Since I was a kid, I've always wanted a car with big fat rear tires like a Lamborghini. Now I finally have a car that can fit them, but here in Japan, no part of the upper wheel/tire can be sticking out past the body of the car. The rear of the X can fit a wide tire farther inside than the front, hence the need for staggering.
A 245/35 and a 285/30 would have the exact same diameter, but the X prefers to have a balance front to rear with all the computer/mechanical trickery, so I plan to put a grippier 255/35 (180 treadwear) up front with a less grippy 285/30 (240 treadwear) in the rear. I realize treadwear is not an absolute indication of grip, but it gives you an idea. This setup should give a fairly good balance of grip front to rear but will only be used on the street, so even without the balance it should be OK as long as the diameter is close enough. The 255s would wear out significantly more quickly due to treadwear rating and being on the front (faster wear on front of X). The 255s are 3.75mm more radius than the 285s. This is about the difference between the fronts and backs of the stock tires when I bought the car used a year ago. The previous owner had apparently not rotated the tires at all, not ideal of course, but also not completely unheard of. So anyway, the diameter of the 255/35-285/30 setup should balance out fairly quickly. I could use the new 255/35s with my used 265/35s (almost same diameter) for a short while to wear the tread down 1mm or so, if everyone thinks 3.75mm radius difference is just too much to start with.
Let me address several other issues that I believe people will also mention, ahead of time.
I know I will not be able to rotate front to back - obviously, so I will rotate L to R, unmounting, remounting and balancing them.
I realize the speedo will read about 4 percent more than actual speed and that the 285/30 tire will lower the car about 12.5mm (1/2 inch) and will leave more "gap" in the wheel arch. These are all fine with me and the lower effective gear ratio is actually a plus for me (slightly more "feel" of power in each gear).
The wheels will be Rays Gram Lights 57Xtreme 18 x 9.5 +30 at all four corners. These are within the approved width range of both tire sizes (see TireRack's site, tire sizes' page, click on specs tab). My calculations show that the rears should be almost perfectly flush with the body, at most sticking out 1 or 2 mm, which I hope I could get away with if the cops just eyeball it. I will use my other set of wheels/tires for the biannual car inspection test, where they are quite strict.
So as you can see, I've done my homework :nerd: but is there anything I have missed? Something else I need to consider? Could this staggered setup in any way harm my car? I certainly don't want to do anything to hurt my baby.
A 245/35 and a 285/30 would have the exact same diameter, but the X prefers to have a balance front to rear with all the computer/mechanical trickery, so I plan to put a grippier 255/35 (180 treadwear) up front with a less grippy 285/30 (240 treadwear) in the rear. I realize treadwear is not an absolute indication of grip, but it gives you an idea. This setup should give a fairly good balance of grip front to rear but will only be used on the street, so even without the balance it should be OK as long as the diameter is close enough. The 255s would wear out significantly more quickly due to treadwear rating and being on the front (faster wear on front of X). The 255s are 3.75mm more radius than the 285s. This is about the difference between the fronts and backs of the stock tires when I bought the car used a year ago. The previous owner had apparently not rotated the tires at all, not ideal of course, but also not completely unheard of. So anyway, the diameter of the 255/35-285/30 setup should balance out fairly quickly. I could use the new 255/35s with my used 265/35s (almost same diameter) for a short while to wear the tread down 1mm or so, if everyone thinks 3.75mm radius difference is just too much to start with.
Let me address several other issues that I believe people will also mention, ahead of time.
I know I will not be able to rotate front to back - obviously, so I will rotate L to R, unmounting, remounting and balancing them.
I realize the speedo will read about 4 percent more than actual speed and that the 285/30 tire will lower the car about 12.5mm (1/2 inch) and will leave more "gap" in the wheel arch. These are all fine with me and the lower effective gear ratio is actually a plus for me (slightly more "feel" of power in each gear).
The wheels will be Rays Gram Lights 57Xtreme 18 x 9.5 +30 at all four corners. These are within the approved width range of both tire sizes (see TireRack's site, tire sizes' page, click on specs tab). My calculations show that the rears should be almost perfectly flush with the body, at most sticking out 1 or 2 mm, which I hope I could get away with if the cops just eyeball it. I will use my other set of wheels/tires for the biannual car inspection test, where they are quite strict.
So as you can see, I've done my homework :nerd: but is there anything I have missed? Something else I need to consider? Could this staggered setup in any way harm my car? I certainly don't want to do anything to hurt my baby.