend doing the actual measurement w/ the laser. Looking at the UCA and LCA and steering arm in front view just doesn't work. Thanks to Dave Borden where I first saw the technique w/ the laser 90 degrees to the rotor.

Todd Buttrick

09-17-2014, 03:28 PM

Craig,

The laser technique is sweet. I have a bump steer gauge but would have to remove my pin drive adapter and caliper to get it rigged up. Like this technique much more. Thanks for the info!

LukasM

10-16-2019, 08:31 PM

Hi Todd!

Not sure if you remember me, I came to visit you in MA about 15 years ago with my girlfriend, uncle and cousin and got a ride in your sweet blue Mark 1. I ended up buying a kit at some point and importing it to Austria, where it sadly sat unfinished for a long time because I lived abroad and then traveled around the world for a few years....

Said cousin has now bought himself a Mark IV kit, and and we have a great garage setup in our home town Vienna with all the tools, so I'm finally going to get back at finishing mine as well!

Since you are one of the very few people with a Mark I, and pin drive 15" wheels like me, are you still running the same setup with SAI mod and SN99 spindles as you did 5 years ago? I have SN95s with the dog leg but could switch them out if the wider SN99 still work without sticking outside the body.

Thanks for your input!
Lukas