How do you calculate the gear ratio on a bike?

Answer 1

Divide the number of teeth on the pedal gear by the number of teeth on the wheel gear. If you have multiple gears to choose from, you then have multiple ratios.

If you are talking about a motorcycle, the same principle applies, but now you have more than one set of gears: the crank to countershaft primary set, the selected gear set, and the mainshaft to wheel set (if chain), or the two sets (mainshaft to shaftdrive and shaftdrive to wheel, if shaft drive). You need to multiply the ratios that are in series at any one moment of time to get the overall gear ratio from crank to wheel.

Answer 2

Multiply the number of gears on the crank with the number of gears on the rear axle. This will tell you how many gears there are, but if you calculate the actual gear ratios you'll often find that there are usually several duplicates. Generally speaking, a 27-speed setup will "only" give you something like 15-18 distinctly separate gear ratios.

Answer 3

Just fine, thank you for asking. The gears on a bike work just like any other set of gears, they allow you to trade power for travel - or the other way around. If spinning the pedals is too easy and you can't crank them round any faster, then a change of gears will make the rear wheel turn more WRT the pedals than before, bringing more resistance to the pedals and more speed to the bike. If turning the pedals is too heavy, then dropping a gear will make the pedals easier to turn on the cost of the rear wheel spinning a bit less for each turn of the pedals

Answer 4

Just fine, thanks for asking.

Bicycle gears do the same as gears do everywhere - they allow you to trade strength for speed, or speed for strength.

By letting the rear wheel turn at a different and adjustable ratio than the pedals, the rider can work at the same level of effort regardless of if he's heading up hill or downhill.

Answer 5

Count the number of teeth on the front and back chainwheel for a given gear combination on your shifters, and divide.

Answer 6

Basically you take the number of teeth up front and divide by the number of teeth on the rear. BMX gear ratio is usually around 2.75, but but some riders want something else.