Is it necessary to instal adjustable rear control arms when lowering the car with H&R springs? If so, do all four control arms need to be changed or will two suffice? I do not expect to race the car (MCS).

 

when you lower the car using any springs or coilovers, the rear camber will get more negative to about 2-3 degrees (stock is neg 1 degree). This is probably fine for cornering, but will add to excessive inside of tire wear in normal driving. If you add the adjustable control rods, you can bring out the top or bring in the bottom or both, to get back to 1 degree negative. I put in both so I could also adjust the toe (once the camber is set, you adjust both upper and lower equally to adjust toe)

If you have DSC, the rear roll sensor is attached to the stock upper control arm, driver side. None of the after market rods allow for this. Furthernore, even if you attach the sensor to the adjsutable arm, if the control rods have rod ends, they will be able to rotate slightly about 5-10 degrees in the spherical joint and this will fool the DSC sensor.

I run with DSC off, wish I had never got it.

 

jlm, so what you're saying is that you can use the marketed "lower control arm" to replace both upper and lower?! You said this can be done in order to adjust the rear toe? Awesome!

Question, what is the stock setting for rear toe?

Cheers,
Ryan

 

Does anyone know for sure if there are adjustable rear control arms that are legal for SCCA STX autocrossing?

 

I measured about 1/16" toe in,s tock, rear, and yes all four arms are identical except that the stock lowers are galvanized and the uppers are painted and the one upper has threaded holes for DSC sensor bracket.

I read on the racing forum that you can change to adjustable arms, but not change the joint type without moving to a Street prepared or Street modified class. Stock uses a polymer bushing, most of the after market arms use spherical rod ends, except the arms from H-Sport, which are adjustable and have polymer bushings. They are on their web site, but I don't know if they are out yet. I don't know about using the DSC bracket with them either.

 

Thanks jlm, clearly further investigation is needed on the subject!
[searches for magnifying glass]


Cheers,
Ryan

 

Ryan and th3118,

jlm is correct. The control arms are the same length, but the upper driver side has a yaw sensor for the DSC.

The H-sport units aren't quite available just yet, but I'll have some here next week I believe, so I can share how they work then. They are the only aftermarket control arms that are SCCA legal. So far as I know, they do not include a provision for the DSC sensor, but I'll tell you for sure when they get here. For STX, you couold use either type - heim joints included. For true SCCA work, I wouldn't even recommend changing the rear camber though. They are about 2 degrees negative when you lower the car - perfect. Incidentally, I just measured the front camber and have 1 degree negative wiht the H&R lowering springs.

I can split the Helix kit up - they work the same top and bottom. I know Graham and Eric were interested in that info. You would lose the yaw sensor though.

Hope that helps!

Randy

 

Randy:
I researched this a while back and even got an interpretation from Solo II rules guy at SCCA that ARCA's with heim joints are NOT legal for STX. The h-sport arms as John stated above are legal for STX class because the bushings and attachment method they use is more like stock.

If I was interested in adjusting the rear camber I would get the h-sport control arms and replace just the lower stock control arms. I then avoid the issues with the DSC sensor and cand dial neg camber in or out. Like John, I wish I had never gotten DSC

I just had an alignment done and the rear camber after lowering the car with the LEDA's is -1.5 w/.1 toe-in.

David

 

Jim and Randy,
Thanks for the info. :smile:

 

I might be a bit confused, so bear with me. If I got the Helix set, and used only two of the arms to replace the lower stock arms, could I then adjust my camber, and still keep the DSC? Then I could have someone else use the remaining two Helix arms to do the same with their car?

 

DK23:
yes, but when you adjust the camber back to 1 degree neg by shortening the bottom link, you could possibly affect the toe. Looked at from the top, shortening both rods on one side will decrease toe-in (the wheel hub will pivot from the lower wishbone fixed end forward of the wheel.) if you only adjust the lower rod, both camber and toe will change; the toe change will be slight.

 

I'm changing the lower arms this week to correct the negative camber due to H&Rs. Has anybody noticed increased tire wear due to toe-in changes with this set up? I'm planning on negative 1 degree rear camber.

 

DK23,

I see that you have 18" SSR comps on your car. Can you elaborate on the other things done on it i.e. suspension items. I am considering putting either 17" or 18" and tend to have it lowered too, I am concerned about rubbing some people are getting. What's your perspective. Thanks.

Peter

 

What rear control arms would anyone suggest? Any preferences?

 

Randy said:
"....They are the only aftermarket control arms that are SCCA legal. So far as I know, they do not include a provision for the DSC sensor, but I'll tell you for sure when they get here. For STX, you couold use either type - heim joints included...."


Randy,
While it's true that the H-Sport arms are legal for SCCA (Solo2), you later say that for STX you could use either type. I think you know that it's not legal to replace the stock cylindrical bushings with heim joints for the SCCA STX class [Solo2 Rules 2003: 17.8 B. reads in part "This does not authorize a change in type of bushing (for example ball and socket replacing a cylindrical bushing)...."]. Also, as you say, lowering the car will get the rear camber somewhere in the -2 degree range, so you could forgo changing the control arms completely.

While one could only replace the lower arms, changing their length to adjust camber will also change toe-in. While there is a stock rear toe-in adjustment (there's an eccentric at the front mount of the trailing arm), you need to buy or make a special tool to make the adjustment and it's not clear that the range of adjustment is enough to compensate for the full range of length change of the lower arms. So, if you really want to be able to adjust rear camber and toe-in independently, you probably need adjustable lower and upper arms. Not the cheapest option, but probably the most flexible.

 

Thanks Rocketspeed - you are absolutely correct in the legality of the H-Sport vs. bearing type control arms.

What I was saying is that the range in camber I'm seeing with the H&R springs isn't really all that bad - you are doing pretty well with 2 degrees or so of negative camber in the rear.

I agree that the best way to adjust the rear if you are going to is to replace all four - though the toe still seems to remain slightly toed in with around .5 negative on a lowered car with the lower arms only being replaced (the toe change is very minimal is what I'm trying to say).

Hope that helps clear things up!

Randy