Hello I have a question about tire sizes for 1999 mustang GT 17x8 wheels. I know this has been covered many different times on here and the club. I have read so many different opinions now that I cannot figure out what size to order. I just picked up a set of 99 gt wheels and now need to order tires. My car is a 1988 tII with stock suspension and fenders. The car has the original turbo rotary in it until I find a good ls1 T-56 for a later swap.

I was set to order 235/40/17 front and 255/40/17 rears until I started to read all of the differences in handling when the tires are different sizes. Also some people say the 235/40/17 will rub in the front and to buy 225/45/17 instead.

So before I order the tires would someone please help me find out how large of a tire I can run front and back on 17x8 gt wheels with stock supsension and not rub the stock fenders. I would prefer for now not to roll or bend the inner fenders.

Thanks for the help

I have those wheels on my car right now with the stock 245/45/17 tires that came from the factory and they fit great. They are tight but they fit. I havent tried them on bumpy roads but just putting around town I wasnt getting any rubbing.

When these tires wear out I have 235/40/17 tires for the front, and 255/40/17 tires for the back.. which I think will fit fine but a safe bet would be the 225 up front.. pretty much anything smaller than a 255 will fit without much effort out back.

Everyone told me btw that those 245/45/17 tires wouldent fit up front and they fit fine. I do have Racing beat springs though which may be a little narrower spring, giving me a little more room than people running the stock springs.

considering you have stock suspension (meaning no camber and a lot of travel), i'd go with 235/40/17 up front. it definately fits. beyond that you'll either need to roll the inner lip on the front fenders, and/or add some camber.
ideally you'd add camber anyway, considering the FC likes as much front camber as you can give it.
in back, go 255/40/17.
if you really cared that much about handling, you wouldnt be on stock 20 year old suspension..

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Thanks for your help I will order the 235/40/17s, and the 255/40/17 for the rear. I know I have so much to buy with the ls1 t56 swap coming that the suspension will have to wait until I get the new motor in the car and running with the new motor in it. The car feels pretty tight for stock it only has 69K on it. But I am sure there is much I can do to improve the handling from the old sagging stuff on it.

Oh on a side note I found a 1998 ls1 4l60e w/ cpu and harness with 70k for $1000. Is that a good deal even though I will have to change the trans to t-56 and the harness and cpu. I am not ready to pull the trigger on buying because from reading on here people have said get a 2000 to 2002 instead of the older ls1.

thanks again.

Just so you know 255/40 will bulge out a lot on back. I use the rule of thumb that you should shoot for +20 mm of tire vs rim width (and never exceed the range of +10 to +30 mm). 255's fit nice and square on a 9" rim. Putting on too much tire just means that the traction you gain in a straight line gets negated by the ugly handling characteristics in a corner from the sidewall rolling over. (My opinion from my one attempt at doing so, some guys do it anyways and claim it's fine)

I'd say you'd be far smarter if you went against the flow and put on 225/45s (all 4 corners) in a nice sticky tire like the Falken Azenis (RT-615) and don't look back. Compound makes a far bigger difference than width. You could go 235/40 but the short tire bumps up the rear end ratio which is exactly what you don't need in a v8 car (and besides last I checked they didn't sell the Azenis in this size and it's by far the best bang for buck out there.)

On engines: 99 and 00 are equivalent. 01-02 use the ls6 intake manifold which is worth about $350 shipped. Don't screw around with half ass pullouts that aren't quite what you want. They really do nickle and dime you to death. How do I know? I started with an 98 ls1 that was automatic...

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Tire/rim combos dont look good unless the tire is bulging a little. The stupid stretched look that drifters love looks retarted imo. a 255/40/17 tire is perfectly fine on an 8" rim. 275 would be pushing it.

thanx for your personal opinion on appearance.
225/45/17 is not stretched on an 8" wheel. its square. 255 is square on a 9.
i would never put a 275 on an 8" wheel unless it was a drag radial. you will gain nothing in cornering ability with that big of a bulge.
to the op- what is it you really want? figure out where you wanna be on the drag<-->cornering spectrum, and that will dicate what to do with tires. the best tires for turning suck for drag, and vice versa.

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Couldn't agree more...

Couldn't agree less...

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LS1 FC: breaking it in, working out the bugs...
Link to my swap (HEY NEWBIE I wrote this for you)

pics are worth like.. a bunch of words.
225/45 on 17x8


235/40 on 17x8


255/40 on 17x8


275/40 on 17x8

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So starting from scratch... what's the best wheel size? 17x8 or x9? (for handling) And does 4 identical tires equal better handling?

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Brandon