Long cage vs short cage - whats the difference

ive no idea. ive bought a veloce rear derailleur and been told its long cage and not suitable for a road bike. is this bollox or not?

Usually long cage is for triple chainsets or very wide gear ratios - helps take up the extra slack on the chain...

^^ bollox.

ive got no idea. he wants 50 for the mech and i bought the long one for 21 so how much difference will it make.

It will mean you can run more chain so bigger cassettes.

I'd probably buy the correct one.

It won't. It'll just allow you to use a bigger cassette if desired, for example an 11-32.

The correct one being shimano obvs.

Beat me to it grumble grumble etc

ten speed veloce long cage rear mech anyone?

Just use it. It will be fine.

The cage length determines how much chain the mech can cope with, which determines the difference between the largest and smallest ratios. The size of the largest sprocket is determined by something else - the knuckle length or something.

^Mostly right. The cage size will determine the maximum number of teeth that the mech will cope with, which is the sum of the difference between the largest and smallest chainrings and the largest and smallest sprocket. e.g. With 39/53 front and 11-25 rear, the total tooth difference is 28 (14+14).

What determines the largest sprocket you can use is whether the upper jockey wheel fouls the largest sprocket. A long cage will have its jockey wheels positioned lower so will manage a bigger sprocket.

These 2 numbers should be available in the spec info for the mech. You can use a long cage mech on a road bike if it suits your purpose, other than the extra weight of more chain links and a slightly heavier mech.

Just use it. It will be fine.

This.

So it doesn't make a huge difference??? I'll just use it then and save £50

It won't make a difference, many will cite some improvement in shifting due to longer arm and whatnot, but in the end it will move your chain from one cog to another with each shift.

edscoble is right on the money here

ive no idea...

Probably best to brush up some knowledge first before embarking into this variable gear malarkey.

Short cage mechs shift sharper, but you'd need to be at least Cat 6 to notice.

Campag have only specced long cage mechs with triples for a while, so you probably won't need it, but it'll work fine.

What does it measure (centre to centre) between the jockey wheels? Where is the B-adjuster screw: by the attachment screw or the upper jockey wheel?

edscoble is right on the money here

Let's just take a moment to let that sink in :-)

Long cage Campag is only needed for triples, but will work fine with doubles. Short cage will be marginally but unnoticeably better, lighter etc if you're using a double or a compact.

Interested in a swap for a short cage Veloce mech? Would mean you were using the 'right' kit and I had a spare that would fit my triple.