So I’m sure there’s been threads about this but I haven’t seen anything recent.

i have a set of Lorinsers LM6s that I want to get on the car with the specs of 20x9/20x11. I am wondering if I can run different tire sizes without the awd lighting up on me . I was thinking 255/35/20 front and 275/30/rear. I am on KW V3 coilovers.

i am open to any advice and tire size recommendations here, thank you!

 

Cant speak to that 11” wide rear wheel fitting, but if you can make it work I would go with the 255/35-20 and use a 285/30-20 in the rear. This will keep you at 1% front to back, which the 4M should handle without issue. Post up a photo if you get these mounted I’d like to see it.

Here’s my 285 on a 9-1/2” wheel.

 

You need to match tires rpm, what is listed on manufacturer sites.
Rule of thumbs say you can mismatch by 3% before lights will start flashing.

 

Thanks, K. You just answered my question. Factory W211 E500 tire size is 245/45/R17. Went shopping for two new front tires and found a great deal on two Continental 245/40/ZR17 Extreme Contact Sport. I understand the 3.8% diameter difference will throw the speedometer off by a few mph, but was worried about other fallout. Even accounting for wear, this seems over the prevailing wisdom of keeping the difference to less than 3%.

 

when I had a sidewall failure due to clipping a curb, I was told front and rear wheels should be within 1/8th or 3/16th inch of the treadwear. I'm suspecting thats a lot less than 3%

 

Diameter difference doesn't mean much in tire comparison as the tire flex/sag under load and each model will have it different.
That is why manufacturers post rpm for each model.
Hard to tell why, but this basic knowledge is very hard to sink in car owners memory.
On other hand, if you find tires with 3.8% difference, to some degree you can play with inflation to bring the difference below 3%

 

... that when INFLATION is seen as a good thing

 

So, Conti Extreme Contact Sport, per tirerack.com, the 245/45R17 has 808 revs/mile, while the 245/40r17 has 841 revs/mile.

so if the /45 tire is going 60 MPH, thats 1 mile/minute, the tire will be doing 808 RPM. The /40 tire will be trying to go 0.96 miles at that RPM and the transfer case will be having to make up the difference. I bet that 4% error makes for a very unhappy transfer case, and it will be heating the transmission fluid (which the TC shares) quite a lot.

I also note that /40 tire is not XL (Extra Load), and has a load factor of 91, or 1356 lbs, while the /45 is XL and has a load factor of 99, 1521 lbs.

 

None of this makes me feel good about different size tires front and rear, no matter the deviation. There were staggared wheels on the W210 E55 I owned - 17"front, 18" rear. It didn't seem to matter. But this rabbit hole is somewhere I don't want to go.

 

Many have done this and have been successful, if your truly set on this, read through the many tire threads on how and which sizes of rims/tires to use. but as LCG says, you have to do it correctly, I have an opinion, FWIW. I would run all the same size, but lots of guys have done this without issues, good luck1