Note that Sheldon's calculation takes crank length into account for gain ratios, but not for gear inches. This isn't a mistake on his part, it's just how those things are defined.

Mr. Brown has good theoretical reasons for the use of gain ratios, but I decided not to include them in the JuniorVelo.com gear calculator. So far I haven't heard from anyone who wants to enter their crank length to get a number almost no one else uses :) .

check out Sheldon Brown's gear calculator. take note of the option that allows you to select "gain ratio" or "gear inches," and it takes into account tire size and crank length.

http://sheldonbrown.com/gears/

i went to one saturday am session at Hellyer with 170mm cranks, 23mm tires, and a 47/14 ratio, which according to Sheldon, yields 88.2 gear inches. it was a good gear for the training session ... don't know about racing yet.

in San Francisco, I ride 47/18, which allows me to climb up most of the hills.

-- Chris Stevens

http://www.docketrocket.com -- Docket Rocket legal courier

Just a reference for those interested in their gearing options. JuniorVelo.com has an online gear calculator which is specifically set up for track use. Some features include:

Showing just the rings and cogs you are interested in.
Highlighting of Junior gear limits for each age category.
Showing traditional gear inches or "actual" based on your wheel diameter (the distinction George is making).
Other options such as rollout distance or speed at a given cadence.

Have fun.[/]

The ratio remains the same no matter what size wheel you use. When you ask what "gear" to use, your answer is based on a 271/4" or 32mm tire size. I don't know ANYONE who races on this wheel size. Therefore the 81 gear (3.00 ratio) will actually range from 78.9 (23mm) to a 77.73 (18mm). Multiply by 3.1416 and you get rollout, the distance traveled with one turn of the pedals.

As for what to use, Junior riders have maximums but not 17 and up. It really depends on yor preference and style. Your lungs shouldn't be on fire constantly just trying to stay with the pack, nor should they be able to jump off the front without you being slow to respond or jump with them.

My preference is a ratio between 3.20 and 3.429, or 48-15 to 48-14. The "gear" would be 86.4 to 92.6, but it is actually 83.64 to 89.63 based on a 21mm tire diameter. A 46-14 will keep you in contention.

ddt wrote:Easy question: what are the gearings people use at Hellyer? I'm putting together a track bike (and hope to get out there more often) and the build kit I have comes with a 46 chainring. Thanks in advance.

For adults start with 88 inches and work around that in small increments. People have won in the A's/B's/C's with that but of course that depends upon your particular strengths and weaknesses and does not include doing well in the keirin.

Almost all of the adult rentals are set up with 81 inches, among other reasons - this is junior legal for most folks that can fit an adult bike and this helps keep the speed down during the beginner sessions - still, talented folks can go fast with this.

edit: as diskzero suggested you can use a wide range of gearing in the Saturday beginner session to get a workout depending upon your fitness but you should use something close to 81 if you are there for beginner instruction to get the most out of it since part of the purpose on Saturdays is to get riders comfortable with riding close to others and it's possible that with a widely different gearing one would not be close to anyone.

Easy question, but it has a lot of answers!

I'll let the more experienced racers add their input, but I have been using a 39x18 for warming up and a 39x16 for faster paced training. I was initially tempted to increase the gear inches, but have found that the more I train, the better my spin gets.