Hi Rex,
In a message to All you wrote:
 RC>  Hello All
 RC>  Anybody know the formula to get a theoretical speed from given -
 RC>  rpm,tyre size, axle ratio, gear ratio..
It's all multiplication and division.
Divide engine RPM by the gear ratio of whatever gear the transmission is in 
to get the driveshaft RPM. Divide the driveshaft RPM by the axle ratio to get 
the tire RPM.
Multiply the tire RPM by the circumference of the tire in feet to get the 
speed in Feet per Minute. Mutiply this result by 60 then divide by 5280 to 
convert to Miles per Hour.
For metric multiply the tire RPM by the circumference of the tire in 
centimeters, then multiply the result by 60 and divide by 100,000 to get 
kilometers per hour.
 RC>     Whats its relation to 4Dos ?
 RC>          4Dos math functions!
4dos is more than capable of making the calculations.
Later
Tony Dunlap, (tdunlap@odot.dot.ohio.gov)
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