Well..., now that I have the Turbo Pinto "running" (sort of) I need to contemplate tires sizes. For the record I have the following:
1973 Wagon
1988, Intercooled, Turbo Coupe engine (otherwise stock)
T-5 with a 3.97 / 1st - .85 / 5th
3.00, 8" rear end
15" wheels I would "like" to use (if it is not an issue)
I'm not looking to make this a drag car. When I finally found a 8" rear end I actually had a choice of 3.00 or 3.55 gears. I opted for the 3.00. At the time my rational was: gas was $4.69 a gallon, the T-5 has an extremely low 3.97, 1st gear and the Pinto weighed 1,000 pounds less than the T-Bird. Thus, the 3.00 gears were compensated for by the lost 1,000 pounds.
Anyway, for the time being I'm using the T-Bird's 225-60-16" tire with the 3.00 rear. While I wouldn't call it a horrendous bog, it doesn't move out quite like the 1,000 pound heavier T-Bird did. But then, the T-Bird had 3.55 gears, - now didn't it.
So what I'm hoping to find is a tire size that compliments the 3.00 rear end, but it also factors for the 1,000 pound the engine no longer has to pull around. I would like to find the Turbo Coupe 3.55, 225-60-16" like performance, but hopefully at a somewhat lower RPM because of the weight reduction.
To complicate the matter I bought some wheels/tires on sale. They were 225-60-15" Unfortunately the tires have flat spots and are useless. But, having invested in the wheels I'd like to stick with the 15".
Here are some calculations I have come up with:
Baseline -
Stock 1988 Turbo Coupe 3.55, .85 overdrive, 225-60-16" tires = 2,525 RPM & 65 MPH (frankly my recollection was closer to 2,200-2,300 as the tach read, but what do I know???)
Proposed -
Turbo Pinto 3.00, .85 overdrive, 195-60-15" tires = 2,301 RPM & 65 MPH
OR
Turbo Pinto 3.00, .85 overdrive, 205-60-15" tires = 2,264 RPM & 65 MPH
And for what it is worth, the temporary current setup is -
Turbo Pinto 3.00, .85 overdrive, 225-60-16" tires = 2,134 RPM & 65 MPH
Anyway, I was hoping there is a Turbo Pinto owner out there running 3.00 gears and has found the appropriate tire size. I'm not into changing to a more "ideal tranny ratios or rearend ratios." That cost is not to be considered. What I am trying to do is purchase a tire size that brings back the stock Turbo Coupe performance (or better) but takes into consideration that it can be accomplish at a lower RPM because of the 1,000 pound weight reduction. My thinking is that the 195 or 205 - 60-15" tires will do that. If someone can speak from experience it would be greatly appreciated.
Pardon my rambling, repeating - I'm just trying to make sure that I can be understood as what what I'm asking.
Thanks, Tom
If you know the hight of any tire and rear end ratio, you can calculate with the link below but here are your numbers anyway based on a 205X50X15 tire size (22.8 inches high)@ 6000 RPM with 3.00 gears. I calculated high end to show you that I would go with 3.40s to use all of the gears. Otherwise you have a 3 speed with overdrive and one you don't touch. IMHO
I'm guessing at some of your T-5 gearing but thats why I put two 5th gears :fastcar:
T-5 Trans...
1ST 3.97.......34 MPH
2ND.2.34......58 MPH
3RD 1.46......93 MPH
4TH 1.00......136 MPH
5TH .85........160 MPH
or
5TH .79........172MPH
http://www.coastdriveline.com/htmlfolder/calculator2.html (ftp://http://www.coastdriveline.com/htmlfolder/calculator2.html)