How thick are the spacers that SLP installed on the SS cars?

And because of their location, one would have to raise the rear of the car MORE than the thickness of the spacer to maintain the same travel as before the spacer. Isn't that correct?

Spacers are 15mm thick.

They are under the bump stops. They don't raise the car at all unless you are sitting on the bump stops already.

Their purpose is to prevent 275/40/17 tires from rubbing the inside of the rear fender under extreme conditions.

Many people say that they are unneeded. I didn't hear that until after I had already bought mine.

My car is not lowered, and so far nothing has rubbed with the 17's and the spacers but I don't see any great advantage to the spacer either.

On a lowered car they might reduce suspension travel by 15mm.

Z28

You don't need them unless you are really low. On my Hawk with the SLP suspension, I removed them right after I got the car. I've run both 275 and 315s in the rear with no rubbing on the street or at the track.

I'm planning to use them (or something similar) for a specific reason.

First off the car works great as is. BUT because I want to I am moving from 17x11's and 315's in back to a 17x12 W/335 tire.

In doing so I want to make the car as close as possible to what it is now.

AND after some carefull measurements and a pretty serious flare added to the stock sheet metal, I want to raise the car. To maintain the exact same amount of travel from the axle to the bump stop I will need some sort of spacer.

So I guess my question is how thick a spacer will I need to If I raise the car 1/2 inch, and still maintain the exact same travel from bumpstop to axle......

How much AT THE BUMP STOP does 1/2" at the fender equal?

.....So I guess my question is how thick a spacer will I need to If I raise the car 1/2 inch, and still maintain the exact same travel from bumpstop to axle......

How much AT THE BUMP STOP does 1/2" at the fender equal?......

That is a harder question than what I thought you where asking.

The bump stop is a type of spring. The rubber / foam will compress at a some rate of pounds per inch. This rate may not be linear, due to the taper of the bump stop.

The next problem is the fact that the motion will depend on the load. So now you have two unknowns, can't solve that with the info you have.

You will have to pick a thickness and test the setup, I don't see any easier way.

Z28

The stock bumpstop is fairly close to the wheel. You will get a little more travel at the outer edge of the tire in roll, but assuming the PHR and roll center is roughly on the same level as the axle, the outer edge travel will be roughly (travel at bumpstop)*(distance from outer face of tire to center of pumpkin)/(distance from bumpstop to center of pumpkin).

I'm running slightly softer-than-stock rear springs, the car is lowered 3/4", and I've run 275 street tires, 275 Nittos, and 275/45-16 Hoosiers (short but wide) on wide rims. Other than the hump at the front inner fender that we all have to beat in, I don't get any rubbing with bone stock stand Z28 bumpstops. I do have a "real" PHR, but other than that I'm not sure why SLP ever bothered with the spacer - it isn't needed.

Lonnie, if you have to raise the tail of the car 1/2" to clear the 335s, it doesn't seem like that great an idea. You're going to raise the CG and (ignoring whatever other plans you have) the roll center. Even if you fix the roll center, raising the CG will probably cancel out most of the advantage of the wider tires.

Thanks. Looks like I have some measuring to do.

Sean if I raise the car up 1/2" ('maybe' less) I will still be slightly lower than stock. And my rear control arm angles will be "better". Roll center isn't a big deal. As next year progresses I'll look into the PHR brackets more and more. They ARE in my future.


The more I think about the things my car did, and what I would like to change, I'm about 98% confident the car will be faster. I know I will be faster in it. But am 98% sure it'll be faster regardless who is driving.

The other 2% of question is because of the added width.

Regarding the load transfer aspect of the higher C/G height, I would think that the extra 1-1/4" width on each side would cancel that out...???

I don't see why you would want to take travel out even after raising the rear of the car. Why not just take the extra suspension travel.

As far as raising the rear of the car take this into account. When I first got my GC coilovers in the front I ran the car very low in front (25 3/4" if memory serves me) and in the back I just pulled the isolators; had a 35 solid bar in front and 21 solid in back. The car had tons of grip and turned very well, but the rear was a little snappy and I think it was from the tall CG in the back and the low one in front.

To prevent rubbing.


I think the extra track will offset the added weight transfer from the slightly higher CG.
Of course I'd have to do the math, but still my hunch even without it.

My car won't be all jacked up in the back raising this up.

About 26-1/4" in front (after I lower it another 1/4") and about 26-5/8" in back.

That's not bad, that's pretty close to were I run my car now, except the rear of my car is 1/4-3/8" lower.