Lighter, race oriented Suspension Parts, Primarily Uprights

[Scargo]

I am working on the cantilevered coil overs in my head and on the internet. No kit yet to measure from...
A chunk of weight would be shed with losing the strut mount and FFR extension bracket. Some weight would be gained with linkage, but I believe the bell crank ratio can allow for smaller stroke, lighter coil overs which can be mounted low and horizontal.
Im still hopeful that I can find a reasonably priced, ventilated racing spindle to adapt. I reserve the option of designing and casting some. Who has that RP printer?

[Xusia]

I am working on the cantilevered coil overs in my head and on the internet. No kit yet to measure from...
A chunk of weight would be shed with losing the strut mount and FFR extension bracket. Some weight would be gained with linkage, but I believe the bell crank ratio can allow for smaller stroke, lighter coil overs which can be mounted low and horizontal.
Im still hopeful that I can find a reasonably priced, ventilated racing spindle to adapt. I reserve the option of designing and casting some. Who has that RP printer?

The strut mount and extension bracket are used to connect the knuckle/hub to the upper control arm - they have nothing to do with the shock. So if you eliminate them, how would you attach the knuckle to the upper control arm?

[D K]

I don't understand why this saves unsprung weight.
The weight of the cantilever arm is heavier the a standard control arm.
Please explain?
Bob

Because you are moving the shock from unsprung mass to sprung mass.
Or, more accurately, a percentage thereof.

D

[Scargo]

The strut mount and extension bracket are used to connect the knuckle/hub to the upper control arm - they have nothing to do with the shock. So if you eliminate them, how would you attach the knuckle to the upper control arm?

As I said, I hope to find a spindle to use where I would only have to lower the upper arm mounting points. If I were to cheap out, I think a stock upright could be modified to accept a ball joint. I had a '64 Chevy Nova SS that had modified spindles for accepting disc brakes. Of course, if I went this route, it would get magnafluxed and stress relieved.

[Scargo]

An RX-8 spindle looks like it might be a candidate for my car's front suspension redesign. I am also looking into blade type anti-sway bars. Another.

[RM1SepEx]

You would need to move the rack, the steering arms are waaaay higher, the Subaru units have the steering arm much closer to the lower ball joint. Time to do some bump steer calculations

https://www.google.com/search?q=rx8+...2F%3B640%3B480

[Scargo]

Thanks. I see that. Well, it was my first reasonable looking candidate. Somehow I did not do my search well enough and I never saw that view of the part. Move the steering arm? Anyway I have hope.

[RM1SepEx]

Google makes almost everything easy re basic searches

You may be able to relocate the rack... I don't have the back flexibility to check and you would need some part dimensions to verify.

Nothing is going to just meet all of your req w/o mods... you are looking at redoing the entire front suspension after all!

[Xusia]

Hey Scargo,

This thread has meandered a bit - remind me again, what problem you are trying to solve with the uprights?

[RM1SepEx]

The existing front suspension is a heavy iron and steel kludge because it re-uses the stock FWD components with provisions for axles.

If I was going to go to cantilever/inboard shocks like on the hot rod you can open up the upper ball joint position, it wouldn't have to be so high as is common now.

you are talking a HUGE rework, just take the low hanging fruit, brakes, wheel tires, perhaps hollow aluminum stub axles and work on other "stuff"

BUT everyone evaluates their goals and spends their own time and money... welcome to the world of hand built cars! :-)

[Xusia]

That's the "what," not the "why." I could make the assumption the goal would be something like better handling, but this car already handles so much better, and is able to brake so much deeper, than the vast majority of cars, I find it hard to believe that would be the goal in this case. Also, Scargo hasn't driven one, so he doesn't even yet know if this is an area that needs improvement.

So, since it doesn't make sense to me, I thought I would ask and get the answer straight from the horse's mouth.

[RM1SepEx]

Only the builder can answer why...

