Cassettes? Gears? Numbers? Help!!!!
 

I'm number challenged! What do they mean? I have a 12-25 (cassette?) on the back and 39-53 (gear?) on the front. Do these numbers refer to the teeth? As an example: The back cassette(?) has a small ring with 12 teeth and the largest has 25 teeth? The front gear/chainring(?) has 39 teeth for the smaller ring and 53 teeth for the larger?

Help me Mr. Wizzzzzzaaarrrrd!

Yup, you've got it maniac.

Any other questions you need to answer for yourself? ;)

peace,
sam

Yep, got it...

The larger the front ring the faster your rear wheels turns, the smaller the rear gear the faster the rear wheel turns.

I.e. 39-25 (39 teeth front and 25 teeth rear) is the smallest gear, 53-12 would be your highest gear.

So what's your question? power/speed/ease of riding?

Gears up front are called chainrings or chainring sets for a double or triple.

Gears in back are called cassettes or cogs. It used to be you would make your own sets of gears in the rear and pick a series of cogs and mount them on a cassette like assembly. Each circle of metal here is called a cog. Now you just change one of the sets which you need new gears in the rear.

A 12-25 cogset is pretty much standard; a good average. Touring or climbing cassettes may go up to 32 teeth, the normal limit for most rear derailleurs. Strong riders and racers may prefer a cogset that goes down to 11, with a 53-tooth "big ring".