Comparing 26" to 29" gear ratios

marky harvey

Hi

The time has come to upgrade my 26" bike with 2 x 10 gears to a 29" bike. As I want to retain the spread of gears I'm not sure whether a 1 x 11/12 will do the job. Working out the gear ratios is easy enough but I don't know how to factor in the wheel size. Essentially I don't want to find that I need to use more force on the pedal on a slow climb with a new bike than that of my current bike.

Any advice would be appreciated.

Thanks

Mark

marky harvey

Mostly XC riding on gravel tracks.

I'm slightly interested in understanding the mechanics to calculate the effort required.

whyamihere

You need to work out the development of the lowest gear, which you can do here: http://www.bikecalc.com/gear_meters_of_development

This is basically the number of metres which the bike will go forwards for each turn of the cranks, calculated by multiplying the gear ratio by the circumference of the wheel. To use the same force on the pedals on a climb, then you need the development to be the same (ignoring changes in bike weight etc).

Generally, 1x11 will have a smaller range than 2x10, but by choosing the chainring size, you can decide whether you lose some range at the top end or bottom end - generally people lose some top end because it's relatively rare to be trying to pedal at 30mph on a mountain bike. 1x12 will give a similar range to 2x10, and again this range can be moved by using different chainrings.

kajjal

The circumference of a 29" wheel is about 11% bigger than a 26" wheel but varies with tyres.

My 29" xc hardtail is 2x10, 24/38 and 11-32 cassette which works well for xc riding. Mainly in larger chainring except longer steeper climbs. This gives a very wide range of gears. My 26" accelerates faster / is more manoeuvrable but has less traction uphill / gets knocked around more by the trail.

nickbotfield

marky harvey wrote:

Hi

The time has come to upgrade my 26" bike with 2 x 10 gears to a 29" bike. As I want to retain the spread of gears I'm not sure whether a 1 x 11/12 will do the job. Working out the gear ratios is easy enough but I don't know how to factor in the wheel size. Essentially I don't want to find that I need to use more force on the pedal on a slow climb with a new bike than that of my current bike.

Any advice would be appreciated.

Thanks

Mark

This is my preferred gear ratio calculator.

http://ritzelrechner.de/

It's nice and visual and has loads of options for chainrings, sprockets, and wheel / tyre sizes.