Gear ratios, are these normal, and is there a formula to use

daniel_b

Hi guys,

just checked the gearing on my Felt and on my gf's Trek.

Trek: 52/38 and at the rear 26/12
Felt: 53/42 and at the rear 24/12

I'm assuming that gives me a marginally higher top gear, but can't tell how a 42/24 compares to a 38/26

Is there some formula I can pump into excel to give me all the ratio's in figures that I can then compare??

Also, are both sets what you would expect, or is either bike missing out on high or low end.

Cheers

Dan

jibi

http://en.wikipedia.org/wiki/Gear_inches

http://www.panix.com/~jbarrm/cycal/cycal.30f.html
http://www.sheldonbrown.com/gears/


george

daniel_b

Thanks George, have worked them all out now.

What's a good combination for a fast downhill run on a roadbike, would it be best to up the size of the large front cog, and or fit an eleven to the rear?

Dan

nolf

If you up the size of a the front chainring, you'll find you rarely use it on the flat or ever except downhill.

You're better off just tucking in as I find even on my 50-12 I've got up to 50mph- I spun out at 35mph, but past that I just pulled in my knees, rested my hands on the top of the handlebars and pushed my chin down on top of my hands.

This will get you a lot faster than a bigger chainring.

If you really want to though, I would have thought you would be better off changing the rear casette as they cost less (I think) and you always have a spare with smaller gears for winter or if you wear new ones out.

oldwelshman

Daniel B wrote:

Thanks George, have worked them all out now.

What's a good combination for a fast downhill run on a roadbike, would it be best to up the size of the large front cog, and or fit an eleven to the rear?

Dan

You do not need more than a 53/12.
If your going down such a steep hill your spinning out then you should just adopt an aero position and you will go faster than you would with a 56/11.

See what max speed you can hit pedalling the gear you have You can get over 40mph pedalling such a gear if you can sprint down an incline before you spin out