I currently have 18x10 wheels on all corners, with 275/40/18's. I want larger rear tires but I'm having trouble getting an exact match on diameter.

I can get BFG KD's, 295/35 rear (26.1 inch diameter) and 275/40 front (26.7 inch diameter). I can lower the rear with some Roush springs to make up for the additional wheel gap in the rear.

The big question is, can I get away with the approximately 1/2 inch difference in diameter without causing traction control sensor issues or will this adversely affect handling? The revolution per minute difference is only about 2%.

I don't think the 1/4 inch radius difference would be noticable as far as looks.\

Any other combination suggestions would be appreciated, but I need at least 275's in thefront due to the 10 inch wheelwidth.

Thanks in advance.

 

The difference in ride height will be undetectable and have no affect on the TCS. I assume that the 2% difference you refer to asRPM is actually MPH (try this if you haven't already: http://www.1010tires.com/tiresizecalculator.asp) and is liveable IF that's all it is. However, a CAI&tuner like the XCAL2 and some custom tunes will allow you to adjust your speedometer for your rear tire diameter (besides waking up your Stang with about 20 or more RWHP).

 

I'll deal with the speedometer later when I get a custom tune, but I need tires now. By RPM, I meant tire revolutions per minute. Should have been more specific.

 

The 295's on the rear will put you at 2.076% faster on the speedometer. That equates to reading 61.2 MPH at 60 MPH actual. No big deal as long as you're aware of it. But get the CAI & tune ASAP, and NOT just for the speedometer correction! LOL!

Have fun and be safe.

 

How is your speedo being corrected for the gears currently?

For what it's worth, my recommendation would be 275/45/18 up front and 295/45/18 in the rear. No need to have such a low profile tire with 18's.

 

Ummm, do you know what the 45 in 295/45 means? A 295/45 tire isnot close in height to a 275/45.

Let me explain. The 45 (aspect ratio) means the sidewall of the tire is 45% of the width (295). So, 275x.45=123.75 and 295x.45=132.75. 123.75 doesn't equal 132.75.

It sounds to me that the op wants to keep as close to the original height as possible.

The link posted ealier is a great place to figure out which size tire is closest in height.

Generally, if you stay with in 3% of the original tire height without a tuner, you'll be ok.

Darkfire, I'm not trying to be a smarta$$, just trying to prevent some inaccurate information.

 

But that's my question. Why stay so close to the original tire size when it can easily be resolved with a tuner? I'm not giving inaccurate information. I'm posting a question. Yes, 295/45/18 will be larger than stock. And it looks a lot better.

 

and if you're putting money into those big tires, why not spend the money and get a tuner and cai so you have some power to turn them with?

 

My speedometer was corrected for the gears by Roush when they gave me the new tune for the smaller pulley on my s/c. The installer said my my speedometer checked out OK on his GPS test.

My speedometer has never been corrected for the tires unless the Roush tuner assumed I had their wheels and tires. I don't even remember what my car originally had. They were 17" bullits that I had the dealership switch to 18" bullits (stock tires), then I bought the Roush 18 x 10 wheels with the 275/40/18's all around.

The 295/45/18 rear with 275/45/18 front might be a good idea, but I don't see a lot of selection for brands. Looks like I could get Goodyear Eagles but not BFG KD's. It sort of makes sense from a standpoint of filling in more fender well, but I wonder if the taller tires will rub? They are basically an inch more diameter in the front and 1 1/2 inches more diameter in the rear.

 

Go with 275/45/18 in front and 295/45/18 in rear.