gear ratio

[Chuck Houin]

i know gear ratio is gear ratio but would like to take it one step farther. How do you figure when you add tire run out to the equasion.(tire diameter) if you put on a smaller diameter tire I know you lose top end speed and larger tire gains top end speed but say you changed tire circumfrence smaller by 1/4" how many teeth on the rear sprocket do you have to change to keep the same top & bottom speed?and what would the gear ratio be then?

[Marc Miller]

I used to know this equation off the top of my head - but always remember that adding another 1/4" of rollout on the tire was similar to taking off a tooth or half a tooth... I can't remember.

For road racing, it would roughly change 150-300 RPM - which was that range... for sprint racing, it should be very similar.

The best way to decipher is to set your gear and run on current tires, mount up a new set that are smaller or larger and note the RPM difference. Rule of thumb is a full tooth is about 150-200 rpm - so you can calculate it that way.

[Rick Zellers]

Chuck

Check this link out for calculations

http://www.pegasusautoracing.com/karting-top-speed.asp

I do not buy parts there but I borrow their info

Rick

[Richard Gray]

Here is a nice, useful, easy-to-use, free software package that allows you to investigate tire circumference, gear ratios and all sorts of "need to know" information. I think you'll find it interesting and it sure helps.

http://www.gregorybraun.com/KartData.html