4th Gen Rearend

[mtwilly]

Thank you again for the help. I do not have the wheels and tires yet as I wanted to verify I was going to be legal on the width first. Will be running a 28x9 slick initially on a 9 or 10" wheel and possibly switch to a 30x9 down the road. From what I can gather (haven't measured mine, yet) the stock width is 64.72". It seems the general consensus is that rear end width is less important (within reason) than the the fact that the suspension and wheel housings are in their factory place. I really just want the mounting surface of the wheel as close to center as possible. Thanks again for all your input! So much to learn about class racing but enjoying it so far!

[CMcAllister]

Deeper wheel = shorter rear = less unsprung weight. I realize there's not a lot to be gained with a 9 or 10 in. wheel, but every little bit counts. And they don't charge extra for deeper wheels or shorter axles.

[Mike Mans]

Here's my question: The rule says it must be a stock width rear end with all of the details everyone has outlined. I've searched the classification guide high and low and I can't find anywhere that they note just what a stock width rear end should be for every car in competition. Anyone able to point me to that? If it's not documented in the NHRA classification guides at this point - it seems like a pretty unenforceable rule.

[Michael K]

Classification guide won't have this info.


The rule book talks about wheel base. Since there are production line assembly tolerances, there is an allowable variation from factory specifications (I can't recall exactly...3/4 inch?). The rear axle width is not addressed, other than stock mounting points and stock width (between backing plates) must be used. I have factory rear housings that vary up to 5/16 inch for the same model of car.


In the spirit of the rules, it would seem that the factory tolerances should be factored in within reason. When asked, division tech would only say that they would not allow stock mounting points to be moved.

[Rob Petrie E395]

Since no one posted it. On a 4 gen F body. If you have a stock length rear end. Using a 10 inch wide wheel you need 7 1/2 inches of back space.

[mannymen]

The trick is to use an 82-92 F-Body “STOCK WIDTH” rearend. It’s a complete bolt-in for a 93-02 F Body. The 82-92 is approximately 4” shorter than a 93-02 rearend. This is what u r seeing in the pics u posted. Now you can use a 15x10 wheel with a more common 5.5 backspace.