Gear Inches & How To Work Them Out.

I frequently talk to people in the store who are interested in knowing the gear inch specifications for their particular setup.  With such a range of wheel diameters, chain ring and cassette choices, today’s gear calc. charts take up many pages. So it makes more sense to give you the simple formula for working out gear inches yourselves.

Make a list of all your chain ring sizes, cassette cogs and the size of your rear wheel.  Once you have all that information, set about doing the calc. below for each combination.

As an example, the calculation for a 700 road bike with a 52 tooth chain ring and an 11 tooth rear cog is as follows;

52(chain ring) X 27(drive wheel diameter in inches) =1404

1404 divided by 11(rear cog) =127.6

So the above combination gives you 127.6 gear inches, this means that with every full revolution of your pedals you travel 127.6 inches. Use the above calculation for every gear and you have your gear inch chart. Remember, the higher the number, the harder it is to pedal.

Another option is to punch in 'bicycle gear inch chart' into your search engine of choice and you will find a list of handy dandy little online calculators. These come and go and honestly by the time you fill out the forms you could have had this done.
Posted on July 23, 2012 .