socci

I know there is endless threads on 4matic w/ staggered wheels and no real definite answer. Some say you can go 0.3" difference in cjrcumfrances and some say 0.1 without any repercussions. So I'm wondering if people can tell me what setup they are running and how long?

I want to go 255/35/19 285/30/19 for thr extra rubber and load rating but it's off by 0.2". I can go 245/35 285/30 which according to Hankook are very close to identical, but the load rating is a 91. I also heard that preface lift w212s transfer cases do not have the tolerance the newer 4matics have, any truth to that? I can't imagine in 2012 they didn't consider tread wear tolerances, but in 2013 they did.
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blegthbloo

No issues with mine so far, but I've only put maybe 7-8k or less on the car with my wheels before it was winter time again... haven't put them back on yet, although I was supposed to a couple weeks ago. I'm part of the 0.1" crowd, but nothing really to back it up yet... better safe than sorry IMO.

kajtek1

Rubber is flexible thing, so the circumference is variable with speed, load and other factors.
What you want to compare are rpm (rounds per mile) as this is what your car drive-train will see.

socci

245/35 is 25.7" with 806 rpm
255/35 is 26" with 775 rpm
285/30 is 25.8" with 782 rpm

So I'm confused, tire size calculators say 245 285 are off by 1 rpm, but Hankooks spec says 24 difference. Why would a time with almost the same circumstance have such a different rpm?

kajtek1

Again RUBBER IS FLEXIBLE THING and NOMINAL sizing is just nominal.
I have seen 2 different model tires from the same manufacturer in the same nominal size having rpm different by 5%.
That is why manufacturers list rpm.
Tire size calculators can give your rough idea, but are garbage for making staggered set up.

socci

Ok thanks for that info. One would just think if a tire is the same circumferences from the same manufacturer they would be close to the same rpm considering they use the same rubber. Do you know the acceptable rpm difference with 4matics?
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kajtek1

You never noticed how tires sag/change the radius under different load?
Some tires are design with stiff sidewalls for load capacity, some are soft for comfort.
Than you have centrifugal forces, that are harder to observe.
I have never seen MB making official statement how much % of rpm difference the ESP and traction will tolerate, but common experience says it is less than 3.
Take a look at donut spares on ML class. I drove on one of them for 60 miles on different roads and had traction light coming only couple of times on sharp turn.

davidjohnbamber

Along with 4matic transfer case potential issues, wheel speed sensors will quickly light up your dash when you have too much of a difference in the diameters between the F&R tires. Don't ask me how I know. BTW "The School of Hard Knocks is not tuition free."

cocobeex

I have a set of DWS 245/30/20, 275/30/20
This set F&R has 2.7% difference. Sometime my traction lights up during cornering.

I also have another set Pirelli PZERO NERO GT 245/30/20, 285/25/20
F&R difference is 0.7%
Runs perfectly fine no traction lights up, unless I go WOT.

I learned from a member here...lol
http://www.miata.net/garage/tirecalc.html