Tire Diameter Difference Front to Rear on Dual-Motor

[Aggmeister2010]

Hi Folks,

I have 22's on my S. Currently have 245/30/22 and 295/25/22 tires on it, but am considering moving to 285/30/22 in the rear to give a bit more "sidewall meat" to insulate against bumps.

My question is - that will give me a 5% difference in tire diameter front-to-rear. On some AWD vehicles, that's acceptable. On others, it has to be almost exactly the same or drivetrain issues will arise.

Obviously ours are a bit different, with two entierly different motors....but my question is, will a 5% difference in diameter have a negative effect on any of the electric drive systems?

 

[serendipitous]

I expect there would be no issues. As you said, there's no mechanical connection, so no differential or slippage or other issues like other AWD cars. And secondarily, the drive system (in my experience) functions not by targeting an RPM of each motor, but by allocating power to the motors. In other words, it's not like it would try to maintain some motor output shaft or tire rotation speed - it just sends power or generates power from each motor and they spin up or slow down based on dozens of factors it doesn't need to care about. I think the traction control system would similarly adapt to the difference in ABS wheel speed sensors since there are already differences in tire diameters in the various OEM wheel/tire combos.

 

[Aggmeister2010]

the drive system (in my experience) functions not by targeting an RPM of each motor, but by allocating power to the motors.

Thank you, that's exactly what I was hoping to learn! That does make sense - the drive system is allocating power based on pedal position and that drives the motor at whatever RPM, and if you were on a long sweeping bend, each tire would be spinning different RPM anyway. So, I should be good!