[D Clary]

Every one want to go fast and get lighter. I am interested in anything that can accomplish that safely and within certain budget restraints. That been said I have dealt with cantilever suspension before and it is not lighter. It has less unsprung weight but the trade off for weight and the monkey motion I don't believe is worth it. The uprights are heave and if you could get more purpose ones made that would be attractive.

[DodgyTim]

I understand lighter is better, but given the lap times the factory R is putting out, I'm not convinced the geometry is too bad

If it were me, and I had the time but not the money, I'd

1 Build the standard kit, with other good lightweight components such as alloy LCA's and light wheels, tires etc
2 Drive it and see how it goes
3 If you are unhappy with it, remove each upright assembly (the subaru bit + the FFR mod), make a jig to suit the upright, then custom fabricate a new super lightweight upright to suit the standard geometry

Replacing the upright without modifying everything else (except maybe the shock) would give the most bang for the effort

[Scargo]

I found this thread about various spindles people were using or considering using for their Locosts. This is a thread from 2007 through last year.
What is stopping me is I don't have a GD front upright/spindle assembly. I need the weight and the geometry before I can start a selection process. Anyone have the weight and can measure the geometry? Look at the linked thread for how they measured theirs.
For instance, a 1999-2005 Pontiac Grand AM has an aluminum upright but it's a McPherson strut design. That might work out quite nicely and require little if any work. It is upgradable to a GM (Corvette, etc.),BBK and is a standard 5 X 114.3 (4.5"), lug pattern.

Yes, there is additional hardware and weight for linked, lever style, inboard shocks and there is work and expense involved. I will certainly get all the "low-hanging fruit" first. The other is the chocolate.
Without rehashing why what I'm proposing is viable and trying to justify it, let me just say that this is a "bucket list" project for me. I'm 67. I don't see myself ever doing a kit race car again. I don't even know if I can drive the thing without looking foolish. I've done OK in my 7:1 p/w STI (and was planning 6.5:1), but I chose to race it just because it was AWD. Now, I'm going back to RWD that will be around 5:1 p/w ratio. I won't know if I still have what it takes till I get it on the track. I'm hoping I'll build something that is unique, competitive and desirable. I don't have unlimited funds for the project but I think that, if I'm careful with my money, I can build almost anything I want. I am still able to do any of the work myself and am really only limited by the lack of a machine shop and a few metal fabbing tools.

PS: I think I misspoke when I used the term "cantilevered". They are certainly levered and linked. I am unsure of the technically correct description.

[metalmaker12]

As far as I can notice at 1/4 tilt 30-40 tighter turns 60-70 straights the car turns in very solid with no roll at slightly lower than required S ride height. I have no front sway bar yet either. It seems to have a very balanced feel and power is everywhere so you have to be careful with the throttle. When the weather breaks I am going take it out to a big open lot and hammer it to shake out the bugs. At this point I see no reason to even think about changing anything. FFR tested this car and it is doing very well with the way it set up. Making it any lighter may also not help, since some weight is good at higher speeds and at some point stability is very important. I am very happy with its power to weight of about 5-6 lbs per hp and see no real need for any more than that. About est 300-315whp, dyno in the next month or so. Keep an eye on my thread. I also only rate power to weight on whp.

Also, what power you running in the Sti, it's about a 3,200-3,300 car so 5 lbs per hp you would need like 650 whp-700 crank

[Bill Waters]

A few of us discussed earlier in this thread that, given that for most of us, anything other than the OEM spindle assembly is going to be impractical or unavailable, that there are a few ways to lighten the entire final assembly and that this may therefore be the best approach for the majority. The Wilwood two-piece rotors & hats and calipers are one thought.

I just received Chassis # 114 on Friday and have almost completed disassembling my 2006 WRX donor, so I haven't been able to finish evaluating all the pieces, but I wonder if we can't also strip a chunk of weight from the front spindle assembly by removing much of the front outer CV housing which serves as the actual spindle unifying the spindle housing, bearing, and rotor. I haven't gotten them apart to weigh them, but it seems to me we could cut a pound or so per wheel here. Does any body know?

