# Bicycle Mechanics - Gears?

Bikeforums.net is a forum about nothing but bikes. Our community can help you find information about hard-to-find and localized information like bicycle tours, specialties like where in your area to have your recumbent bike serviced, or what are the best bicycle tires and seats for the activities you use your bike for.

View Full Version : Gears?

DaemonLee
02-20-06, 10:54 AM
You've all probably heard me stating the n00b-ness of myself, so here's another death defying question. :(

On the crank, I have 3 sections, on the casette in the rear, I have 7.

What ARE those gears for?

Because, I have never ventured past 3-1 to 3-7

juicemouse
02-20-06, 11:13 AM
No worries, we all start somewhere.

http://sheldonbrown.com/gears.html

MichaelW
02-20-06, 11:15 AM
The front 3 give you 3 different ranges:
small ring =low (easy to pedal uphill)
medium
large ring=high (for downhill or tailwind).

In theory you can use any front chainring with any rear cog to give a choice of 21 gears.
In practice, the 3 ranges have a considerable overlap. You can work out the overlap by calculating the ratio in gear inches (http://www.sheldonbrown.com/gloss_g.html#gearinch)

A further practical limitation is that you should avoid the crossover gears which can lead to excessive wear and strain on your chain. Small/small and large/large combos can all be replicated using a straighter chainline.

DaemonLee
02-20-06, 01:00 PM
So, basically...Let's see if I have this right (First number is the crank shifter and the 2nd is the Rear Casette Shifter, The Derailler(sp) )

I'm in 3/3 and down**** to 3/2 then 3/1 and then can I shift to 1/1 without the chain jumping? 1/1 being the small ring.

MichaelW
02-20-06, 01:07 PM
You need to work out your shifting pattern for yourself, it depends on your exact setup and where the overlap is. I often use different "routes" depending whether I am shifting up or shifting down.

It is best to stick in the middle ring for most riding.
When you get to M/1 (middle ring/largest cog) you can shift to S/1 but this is a big step change in gear ratios. I often upshift to S/2 for an intermediate gear.
On the upshift, I go from S/3 to M/1 to avoid big steps.