I have larger tires than stock (285's). Does anyone know how much they threw off my speedo and odometer? I've just been guessing 5 mph at 65. But it would be handy to know so I could figure out my actual mpg.
Thanks guys

 

My truck has 285's also, originally came with 265's, and as far as I can tell, it's dead on. I'm not sure if maybe it was calibrated incorrectly from the factory, but I followed my wife down the highway with cell phones and when she was reading off her speeds to me, I was always within 1 mph. If you went up from a 265, it's not that big of a deal, if you originally had 245's, I still wouldn't think it would be off more than 2 or 3 mph...just guessing though.

 

Would need to know your original size tires and your current size tires. Not just the width - the complete size.

 

Use the milemarkers on the highway. Divide the # of sec.it takes to run a mile into 3600 (sec. in an hour). 60 mph 60 sec. 80 mph 45 sec. Try to be consistant with speed. Do it over a few miles to insure marker accuracy.

 

I have 285's on my truck and its dead on too. I checked with the radar set-up deals they put out on the road and with other people and no problems yet. This of course with my truck coming stock with 265/75/16 .

 

I don't remember which tires my truck came with, but its a z71 so I'm guessing the 265/75/16's. In some ways I'm hoping the odometer isn't dead on because it's depressing calculating my gas milage when I fill her up. Any math wizz's out there that could figure this out? Otherwise I'll find a stop watch and put my truck in cruz control on the highway. Mile markers are the white stripes right?

 

use the calculator on www.eunos.com/tirecalc

 

Thanks black yukon that was exactly what I was looking for.