Bill

[Mechie3]

I don't know the actual weight, but a lot of us have cut off the CV housing right where the ABS ring mounts.

[longislandwrx]

You can also remove the dust shields, bolts, and mounting tabs which will save some weight.

[Bill Waters]

I wouldn't be surprised if all these measures cut 2-4 lbs. from each wheel. Not bad.

Bill

[Scargo]

...I also only rate power to weight on whp.

Also, what power you running in the Sti, it's about a 3,200-3,300 car so 5 lbs per hp you would need like 650 whp-700 crank

I'm running at 400/400 in the STI. I said I was planning for 6.5:1 in the STI. It's right at 3K lbs. so 3,150 with me in it. My build was going to make 475 easy. That's where I came up with that number.
Now, with the motor destined for the 818 I will dial it back. I am going to run a dry sump. I am planning on running an undermount turbo if it will work. I misspoke when I said 5:1. I meant 5.5:1 if I shoot for the ST1 class with NASA.

[Oppenheimer]

Just like HP is not as important as power/weight ratio, its not unsprung mass, but rather sprung/unsprung weight ratio that is going to have the impact to feel and confidence (we buy and build and track these things for the fun of it, and fun is not soley dependent on lap times).

The 818 greatly reduces the sprung weight, but the unsprung weight stays the same. So the sprung/unsprung ratio suffers compared to donor. So this unsprung lightening effort seems like a worthy cause.

The thought that seems the most intriguing to me is the idea to look at suspension components from other Subies. Maybe older, lighter vehicles that hopefully share the same basic geometry as the intended donors. Seems like we need some Subie experts that can help out here.

[Xusia]

The sprung/unsprung ratio is something I hadn't considered, but since these cars use completely different suspension designs, does it really apply? For all intents and purposes, that's like comparing the sprung/unsprung weight ratios of a Evo and a Boxster. A comparison can be made, but is it of any use?

[Scargo]

RE, Using other Subaru front suspension components:
I have thought along similar lines and don't know the answer. I have been focused on GR bodied STIs and little else. Way back, I kinda wanted an SVX until I read the revues and thought it would end up being a white elephant.
The BRZ is Subaru's first RWD car that I can find. It and the Scion share the same McPherson strut design. Perhaps it might be lighter, but it's still a compromise I'd prefer not to use (of turning a McPherson strut suspension into an unequal arm suspension).

[jimgood]

I don't understand why this saves unsprung weight.
The weight of the cantilever arm is heavier the a standard control arm.
Please explain?
Bob

Cantilever is the term FFR use and they use this design on the '33 Hot Rod. Moves the spring and shock inboard. When they are mounted outboard (most situations), some percentage of their weight is sprung (attached to the frame) and some percentage is unsprung (attached to the lower control arm). So only a percentage of their weight is considered unsprung.

Should be pretty obvious by looking at the pic of the front suspension below.

[jimgood]

PS: I think I misspoke when I used the term "cantilevered". They are certainly levered and linked. I am unsure of the technically correct description.

Cantilever is the term FFR use and they use this design on the '33 Hot Rod.

I don't understand why this saves unsprung weight.
The weight of the cantilever arm is heavier the a standard control arm.
Please explain?
Bob

Moves the spring and shock inboard. When they are mounted outboard (most situations), some percentage of their weight is sprung (attached to the frame) and some percentage is unsprung (attached to the lower control arm). So only a percentage of their weight is considered unsprung.

Should be pretty obvious by looking at the pic of the front suspension below.

[Xusia]

Wow. It would be really nice if that front end was an option on the 818.

[Scargo]

Attachment 26052I'm back at it again. Do aluminum spindles have a place in road racing? I think of how the brake heat might affect them. I know there are some being used out there; usually they are special designs, often large, thin, open castings.
2677.jpgrds-1000c1.jpg
For a Subaru:
67-2011-11-04-upright-1.jpg However, I am trying to get away from a "compromise front suspension", even though these would pair well with the 818 parts.
Just read that the MSI parts do not save weight.

