[nielsensmn]

Hello all, I have a 2008 Mustang GT/CS, lowered 2 inches and I'm planning on getting the 18x10 Shelby Torque Thrust M chrome rims for the rear of the car. What would be the largest tire I can place on that particular rim and would I have problems with the fit of the tire in the wheel well with the car lowered? I've heard 275/40ZR18's are the best fit for this...true?

[Shack]

I think you can go 305 in the rear

[sqidd]

Originally Posted by Shack

I think you can go 305 in the rear

Probably not on that rim though.

The biggest tire you can put on a rim depends on the manufacturer and model of tire. Not all 275’s are equal for example. One manufacturer may have designed theirs for a 9” rim while another designed theirs for a 9.5” rim. You need to first figure out what tires you want and then get the size that they recommend for a 10” rim. That information is available on Tire Rack and Discount tire.

As far as what will fit under the car that has a lot to do with what tire you are talking about. I have seen S197’s with 335’s (13.2”) on them but they were drag radials and I imagine the 335 didn’t exactly reflect the true diameter of the tread. A lot of tire manufacturers will label their tires optamisticaly for fashion purposes.

I currently run a 10.5” rim with 295 (11.6”) BFG Comp TA KD’s. The car is lowered. When I get the rims I want I will be going with a 315mm (12.4”) wide tire on a 11.5” rim. But to do that I have to get the wheel custom widened because no one makes them in that size and I also need to spin out some thin spacers to go between the wheels and rotors or the tires will rub.

So the quick answer is that a 295 is about the limit for tires that are labeled accurately and unless you can do some creative/custom fitment you won’t be able to play with wider tires.

[stlwagon]

Biggest street tire I've seen on a 10" rim is a 325.

[sqidd]

Originally Posted by stlwagon

Biggest street tire I've seen on a 10" rim is a 325.

Yeah, but did they fit right?

[stlwagon]

Originally Posted by sqidd

Yeah, but did they fit right?

Who cares, they looked good and that's all that matters.

[sqidd]

Originally Posted by stlwagon

Who cares, they looked good and that's all that matters.

Crap, I keep forgeting that

[travelers]

Originally Posted by sqidd

Crap, I keep forgeting that

That seem to be the most important, not performance. I have 295/45/18s on the back but I'm not lowered. You have to be concerned with if the tire will hit the inner wheel well radius.

[nielsensmn]

So, logically, with 18 X 10 Shelby Torque rims...I should be able to put a 275 to 295....possible a 305/40 or 45 ZR 18 tire on that rim and fit on my car......depending on the maker of the tire?

[Porky Pig]

Did you install an adjustable panhard bar? If the car is lowered 2" the rear is probably offset to the drivers side and can interfere with a wider tire.

[sqidd]

Originally Posted by nielsensmn

So, logically, with 18 X 10 Shelby Torque rims...I should be able to put a 275 to 295....possible a 305/40 or 45 ZR 18 tire on that rim and fit on my car......depending on the maker of the tire?

It all depends on the tire manufacturers recomendation for rim width. There is a pretty big spread, that's why it needs to be researched. 275's-295's are pretty reasonable. A lot of tires will work with a 10" rim.

I doubt you will find a 305 that is recomended for a 10" rim though.

And keep in mind that no matter how wide the tire you put on is its "net" width will be determined mostly by the rim width. For example, you could get a 335mm tire to bead up on a 10" rim but the tire will not measure out to 335mm wide anymore. The sidewalls will be pulled in A LOT which will make the tire narrower and the center of the tread will baloon out in the middle so the tire will wear out a strip right down the center of the tire real fast and your effective contact patch will be greatly reduced.

I deal with "wider tires are better" dumbness constantly at the track. On a motorcycle the hot size tire is 190mm wide. That tire needs to be on a 6" rim but a lot of people put them on 5.5" rims. By only changing the rim size 1/2 inch the 190mm tire gets pinched down till where its about 182mm wide and the center of the tire gets taller, the contact patch gets smaller and the sidewall performance while on the edge of the tire (which is basicaly the only "suspension" you have) goes to crap ad there is a major loss of traction. I get these guys all the time saying there bike "feels funny" ad can I do something about it and i say yes.....and point them to the tire vendors with istructions to go get a 180mm wide tire.

The change is so dramatic that I can tell a bike has a tire o it that is too wide for the rim within the first 2-3 corners of my out lap which is at a very slow pace because I am waiting for the tires to come up to temp. If I had to guess I would say that a tire 10mm too wide would impact my laptimes by about 5 seconds.....which may as well be a year.