switching chainset between double & compact

[tcashmore]

Just a quick question of if it is a simple process to switch between chainsets for different purposes without having to change anything else e.g. BB, front & rear mech. I currently have a shimano da double and would like to invetigate fitting a compact for longer/hilly sportivs ?

Many Thanks

 

[skwerl]

you'll probably need a different length chain (but maybe not) and will have to move the front mech. should need a new cassette as well. compacts work by using a wider range athe back as well as front. may well need a new rear mech (ie a medium cage) depending on how much chain slack it's going to have to deal with

 

[jimboalee]

I have mixed feelings about compacts.

On one hand, they allow the bike to have one lower ratio, therefore slightly easier to ride, thus encouraging folks to buy bikes and go cycling.

On the other hand, a bike that weighs less than twenty pounds shouldn't need a compact. All it needs is a pair of strong legs. 39 x 25 is low enough for a twenty pound bike.

IMHO, changing from a double 53/39 to a 50/36 is defeatist. 39 x 25 is the same as 36 x 23.

If you already have 39 x 25, leave it alone and work on your quads and glutes.

 

[RedBike]

It all depends on what you're currently running / what you intend to purchase but in theory you might be able to get away with just swapping the chainsets over.

Obviously you will need to check your new compact chainset requires the same type of bottom bracket.

A compact chainset (as in 50x34) will give you a slightly larger range of gears. A short cage rear mech probably wont be able to cope with an 11-25tooth (or above) cassette, the gear range will just be too large.

 

[Big John]

I swapped from a 53 x 39 to a compact 50 x 34. It gave me one extra lower gear and I lost one high end gear (worked it out on paper!). I didn't change the rear mech, did minor adjustments to the front mech and all was well. Was it worth it? Sort of. I did the Tour of Wessex and needed every low gear I could get but still needed more. I guess a compact is a halfway house instead of going whole hog and changing to a triple, at a lot more expense. I've since changed back to 53 x 39 as the racing season is nearly upon us.

 

[fossyant]

I'd say, if thinking about compact, go with a triple instead - gives you the 'get out card'....