The racing manual gears for F&S chassis, and the ZX chassis. You will find that the chain lengths are different also. The new ZX chassis in most cases use the 76 link chain, and .83-1 gear ratio. Which sled do you have?
If I follow your question correctly...the speeds are theoretical. When drag racing you don`t want to be in OD or .83:1 for best belt efficiency. For top speeds and lake running the overdrive comes in handy. Gearing is usually a higher ratio than the sled can use (lower numerically). The thought is that gearing changes that reduce ratio limit top speed. In some cases it may increase top speed. The chaincase gearing multiplies TQ to the track. You can easily get too much TQ to the track by droppig too far. In one case a 1 tooth drop on a 583 from 22/40 to 21/40 netted an increase of nearly 10 MPH top end observed on the speedometer. The reduction of ratio allowed the clutching to perform to it`s fullest for the general weight and riding conditions. I`ve found the gearing chart to be "optimistic" overall, but also feel that the lower RPM numbers are closer to reality. Hope this helps.
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