s197richie

This thread might get moved, but its half tire-rated and half gear-related so I put it in general...anyway:

My gears should (!!!) go in tomorrow night, they're 4.10s and my xcal will correct the speedo for me. But, I also have 275/40r17 NT555Rs mounted up, replacing the factory 235/55r17s...so my true final drive will be a bit shorter, right? And the speedo may be a bit off? What should my true final drive and speedo error be with the drag radials? (not sure if the xcal will allow me to recalibrate for such a small difference in tire height)...thanks...

hammeron

to tired right now for the calculator, why not just
account for the new final ratio and then the new tire
dimension in your sct and be done with it




[IMG]local://upfiles/37808/F9CB303507994BC8803CB06D55C410AF.jpg[/IMG]

s197richie

okay, wasn't sure if the sct would correct for the aspect ratio going from 55 to 40, thought maybe it only did rim diameter changes, but looks like it will...thanks...
how about the final drive? Technically should edge it to a little shorter than 4.10, right?

jdmcbride

Stock tire diameter = 690mm or 27.2"
275/40/17 diameter = 652mm or 25.7"

The new tires will be 5.5% shorter than the stock tires. Your xcal will be able to adjust for the shorter tires.

D_Gusler

agreed, most deffinetely a cool feature on the XCAL

hawgman

Take the stock tire height, divide it by the new tire height, multiply it by the gear ratio. That will give you your true gear ratio

So... 27.2 / 25.7 * 4.10 = 4.33

moosestang

That's give me 4.0 gears with my 275/50/17's. Nice to know I could have 4.30's if I need them.

s197richie

thanks everyone...

Stoenr

Welcome to the 4th gear finishes on the strip.

moosestang

Do you have gears? I thought you had the stock 3.55's.