Have a drive train light pop up on my dash after new wheel set up installed

[Germms]

I just got a new set of wheels and tires set up on my 2018 gt2 awd and then this light came on anyone deal with this issue? I'm thinking it might be the tire size difference running 245 front and 295 rear

 

[Snicklefritz]

It isn't the width that is at issue. You probably are AWD with disparate OD front and rear. Don't do that! You'll kill your transfer case.

 

[Germms]

It isn't the width that is at issue. You probably are AWD with disparate OD front and rear. Don't do that! You'll kill your transfer case.

Okay what do you mean by disparate OD front and rear are you talking about how the diameter should be the same or really close?

 

[95oRANGEcRUSH]

What are the dimensions of your wheel and tire setup?

 

[Germms]

What are the dimensions of your wheel and tire setup?

Wheel and tire front 18x8.5 et30 245/40/18
Rear 18x9.5 et40 295/40/18

 

[Snowwhite]

Rears need to be 295/35. Second number is a percentage of the first. 245*.45=98. 295*.35=103.25. 285*.35=99.75 would be a better choice for AWD.

 

[Germms]

Rears need to be 295/35. Second number is a percentage of the first. 245*.45=98. 295*.35=103.25. 285*.35=99.75 would be a better choice for AWD.

Gotcha so what matters more is the aspect ratio and keeping it as close as possible to one another whats the max that it could be for awd

 

[Snowwhite]

Sorry I typed 245/45 but the calculation is for 245/40. You can’t have more than a 1% diff between axles with AWD (or RWD, really…the traction control kicks in above a certain speed if there’s too big of a difference anyhow.)

 

[Snicklefritz]

Okay what do you mean by disparate OD front and rear are you talking about how the diameter should be the same or really close?

Wheel and tire front 18x8.5 et30 245/40/18
Rear 18x9.5 et40 295/40/18

Yes, really close to the same OD. Not 6% off. Your rear OD is 1.06 bigger than the front OD. No wonder your warning light kicked on!

 

[oddball]

Tire manufacturers publish an "effective rolling diameter" of their tires. You need those to be same on front and back for an AWD car. I'm surprised your tire shop didn't warn you.