Equipment Question

Eager Rider said:

try to custom build my next bike still new to the componets,..what is the difference when it says 10spd Cassette: 11-23, 11-25, 11-26, 12-25, 12-26?

Also when the say 170mm, 172.5mm, or 175mm crankset? and what difference does it make.

Each of those cassettes (rear gear cluster) will have 10 sprockets, with the range from smallest (highest gear) to largest (lowest gear) as indicated. So what your choices have to do with how high of a gear (small sprocket) to you want, how low of a gear (large sprocket). Only you can decide which is best for you given your front chain rings, your strength, and the type of riding you do. Some people (like me) give up the 11 tooth sprocket just because they can't push it except for significant downhill/35+ mph situations, and need a lower gear, and would rather have a slightly tigher cluster between small and large.

That said, if you change your mind later, it's not a huge, expensive deal to buy a new cassette and install it yourself, or have it installed.

The crankset numbers have to do with the length of the crank arm. If you're of the backward US crowd (like me): 170 mm = 6.7 inches; 175 = 6.9. So the difference is very small, less than 1/4 inch.. There are (probably) valid discussions about ideal crank arm length for a given rider and how it affects certain riding situations, but in my purely amateur opinion (1) the differences are very small if even perceptable and (2) you probably couldn't predict which length any individual will prefer unless that individual actually rides and compares. If you don't have an opinion, you're probably best to just follow your bike builder's advice.

The crank length will definitely affect your seat height, but you would only notice that if you were setting up identical bikes with different crank lengths.

Myself, I just ride whatever crank is on the bikes I've bought - I buy for the frame size and fit, and never have paid attention to crank arm length. Others are more sensitive, I don't dispute it, but it's never been a factor for me.

What about the Crank 50/34, or 53/39?

Eager Rider said:

What about the Crank 50/34, or 53/39?

Get the 50/34. I have been riding for some time but rarely ever use my 52 tooth large ring with the smallest sprockets in back.

Bear in mind that high RPM gives efficient power output. You want to be pedaling about 90RPM, or almost as fast as you can without causing your hips to move up and down.

Then again, I never bomb down hills at 40 or 50 mph. apparently some do.

Eager Rider said:

What about the Crank 50/34, or 53/39?

- refers to the numbers of teeth on the chainrings (ie , the gear wheels
on the crank).

- the smaller they are , the easier it is to pedal.

- small chainrings are sometimes called "compact".
.

EagerRider, given the kind of questions you are asking, I'd think you should study a bit more before jumping into your first build. A good place to start would be through Sheldon Brown's site.

http://www.sheldonbrown.com/