what tire should I use?

gearhead101 said:

i have 17x8 bullit rims on my 95gt and i want to go as wide as i can with a 40mm profile tire what do you thaink 175/40r17 or 165/40r17

Click to expand...

For a 40mm profile you should be okay up to 245/40R17.

A 40 profile tire isn't in MM, but percentage of the width, so a 245/40/17 has a sidewall profile that is 40% of 245 which is 97.79mm or 3.85".

The stock sized tire for that wheel is 245/45/17 which is a 25.68" overall diameter.

A 245/40/17 is a 24.71" overall diameter....almost a whole inch shorter of a tire.

A 275/40/17 is 25.66" overall diameter....same as the stock tire height so no speedometer error.

I have 4 sets of wheels for my 2 mustangs. A set of prostar big n little with ET streets for each and a set of 17x8" street tires for each (one set are the grey bullitt wheels). I run 245/45/17 on the fronts and 275/40/17 on the back.

Here's a good online tire size comparison calculator
http://www.1010tires.com/tiresizecalculator.asp

I used to run the same sizes as Last5.0 until I recently got new wheels. Now I have 275/40 on front and 315/35 on back.

What is the width and backspacing on your front skinnies Last5.0? I want to get a set but don't want to have problems with them rubbing on the brake calipers. Yours look very nice on it.

Mine are 3.5" wide and they only come in one backspacing, something like 1.75". They do not clear the brakes unless you run a spacer or modifiy the caliper. Without modification you would need like a 1/2" spacer. If you remove the crossbar on the caliper you only need like a 5/16" spacer. If you grind the caliper face so it's flat and not "humped" you don't need a spacer. I've done all the above years ago and I believe in that pic I had the caliper ground flat and no spacer. I've since sold my stock modified calipers and switched to the '99+ dual piston PBR calipers and run a 3/8" spacer without modifying the caliper at all and the wheels still stay just inside the wheel well.

BTW, that pic was taken during a launch so the whole car is raised up on it's way to getting some daylight under the tires. The car sits real low normally.

If doing it all over again, I would just get a bit wider wheel, like a 4"-6" with enough backspacing so no spacer or modification is necessary