Stockstangs

I installed a set of Steeda sport springs on my 91 GT convertible. I am running 17x9 Cobra R's. The front is 225/45. The rear is 275/45. Every time I hit a bump or have a passenger in the rear the car bottoms out and cuts into the rear sidewall. I spoke with a tire shop today and asked if I dropped to a 245/45 on the rear, if this would remedy my problem. He said both of the tires are the same height and this was normal on a Fox. I don't really know much about tire sizes. Has anyone had this same problem with clearance? If so, how did you remedy the problem? I really don't want to raise the car back up, but I don't think it is safe for the fender to cut into the sidewall every time I hit a bump. Any suggestions would be greatly appreciated. I also have replaced all 6 of the shocks if this info helps. Thanks for your time!

AdderMk2

Front tires are too small, rear tires are too big.

You have a 27" tire and are using the wrong springs for your application.

Run a 275/40/17(rear), and use a 1/2" urethane spacer to make up for the additional weight in the rear.

Stockstangs

The rear are 275 40 I was wrong on the op. I am using a half inch spacer on the rear.The problem isn't with width it is with height. When I hit a bump the fender well cuts into the sidewall of the tire. If I go down to a 245/45 would this solve the issue? I put the small tires on the front because at the time it was all I could afford. The only reason for such large ones on the back is I got a good deal on them. Is there not any size tire I can run without having to switch out the rear springs to remedy this problem? Would going back to a 16' Pony style wheel fix this problem. Thanks for the advice!

Stockstangs

Sorry I just caught the bit on the spacer. I am not a mechanic so this may be a stupid question. Where do I put the spacer at? Is it something I can do myself or do I have to remove the rear spring to install it. Can I buy the spacer at most mustang supply houses? I apologize for all the questions, this is the first Fox I have lowered. All of my other ones I left stock height. Thanks again!

.boB

Both tires are pretty much the same height/diameter.

But, the 245 tire is 245mm wide, and the 275 tires are 275mm wide. Wider tires with a lowered suspension often cause rubbing. You need a narrower tire to fit inside the wheel well.

As for the bottoming out, that tells you the suspension does not have enough range for the roads you are traveling. Once the suspension hits the rubbers, you have infinate wheel rate, and that's a very bad thing. How much did the new springs lower the car? How's your alignment? You'll need to raise the suspenion up a little bit. As he said, use a 1/2" spacer and see what happens.

AdderMk2

Are you using a spacer on the wheels, or the springs?

245/45/17 is the same height as a 275/40/17. Stepping down to a smaller wheel isnt going to affect the diameter of the tire.