It is not that which concerns me but the position of the hole, which is shifted in order to change the geometry, so that one gets toe-in instead of toe-out, under compression. Isn't the hole's position on the "bump steer" bushing different? It might be parallel to the original axis but isn't it shifted in a certain direction?

 

Offset bushings are allowed in SP, where I believe the metal content bushing rule is the same as ST. You can run a delrin bushing with a metal sleeve to gain the same benefits as full metal. The STU BMWs run offset delrin bushings.

Cats - In STS you have to run a stock cat, some of the honda guys won't even run common OEM replacements for fear of protest. I don't know about STS2. In STX, the WRX gets an advantage since they can replace mutiple cats with just 1 hi-flow.

Manny - DPs are not legal for stock.


Rick

 

Read up guys. 14.8K specifically allows the change in pivot point from the allowed offset bushing. In this case it is usually shifted down to reduce bumpsteer. How much I don't know and in what direction I am not sure either.

Another point to be made. The rules about bushings talk about metallic content relative to the entire bushing volume. OEM bushings have more rubber than most aftermarket poly kits (Works, Energy) so the amount of metallic content (percent volume) will drop in comparison to stock when changing to them. Now if it just plain has less or the same amount of volume (not % volume) that would only help someone in trying to abide by the rules.

Edit:
Download the 2007 rules for free....
http://www.scca.com/Solo/Index.asp?I...0&x=050|070&~=

 

It this particular bushing really that important to the STU class? You don't want to lower the car that much anyway. Street tires need softer springs than R-comps and you'll need suspension travel to get your car to stick on most a/x lots.
Any of you long time STU Evo drivers have any input on this?

 

I mention the Whiteline bumpsteer kit as it's usually part of RobiSpec's KWv3 suspension package that he does.

 

It's not a make or break modification but it does help a little.

 

Suspension bushings wont lower the car, they improve feel and control by getting rid of 'slackness' inherent in the suspension with the softer rubber OE bushings and give the car a more 'direct' feel. Rear suspension bushings are said to reduce corner exit understeer by reducing the dynamic toe changes you get when the rear suspension is compressed.

 

I know they won't lower the car. The reason behing the rear bumpsteer kit is to alter the geometry of the rear suspension to prevent said bumpsteer. I was just asking if these particular bushings were necessary because we don't necessairly want to slam the car to the ground. My understanding was that these bushings were really only needed if you lowered the car significantly.

 

Ok, I see. My understanding is that some feel you may still hit the bumpstops even with the relatively mild lowering (~1") you will get from performance springs or coilovers.

 

Splurta...you are correct. It really helped in lower the understeer. I installed the Whiteline bushings in the rear. I installed the 388 for the toe control arm...not the 588 which is the bumpsteer kit. I had issues installing the 588, so I gave it to a friend. The Whiteline bushings give you a better feel of the road...I don't think there was a noticable increase in vibration or anything too.

Dennis

 

You may have your kit numbers switched. I believe 588 is the kit for control arm inner bushings and 388 is for the rear bumpsteer kit.

 

Thanks Dennis, that's great to know. Did you make any other changes when you installed the bushes (besides maybe alignment)? Just wondering in terms of isolating the source of the improvement. Also nice to know noise vibration increases were minor. Thanks!

Dave, sorry if I misunderstood you earlier btw.

 

Evo8RA...I might have got them mixed up...but they are both for the toe control arm. One is off-set (bumpsteer kit) and the other is not. I installed the one that wasn't.

Splurta...When I changed the bushings, my alignment went from a 1/16th toe out (rear) to zero toe and I got more oversteer with zero toe and the bushings. I autocrossed today with KW Variant 3's (just installed them last week) and the Whiteline rear sway bar and it was almost neutral. I'm pretty happy with my set-up now...I haven't decided if I'm going to install the front Whiteline swaybar before the SD National.

Dennis

 

Don't do it Dennis! But that's just .02 worth

 

Wow, I am planning on installing rear suspension bushes (not sure whether it will be Works, Whiteline or Energy) so its great to hear that there is such a noticeable and positive effect. Thanks for the info Dennis.
Jason