Steve,
I think somehow you got the first formula mixed up a little;
>Some handy formulae:
>
>rpm@60mph=
>(mph)*(revmotor/revaxle)/((60min/hr)*(revmotor/revaxle)*(miles/tirerev))
>
The differential ratio, which you indicate here by "(revmotor/revaxle)"
should only be in the denominator. You don't make this same mistake when
you re-arrange the equation in terms of speed. Also, the first equation,
when corrected, is good for all speeds, not just @ 60 mph.
Bob
At 09:55 AM 3/26/99 -0800, Steve Laifman wrote:
>Tigers,
>
>With the talk about speedo calibration, I thought I'd dig up
>some of the "rolling diameter" given by tire companies.
>Now, these assume the wheel width is appropriate for the
>tire aspect ratio ( 98, 95, 70, 60, etc.) as the diameter
>will decrease if it's spread too far. Most are appropriate
>for the Tiger, in the moderate width ratios.
>
>Per Mike Taylor (page 223):
>Stock Original Tiger-
>
>Tire Circumference 15.90x13
>D (in.)= 23
>Miles/rev = 0.001140413
>
>
>Popularly used:
>
>Tire Circumference 185/70R13
>D (in.)= 23.2
>Miles/rev = 0.00115033
>
>Some handy formulae:
>
>rpm@60mph=
>(mph)*(revmotor/revaxle)/((60min/hr)*(revmotor/revaxle)*(miles/tirerev))
>
>mph=((revmotor/min)*(60
>min/hr)*(Miles/tirerev))/(revmotor/revaxle)
>
>(miles/tire revolution) = (3.14159*rolling diameter,
>inches)/(12*5280)
>
>mph @ rpm = ((rpm*60)/(gear ratio/rear end
>ratio))*(3.14159*rolling diameter inches)/(12*5280)
>
>This last formula can be used to calculate the (mph/1 rpm)
>for each gear. Then, just multiply this number times the
>rpm in any gear, and you've got the speed in that gear at
>that rpm.
>
>
>For those not familiar with equation notation used in spread
>sheets:
>
>Notation: "*" is 'multiply'
> "/" is 'divide'
> Procedure:
>
>Always solve for the number within a set of parentheses
>"(12*5280)" before applying that result to the next
>operation. That's why you see "(( " multiple parentheses.
>There should be an equal number of ones facing one
>direction, as the other or the equation is incorrectly
>formatted.
>
>These can be plugged into a spread sheet, with the proper
>cells referenced, and curves of the resultant speed vs rpm
>can be made. Pick your shift points by knowing your engine.
>
>Steve
>
>
>
>
>
>Steve Laifman < One first kiss, >
>B9472289 < one first love, and >
> < one first win, is all >
> < you get in this life. >
>
>
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>
Robert L. Palmer
Dept. of AMES, Univ. of Calif., San Diego
rpalmer@ames.ucsd.edu
rpalmer@cts.com
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