Spider speed vs rpm

[LEN_LEEB@xxxxxxxxxxxxxxxxxxxxxxx]

     My apologies to Jaap in Holand. I attributed Alan's post on speed vs 
     rpm to Jaap. Been trying to catch up on my digests, and read the 
     latest ones first!
     Alan wrote:
     >>>>Snip....
     Using the formula above, I'm coming out with 19.58 mph per 1000 rpm, 
     or 78.32 mph at 4000 in fifth.---seems too high, or else everyone else 
     on 280 (at least the fast ones) is doing over 80mph.--
     ======================================================================
     Regards,
     Alan G. Lambert___________________________________<gerard@domain.elided>
                *******Los Altos, California (office)*******
     In my Spider, the rear end ratio is 4.1, and using approximately the 
     same size tires, I get 22 mph/1000 rpm in 5th. Taking Alan's ratio of 
     4.556 divided by my ratio of 4.1 and dividing that number into the 
     speed per 1000 gives about 19.8 mph/1000 for the higher ratio rear 
     end.  So, at 4000, you would be doing about 79 MPH. The only sources 
     of error are 1. tire size, and 2. tach calibration, and 3. tach 
     reading error. The other factors are fixed, ie, gearbox and axle 
     ratios. So the best advice is to find a section of road that is 
     measured, try to hold to 60 mph, and time the run from the start ot 
     the end of the mile. The time should be exactly 60 seconds if you hold 
     60 mph. Less time = higher actual speed, or speed = 60/time.
     Len
     

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