Dirt Jump Bike

[Rourke]

So I have a garyfisher mountain bike with front suspension and 21 gears. I usually ride the bIke jumping curbs doing wheelies... It's a fairly small bike and heavy bike so I would like to make it lighter and better for street and dirt jumping. So I think I should get a new chain and take the derailer off, that would shave a bit of weight and save me from putting my chain back on every time I do a nice dirt ramp. In order to make it single geared, would I need to change the whole rear tyre or can I buy a gear to fit it? Same with the front 3 gears.

[Tomm]

You probably can't simply take the gears off - you will need some way to tension the chain otherwise it'll fall off all the time. I am assuming your bike has vertical dropouts, so you will need some sort of tensioner to replace the derailleur. This will be marginally lighter but probably won't do a better job of tensioning than a simple rear derailleur. You can buy kits to change the rear cassette to a single ring (with spacers).

One option to save weight would be to take some of the front rings off (depending on what gearing you want, probably leave the middle one) and the front mech/shifter. Then get a road rear mech (E.g. Shimano SORA or similar) or short cage mech which will help keep better tension.

Alternatively, save up and get a dedicated street bike, it'll be a lot better than a bastardised mountain bike. I hear this is a steal: