I'm at a sticking point right now. I currently have aftermarket box-tube rear LCAs with poly. I've been trying to determine what I'm going to use to replace them.

The sticking point is that as of right now, I'd like to have the option of running the car in DSP in both SCCA Solo and *possibly* Time Trials. All the other mods I have are DSP legal, but the LCAs are not.

The quick version of the rule: Rear LCAs must be STOCK, but I can change/replace bushing *material* only. (see the below for clarification)

My understanding an experience tells me that full poly bushings will bind the rear axle with my suspension compliance. I'm also not fond of rubber. My questions are- Would rubber on one end and poly on the other allow for enough twist (with the stock steel arms) for good linear suspension travel under roll? What about Poly/1LE? Would 1LE/1LE be better? Can you still get 1LE bushings? Would the stock arm stamping allow enough flex in itself (and is this healthy?)?

I basically see 3 possibilities-

1. Use the stock arms with some combination of bushings and be 100% compliant with the rules.

2. Say "screw it" and buy the double-rod-ended arms I want, run DSP, and hope no one cares enough to protest.

3. Use stock (actually probably G-body for the "reinforcement") arms, poly the body end, and sneak a spherical inside a poly spacer on the axle end.

#3 is the worst in my mind, since I'm obviously trying to circumvent the rules without being noticed (since I don't think anyone would pick up on it). At least with #2, I can say defend on the basis of not trying to hide it, and DQ'ing myself if the issue comes up (not a great way to go either). I'd rather not bump up a class all over one non-compliant part...

Clarification- the rules are written to specifically disallow any interpretation that might allow a spherical, from the "same percentage of metal" to the 'even if the factory allowed twisting via bushing compliance, you can't change bushing style from cylindrical to spherical'.

So if I were to go with choice #1 (stock arms with bushing change/replacement only), is there a combination that would be firm, yet allow enough articulation to avoid bind under roll?

 

https://www.thirdgen.org/forums/afte...poly-ball.html

Get those. Sleeve or mill the bushing parts to fit stock arms.

Cut the top section off another set of stock arms the width of (width against o.d. of flat sides - 2xwall thickness) Tuck it up inside a slight bit lower than the main arm material; weld it in and smooth it, paint it black.

G-body swaybar spacers add rigidity? I guess a little.

 

The rules clearly say "the rules are written to specifically disallow any interpretation that might allow a spherical". So the mono-***** won't work as they are spherical. I would probably run rubber/poly, as much as I hate poly.

 

FYI: Some F-bodies were equipped with reinforced LCA's as noted below.

https://www.thirdgen.org/forums/susp...ml#post4997928

JamesC

 

If your wanting to be sneaky, stuff your rodended control arms inside your "stock" arms. Section the center of the stock bushings so it "looks" like you have rubber there, then box in the bottom.
I have heard of that being done b4 ....

 

Ah, so the reinforced arm would be truly compliant with the rules. This is the same as the G-body unit then, from what I am reading... (since I assume they're easier to find...)

That still leaves the question of the bushings.

jmd- as 87350IROC pointed out from my earlier post, I can not legally change to anything spherical.

87350IROC, thanks for the opinion, and that's the direction I'm leaning. I'm not fond of poly in some situations, but there are others where it's acceptable. I'm less of a fan of rubber in something that's supposed to be axially rigid...

Has anyone ever done this combo? I'm figuring no, since aftermarket units are so damn cheap...

TTop350- I have a set of stock LCAs and poly bushings sitting here, and was just about to take measurements of the poly bushings to do just that. I'd only probably do it on one end, so that you couldn't grab the LCA and twist it on its axis... I have decided that I will make a set of them, even if I don't actually run them, just to see if it will work.

 

Do you mean ESP? Thirdgens can't run DSP.

If you can't go spherical, I'd just get some new bushings in stock arms and call it good. The stock LCAs really should only see axial loading and for that purpose in Autox, they are way more than adequate.

The "reinforced" arm is not really a reinforcement, that piece of metal is in there so that when you bolt your swaybar to the LCA in your Gbody, you don't crush the arm. I suppose it could act as one but again, these things see mostly axial loads. I don't think you are going to find much by messing with them a whole lot.

 

Yeah ESP. My other car used to run DSP.

Would you recommend any bushing combo, or just rubber replacements?

It's more the Time Trials and Hillclimbs that I'm concerned about. We use the SP and SM classes (along with all the Club Racing classes), so that's really my target. I'm not fond of autocrossing really.

 

for an all out effort I'd be tempted to cheat and cut the poly or rubber sides off some normal bushings and put them around some monoballs.

That said, real world I'd reenforce the stock arms and install poly bushings and keep them lubed, they will not bind as long as they're lubed. Me being me, I'd find the stiffest poly I can find, drill them for zirks, cut flutes (which will make them a little softer) and religiously grease them (or if you can find bushings already fluted that would work too). I'd bet that done right you'd have a hard time telling them from rod ended arms except that they would be quieter (and if they start squeaking you need to lube them again).