(Did a quick search, but couldn't find a clear answer, so here goes...)

When changing to bigger wheels (and wider tyres to go with them), I know you want to keep the circumference of the wheel/tyre combination as close as possible to that of the standard wheel/tyre combo. My question is this: how close is ok? 1% deviation? 2%? 3%? What is too much?

The main motivator is that with the wheels/tyres we're thinking of for my wife's new car (R34 Skyline 25GT-t), there would be a difference of 1.7% at the front, and 1.3% at the rear.

Cheers

In general 3% will not have an effect on the ABS systems etc. For AWD vehicles try to avoid different diameters rear vs front as the systems in the car can interpret the smaller diameter tires as tires that are slipping. This will cause the differentials that sent torque to gripping tires to run too much and perhaps fail prematurely.

For the Skyline we don't have specific advice since the car is not available here . . . but we have noticed with Infiniti G35 & Nissan 350Z, distant cousins of your car, that if make a large percentage front vs rear or vice versa this can cause the traction to control to engage too often or not enough so best make same percentage change front vs rear.


Cy@tirerack.com
Performance Specialist
Moderator www.automotiveforums.com. To place an order please call 888 541 1777 Ext. 622 or for internet orders through www.tirerack.com please mention my name in the previous contact field directly above the Place Order button on the Order Summary page for quick, efficient & professional service. If replying to this email please include original message to ensure a prompt response.

Thanks for that speedy reply :)

I know about 4WD systems like ATTESSA not liking different diameters front to rear, but as the GT-t's RWD, that's ok. Would the changes I quoted above (1.7% front and 1.3% rear) affect the traction control, do you think? (I know you don't have experience with the Skyline, but as you say, the TCS on the G35 and 250Z ought to be similar.)

thanks again. :)

Based on what we've run on the G35, you're probably not going to have problems . . . I would search the web for Skyline specific site just be to be sure


Cy@tirerack.com
Performance Specialist
Moderator www.automotiveforums.com & www.focaljet.com To place an order please call 888 541 1777 Ext. 622 or for internet orders through www.tirerack.com please mention my name in the previous contact field directly above the Place Order button on the Order Summary page for quick, efficient & professional service.If replying to this email please include original message to ensure a prompt response.