255 vs. 285 - effect on power?
 

Can someone help me out here, I'm new to the whole putting larger than stock tires on thing? I'm looking to go with 33's, 285/75/R16 or 255/85/R16 to be exact. I realize I'm going to see a drop in power, but what affects this most, the weight of the tire or the radius? The 255's will be slightly larger in radius but obviously a fair bit lighter. Can anyone tell me how much of a difference I'll notice between these two tire sizes?

Oh, by the way it will be a 6sp if it matters. I say "will" because I'm in my sixth month of waiting.

Tires have no effect on power.

Tire diameter changes your overall mechanical advantage. If you are running 2500 RPMs in 6th gear at 60mph right now and you put larger tires on, you might be running 2500 RPMs in 5th gear at 60mph instead, but your engine will be working just as hard and outputting just as much torque, and burning the same amount of gas as before. You'll lose some of the advantage of 1st gear, but I haven't heard too many people complaining about their 1st gear performance. Don't worry about what gear you're in, worry about keeping your RPMs in their happy place, and you won't notice the difference. They will negatively impact your crawl speed though.

Tire weight increases the rotational inertia of the system (like adding a heavier flywheel would). It resists changes in speed more. This means it takes more torque to increase speed and takes more brakes to decrease speed, but it also means that the Jeep will want to keep moving when you want to crawl over a rock at slow speed, rather than stalling.

-E

I guess what I meant was perceived power, not real power. I hear everyone talking about how sluggish it feels with larger tires and I'm just wondering if the weight difference between the two sizes will make much of a difference in this perceived power. Thanks for the response.

I think this is mainly because people think they are losing something by not being in 6th gear all the time, when in realty they aren't. They are shifting by vehicle speed rather than engine speed (I'm going 70mph, I should be in 6th gear!).

-E

To be perfectly honest...and I'm not sure if anyone else has anything to chime in with, but just recently put 295/75R16's on my unlimited and although it is a little slower off the line then my previous tires, once rolling, acceleration isn't an issue and the engine is completly stock. Seat of pants feels like the rolling accel is actually quicker. I have NO regrets to going with the 33's! Now I just gotta get my BB done!