daverr

iTrader: (1)

im trying to figure out what would be the best rear gear ratio for my setup.i find that at the end of the quarter mile ,my motor is spinning at about 5300 rpm.my motor achieved max hp on the dyno at 6600rpms. so i need to bring my motor up to 6600 rpms at the end of the quarter mile. i figured i need a 4.27 ratio using this equation (3.43/5300 )* 6600=4.27 .is this ratio correct for my car.

IHI

iTrader: (1)

What size tires are you currently running, shift points, most common tire sizes are 26"-28", *depending on your power* it will be a little different. I used to have a 3.42 gear, running 26" slicks netted my 5K at the finish line, this year got 27" since in the beggining my gear was still a 3.42-still crossed at 5K. Installed a 3.73-still with the 27" tire and now I'm finally at 55K since my motor is ALL done @6 and I street drive when it's nice out. I've seen 4.11's put cars w/ 28" slicks anywhere from 6-68 at the traps.

daverr

iTrader: (1)

i have 26 in wheels.i shift it at about 6700 rpm.

AlkyIROC

With your current tires, 4.10 would be a good choice because the next jump is to 4.56 gears. I wouldn't recommend going to a deeper gear without more tire though. A taller tire puts more rubber on the ground from front to back. That improves traction better than a wide tire. The trick is to stuff the tallest tire you can into the wheel wells then calculate the best gear to go with those tires. A 28" tire will usually have no problems fitting depending on the width of the tire and the rim backspace.

Not all tire sizes are the same. I had some MT ET drag 28 x 9 tires and they were actually 27.3" tall.

My current tires are Hoosier 29 x 9, 4.56 gears, shift at 6800 and go through the traps around 6800.

Even though your dyno time says your peak hp is at 6600, that doesn't mean that's the top end. You actually want to go through the traps at or just above your shift points.

84zeddd

Try this one, (rpm x radius x .006 /mph=gear ratio)
ex. 6600 x 13 x .006 /110= 4.68
So here you would choose probably a 4.56 gear.

OMINOUS_87

Stephen 87 IROC


Do you have any experience running a 27" or 28" ET Street on a factory 16x8 rim? GTA crosslace wheel.

daverr

iTrader: (1)

thanks for the replys everyone. OMINOUS_87 i wouldnt recommend using slicks on the gta honeycomb wheels. for my gta i bought 15x10 welds with mickey thompson 26x10 slicks.

dave

OMINOUS_87

What would be the issue with running the stock rim?

AlkyIROC

I don't recommend any 16" rim. Buy a set of 15" rims and a set of slicks only for the track.

Hmmm. Using that formula, I should be using 5.37 gears instead of the 4.56's. I don't think that's right.

OMINOUS_87

I run 17" billet rims on the street. I have my factory rims just sitting in the garage, they would be only for the slicks. What is the reason behind your recomendation of not running a 16" rim.

AlkyIROC

Tall rims are good for street tires and road course racing where you want a short sidewall to prevent tire rollover in turns. A drag tire wants a tall sidewall. It helps the tires launch better. A tall rimmed tire would have a very stiff sidewall since there is very little sidewall in a factory style tire size.

15" rims also have a much better tire selection available.