Tire upsize?

I went from 265 to 285's and I pull mine just fine. I have a 35 ft TT and it weights in at 8500 lbs.

I went from a 265 to a 285 both series 75 and it was a terrible mistake - even with extra power. Then I went to a 285/70 and it works well. (our TT was 7300#)
If you tow, don't go much bigger in dia or it will suck.

Larger tires will change the effective gearing by an amount proportional to percentage of the diameter. That may be a small amount. However, larger tires weigh more. Your OEM tires might weigh 50 pounds each while the proposed 34" tire weighs 65 mounds. You will likely feel that in terms of more fuel used, increased brake wear, and slower acceleration.

I experienced exactly this with my prior tow vehicle. It sure looked sweet, but going back down to stock size really woke the truck up.

You are talking maybe a half inch over all Siam difference. Your 3.73 might now be a 3.6-3.65.....3.55 at tallest. A 2" inch taller tire would put you at a 3.42 effective ratio.
Your rim will not matter, as both tire sizes are 275mms wide. Only difference is that sidewall height.
Marty

The sizes you list are only going from a 32” to a 33”. The upsize tire will have a slight effect but I doubt you'll even notice. You'll have no problem with your 7k tt. Even with 35s you’ll be fine. You’re not even towing half of what your stock truck is rated for. When you go 37's+ you want to consider regearing as the change is significant.

I have 35's on my truck and the only difference is a slight drop in mpg. Less than 1mpg difference which I blame more on the aggressive AT tread. I did have the speedo corrected and lifted the front (2" level) so they don't rub. Biggest issue is visual. Looks great without the tt but it sits slightly ass low with the tt hooked up since it doesn't have the factory rake anymore. Could add a spacer in the rear or add bags but it doesn't bother me for the few times a year I tow.

Iraqvet05 wrote:
The OEM 275/65/18 Continental tires on my F250 are well worn at 33k miles. I have been debating up going with a taller and/or wider tire to fill the wheel wells a bit more. Much of the info I find on the truck forums involve guys trying to stuff 37" tires on a factor truck but I don't want to go that extreme. I understand a taller tire will throw off the speedometer a bit but will a 275/70/18 (or similar 34-35") tire effect towing my 7000 lb trailer? I have the 3.73 gears.

Yep. You are in effect changing your rear gear to a higher gear. So that will hurt your towing ability. Your truck will have to work harder to do the same thing. You are giving up MPG, and power, and torque.

Go up in a gear, go down in towing ability. You need to look at wheel width when going up in tire size. Often times a bigger tire is going to need a wider wheel.