I got new 315/75 R16 tires put on my truck a couple months ago and have been unable to get the speedo right since. I checked the spec sheet for the particular tire I got and it listed it at 615 revs/mile. So I went to the dealership and told them to reset the computer to that spec. It's still way off. So either: 1) they didn't change anything or 2) the 615 number is wrong. Do y'all have any idea which it might be? Does that number sound too high for this size of tire?

The problem is, I can't really go back and keep checking cause I already took it back once and had them double check it. But that was in conjunction with some other problems, they were running way behind, and I doubt they even hooked it up to the computer. So now I'm in another town for about a week and COULD take it to the dealership here, but I'd hate to pay the freaking $75 fee and not even know how to tell them to fix it. So...HELP please!!!

Thank y'all.

 

I forgot to mention that I paced myself on the interstate a few days ago and it was absurd. When the speedo said I was going like 75, I was really going 87. When it said I was going 65, I was really going like 75.

 

That sure sounds like they didn't do anything.

I bet, like most dealerships, they didn't know how to do it and didn't want to admit they didn't know how.

Or, less likely, they forgot to click "save" after they changed it.

Take it to the Dealer where you are and tell them you tried to have your local Dealership do it, but they failed,
they just might be nice and friendly and looking for a new customer and do it for free.


phox

 

The revs on a 315/75 should be 582.85. Your calculation appears to be for a 285/75 or 305/70.

http://www.stamey.info/Truck/TireSizeCalculations.htm


Chris

 

I didn't make any calculations. Here, look at the Trailcutter R/T here in my size. http://www.jetzontire.com/JetzonCatalog10_04.pdf

 

I did my calcs from my head, so I could be wrong, but considering your current results from pacing, I'm betting I'm closer than they are. It's easy enough to figure out what's right. Just take a piece of string and wrap it around your tire, as best you can, roll over it if necessary. Pull the string up until it meets the other end, mark it, then pull it out of there and measure it. Take that measurement and divide (5280 ft [one mile] X 12 = 63,360) / [your string measurement]. You'll then have the revs per mile.

Chris

 

Alright, I got it changed to 583 at an out of town dealership. They did it for free this time! :-D

 

Have you checked it yet? Like with the mile markers on the highway?

Chris

 

Yep, looks right! Thanks for the help guys!