mzgp5x

Nice ride! What tires and brakes??? I had 5/16" rear wheel spacers on my 17x11 wheels (now deleted). Difficult to see how everyone has their set-up unless I roll under the ride. (97ss 383 D1 M6) B.

Chewbacca

I guess this is directed to me?

Kumho V710s for financial reasons only (the Hoosier A6 appears to be the faster tire).

LS1 front brakes - original LT1 rears

FWIW I wound up needing a 1/2 spacer all the way around. I don't think my cheapie Chinese wheels meet the advertised offset though.

MTL_Z28

Injuneer, I noticed in the picture you posted, the rear jounce bumpers have been modified to accomodate the larger wheels, but the car also has the Air Lift 'drag bags' in the coil springs (looks like the eibach drag launch kit)... Wouldn't the air bags help to prevent the car from bottoming out, thus making the bump stops useless? I spoke to a tech at Air Lift tand he said with the drag bags installed and inflated there is no need for the rear bump stops?? Interested to know what you guys think about this info...

Injuneer

I no longer have the air bags -they were just temporary..... replaced with a Spohn drag-style sway bar.

Injuneer

The reason is explained in the writeup on the Wheels & Tires FAQ post. These cars are simply not all the same. What fits on one car will not necessarily fit on another. Don't know it its build tolerances or what. And some people don't want the rear wheels sticking out that far.

Chewbacca

You see, the thing about that is the build tolerances only factor in to what combination of spacer size and wheel offset you'll need. You simply don't have to grind on the bumpstops or hammer the inner fenders if you get the offset and/or spacer thickness right.

There are literally dozens (maybe hundreds, I don't know) of guys racing on these wheels in a class where you can't legally touch the inner fender or grind the bumpstop to fit a larger wheel. I'm not saying that nobody has ever taken the shortcut and done it, but it would sure stick out like a sore thumb in impound.

Injuneer

Its very simple to understand that using a spacer will move the problem away from the inner fender liners, and away from the bump stop bracket. But the wheel/tire moves outside the fender by the width of the spacer. You are also now using a spacer on studs that are subjected to complex combined stresses. For those of us who are not subjected to a racing class rule that prohibits hammering the fenders or grinding the jounce bumper bracket, it becomes a matter of personal preference. Mine is to do the hammering and grinding (or hacking as you choose to call it) and keep the tires under the fenders. I also refuse to use a spacer on the rear wheels for drag racing..... strictly personal preference, tempered by the ability to analyze the stress issues.

You prefer to roll the fender lip. Even with no spacer, I had to roll the fender lip, or the body would torque far enough to the side an very hard shifts (,6600RPM with a Street Twin and Drag Radials) to put the lip into the sidewall of the 315/35 BFG Drag Radial.

Conversely, I used 15x10" 7.5" BS Pro-Stars with 28x11.5-15 QTP's, and had to do no other modifications to the rear wheels wells. Yet another member here, with the exact same configuration had to physically remove the inner fender liner above and including the jounce bumper to avoid rubbing. The variation in "build" is significant.

It comes down to how you use the car, and what "rules" you are limited to. Autocross and drag racing may require two different approaches. You call it hacking up, I call it making a personal choice.

Chewbacca

Stresses to the studs induced by a wheel spacer are less for drag racing than it is for cornering on a given car. How much less? I can't say. Think about the forces involved and how they're applied though. If you have data that says this is incorrect, I'd be interested in seeing it.

The factory wheels are not hubcentric. The studs are already taking the full brunt even on factory wheels.

ARP studs are stronger than stock. If a 3500 lb car cornering at significantly over 1 g doesn't have a problem with studs and spacers, I can't see a streetable drag car ever having a problem. Hell, I used to work with a guy (NHRA divisional event x-Stock class winner) who would pull wheels up launches on spacers as thick as mine. Never had a problem. No numbers or analysis to back it up, only experience. Once again if you have the data, I'd like to see it.

A 28 inch tall tire is a helluva lot taller than my 315 R compound. Apples to oranges.

I'm on my bumpstops all the time. I'll get on them from a hard launch just as you would (just won't stay on them as long ). No rubbing.

I don't know what else to say other than has anybody actually tried to get the backspacing right through spacers once your wheel offset has been selected?

This is the crux of my argument with the "break out the hammer and grinder" mentality around here. Someone who doesn't know better would think this is the only way to fit a 315 tire. That's simply not the case and I wanted to document this fact for future searches.

Why do I care? Let's say some kid buys a car, likes the look of 315s and is into drag racing. He busts out the hammer and grinder to make them fit. Now let's say a few years later he wants to try his hand at autocrossing. Guess what? He's screwed if wants to get serious about his new hobby. Those modified fenders and bumpstops just put him into a very ugly class.

I was that guy (not with 315s though) a long, long time ago. I didn't know any better and followed the prevailing wisdom for modding my car. I wasted a lot of money and a lot of time because I didn't think for myself. That's all I'm trying to say.

GreenDemon

When I bought my 17x11 ZR1s and 315 sumitomos and put them on my '95, the first time I set it on the ground, you could hear the wheel scrape the bumpstop once it set down. The first time I loaded up the back, I almost destroyed the two rear tires from the fender lip scraping the shoulder of the tire (top of the sidewall). Like it was said before, some people may not have problems based on the car or the offset or whatever. But in my case (and as is the case with many other people) there simply wasn't anywhere else for the wheel to go. If the wheel went further inside the fender to avoid rubbing the bumpstops would have eaten the tires alive. And the same is true of the fender.

I haven't had to roll the fender lips on my 98 yet, but that's mostly because I don't have people in the back anymore, because I don't want to roll the lips unless it's professionally done.