Tiagra lever failure in cold weather

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simonmain1

Tiagra lever failure in cold weather

Postby simonmain1 » 16 Dec 2008, 11:12am

I have a very odd effect. My Tiagra rear gear shift works fine when the bike is warmer than 10oC but when I take the bike outside on these cold days it will no longer engage to change gears (going to larger cogs only). It just feels floppy. On heating the bike up again it engages and works fine.

Has anyone else ever seen this?

Simon

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robwa10
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Postby robwa10 » 16 Dec 2008, 11:35am

Could it be the cables instead of the changer itself?
If not then it sounds like moisture or condensation are getting into the shifter then maybe freezing the ratchet open. Though having typed that it does sound very far fetched.
But hey I've seen stranger things happen. :)

simonmain1

Postby simonmain1 » 16 Dec 2008, 11:50am

The fact that there doesn't seem to be any resistance at all when it is in the non-working state makes me think its not anything within the cable...

I did think of just spraying everything with WD40 to displace water but then came to the conclusion that it is like this below 5oC so can't be freezing...more like something right on the edge such that thermal contraction is causing the effect...

PW
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Postby PW » 16 Dec 2008, 11:58am

Maybe 15 years ago 2 of us used to go for night rides up on the moors in all weathers. My pal had a 6 speed indexed mtb with thumb shifters, I was on Campag friction. In spring and late autumn he used to have a problem with the indexing going off on frosty nights, or if it was re-adjusted it wouldn't work next morning 700 ft lower in the valley bottoms. It doesn't happen with my modern 9 and 10 speed stuff but then we don't have many nights at -10C any more!
If at first you don't succeed - cheat!!

Edwards
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Postby Edwards » 16 Dec 2008, 2:52pm

I had a similar problem of changing down not up on a 105 rear mech. It turned out the mech had a week spring and was not pulling the cable hard enough.
This is what I would do.
Allow the bike to get cold having changed into bottom gear.
Change up 2 while gently pulling the inner cable at the down tube.
Warm the rear outer cable with your hands.
Warm the rear mech.
If the mech moves at any of the stages above you have found the main problem area.
If it is the cable at any point it is a good idea to replace the whole inner and outer set up.
Keith Edwards
I do not care about spelling and grammar

hamster
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Postby hamster » 16 Dec 2008, 3:06pm

The grease in the cables could be hardening and going waxy.

PW
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Postby PW » 19 Dec 2008, 6:15pm

That may well be Simon's problem - it wasn't the cause of my mate's malfunction though, his worked prefectly if re-adjusted or if the friction option was selected. We concluded it was a cable shrinkage problem. Combined with the fairly crude indexing on mountain bikes of that period I still think we were right.
If at first you don't succeed - cheat!!

Cyclenut
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Re: Tiagra lever failure in cold weather

Postby Cyclenut » 19 Dec 2008, 10:34pm

simonmain1 wrote:I have a very odd effect. My Tiagra rear gear shift works fine when the bike is warmer than 10oC but when I take the bike outside on these cold days it will no longer engage to change gears (going to larger cogs only). It just feels floppy. On heating the bike up again it engages and works fine.

Has anyone else ever seen this?

Yeah, my 10-ish-year-old 8-speed 105 levers behave exactly the same. This crimbo I need to get around to soaking them in oil and renewing the outer casings.

Hardened grease in levers and/or casings (as one has suggested already) is surely the culprit and I think its unfortunately in the levers, since pulling real hard on the cables to overcome any cable friction doesn't help the release shift at all. Some spring-loaded widget in there just isn't springing like it should. :(
Chris Juden (at home and not asleep)