[tgriffith]

wade,,Ive done alot of testing on tire sizes.....what I have found through the years is it just really depends on your car.

Automaticly, the tire size of a larger rollout tire should result in in quicker ETs BUT and I say "BUT" how it actually works on the track is a different story.

the first thing to consider is how much rolling weight affects your car.....Big Hp cars dont see as much of a difference as a slower car.....in theory, Ive been told that for every 1 lb of rotating weight = 5 lbs of weight on the car and since its directly on the front,,,that makes a bigger difference on a lower HP car.

another big factor is transfer of weight......if you have a 25 tire vs a 28 tire on a big hp car, your taking nose weight off the car and in turn helping it hook better but how it works out on the track again is different because even though you have killed rotating weight,,,you have dropped the front end a couple of inches so what does that do???

here is an example on a car that I had,,,,I was having issues going red, so I stuck on 28`s in place of the 25s I had on the car,,,,,it got worse??? and also was slower??? didnt make much sense.....I also picked up .04 in 60ft but by 330ft, only .02 and by the 660 mark was even with a reduction of 1mph,,,,in the 1/4 was down .04 and almost 2 mph...

after testing numerous runs and switching back and forth,,,was getting consistent results and here is what I believe was happening,,,,,with the bigger tire,,,more rollout AND car was raised was planting the tires better....thats why the 60 was better than what it should have been....BUT the extra weight of the tires and the loss of aerodynamics cause an incremental et loss down track. ANd because I was getting the nose out off the ground and planting the tires better, the car reacted quicker and thats why the red light got worse.....this car was a 85 camaro with a 305...at the time it was E/F fuel injected at I think, about 3500lbs.

On my vega,,,,(bracket car) she will run about 5.90`s and the difference between 24`s and 26 is almost non existing,,,may .01 quicker in 60 and carries that down the line..

the best thing I can tell you is if you dont have to spend a ton and have access to different sets,,,the only way to know for sure is just test them. BUT if your looking for ET gain,,dont automaticly see a difference and settle with it. With the camaro, I did finally settle on 26`s and with some twiking with front end height, tire pressures got the car quicker than it was and tuned in the RT`s......also different manfactors have different weights and tire sizes.....for example,,,I have a set of new goodyears 27x5 that when on a rim, look like mudgripps......the same set of hoosiers are much smaller as width and weight

hope this helps