Bicycle gears help?

Question

What are the best gear combination for a 21 speed bike?

Also in some gear combinations there is a clicking, and in others there isn't.

Answer 1

First, it might be beneficial to call the bike a 21 GEAR bike rather than a 21 SPEED bike since the gearing has nothing to do with speed.

Regarding the "best" combinations, there really aren't any. The idea is to shift gears as necessary to maintain your pedalling speed or "cadence". This will make the most efficient use of your energy as you ride.

There is one combination, however, that should NEVER be used on ANY bike. That is the big sprocket (cog is the word) on the back coupled with the big sprocket (chainring is the word) on the front. This causes a lot of stresses on the drivetrain and will cause premature wear.

The reason there is clicking could be several. First, the gears could be out of adjustment especially if it is new and has been ridden just a handful of times or if it was never adjusted in the first place. Second, many entry level bikes just don't have the ability to be adjusted so there is no noise. Third, the drivetrain could be dirty or dry (no lube). Finally (not REALLY finally- I'm just getting tired of typing) it could be rider inexperience and the sound may be normal.

Answer 2

There really is no "best" gear combination.  Bicycles have multiple gears to allow you to be able to pedal at your most comfortable cadence regardless of the terrain.  In general, a cadence between about 60 rpm and 100 rpm is best for most cyclists.  You will find your own best cadence is somwhere in between having your leg muscles burn (too slow) and your heart and lungs burning (too fast).

If you were to calculate gear ratios, you will find there are several redundancies.  This is not really a problem, it simply means you can shift up and down on the rear cog, without necessarily having to shift the front chainrings too much.

Unfortunately, not all gear combinations are usable.  When you hear clicking sounds it may well because you have shifted into a gear combination that should be avoided.  For example, you don't want to be in your big front chainring and your big back ring nor do you want to be in your little front chainring and your little back ring.  This is called "cross-chaining" and it puts a nasty side load on your chain.

Hope this helps.