Hey all:

I just put BFG gforce KDWS's (245/55/18) on the R/T stock road track rims. They fit well and look great. AA Traction, 400 treadwear and hopefully more durable than the Michelins (which were not too bad but really expensive).

I had programmed the stock tires with the Superchip to 27.5 inches (from a thread I can't find now).

Tirerack says:
OEM = 28.4 diameter
new = 28.5
Mazda.net says:
OEM = 28.2
new = 28.6

Of course each manufacturer is different, but I'd like to be in the ballpark.

At 28.5 it seems the speedo is a little fast, but it doesn't seem like a huge difference from 27.5.

Any thoughts on what size to program?

Thanks as always

 

You’re doing the right thing and have a close calculation what the tire diameter should be. There are several ways to to fine tune, the easiest is to pace with another car and adjust from the speed difference.

 

Thanks Mango -- I did just that. It seems to be about 2mph off (fast). So it looks like I hit it pretty close.

Hope all is well with you in TX....

Again, thanks for all the help

.SG.