New guy here who is interested in a first generation Mustang as a project car and autocross candidate. I'm currently looking at a first generation Mustang to run in one of two SCCA autocross classes. One of the classes (STX) allows a maximum of 265 with tires on a 17x9 wheel (max OD is than 25.4"). The other class (STU) allows a maximum of 285 (max OD is 25.9") tires on 18x10 wheel. Rules dictate that you may not flare the fender, but you may roll the lip if the fender has any to create a flush inner fender space.

I talked with Mike Maier of Maier Racing (www.maierracing.com) and it sounds like the 67-68 has slightly more fender clearance than the 65-66 Mustangs. I can spend the time and money getting the wheel fitment right if the tires have a chance of fitting.

So, my question is this, does anyone have any any experience in terms of fitting tires that big on a first generation Mustang? From a few build threads I've seen, it looks like 285 on the back in both cases won't be an issue, but 265/285 up front could be, at least on the early Mustangs.

Thanks all!

 

I had 225/R15 in the front and they rubbed. I'm certain that a wheel tire size like you are talking about would rub......

 

Actually a 9" wide rim is also a problem.

 

I should have also asked about what sort of backspacing you guys are using as well. Any width will work on with stock suspension with the correct backspacing since the tires should sit below the bottom of the fenders. I've just seen a number of cars with wider front tires, but wasn't sure what sort of clearance inside the fender there is with proper back-spacing.

Example: http://www.understeer.com/mustang.shtml

Clearly you can see there's further room towards the frame rails of this Mustang, but is there an inner fender that was removed from this car that would limit the inner wheel width? 17" rims would have no problem clearing the A-arms, steering rack, etc. I just haven't seen a good picture of the car from the underside to see what limits wheel incursion towards the frame.



Thanks for all your input guys!

 

Any wheel on a classic with original/mostly stock suspension will require a wheel with the backspacing of up to 4.5". Anything over will his the ball joint on the UCA. You can run spacers if the wheels don't have the correct backspacing, but too far and your fenders will eat the tires up when you hit bumps or the tires will mess up the fenders.

I ran 16x7s with something like a 4.9" backspacing and 1" spacers. They hit my fenders pretty good, but weren't sticking out far enough to do damage. A 9" rim would fit, but its all about that correct backspacing. It will be a tight fit, but I know for 67+ will be better than 65-66.