BMX - Gearing selection

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Land2Sea

01-14-03, 09:06 AM

My son is starting racing and I am trying to help him figure out what is the best gear selection for him. He currently has 42-16 with 20x1 3/8 setup. The rollout using http://www.nzbmx.homestead.com/files/bmx_gear_calculator_online.htm
calculates to be 55.125, but I have no idea what this means. What is rollout, something to do with revolutions of??? He has long legs for his age & height.When changing gearing, how do you determine whether to change the front or back? Thanks for any help!:confused:

MichaelW

01-14-03, 10:45 AM

Sheldon brown coverers both ways of measuring the total gearing:
Gear Developement and Gear Inches.
http://www.sheldonbrown.com/gloss_g.html

The other factor in gearing is the length of the cranks, but this is usually ignored by average male sized people.
It is usually cheaper and easier to change the rear cog, but when cog size starts to get too big or small, swap the front chainring size.

Land2Sea

01-14-03, 11:12 AM

Michael
What determines if the cog is getting too big or small? Thanks!