MillerLite

Hi guys,

I have done some research but still getting not a definit answer.

I know cant different tire diameters with the X drive so here it is. Got some temporary 20s since my oems were worn out. Following specs


Front
20x8.5 w 225/35/20

Rear which I think is were the problem lies.

20x10 w 255/35/20

They fit well but the traction light comes on at 40mph.

Any suggestions for rear size tires to cure this.


Thanks in advance for the much needed help....

MillerLite

Anyone with some input on this? I can change the rears maybe for some 25 series?

Lotus99

Just go to a tire size calculator like 1010tires or willtheyfit

MillerLite

I have been doing the calculations, but my question is how close do the numbers have to be ...

If I go with a 245/30/20(661mm) rear and 225/35/20(665.5mm) front will this difference still give me problems ?

wcr3d

I don't know if this will help, but what you need to find out is "rolling diameter". From what I understand they have to be like 2% of each other. Which is very close. I have seen where even replacing tires of the same size, just due to wear from front to back being enough to send the error.

luigi524td

There's a comprehensive xi wheel and tire thread - you really really need to research (or at least read through) it!

For openers, the tire size you've indicated for the fronts is SERIOUSLY UNDERSIZED (load capacity) and might actually be dangerous for most driving situations.

Even if you're not buying new tires, TireRack's guides will help you identify the proper tire size for your e61 and wheel rim diameters of all sizes. As was already noted, it's important to maintain the correct rolling radius (diameter) as "original" specs. So, cross index 245/40x18 with the proper tire size for a 20" wheel. As always, clearances vary from model to model ... so be sure to spec for a "touring" as it may be different than a sedan (esp with suspension clearance).

Lotus99

Sorry, that's incorrect. It's 245/40-18.

luigi524td

Thanks for catching my "miss-typing" ... trying to do 4 things at once

Lotus99

No worries, you contributed more than I did.

MillerLite

Thank you fpr the replies guys, decided to buy 4 new tires at the correct sizes, car rides beautifully and I really like the look. 20x10s have a nice deep concave to it.

Just ordered yhe the H&R springs for her and next and some engine mods

Intake
Charge pipe
Down pipes
Chip

Let me know what you guys think...