teej281

Well I'll just say this...with that much power there is no way I'd be taching out my stock shortblock to 6800rpm. I'd want to keep it below 6500rpm to save the shortblock. I still dont think that you need anywhere close to that gear, and actually think you would be better off with less.

uberstang1

Are you taking in account the larger diameter of the 28inch tire compared to persay the 315/35. The 4.30 gear ratio is vastly different with a 28inch tire compared to the 35 tire. I don't think the RPM will be as high as you think passing down the 1/4, with a smaller sidewall tire maybe but with the 28 it should be equivalent to the car running a stock wheel and tire with a 3.90 gear ratio.

uberstang1

This is a guy with a 03 Mach 1 with 360rwp. Hes running a 4.30 with a 315/35/17 and crossing at 6400. With a larger diameter tire like a 28" it will be crossing at a lower RPM.

teej281

I'm using cliffy's calculator and the numbers it's giving me. Go ahead, try to say cliffy is wrong. I plugged in a 325/50-15 wheel size and a t45. Check it for yourself. Plus you're gonna be trapping around 120 if I guestimate right.

uberstang1

According to the calculator at 6500rmp Ill be at 121mph, plenty of room left for a car that redlines almost 7k. I have no fear running the car to 6500 because I've always taking it above 6500 on the street. Also the calculator is calculating the 325/50/15 as a 26.9inch tire. If the calculator is off and the 325/50 is a true 28 inch tire when you recalculate with the 28inch OD it changes everything by a good amount.

uberstang1

Mathematically a 325/50-15 should be 27.25"x12.25"...however given that its a radial I'd figure the tread would wrap a bit and be closer to a 28x10.5-11