Working out Gear Ratios

[Bugner]

Hello All,
I am looking at 2 bikes.

Marin Toscana which has 50/39/30 triple and a 11-26 9 speed cassette

Genesis Croix De Fer which has a 50/34 double and a 12-25 10 speed cassette.

How do I work out the gear ratio's and calculate what the lowest and highest gears are comparitively?

Any help appreciated

 

[Cullin]

Hi,
I think Sheldon Brown can help you out.
http://www.sheldonbrown.com/gears/
Cheers

 

[jimboalee]

http://www.machinehead-software.co.uk/bike/gears/gear_calculator.html

Have a look at this, then bang out a spreadsheet for yourself.

 

[cadseen]

Yes use the charts, gears are calculated in inches. before 700c wheels which are just smaller than 27 inch wheels. a typical gears would be a 48 chainring and a 16 sprocket on the back. calculation is chainwheel/sprocket * wheel diamter

this would be 48/16 * 27 = 81 inches.

 

[Cope]

http://www.machinehead-software.co.uk/bike/gears/gear_calculator.html

Have a look at this, then bang out a spreadsheet for yourself.

Looks like an ok program - shame it's crippleware and one can't use a triple, or more than 6 speed on the rear.

 

[jimboalee]

Knock up a spreadsheet like this.