Hi Guys,

Got a new (to me of course) 08 CTT here. Vehicle came with the Sport Techno 20's in staggered sizing with 9's up front and 10's in back.

It currently has 275/40/20's all the way around as it came from the factory. I'm sure they did that to keep the total diameter the same front to back for the 4WD system.

To my eye the 275's look too small on the 10 inch rims so I want to do something about it. My plan would be to put 315/35's on the wheels which would result in a total diameter of 728.5mm on the rear. The front 275/40's would remain as they currently are, 728mm total diameter.

Assuming my math is correct, does that 1/2mm in total diameter difference potentially pose a problem for the driveline?

I see someone here has already done it but no feedback on issues.

Thanks!

 

In short, the key to aftermarket diameters is to install diameters within +/- 3% of OEM. Beyond +/-3% may produce an ABS malfunction. With that said: a 315/35/20 would not pose any issues. In fact, the diameter difference is a mere .07%. However, a 315 is better suited for a 10.5 - 12.5 rim width. 305/35/20 @ a .89% difference would be my maximum. Good luck.

 

Thanks for the feedback Ruben. I figured shooting for the minimal difference in diameter was the best way to assure no issues but I didn't realize a 315 does seem to be too wide for a 10 inch rim (based on math).

Oddly though, the photo I posted from another user here is a 315 on a 10 inch rim and it looks like the same sidewall bulge as the 275 on the 9 inch front. So I don't know if it's enough of an issue to warrant the added rotational difference of the 305 option you suggested.