Need a top pull front mech for CX - any ideas?

munkster

OK, got a Tiagra triple road chainset on a GT CX bike, the bike has top pull cable routing and the "Wire Roller Set" wotsit that converts the frame for bottom pull front mechs just seems to not work, the mech cable fouls the clamp for one thing which kills the tension in the system.

Anyone got any recommendations for top pull front mechs that will work with a 9 speed Tiagra chainset? The internets found a "Shimano CX-70" but not sure if this will work with 9 speed triple (it's touted as 10 speed double) and at £25 I don't particularly want to take the risk if it isn't going to work...

Thanks for any intel.

sungod

doubt the cage on a double front mech will have enough clearance to work on a normal triple

seems odd that the cable is fouling, can you post pics showing the complete cable path around the pulley and also up to the fd cable clamp?

munkster

Here's some pics. Having never used a braze on front mech before I used the clamp off an old Shimano 2300 that happened to fit this seat tube. Not sure if that's the issue? Have tried rotating clamp (to get the bolt out of the way of the cable) but gets the mech cage all out of line if I do that.

Any the wiser? What's the deal with the roller thing - does the bolt have to be loose? Tight? Somewhere in between?

munkster

Actually I wonder whether the roller thing is upside down?! Should the writing be the right way up. Embarrassing if so, but a quick win if it is the case!!

majormantra

Not sure about that roller, but on the Ridleys we have at work the cable enters the right (driveside) of the roller first and then crosses over itself, so it has a clear run to the mech.

Just looking for a pic to demonstrate...

majormantra

Ok, it's a bit close-up, but like this:



Would that work with your setup?

munkster

Good lord, hadn't even occurred to me the cable had to cross over... I've flipped it upside down and it seems to not foul quite so much, that's a start I guess... Will have to do more digging I think, cheers though.

munkster

Problem now is that the front mech (even with H limit screw at max) won't swing out far enough to give the mech a chance to get to the big ring.

The triple Tiagra has a fairly thick spacer on the driveside - can I remove that? The chainline should be 45mm, it seems a little more than that... If i remove the spacer will that cause issues on the NDS?

sungod

if the fd won't move out far enough you probably need to increase cable tension

with the limit screw all the way out, you can test this just by pushing on the cable, if the cage moves out then you know that more tension will do it

munkster

Ah, update on this, not long after I posted that I discovered that my LH shifter has actually died (or rather won't return to the lowest ratchet) during this process, which would explain the FD movement problem. Sorted the fouling issue, which is good though, just need a new shifter now, they're quite cheap aren't they? :shock:

desweller

Check the inside of the shifter for frayed cables, the bastard strands get everywhere if you're not careful (not that this has happened to me, precipitating hours of sitting at a desk with poxy tweezers trying to repair my borked shifter, perish the thought).