Yes, within certain limits. Tire circumference varies from brand to brand and with wear. That has an effect on the results. You need to know the primary drive ratio, gear ratios, final drive ratio, and circumference of the drive wheel the calculation for speed is:

MPH = 60 * RPM / primary ratio / gear ratio / final drive ratio * circumference in inches / 12 / 5280.

A little algebra will let you figure RPM from MPH. For my '05 with an assumed rear tire circumference if 79.38 inches I'm going about 35 MPH in 3rd gear at 3000 RPM.

My assumed tire circumference is calculated from the needed rear tire size of 150/70 17.

 

Thx guys. I'm being lazy now ...has anyone already worked it out for a GS?

 

Sure. Where do you think my numbers came from.

Well, I worked it out for my '05. The numbers might have changed for an '08.

 

Cool thx Marc