With the spindles below there is the issue of the LCA ball joint. Can you adapt a ball joint to the LCA? It would need to flip 180 degrees. Do I scrap the Subaru LCA for something better and change the mounting points? Most of these come with no drop or 1-2" of drop.

For '64-'72 Chevelle, Cutlass, El Camino, GTO. Uses sealed ZR1 Corvette hub assembly. Any brake kits for late model Corvettes will fit. Sturdy aluminum!
prd_136.jpg
Pinto style:
spindle_830-9807-sm.jpgThese light and strong spindles might be better sized for an 818. I'm guessing BBK's are not a problem.

Some parts I'm considering. Talk amongst yourselves... Talk to me...

[Scargo]

In the same context as above, is using adjustable control arms, top and bottom a good idea? We have the FFR supplied UCA which seems to get clamped (with the three bolts) into a stationary position. I found multiple "adjustable" LCAs for various cars that seem like they might fit the bill except I worry about how rigid and race-proof they might be. Here is an example:
FR-S_front_lower_control_arms_02.jpg
I perceive a lot of moving/movable parts and possible flexibility.

These, for an E30, are what I may try to copy if I fab my own, but with Hyme joints.
product-1.jpg

BTW, the stock STi LCAs from my '08 STi weigh 7 pounds each, which includes the ball joint. I can't find a way to adapt them to a spindle that accepts the tapered shaft of a ball joint.
Anyone care to comment? Please!

[Santiago]

I have an Agent 47 SLA system on my Mustang that uses lower control arms that look like the first one you posted. There's no slop in them at all, since once mounted the pivot points are stationary. They can be plenty race-proof, but you need to attend to some basics (that should've been done on the A47 kit...grrrr!) or maybe just be aware of a couple of needs this style has.

1. The main arm's bracket takes on the full brunt of braking forces (as transmitted to it via the strut). So the bolt used here should be an AN bolt (shouldered according to proper thickness requirements). DO NOT use a regular threaded bolt, and really no suspension bolt should be fully threaded ever regardless of what grade it is (which has no bearing on the threads' tendency to chew into surrounding steel) - take a look at every OEM bolt in newer cars, they all have the proper shoulder length for their application. The kit I received didn't have the proper bolt, and I didn't know any better back then. Sure enough, the vibrations eventually wallowed out the hole. In the process it weakened the surrounding steel, which led to the bolt doing tiny shifts in its (now) oblong hole. Under heavy braking, that was fun! So to prevent that, make sure you precisely drill that hold and get an AN bolt that fits w/such small clearance you almost have to tap into position.

2. That same hole/bracket takes a beating with a heavy car like the Mustang. I don't think the 818 is going to be as punishing, so I think the sort of 1/8" thick stock used on the A47 arm would be adequate. If I build my own for the Mustang I'll likely opt for a heavier stock on this particular bracket. The previous set of arms also didn't have wide spacers to spread out the clamping force on it and the hole also puckered a bit as the surrounding steel buckled (another reason to go thicker). I think the idea many builders have in making these arms is to make them as light as absolutely possible, but they end up skirting safety limits in the process.

3. Some of my experience is likely due to shoddy communication between customers and A47, as they repeatedly gave me the wrong torque specs and such. I finally just went ahead and used broader engineering guidelines, switched to AN bolts, broader hardened washers, and gave the bolts more torque to keep movement to a minimum. I haven't had any trouble with the arms since, they articulate phenomenally well, and the range of adjustment they permit for whatever alignment specs you desire is pretty sweet.

Best,
-j

[Scargo]

Thanks, J.
I'm liking these for a BRZ from Racer X Fabrication. $609. Includes ball joints.
5_FrontLowerControl.jpg

[Scargo]

Just look at this cool suspension hardware that's on a Lambo.
2012_Aventador_1600_Sus_Fr_OA_tireon-thumb-717x478-100748.jpg
More at http://www.edmunds.com/car-reviews/track-tests/2012-lamborghini-aventador-suspension-walkaround.html