Which front derailleur

[Ebo100]

I need to get a new front derailleur for a bike I am rebuilding, apart from top or bottom operation are they all the same?

The old frame I am stripping has a shimano STX 34mm bottom pull but the new frame is 31.8mm so can I buy any shimano top pull 31.8mm?

[Pupp]

Braze on fitting or band is the usual other distinguisher... as you mention 31.8mm, looks like you are replacing a band type that clamps around the seat tube.

There are probably other oddities over the years but think these will be the common variations.

No reason I can think of why a top pull couldn't be substituted provided there is a ferrule for the cable or some means of parking the cable outer above and in line with the derailleur arm.

Edited by Pupp on Wednesday 22 April 20:25

[Ebo100]

Thanks for your reply. The replacement frame is set up for a top pull so I should have no problems there regarding ferrules etc, I am already putting new cables on it. I was more concerned about the travel across the cogs. A look in the bikes shop and ebay gives a huge variety of derailleurs so would it matter if I picked a shimano deore or altus

[gazza285]

The only other thing to take into account is the number of chainrings at the front. I presume that you need one for a triple chainring.

I have a derailleur here that would fit a triple, and while not an STX one, it is of a similar vintage. You can have it if you want.

[Justin S]

Depends on the chain set as well. If you are using the standard chainset , then later derailleur that is more modern might be for compact design, so the mech wont follow the chainset and may give rubbish shifting. If you are using the old chainset, then check the outer chainring dimensions for the new mech capacity matches that.

[Ebo100]

gazza285 said:

The only other thing to take into account is the number of chainrings at the front. I presume that you need one for a triple chainring.

I have a derailleur here that would fit a triple, and while not an STX one, it is of a similar vintage. You can have it if you want.

Thanks very much, PM incoming

[gazza285]

Ebo100 said:

gazza285 said:

The only other thing to take into account is the number of chainrings at the front. I presume that you need one for a triple chainring.

I have a derailleur here that would fit a triple, and while not an STX one, it is of a similar vintage. You can have it if you want.

Thanks very much, PM incoming

A failure, mine is a 28.6mm clamp, sorry.