Tire size question

[chivas]

wondering if 295/35/20 will work for the fronts on a 4.6 v. 275/40/20.

sure the profile is thinner but the width is wider so the ratio should remain about the same.

Thoughts?

Thanks!

[crystalworks]

Originally Posted by chivas

wondering if 295/35/20 will work for the fronts on a 4.6 v. 275/40/20.

sure the profile is thinner but the width is wider so the ratio should remain about the same.

Thoughts?

Thanks!

Just make sure the overall rolling diameter from the front tire to the back tire is the same. As long as that is the case... you shouldn't have a problem. 10mm extra track width shouldn't interfere with the suspension or fender liner I wouldn't think. Might want to take the tape measure to it just to verify.

[oldskewel]

By my calculator, the revolutions per mile on those two tire sizes are 717.0 and 703.7 = a difference of 13.3 rev's per mile. I'm assuming that the rear tires are close to the 703.7 value. What matters is the match from front to back (side to side too, of course) - so if all 4 tires went up to around 717 that would be fine.

That is too big of a difference, according to your owner's manual I expect (it is for my E53, which is different).

The excessive difference can cause problems with the transfer case. With later models than mine (2001), x-drive maybe?, there are other concerns for when the AWD computer thinks slip is occurring when it sees an excessive difference and tries to compensate.

[chivas]

thanks! i was wondering about the variance between the two and if it would even work. apparently not.

[Qsilver7]

Input the recommended tire sizes + the ones you're considering in this tire size calculator link below. If the overall diameter/circumference is GREATER than/LESS than 3% (+/-)...then it won't work well: Tire Size Calculator - Tire & Wheel Plus Sizing

[chivas]

Thanks! Got new tires that's the same size as OEM.

[jdstrickland]

Because the X5 is AWD, you need all four tires to have the same number of rotations per mile. A variance of a few revolutions is not a problem, but when the variance becomes too high then the t-case will not be happy and the DSC will throw a fit.

Calculate the diameter of the tire by multiplying the width by the aspect ratio (295 x .40 = 118) to arrive at the sidewall height in millimeters. This is one sidewall, so double this to 236. Divide by 25.4 to convert to inches, 9.29. Add this to the diameter of the rim, 19 + 9.29 = 28.29. This is the overall diameter of the tire. Multiply by 3.14159 (pi) to get the circumference, 88.879 inches. Divide a mile (in inches, 5280 x 12 = 63,360) 63,360 / 88.879 = 712.879 to get the revolutions per mile. My example used a 295/40x19. You can change the size accordingly and find the revolutions per mile of your tire, and proposed new tire. Alternatively, sites such as tirerack.com and tires.com have calculators that do this for you.