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## Fwd: RE: TOP SPEED AND RATIOS

 To: "spridgets@autox.team.net" Fwd: RE: TOP SPEED AND RATIOS Bob Van Kirk Wed, 15 Mar 2006 19:11:01 -0800 (PST)
 ``` Here's another guide for figuring ratios and speed thanks to Glen Byrns. >From: grbyrns@ucdavis.edu (Glen Byrns) >To: "Robert Van Kirk" >Subject: RE: TOP SPEED AND RATIOS >Date: Mon, 12 Jun 2000 22:42:32 -0700 (PDT) > >Here's how I figured my theoretical speed at various rpm's: > >Mark a spot on one rear tire and roll the car so the mark touches the >pavement. Mark the pavement at this point. Roll the car forward with you in >it (for highest accuracy) until the mark on the tire is again on the ground. >Mark this spot and measure between them. This is the distance the car moves >forward for each rotation of the axle, call it "C". In my case, C=69 5/8" = >69.625". > >With a 4.2 rear end, the drive shaft will turn 4.2 times to turn the rear >axle one revolution. Assuming a fourth gear ratio of 1:1, then at 6K rpm, >6000/4.2 = turns of rear tire per minute = 1428.72. Multiply by 60 to get >turns per hour, = 60 x 1428.720 = 85732.2 >This number times the number of inches forward for each turn you figured out >earlier(C)tells you how many inches forward for each hour at 6k rpm in >fourth. Divide by the number of inches in a mile(63360) and you should get >miles per hour. > >{(rpm/rear end ratio)x 60 x C }/ 63360 > >So for a 4.2 rear end, 69.625 inches per turn of tire, fourth gear: >(6000/4.2) x 60 x 69.625 / 63360 = 94.18 mph, at 5k rpm = 78.49mph Tired of spam? Yahoo! Mail has the best spam protection around ```
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