bigger diameter tires..faster?
 

ok so im lookin at 255/45r20 tires and i want to know if the take off/1/4 mile of the truck will be faster with the larger diameter tires i will have really heavy rims in the truck though aswell so im not sure if the weight would have anything to do with it but there 20x8.5 in. rims that weigh 37 lbs each so there a pretty thick chunk...what do u guys think

RE: bigger diameter tires..faster?
 

Actually, the closer the rotational moment of inertia is to the outside diameter of the tire, the more difficult this tire/wheel combo will be to accelerate (and decelerate). So now since you have a large, heavy rim, your acceleration and braking will both suffer because of it. That is why just about anyone that does a big rim/tire combo upgrade should also attend to the braking concerns of the vehicle.

If the rotational moment of inertia were the same between your stock rim/tire and the ones you were switching to, but the new combo was larger in diameter, you would effectively change the overall gear ratio for the worse. This would make you loose speed off the line, but gain it at the other end of the track. Now would you gain enough at the opposite end to make up for the lost time at launch, probably not. You would most likely see a slower 1/4 mile time with an increased 1/4 mile trap speed. EX: stock you might see 17.1sec@79mph and with the larger rims you may see 17.8sec@83mph (completely made up numbers!).

RE: bigger diameter tires..faster?
 

if your going to go with a bigger tire and want your acceleration to be the same then go with a lower gear the only drawback is that the lower the gear the less top end speed you will have but u will get there quicker and since you have a 4x4 you would have to do the same gear in front and rear i think you have 3.08 gears a good gear ratio would probably be like a 3.73 or even a little higher

RE: bigger diameter tires..faster?
 

I have a 2000 LS and my stock ratio is 3.42 should be the same for '01. And he would have to go lower than 3.73's. I would guess something above 4.10's ??? but that is only a guess since I have not researched the diameter of the 20's.

There are sites out there that will help with that but I would do a search for them...