Hi,
My left shifter shifts the chain onto the big front ring, but when I let go of the lever it jumps back down to the small ring.
I was on a ride today and and heard a big “click” like you hear when the shifter cable snaps so assumed that was the problem and rode home.
On inspection it seems that something in the shifter mechanism has gone wrong. Perhaps some sort of ratchet?
I have shimano 105 on my other road bike and that shifter is quite different so I can’t tell what the problem is by comparing them.
I don’t know exactly what model ultegra it is. It is 10 speed but I can’t see the model number. I was told it was near new when I bought the bike.
Anyone know what the problem might be, if it is ilkely to be fixable and if likely I can fix it myself - I do most maintenance on my bike.
Cheers
If the cable is under the bar tape, it’s Ultegra 6700. If not, it’s 6600. Unfortunately, Shimano internals aren’t easily found.
Thanks. Its ultegra 6700 then.
Sounds like the mech inside the shifter let go. I don’t think its repairable (I could very well be wrong). Were it me, I’d just get a new one as cheap as I could find one (new) and be done with it.
Start by pulling the brake lever slightly and spray the hell out of everywhere you can find, with WD40 or CRC. From what I know, this is about the only repair you can do to STI shifters.
Much like the mind of a woman, nobody really knows what goes on inside the Shimano STI levers. It’s magic! 
I’ve had Ultegra 9 speed, and 10 speed 6600 and 6700. Recently the 6600 had the same issue you mention. Tons of WD40 and it miraculously fixed itself. The thing with the WD40 fix is that you need to keep it lubed fairly regularly, to keep it fixed. I give it a shot every 800-1000km or so.
IF that doesn’t work, then you’re up for a new pair. I’d suggest you keep an eye out, on your favourite online sites and buy a new pair when you can find them on sale.
If his fix works… go get a wet graphite lubricant from Napa or another auto parts store. The wet lube will free it up and the graphite will keep it slick in the future. … not sure how the housings react to being lubed… I’ve heard bad things in similar posts on my motorcycle forums
Start by pulling the brake lever slightly and spray the hell out of everywhere you can find, with WD40 or CRC. From what I know, this is about the only repair you can do to STI shifters.
Much like the mind of a woman, nobody really knows what goes on inside the Shimano STI levers. It’s magic!
I’ve had Ultegra 9 speed, and 10 speed 6600 and 6700. Recently the 6600 had the same issue you mention. Tons of WD40 and it miraculously fixed itself. The thing with the WD40 fix is that you need to keep it lubed fairly regularly, to keep it fixed. I give it a shot every 800-1000km or so.
IF that doesn’t work, then you’re up for a new pair. I’d suggest you keep an eye out, on your favourite online sites and buy a new pair when you can find them on sale.
I have successfully taken apart a 9 speed shifter and built it back up, took me about 7 hours 4 of which were spent on the floor of my garage looking for snap rings and springs. Total waste of time. At the end of the day I just cleaned everything and re-built it, still works fine 5 years later.
If I could do it again I would do what you said, spray the hell out of it. Maybe replace cables and housing and hope for the best, otherwise look for a 105 or tiagra option. Maybe buy the set as it’s only a matter of time before the right goes.
Maurice
For stuff like STI shifters and Sturmey Archer 3speed hubs, I’ve learned the trick it to open/undo them inside a large clear plastic bag. At least then, when they explode, you know all the bits are in the bag! Saves hours and hours of looking in every nook and cranny in the garage!
Thanks guys. I took it to a bike mechanic who said it was knackered and irrepairable.
I like to fix everything I can but this looks like I could spend ages dismantling it and find I need an unobtainable part.
I’ve found a good deal on the 7900 durace shifters for not much more than new ultegra shifters. Think I’ll get those and sell the perfectly ok right ultegra shifter to offset some of the cost. I have 105 on another bike and don’t like it as much, the shifting requires more movement and the whole unit is a lot bulkier than the ultegra.
This is my race bike and I’ll be racing with it quite a lot this year so don’t mind spending a little extra on dura ace for the peace of mind.
PM me if you want to buy a used ultegra left shifter. I replaced the pair when the right went belly up.