View Single Post
Old 01-23-2017, 12:18 AM   #7
izzy_Britton
Registered User
 
izzy_Britton's Avatar
 
Join Date: Apr 2013
Location: Nor-Cal
Posts: 632
Re: Q- speedo off & bad MPG

Quote:
Originally Posted by 46stude View Post
Well, there's maybe an inch of height difference, which really isn't enuff to kick the speedo out like that.

And, it read the same with the 70s that were on the Burb when we got it. Forgot to put that in my original post.
not to argue, but just wanted to split some hairs... for information purposes, ya know?

245/75/16 = 95.72 in circ. 30.47 in height

265/70/16 = 96.15 in circ. 30.61 in height

265/75/16 = 99.43 in circ. 31.65 in height

What does this mean and how does this effect us?

the difference between a 245/75/16 and 265/70/16 is not noteworthy BUT...

If you change from 265/70/16 to a 265/75/16 that means that if your speedo reads 60mph, your actually moving at 62.05 mph, meaning a 2.05 mph difference.

If you change from 245/75/16 to a 265/75/16 that means that if your speedo reads 60 mph, your actually moving at 62.33 mph, meaning a 2.33 mph difference.

I am not a gear ratio kinda guy but I do know that changing the tire size changes your rear gear ratio slightly and that slight amount will undoubtedly change the way your ecm reads your tire rotation vs rpm, which would change your shift points and your speedometer reading. i dont know what the fullest extent of this all means just because i am simply thinking out loud but, i would assume that this means your fuel economy would change.

this would be the exact same as changing the rear axle for a different gear ratio, everything would change, drastically. 4x4 people would know a heck of a lot more than i could ever begin to understand.

-Izzy
__________________
WHO_DCTC - Wifes 05 Z-71 Build - Now defunct as she decided she wants an Escalade too
Cream Puff - LS'd Square - Slow going on the back burner
Tripple Threat - 3 Wrecks for the price of one build thread
Project Delongdium - Step-Sons Plastic Clad 2003 Avalanche - DONE and Delivered.
izzy_Britton is offline   Reply With Quote