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I run about 50k miles a year over a 65mph highway. I would like to improve mpg for cost reasons. Ive read about how going from 4:10 to 3:42 can get you 20+ mpg, but havent wanted to deal with cost or shop work to change over. WHAT I WANT TO KNOW, is can you get the same effect by just putting on larger tires? Shouldn't for a tourqe happy diesel, this be a good thing? (aside from having BIG tires)

http://www.dieselplace.com/forum/smileys/Big Smile.gif PROs vs. CONs? http://www.dieselplace.com/forum/smileys/Unhappy.gif How would it change drivability?

The thing with tires is that bigger mean more contact surface with the road, more aerodynamic drag and more weight. Those factors will nullify some if not most of the benefits. I've heard of some people having limited success with 235/85 tires wich are available in 10 ply.

My personal experience goig from 245/75 to 265/75 is that it is about the same. My reasons were different however, I needed the 800 lbs more in capacity on my rear axel.

I posted this in the 2500 & 3500 trucks forum:


You could go to a 255/85/16 tire. It is a tad taller than a 285/75/16 by about a half inch and wouldn't be as wide and thereby eliminating the 285's huge rolling resistance. This would be better than going to the 3.42's. As Camstyn said, with 3.42's the truck probably couldn't pull itself out of it's own way until you got going on the highway. I think that any benefits gained by going to the 3.42's would be negated by the decrease in town-driving mileage. Case in point, my brother's 99 1500 5.3 gasser picked up 2 mpg when he swapped up from 3.73's to 4.10's.....go figure.Edited by: Heartbeat Hauler