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My f. derailleur won't shift consistently, any suggestion?(13 posts)

My f. derailleur won't shift consistently, any suggestion?LinuxDude
Dec 1, 2002 8:35 AM
I have an older 8-speed Shimano 105 group on my Bianchi. The rear transmission works fine. However, the Front has a problem of down shifting. You have to give it many attempts before it can downshift. On the other hand going from chainring 39T to 53T is no problem at all. I tried experimenting with another front derailleur (Older 600) on this bike and that was operating perfectly. Which suggests that the STI shifter is fine. On the old 600 shifter, I noticed a tighter spring, though. Could it be friction or tension problem in the cables? Or is something wrong with my front derailleur?
Any suggestion or comments would be really appreciated.
re: My f. derailleur won't shift consistently, any suggestion?Spoke Wrench
Dec 1, 2002 9:16 AM
My first impression would be that the derailleur just isn't moving far enough to the left when you shift. Four things can make that happen:
1. Low gear limit screw adjustment
2. Cable tension
3. Positioning of the derailleur in the seat tube (cage parallel to chainrings).
4. Derailleur just won't move inward far enough (could be related to a too short bottom bracket spindle).

I'd systematically address them one at a time. Keep in mind that the low limit screw adjustment is also related to cable tension. I generally just unhook the shift cable until I'm sure that the low limit screw is set right.

Good luck!
re: My f. derailleur won't shift consistently, any suggestion?mackgoo
Dec 1, 2002 4:16 PM
Did this just start happening after working fine?
Lube, lube, and lube?Kerry
Dec 1, 2002 4:50 PM
You don't mention if the pivots on the derailleur have been lubed, if the shifter has been lubed, or if the cables have been lubed. Along with the other posters' suggestions, consider cleaning and lubing everything along the shifter pathway. Sluice the STI unit with solvent (WD40 works well) and then relube with TriFlow or something similar. Pull the cables from their casings, wipe them clean, lube with oil. Check the BB cable guide for cleanliness. Take the derailleur off the frame, disassemble it as far as possible, clean as much as possible, lube all pivot points and work back and forth by hand. The fact that the 600 derailleur works and your 105 doesn't suggests maybe internal friction in the derailleur pivots or a weaker spring not strong enough to overcome friction in the cables or STI shifters.
Have you lubed where the cable goes under the BB?retro
Dec 1, 2002 5:01 PM
Everybody forgets that, including me. I always screw around with the shifting for about half an hour before I remember it.
re: My f. derailleur won't shift consistently, any suggestion?LinuxDude
Dec 1, 2002 5:35 PM
Thanks, for all your helpful comments.

This bike setup is completely new. I had these 105 parts on my Specialized Aluminum bike and transferred them to this Bianchi Columbus steel frame. Therefore, the cabling and the Derailleur are new and well lubed. I was meticulous when setting up the cables to reduce friction as much as possible. They are also lubed. I put a few drops of oil in the pivots of the derailleur but I did not completely overhaul it (if that is possible?). I also did not lube nor oil the STI shifter because I wasn't sure how. How does one actually sluice an older STI Shifter mechanism? Does anyone have one of those Shimano exploded parts chart or maintenance manual (pdf)?

Spoke Wrench, one thing I forgot mention is that when trying to downshift it seems that the shifter doesn't catch the cable. Therefore, the der. doesn't move at all (most of the time). It's not like it down shifts half way. But when it shifts, which is occasionally, it does so perfectly. So, I think that der. adjustment is not the culprit.
Ah Ha!Spoke Wrench
Dec 1, 2002 5:45 PM
In that case, try blowing out the inside of your shifter with compressed air. If you don't have access to an air compressor, try shooting some WD-40 in there and work the gears a few times. Bet that does the job at least for a while.
8 ball says: "All signs point to shifter."Kerry
Dec 2, 2002 4:32 PM
The fact that the ratchet is not catching every time really says it is the STI shifter. Per SW's advice, squirt the WD-40 in there while shifting through the gears. A visual inspection will guide you to openings (might do this with the bike upside down). After you've loosened things up thoroughly with the solvent (let it drip!), consider a TriFlow chaser so that you leave some thinner lube behind. Once the WD-40 evaporates, you have the same lube package you had when you started. If you continue to experience the problem after a rinse 'n lube, you get to buy a new shifter.
exploded views (pdf) are on shimano europe website.PeterRider
Dec 2, 2002 11:22 PM
My f. derailleur won't down shift consistently, any suggestion?LinuxDude
Dec 1, 2002 5:37 PM
Thanks, for all your helpful comments.

This bike setup is completely new. I had these 105 parts on my Specialized Aluminum bike and transferred them to this Bianchi Columbus steel frame. Therefore, the cabling and the Derailleur are new and well lubed. I was meticulous when setting up the cables to reduce friction as much as possible. They are also lubed. I put a few drops of oil in the pivots of the derailleur but I did not completely overhaul it (if that is possible?). I also did not lube nor oil the STI shifter because I wasn't sure how. How does one actually sluice an older STI Shifter mechanism? Does anyone have one of those Shimano exploded parts chart or maintenance manual (pdf)?

Spoke Wrench, one thing I forgot mention is that when trying to downshift it seems that the shifter doesn't catch the cable. Therefore, the der. doesn't move at all (most of the time). It's not like it down shifts half way. But when it shifts, which is occasionally, it does so perfectly. So, I think that der. adjustment is not the culprit.
So is it possible to overhaul the Shimano STI Shifters?LinuxDude
Dec 3, 2002 3:49 PM
In theory, it's possibleKerry
Dec 3, 2002 4:49 PM
But in practice, you can best consider them to have "no user serviceable parts inside." Once STI shifters have gone funky, you're buying new ones.
Problem Solved!!! Thank you all.LinuxDude
Dec 3, 2002 9:00 PM
The culprit was the bottom bracket cable guide. I had the older type guide mounted (original on the frame), which was longer and tighter thus causing more friction. I changed to the new one, put some oil and dang. Now it shifts 100% of time. The half-shift works too now. 8-)

But if it wasn't for you guys making me concentrate on the friction and guide issue I would've never figured it out. So, thanks a lot.