STI Disassembly. Don't do it.

1964johnr

Rear mech cable broke in the shifter in the worst place possible, underneath the mechanism. No amount of cajolling was going to get the cable and barrel end out from there. The change mechanism was stuck solid. So, after a couple of hours of watching you tube videos I figured I had nothing to lose by taking it apart. I knew the odds were against me. Taking everything apart and remembering where the components go was not a problem. It's a Tiagra shifter about 10 years old. There are two main issues with the rebuild. The first can be solved for £2. There is a part which is needed to get the return spring on the shifter in to the correct position. Searching on line solved this. SJS Cycles stock this shimano part. It's a very small metal tube. See video by RJ The Bike Guy on you tube for how it is used. The second issue is more difficult. There is a spring which is under tension on the front of the shifter which uncoils on disassembly. Trying to retension it is proving incredibly difficult. It must have been put on by machine. If I can't solve it, it will be a second hand shifter from E-bay for about £20. So, my advice would be. Make sure you replace your mech cables on a regular basis. If you break a cable inside the shifter, it is possible to remove it in most cases. If it gets trapped under the mechanism and the gears wont move then you have a problem. I have also learnt that the earlier shifters were much easier to take apart and reassemble. I wonder if Shimano have now made it much more difficult so that you have to buy new ones. Incidently, I am led to believe that newer shifters have a plastic part directly under the shifter which can be removed by taking a screw out to gain access to stuck cable end under the mechanism.

DeVlaeminck

They are a nightmare and were going back a bit too, I tried and failed with some 9 speed dura ace going back to when they were current kit. Campag ergos on the other hand are very user serviceable.

raisinberry777

1964johnr wrote:

Incidently, I am led to believe that newer shifters have a plastic part directly under the shifter which can be removed by taking a screw out to gain access to stuck cable end under the mechanism.

That is correct - I had a cable break in a similar spot in a 105 5800 lever and it was very easy to get out after taking that screw off to gain access to that area.

ben@31

I once disassembled my rear derailleur and changed the cage. When I put it back together again it took me hours and a lot of head scratching and reassembly to work out why the chain was now slack? Apparently the cage isn't just fitted like it looks but it's round 360 degrees under spring tension. Hours of my life wasted.

Matthewfalle

I had roughly the same thing on an Ultegra 6800 brifter. I thought about taking it apart then thought that was a silly idea so drilled a hole in the side.

Old cable out, new cable in, works perfect. Took 8 minutes.

Always remember to think out side the box (or shifter in this case).

nicklong

Exactly the same thing happened to me with a 6800 shifter. Cable snapped, end got stuck inside the shifter and without thinking carefully, I ended up accidently flicking one of the million little tension springs whilst sticking bits of cable around to poke the broken piece out.

Bought a few spares to fully dismantle and rebuild the shifter from SJS, eventually (with the help of some pliers and a huge amount of luck and patience) managed to get all the springs back in place. The sense of accomplishment was enormous, probably my proudest/geekiest moment all year.

I felt like I'd just reassembled a Swiss watch mechanism. Quite impressive mechanical engineering once you're inside looking around.

cycleclinic

I have always managed to get the cables out when they come into the shop snapped. I could have told you taking one apart is going to give a you a fustrating evening.

lvquestpaddler

Thanks for the heads up on this....my ancient steed is a 9 spd Tiagra of this vintage, but it gets well looked after and just changed both gear cables in the summer.... I reckon if I crash and burn and destroy one of these STI's it'll be hard to get a replacement 9 spd one....9 looks almost obsolete in the quest to get people to keep renewing/consuming and wanting the latest flashy thing.....

lesfirth

nicklong wrote:

Bought a few spares to fully dismantle and rebuild the shifter from SJS, eventually (with the help of some pliers and a huge amount of luck and patience) managed to get all the springs back in place. The sense of accomplishment was enormous, probably my proudest/geekiest moment all year.

.

That is what it is all about. Well done. It is a feeling many people will never know.

shirley_basso

While 11sp shimano is vunerable to cables snapping inside the shifter, it does usually give you a bit of notice as the shifting quality deteriaorates significantly.

I've ignored it every time and this been punished as above

raisinberry777

lvquestpaddler wrote:

Thanks for the heads up on this....my ancient steed is a 9 spd Tiagra of this vintage, but it gets well looked after and just changed both gear cables in the summer.... I reckon if I crash and burn and destroy one of these STI's it'll be hard to get a replacement 9 spd one....9 looks almost obsolete in the quest to get people to keep renewing/consuming and wanting the latest flashy thing.....

Not obsolete at all - new 9 speed Sora stuff is compatible with all previous Shimano 9 speed stuff, so plenty of years of compatibility still to come.

briantrumpet

While the original cable inside my 9spd Tiagra from 2010 is still going strong, the cables in my 10spd Ultegra and 11spd 105 shifters need replacing annually. I think that the flexing in two different directions (in the shifters that channel the cables underneath the handlebar tape) causes much more metal fatigue than just the flexing in one direction round the barrel in the shifter. And yes, a pain if you don't catch it in time.

Moonbiker

You should stick to downtube shifters.

pblakeney

Moonbiker wrote:

You should stick to downtube shifters.

Or Campagnolo.