Allow Alternate Control Arms in STL?

[Greg Amy]

I've got a request into the STAC to allow alternate control arms in STL. Looking for feedback.

My intent is to allow alternate control arms for the purpose of weight reduction, such as this:



...to replace this:



Honda's arms are made of cast iron and are seriously heavy; using something like this would reduce weight on the car while not functionally changing the geometry.

Other members of the STAC have legitimate concerns that such a rule could be tortured to allow a function other than this. I see how alternate arms could be used to changed camber and caster (already legitimate changes) but as long as you don't change the points to which they attach you cannot change major suspension geometry functionality like roll centers.

Note that alternate arms are already allowed in STO and STU, as is some level of change in pickup point location. I am *opposed* to changing pickup points in STL.

I'd like to hear your feedback and intorturation on this idea. We tabled this item for more discussion at the next concall.

Convince me it's a bad idea.

GA

[CRallo]

I'll write a letter in support of such an allowance, if you can get "world market" engines into ST.

The way I see it: in any ST class all the suspension links should be open. Just don't touch the pickups. That last bus already left in the "higher" classes though :/

[Chip42]

do you advocate stock arm geometry, or adjustable / open? if the after market arms must be identical to the stock piece in temrs of critical dimensions, than this is a no brainer - do it. if locations of bushings or the distance between them were to be opened, this would need more vetting.

FWIW the EJ/K/M rear arms are stamped and pretty light by comparison to the DC2/EG cast ones, but they bend if you look at them wrong.

[Greg Amy]

do you advocate stock arm geometry, or adjustable / open?

I strongly advocate stock pickup points on the chassis and no modifications to attachment points on knuckes/uprights, etc (unless otherwise allowed, e.g., struts). There's already verbiage allowing alternate upper control arms for the purpose of camber adjustment, as is spherical and such.

I suggest it would be virtually impossible to police the distance between the bushings, but in reality that change would be similar to that allowed by upper arms (camber) and track (wheel spacers, though without the scrub radius that spacers cause).

...but they bend if you look at them wrong.

Yeah, I've thought of that...I'd probably bend them on a regular basis, too...

[Chip42]

but in reality that change would be similar to that allowed by upper arms (camber) and track (wheel spacers, though without the scrub radius that spacers cause).

the ability to de-camber the wheel from the lower control arm will shorten the static hub-hub distance on that axle, which means the ability to run wider tires/wheels and different offsets which might otherwise violate the track width / exposed contact patch (if that is enforced in STL, can't remember).

in concert with the upper arm, this would also allow the tailoring of the camber curve to some degree, though typically it wouldn't be very useful.

dunno if it's a problem, just awanted to throw that out there.

[DoubleXL240Z]

I think you opening a door that will release many animals, and getting them back in will be impossible.
The problem I see is that when you say "alternate" you see one of those off-the-shelf stock replacements. When I hear alternate, I think of all the endless possibilities that can be constructed to obtain the geometry I would like, using the stock pickup points of course!
Fabricated, CAD designed, pieces of engineering magic. Oh, did I say it would be inexpensive?
Is it a necessity, or is it a this would be cool to have?
I would like them on my E30, but the standard steel arms cost 86 bucks, the M3 aluminums are 320! I could build some cool stuff for 640 bucks!!!

[Matt93SE]

My opinion is that it would be within philosophy of the class, although since STL seems to be "choked down" compared to STU and STO, then I would say allow alternate control arms but you still have to keep factory pickup points, and no reinforcement around the pickups if that's not allowed yet either.

STL cars should be light enough not to "need" reinforced pickup points. i.e. Miatas have been racing for over a decade with stock pickups and you don't see them blowing upper strut mounts through the hood.

you could also do a "arms may be modified as long as they are recognizable as a stock part".. this defeats the purpose of exchanging cast steel for aluminum, but allows the car to have a decent alignment and camber curves. this is Super Touring after all. not Showroom Stock Touring.

[Chip42]

I think opne material arms are well within the philosophy, but think that there must be limits on the geometry adjustments. the mounts are fixed, that is a given and I think a good place to keep STL. I would allow IT-type slotting and reinforcement for strut towers, and some reinforcement for STL upper arm mounting points. lower are currently allowed 6" radius of reinforcement.

to keep costs down to some degree, maintaining stock arm critical dimensions on at least ONE arm in an SLA setup, and on the lower arm OR shock tower (camber plate) in a strut setup is completely acceptable. audi/VW's quattro 4 ball suspensions as well as the mitsu/chrystler/kia/hyundai 3 ball knockoffs all count upper or lower arm or arm pairs for this purpose. hybrids, like the toyota super strut etc... should be judged as SLA. rear beams, multiblades, 5 link types etc... will need a better rule than I can come up with at 11:30 pm.