Overtaxed

I talked to a tech at my Lexus dealer and he strongly recommended against running different sized wheels/tires front and back.

He said that a different overall diameter front and back will confuse the electronics in the car, if nothing else the VSC.

If you run 245-40 front and 265-35 back then the car will think that the back wheels are rotating 0,95 percent faster than the front. If my calculations are correct.

So I guess that if your back wheels actually lose grip and start spinning then the traction control would kick in sooner.

But the question is how big a difference in rotation between the wheels is necessary before the VSC or ABS is activated?

gs4power

Hi Overtaxed,

It depends on what sizes you're running. Check this out:

1.- 245/40 18 807 revolutions/mile

2.- 275/35 18 812 revs/mile

3.- 265/35 18 819 revs/mile

4.- 235/40 18 818 revs/mile


Combining options 3 and 4, or even 1 and 2 result in negligible differences, the electronic sensors won't even notice them. The Lexus-endorsed L-tuned wheel upgrade uses sizes 3 and 4.

Overtaxed

Hi gs4power,

Both these two tire size calculator show different values than the ones you posted:
http://www.miata.net/garage/tirecalc.html
http://www.powerdog.com/tiresize.cgi

But still, the differences between the sizes are about the same as what you indicated.

I've been thinking about keeping my 245/40-18 in the front and swapping the rear to 255/40-18 (I don't want to go to 275/35 for many reasons). That's a diff of 1.2% (10 revs/mile). I haven't seen anyone with a setup with such a big diff and I'm nervous that could cause the ABS and/or VSC to kick in all the time.

gs4power

Hi Overtaxed,

The values I posted are for the Toyos T1-S, sorry I didn't mention that. The specs/test conditions among different tire manufacturers differ slightly. For instance, if you change the air pressure of the tires you may get different revs per mile results.


If you want to keep your 245/40 front tires, and want a staggered setup, the 275/35 option is the least likely to generate unwanted results. IMHO, why bother with a 255/40 in the rear (only 10mm wider) ? Simply get 245/40 all around and don't worry about the ABS/VSC glitches. Good luck w/your selection!