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Author Topic:   MPH
phelps
Dirt Full Roller

Total posts: 58
posted March 16, 2002 09:31 PM
We are running on a 3/8 high banked clay track, just getting into street stock & I am wanting to know what gear to run. We are running 27x10-15 hoosier take offs 6700 to 7000 rpm. I looked in the tool box, but without MPH you can't figure it. So I guess my main question is what MPH do you think I will run? Oh ya, metric car 3200# .

redneck racing
Dirt Freak

Total posts: 276
posted March 17, 2002 02:06 AM
Take 3600xlength of track and divide it lap time in seconds. For gear ratio take the avg.rpm x the tire circumference and divide it by the avg. MPH x 1056 for tire circumferencce measure around the right rear tire. This is from Steve Smith STREET STOCK CHASSIS TECHNOLOGY book.

[This message has been edited by redneck racing (edited March 17, 2002).]

phelps
Dirt Full Roller

Total posts: 58
posted March 17, 2002 04:20 AM
I have no clue about lap times or MPH, thats what I need to know. I've asked around here & have got answers from 60mph-90mph. Thats a big diff.!!! I know you can't tell me exactly but I would like to have a general clue of where to start. There is a big differance between gearing it to hit 60 on the straights than hitting 90.

snowman
Dirt Maniac

Total posts: 140
posted March 17, 2002 09:01 AM
Phelps, I understand your position, You need to know one or the other. But,it is hard to anwser. Not only does one have to consider the length, Degree of banking,radius of corner,HP and car weight and suspension will make a major difference in the MPH. I would hate to be the guy who steered you wrong on such an expensive proposition.

I can tell you that at a local track 3/8 on the bottom, 1/2 on the top, medium banked, that the gears run are mostly high 5's to 6.0. I have a 6.0. 5.88 seem to be a common number for some,as they can achieve it using stock parts. With the roll out of the tires, figures out to 91 MPH.

This is for the stockcar class,which is no where near stock.

The purestocks probably do run about 60, so it is no suprise that you are getting replies of 60-90.

On another nearby track, 1/4 inside, 3/8 outside, 6.30's seems to be prefered,some run as high as 6.50. I personaly don't know thier RPM or roll out,so I couldn't say on MPH.

I hope something here helps, Perhaps if you posted the track and class that you will be running,Someone here will be familiar with it,and be able to provide a more difinitive anwser for you.

Good Luck

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