Mech conversion, possible?

[Twisty]

I've just done something pretty stupid.

I finally found a NOS XTR M952 front mech in the local classifieds with the right clamp size so I excitedly bought it and installed it on my bike. I couldn't work out why I was having problems adjusting the mech and it was then that I realised that I was trying to install a top pull mech on a bottom pull bike :facepalm:.

If I switch the clockwise wound spring to an anticlockwise one then would this convert the mech to bottom pull?

 

[Thias]

I dont think, this is possible.
There is 4 different versions of front derailleur in the 952 range. Top or bottom pull and each of those top or bottom swing....

 

[itscervo]

If I switch the clockwise wound spring to an anticlockwise one then would this convert the mech to bottom pull?

In short no. The springs for top/bottom pull are both wound clockwise, but the tangs are in different positions. In the link you'll see the difference between the springs & arms which are interchangeable. I got mine spare arm off a very cheap scrap mech.

https://www.dropbox.com/sc/bgsvi54ql3qf ... nfOkDD9kMa

 

[Twisty]

ARRGGGGG, now I am even more frustrated. I had a bottom pull 950 mech with a broken cage but it went to the charity bikehub with most of my other spare parts when I emigrated to Singapore.

Anybody got a bottom pull arm to swap for my top pull one? My mech is NOS too.

Otherwise I might try try make my own spring using an old bicycle spoke.

 

[ishaw]

I don't think so as you will still have the top pull pivot and cable mount. What size mech clamp are you after?

 

[Twisty]

Re:

I've got a 31.8mm clamp, top swing, i'd need to check if a bottom swing mech would fit below the bottle cage boss. Based on the earlier post/picture it looks like the pivot&spring can be interchanged from the bottom pull to the top pull on the top swing mech at least.

 

[FluffyChicken]

I dont think, this is possible.
There is 4 different versions of front derailleur in the 952 range. Top or bottom pull and each of those top or bottom swing....

952 was Top-Swing(tm) only
Came in the 3 band sizes and e-type.

you need to switch the pull arm as mentioned above. I don't know if you can switch to the later mutli-pull arms and have it loop over the top.
If you revered the spring you'd just end up with big ring normal, rather than granny ring normal ?

For reference bottom pull m952

 

[Twisty]

If I reverse the spring it would make the mech work with bottom pull, but I am not sure if being top ring normal would be horrible or not, I am also not sure if the sharp angle at the cable clamp would cause too much stress on the cable.
The rear derailler is rapid rise so the front mech being top ring normal would then make things match, but I suspect it is important to coax the chain up carefully with the thumb rather than mash it up with the force of the spring.

The mech on the bike, is an XT M739 and needs replacing because the cage wobbles a lot. The cable arm pivot boss spacing on the XT mech is different to the M952, I assume to convert to a proper bottom pull I am limited to looking for a pivot from an M950 or M952 mech.

 

[FluffyChicken]

Buy a top pull frame, problem solved

 

[scottproonly]

Re:

I once used a top pull 952 mech as a bottom pull with some interesting cable routing! However it only worked with gripshift as the indexing was well out.