cdso

So, for us X guys, you can go with a wider tire in the back provided the aspect ratio evens out the overall diameter? Am I understanding this right?

I think the 19s from the coupe come with 45s up front and 40s in the rear.

DEC1

That's definitely my impression...but why would you really want to go with wider in the back?

That would keep you from rotating front to rear...is more expensive...and minimal impact other than somewhat wider tire from back view...there may also be something negative to having stickier rubber (due to width) in the rear as it relates to the AWD.

I had an '08 coupe and not only are the stockers wider in the rear but the rims are also diff widths.

To go with the same size tire all around (which I did on coupe) I needed to stretch the rear tires slightly to fit on the wider rim. I wasn't unsafe and it was almost unnoticeable but I wouldn't do that again.

My plan is to go with 8.5 wide x 19 and put 245/40/19's all around (which is same size as coupe fronts) That's plenty wide... in fact .800" wider than stock (9.65"vs. 8.86") This would also reduce my sidewall height to 3.86" which should look great compared to current 4.43"

BTW: got all this info on Discounttiredirect.com...awesome site for info on tires and wheels...thanks guys!

cdso

That would make it easier for me since I want to go with the coupe's 19s. Much easier buying a full set rather than trying to buy 4 fronts or 4 rears. Otherwise I would definitely go with the same size all the way around. I think 19x8.5 would be perfect for us since the sport comes with 18x7.5.

Neal@tirerack

iTrader: (2)

Make sure the outside diameter on front/rear are the same and you will be ok. If the diameters are different front/rear then you run risk of damaging diffs/transfer case.

09xs

well if its 225/45/19 (fronts) 245/40/19 rear - your saying dont do it bc there will be damage done?

cdso

I would think it would be ok since according to those #s you're running a 40 series in the back. Wouldn't the overall diameter of the wheels and tires be able the same since the sidewall in the rear is smaller?

09xs

Maybe its me I'm not following you.... Same 19 inch rim (in diameter - not width) in front and back but the front is running a 45 rear runs 40 the overall height has to be different from front to back but my question is what's the exact height difference (correct me if I'm wording this wrong) and is it close enough to get by with no problems- too many yes and no's !!! Lol FML

vactor

if the difference between front and rear rolling diameter is less than 5% then the awd system is inactive. once it passes this threshold by way of the abs sensors, the awd ecu starts to transfer power to the front wheels. staggered wheels with tires that result in a different rolling diameter will result in the percentage channging, either it will be greater than 5% and the car will always send some power to the front wheels, thereby greatly reducing the center diff clutch life and increasing the diff oil temps, or it will take more than an actual 5% difference in wheel speed to activate, meaning that the handling and saftey characteristics will change, possible transferring too little power to the front wheels under certain circumstances. either way, a different rolling diameter (staggered wheel width) is probably not a good thing on these cars.

911turbo

iTrader: (3)

what about the GTR? the GTR has a ton of pics staggered of like BBS LM's and stuff

vactor

what does that mean? pictures? really? from Nissan? as far as i know the GTR is only offered with one set of wheels. the point is, the ecu is programmed at 5% with the G37X, and i am sure that for the GTR or another car it could be a different program, but for us, the wheels and tires should be the same.

09xs

I'm lost. So if its programmed at 5% can it be changed?? Or could this wheel difference be less than 5% how do I get actual facts as u can tell- u guys know more about this than me.

vactor

what's to know? 5% is 5%. never heard of anyone being able to reprogram the torque distribution, neither from cobb or uprev etc. not to say it cannot be done, but i have never heard of it BEING done. as i said, if the difference is less than 5% it will work fine, but it might activate torque transfer earlier or later ... depending on the difference etc. again, the safe and reliable advice would be DON'T DO STAGGERED ON THE G37X! use the same wheel and tire sizes front and rear. easy advice to follow, especially if you are not familliar with these cars.

09xs

Well that makes more sense. Fk it.

911turbo

iTrader: (3)

go look up like greddy GTR and you will see their staggered offsets and such.

vactor

so what? did greddy change the parameters of the awd system? what is the rolling diameter difference? did they reprogram the awd ecu? are there longevity tests on the center diff clutch? just cuz someone has done it does not mean one should. any info on this gtr (and of course, this is a G37 forum)? how does your reply help give us more information on what works and what does not and why?