Gears on Road Bikes

[tango_kid]

Hello,
i have just read a post which talkes about strange gearing numbers with dashes in :s

Now my mountain bike has 6 gears on the right and 3 on the left, that's simple to me. But are road bikes different and if so, may somebody please explain the difference?
Cheers,
Mike

 

[tyred]

People are referring to the number of teeth on the rear sprocket and front chainwheel. For example, my old MTB has a 14 - 28 5 speed freewheel, which tells you that the lowest gear is 28 tooth and the highest is 14 teeth, with three others somewhere in between. On the front I have a 48-38-28 triple, i.e, 48 teeth on the larger outer ring, 38 on the middle and 28 on the small inner ring. My lowest gear is 28/28, i.e, a 1:1 ratio, using the smallest chainwheel with the largest sprocket on the back. My highest gear is 48/14, using the largest sprocket on the front with the smallest on the back. The larger the front chainwheel and the smaller the rear sprocket, the higher the gear ratio, i.e, the rear wheel rotates more times for each turn of the crank. Wheel size also needs to be taken into account. Small wheels lower the effective gear ratio.

 

[tango_kid]

Thankyou very much, much appreciated
Cheers