So did you go with 265/60-18s?

The OP never reported back - so who knows? :dunno:

FWIW, I still think it's a bad idea - for the reasons already mentioned PLUS you'll have no spare tyre, since the factory 235/65-R17 that has the same rolling diameter as the 255/55-R18 tyres won't match the larger 265/60-R18 and you'll munt your transfer case if you have to drive on the spare (>5% difference in diameter)... :yikes:

I did something i havent seen yet, & mounted 305 40 20's on my 10.5 square setup. I had 315 35's all around & i just couldnt take it in NYC. It wasnt bad but it wasnt good either. I made it work.

The 305 40 20's have been the best decision ever. I do think they rub slightly on turns but i can live with that, because they dont rub on the highway or anything. Car drives so much more awesome & still feels amazing. I think they are also just about at the max tire size for the E53 as they fill up the wells horizontally. I cant say for sure as my car is also lowered a bit.

Hey BigBody.....do you mind posting pics?

Just curious how it looks....thanks!

I think there are coding options for tire sizes available, if I remember correctly. The factory 20" IS tires are actually smaller circumference than the stock 18" tires. Because of this I think there is actually coding to account for this, but I will need to go back and check for the IKE.

Interesting! I've been running a square set of 275/40R20 on my E53 for about 15 years with about 24k miles on the odometer after switching them. No re-coding was done.

I used this site:

https://tiresize.com/height-calculator/

to calculate:

275/40R20 is 28.7" tall (diameter), 90" circumference, 704 revs/mile
255/55R18 is 29" tall, 91.2" circumference, 695 revs/mile (my original wheels were Style 74 18")

So does that mean my odometer is overstating the mileage by (1 - 695/704) * 24k, or about 307 miles?

I don’t have the car at the moment, but i will absolutely post up some pics :thumbup::D

I'm not saying recoding is necessary to run different tire sizes...the DSC will not be able to know that unless its parameterized. I am implying that the speedometer will be off more/less than the typical 3mph that BMW purposely does. But that's a good point with the revs/mile. It looks like it'll be off slightly more than 1% difference. It's on my todo list for checking the coding because I thought I saw an option for performance tire size.

Understood :thumbup: At 80 mph the speedometer will be off by about 1 more mph.

Max tire Size for Stock E53
 

The opposite. Bigger tire means you are going faster/farther per rev. The odometer thinks you went 695 per mile but you went 704 so you went about 300 fewer miles than the meter reads