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-   -   Autoshifting == Replace brifter? (https://www.bikeforums.net/bicycle-mechanics/453097-autoshifting-replace-brifter.html)

xerotope 08-11-08 10:02 PM

Autoshifting == Replace brifter?
 
Hey all,

So I was having some autoshifting issues in some gear combinations on my 2005 Trek 1500 (Shimano 105 componentry). Mostly 4th or 5th gear on the cassette. The chain isn't stretched, and the cassette teeth looked fine to my eye. I had adjusted the derailer so it was up and down shifting fairly smoothly, but wasn't able to reproduce the problem on the stand.

In preparation for an upcoming ride, I brought it into a shop for a professional tune-up. Well, they said I need a new brifter to the tune of $150. This was a bit of a shock, since it generally shifts fine, except for the occasional autoshift. Unfortunately, this is my California bike, so it's my girlfriend who dealt with the shop, and she wasn't able to get much more out of them other than "it's messed up".

I've read Sheldon Brown's page on the matter, and he does not list "broken shifter" as a possible cause. (I am planning to try greasing the cable-run on the bottom bracket and lubing the housings).

Is there a clear way to tell if the shifter is actually broken? And could that be the cause of my autoshifting problems? If I'm going to lay down $150 on a new shifter, I might as well pick up the Ultegra set that shows up on chainlove occasionally.

Sturmcrow 08-11-08 10:28 PM

Sounds sketch to me. If it is the brifter you'd probably be best off spraying it out with WD-40 thoroughly and then relubing it with something. That should fix any problems caused by crud under a ratchet or something of that sort. Plus, then you're only out 40 cents worth of WD-40 and it won't hurt anything (unless you get a mess all over your bar tape).

SoreFeet 08-11-08 10:43 PM

Check the cable for fray. The shifter is what dictates the amount of cable that is pulled. If the cable is worn it might not have the ability to pull enough cable.

Change the cable and see what happens. Its cheaper than 150$...maybe there is a small amount of damage to the cable housing that isn't so easy to spot.

The plastic bottom bracket cable guide could be slipping around from the screw it threads into. Inspect it for any signs of scrapes and wear.

Once you rule out the cable issues it could very well be the shifter. If that is the

Try the cable/housing swap.

Is the rear drop out bent?

I reckon friction is pretty spiffy too! That would cost you about 50$ for new ones.

rogerstg 08-12-08 06:05 AM

Brifters are not usually a cause of autoshifting. It's normally a half turn or so of the barrel adjuster to fix it.

nitropowered 08-12-08 07:03 AM

No! the LBS is trying to screw you. First check the hanger alignment. Second check to see if you have any stiff or bend chain links (pedal backwards and if you see the derailleur jump, you have a stiff/bad link) Third check to see if you have a bent tooth on the cassette. This rarely happens but it happens occasionally. It may be bent just enough that the chain catches up on it and causes your auto shift. Then finally change out the cables and housing and check the BB guide to be safe.


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