Discussion: Gearing

There's one more factor to take into account besides the number of teeth on the chainwheel and cog, and that's wheel diameter. Get a tape measure and compare the diameters of your road bike and mountain bike. I can't remember what you have, but if the diameters are different, you have to calculate that in as well (and also on the new bike). A larger wheel makes for a higher gear.

Ah, good point. And I'm assuming it's the rear wheel size that matters...

Unless you're on some sort of odd bike like a recumbent, your front and rear wheel sizes should be the same.

Well, specifically, it's the drive wheel that matters, though front wheel drive bikes are even more rare than recumbents. And Clint is right that most bikes have matching wheels front and back, but my brother and I own a bike very similar to this one:

Finally, for effort you need to include crank arm length. Longer cranks give you more leverage. But then you need longer legs, too.

You're probably most comfortable if you have the same crank length on all of your bikes.

Does it make a difference if the owner of the legs is a crank?