cabman

I have a 2011 Specialized Tricross Comp (purchased last August through the Specialized Dealer employee program, so it should still be under warranty). I'm currently on a bike trip on Vancouver Island, BC, Canada, and my left (front derailleur, triple, 105 groupset with full internal cable routing) shift lever has stopped working. Once the shifter is positioned all the way into the largest chainring, it won't downshift anymore. This problem exists both with and without cable tension, and I have already tried flushing the mechanism with WD-40 to no avail.

I took the hoods off both sides (to look at the working shifter for comparison) earlier today and found that the problem seems to reside in the forward cam follower in the nonfunctioning shifter. For those unfamiliar with the internal workings of these shifters, the cam follower is mounted on a pivot point and is spring loaded so that the following surface, by default, mates with a toothed index wheel. When a lever arm on the cam is pushed down, the mating surface is released, and the index wheel is allowed to move to the next smaller chainring position. In all gear positions except the largest chainring position, the part of the shifter that actuates the cam follower when the downshift lever is pressed seems to be working just fine, and the ratcheting mechanism of the shifter works through all positions. However, in the largest chainring position, the cam follower actuating piece just runs straight into the cam follower lever arm, pushing the cam follower surface toward the index wheel instead of away from it. It is almost as if the cam follower has rotated too far, making me think that the index wheel itself may have developed some sort of deep groove that isn't supposed to be there. I drew a diagram of the main parts of this mechanism, which is attached. Black is the neutral position, green is the position in which the index wheel is allowed to move one "click" forward, and red is the position in which the cam follower is stuck and unable to allow downshifting.



I've verified all this, as I can force the shifter back into a functioning state by using a small screwdriver to manually lift the cam follower off of the index wheel and downshift one "click" so that it is no longer stuck in the biggest chainring position. After doing this, it all works fine until I shift back up into the big ring.

Since the bike is so new and has barely been used (has around 500 miles, as I have another road bike at home), has been kept mostly inside, and has been well cleaned and taken care of, I seriously doubt that the shifting mechanism is gummed up. Yet, at the same time, I can't see why it would be showing this behavior unless there is a pretty big design flaw in the shifting mechanism or if a part physically broke. I haven't felt any popping or noticeable breaking of parts, so I'm really pretty stumped.

I'm good on shifting right now--I rigged up a cheapo bar end shifter to get me through the rest of the trip, but I'd like to get this figured out as soon as possible. A big reason I bought this particular bike was for the cable-less 105 shifters, which have proven solid in previous generations, so it's kind of disappointing to have this happen so soon into the bike's life. Has anyone else run into this problem? Did I just end up with a shifter with a crappy die cast part that failed? Should I try more WD-40?

Thanks in advace.

Cheers!

Carl

Kimmo

It seems too soon for your grease to have gummed up, and anyway, you've identified an issue that prolly isn't due to sticky grease.

Could a spring have come off that cam follower? Prolly hard to tell without disassembly...

How isn't this a warranty job?

well biked

+1. It's not like Shimano isn't familiar with the process of replacing STI front shifters in recent years, I know we've had a lot of them replaced that have come through our shop. But they were all 5600 series shifters, I've not seen any problems with the 5700 stuff. Still, it's clearly a defective shifter on a current year bike, I advise having it warrantied.

cabman

Yeah I'll definitely get it warrantied when I'm back in the states. Hopefully it's not too slow. I really expected more out of the 5700 levers, but I guess the one I got was just a dud... Anyway, at least the issue is out there now, maybe my explanation will keep someone else from having to take their hoods and bar tape off in the future.

And I don't think a spring or anything just fell off. The screwdriver trick requires pulling the cam follower up against spring tension that's holding it against the index wheel.

One other thing that I'm remembering is that it seems like the problem started out a bit intermittently, though the first few times I remember it being hard to downshift could have had some other cause. If it had come on really slowly, I might think that something may have gotten lodged in there somehow, but I'm pretty sure that's not the case.

Kimmo

Hopefully it'll keep someone from buying STI. They're made of fail and poo.

I'm reminded of a 42" plasma set I just scored for nix due to a 2" vertical black line... Googled the fault; thought I was in for an easy fix where you just re-solder some components on a ribbon connector to fix some dry joints, but no. the S42SD panel in mine was a bit different; instead of a couple of surface-mount resistors, a couple of chips are glued on. So now my only (ridiculously faint) hope is to somehow cannibalise a ribbon with chips off another S42SD and somehow find a way to splice that ribbon cable, at about 4 conductors a millimetre...

Fail and poo.