A new service girl at my Infiniti dealer is working on some tire prices to compare against Discount Tire and she told me the mechanic said staggered tire sizes will tear up the drive train. I have 245 on the rear and 235 on the front. I planned on going 245 all the way around just to simplify things, but anybody ever heard any logic to this?

 

If the front wheels are rotating at a different speed than the rear ones (because they are different sizes), you can burn out the center differential. It's just how AWD cars work. I suppose if you are careful and make sure the diameters are close you might be able to get away with it.

 

Yes. Besides being clearly stated in the Owner's Manual, it's all been discussed here in numerous threads many times before too. The issue has to do with different diameter wheel/tire combos between front and back will result in stress being applied to the drive train (ie. front and rear differentials, transfer case, transmission) since it is AWD . When the car is in gear, there is torque applied through the transmission to the transfer case and on to the differentials both fore and aft. As each differential turns, the connected wheels should be turning the same amount, and hence traveling the same distance for each rotation; the system expects them to be in sync. When you put dissimilar diameter wheels between the front and the rear, there is tension, or 'feed back', passed into the drive train as the smaller diameter wheels are forced to travel farther to keep up with the larger diameter wheels and vice versa. The system can tolerate some degree of variation, and many feel comfortable relying on that to run staggered sizes, but Infiniti's policy is to specify the preferred use of identical wheel sizes, diameters, tread design, and treadwear. If you choose to run staggered wheels, do your best to match diameters as closely as possible. The (incomplete) sizes you listed, 235 and 245, don't quite tell enough to determine your overall diameters.



BTW, before you bought your car, didn't we discuss the concerns of getting an AWD car if you didn't really need one (given that you're in AZ) ? Or was that someone else?

 

i got 275/30/20 in the rear and 245/35/20 in the front and i have no problem onmy 08 x.i havent had any problem...

 

Yep, that's only a 1% difference in diameter. I haven't heard anybody report any problems with that small of a difference. But remember, if any part of your drive train (post engine) ever does act up, you'd be wise to swap back to oem sizes before you take it in for service.

 

vqsmile summed it up very nicely. If you're not rocking aftermarket wheels with concavity, lip, etc I don't think there is an andvantage to running staggered with a stock wheel set up. Go with the same size tires. If you must however, make sure your rolling diameter is less than 1% different.

 

I was the guy you were thinking of, but when I was discussing prior to buying it was the simple fact of an X model not needed in AZ. I love everything about the car and don't feel I am missing anything or bought the "wrong car" because it is an X. I have put about 17k on the car already and love it. Just questioned the staggered tire setup. My setup is 235/50/18 and 245/45/18.

 

The rims are stock S model 18" rims. The front current tire size is 235/50/18 and rear 245/45/18. I will be switching to all 245/45/18.

 

With those current sizes, you are just over 2% difference. Of course running the exact same tires is preferable, but a few alternatives might be to run either a 255/45 in the back with your 235/50 in the front (0.7% difference), or to run a 225/50 in the front with your 245/45 in the back (also a 0.7% difference). Running a 245/45 in the front is definitely do-able, but there are some compromises. The tire is a bit wide for that narrower front rim and you will be more prone to pick up NVH issues in general with the larger size treads up front.

 

Thanks everyone. Just switched to Yokohama YK850 with 225/50/18 in front and 245/45/18 on the rear. Look great and quieter than the Toyo Proxies I replaced. Also found out the front and rear rims have different offset so there was no real benefit getting 245 all around. Had Discount Tire install today and matched the $100 off from Discount Tire Direct. May consider like I read in another post to switch the car to rear wheel drive and deactivate the all wheel for now.

 

I was just thinking about this too. I have been running 245/40 18's all the way around for a year and a half on 18" wheels that are 8.5" wide front and 9.5" wide rear. Even with the slight stretch on the rear they are very similar diameter wise and I've had no problems. I recently got a tear in the sidewall of my front driver's side tire and I'm thinking it would look better to get a similar stretch on the front. The closest size I've found to accomplish that is 215/40 18 that is still reasonably priced but it seems to be a 3.7% difference or about 30 revolutions per mile which makes me nervous. Anybody work for Infiniti or know of the tolerance the AWD has for difference front to rear?

 

I don't think I've ever seen anything officially published, and dealer will just tell you to run the correct size only, but I have heard that the 'relative' limit for VDC on the RWD models is only 3%, so you may well be pushing it with AWD sensitivity on top of VDC sensitivity. I've got RWD and with only a 0.7% difference and I can tell the difference with how much easier VDC triggers so, even with just RWD, I wouldn't go anywhere near 3.7%.

EDIT: just noticed you're 1st gen, so yours may be different.

 

I was able to find a set of 215/45 18s which puts the diameter within .4% which makes me much more comfortable.

 

215 wide, are you going to be cutting pizza?

 

^ OK, now that's funny!