Gearing question

pbassred

I understand how gears work and what they do so that leaves Google with little to offer. I'm struggling with "why".
I understand why most people are happy with a compact crank while some head-down pro-peloton guys and super grinders will want 54 teeth at the front. Its the cassette that bugs me. My CX bike has a 10 speed 11-32 cassette. since 11 is the fastest you can get, that's reasonable. The question is: Why wouldn't you want a 32 (or bigger) as your lowest? Why do road bikes stop at 28? What is the gain in less?

imposter2.0

pbassred wrote:

The question is: Why wouldn't you want a 32 (or bigger) as your lowest? Why do road bikes stop at 28? What is the gain in less?

The gain is in having a more usable set of close ratios for racing purposes where you generally tend to stay down at the longer end of the cassette. Although there's no particular reason why non-racing roadies should not select any ratio they prefer, according to where they ride and their level of fitness.

pinno

A compact 34 front and a 32 at the rear is about as low was you would want for the road. It's ostensibly a 'granny gear'. Off road is a different matter.
Unless you are XXXL, most can get up even the steepest climbs in 39 x 27 (even if your cadence is a little slow)

In pro terms, gear ratios will be changed according to terrain. 'Super grinders' or sprinters as they are more commonly referred to, will still have a high cadence and if Cavendish couldn't keep up in 54 x 11, then it's time to hang his cleats up.
On the other hand, Cav will be 'grinding' it out the back up the Galibier and he'll be no where near his 54 c'ring (even if he had one fitted). Those guys (the Tony Martin's and the Dagenkolb's of the cycling world have massive engines) but at 40mph, 54 x 11, is still a cadence of 90rpm.

I would like to know what gear ratio's were ridden by the pro's on some of the super steep stage finishes in last years Vuelta.

Interesting chart:

http://www.bikecalc.com

Gives you gear/cadence values.

benjamess

pbassred wrote:

I understand how gears work and what they do so that leaves Google with little to offer. I'm struggling with "why".
I understand why most people are happy with a compact crank while some head-down pro-peloton guys and super grinders will want 54 teeth at the front. Its the cassette that bugs me. My CX bike has a 10 speed 11-32 cassette. since 11 is the fastest you can get, that's reasonable. The question is: Why wouldn't you want a 32 (or bigger) as your lowest? Why do road bikes stop at 28? What is the gain in less?

Try going from first gear to third in a car on a steep climb. Similar thing with a 10 speed 11-32. Constantly adjusting speed and cadence to help with gear changes.

kajjal

Just choose the gears that suit you and your riding. Pushing too hard gears is no fun and causes injuries.

simon_masterson

It's becoming less relevant with more sprockets at the back, so the jumps are smaller, but seriously low gears require different mechs, and some people would rather 'look pro' and struggle up the climbs than fit a triple. Which is ironic, considering that they have been used on mountain stages. With that said, there's only so low you can go, and there will come a point at which you will have to grin and bear it/get fitter/get off and push. Just fit the gears that fit your needs.