245 vs 265

I'm thinking about upgrading the stock 245's to 265's on my 2500HD 6.0/4.1. Will this be enough of an increase to see any power loss? I don't want that. When I went from 265 to 285's on my 1500 I noticed some power loss and a drop in mileage. Alson, how much will the 265's drop the rpm's? Could there possibly be some gains in mileage?

If you go from a 245 to a 265, I guarantee you will see a loss in both virtual mileage and actual mileage per gallon. First, if your truck had stock 265's with 245's added later, you mileage would seem a lot better, because your truck thinks it is going more miles than it actually is. However, if you are used to driving on 245's, and switch to 265's, your mileage will automatically decrease if you were never taking into consideration the smaller diameter tires. Also, it takes more torque to get a 265 going versus a 245, due to the smaller diameter. All things to keep in mind.

I did this upgrade on my 2500 and there didn't seem to be a significant power loss with the 3.73 or any difference in mileage. With the 4.10 you won't notice anything. The larger diameter and heavier mass pretty much cancel each other out. With the heavier axles and transmission of the 2500 the relative difference is much less than in a 1500. My boss has the same truck you do with 315/70's on it and it moves just fine.

245 to 265 will should be none. You will not lose mileage b/c this is tire width, not height. if you change from say a 70 series tire to a taller size you will have to change your speedo.

I'm pretty sure that the 265/75 is not only wider, but taller as well compared to the 245/75. I tend to agree with the earlier post that with a 4.10 rearend I wouldn't think that a little increase in tire size would effect the power much. Geez, this thing runs 2400 rpm's at 70 in OD! My 1500 with used to run at around 2100. There's nothing wrong with the stock tires, they just look so puny on a heavy CC pick-up.

I'm running 265's on 17inch wheels with 4.10 gears. My tach's running at 2200rpm at 70 mph. Lots of power and good mpg with a 5.3L auto 4x4.

I have 265's in place of my original 245's on both my Silverado and Suburban. Both of them are 2000 4 wheel drives with the torsion bars cranked to level. In both cases there is not any appreciable difference, other than the fact that the trucks look much better in my opinion. I might even try 285's next time around. Hey, in the snow, tall and narrow is the best way I know to keep the shovel in the butt end of the truck vs. in my hand!

245 to 265 will should be none. You will not lose mileage b/c this is tire width, not height. if you change from say a 70 series tire to a taller size you will have to change your speedo.


You are wrong. 265's are taller than 245's, depending on tread depth, by as much as two inches taller. Therefore, if a truck like mine came original with 265's and had 245's put on it, the speedo would be off. When I bought my truck used, it came with 245's on it. I knew the weren't stock because inside my door it said OEM was 265. My speedometer was off like 4-5 MPH and I noticed a difference of about 9-10% in miles. With 245's, if my odometer said I traveled 320 miles in a trip, I actually only traveled 300 or so. So, to figure out my actual gas mileage, I multiplied total miles by .09 and figured it out that way.

i did loss power when i got 265

The 265s are not so much bigger that the size or weight will cause a loss of power. But since the tires are taller so it will have the effect of lowering you gear ratio slightly. This will give better gas mileage,but you can not accelerate as quickly, so it feels like the truck has less power.

When I bought my HD used, the dealer already upgraded it to 265's. They looked better, but I traded them in for 285 Yokohama's. Looks much better now, and still tows great with the 4.10's. (about 3.80:1 effective ratio with the large tire) The milage is about the same (14 mpg) after figuring the odometer difference. I can still tow an open car hauler 70 mph in o/d (tow/haul mode) at just 2000-2100 rpm and the trans temp stays low.

Anything less than 4.10's I'd recommend a gear change when going up 2 sizes. I did the same tire swap on my last truck with 3.42's and it sucked. No more towing ANYTHING on o/d, and the milage went down the drain.