Taking apart STI shifters

BungedUP said:

People seem to give up on their STI levers when they fail. Has anyone here tried to take them apart to fix them? What has your experience been? Please post photos if you have them of dissassembling the levers (including failed attempts too).

It's not worth the effort...

BungedUP said:

People seem to give up on their STI levers when they fail. Has anyone here tried to take them apart to fix them? What has your experience been? Please post photos if you have them of dissassembling the levers (including failed attempts too).

No user servicable parts inside. If hosing them out with wd-40 and relubing with triflo doesn't fix them,they are toast with a couple of exceptions. Some problems are caused by a loose or missing screw at the upperbackside of the levers that can be replaced,and there is a return spring that can be replaced.

boudreaux said:

No user servicable parts inside. If hosing them out with wd-40 and relubing with triflo doesn't fix them,they are toast with a couple of exceptions. Some problems are caused by a loose or missing screw at the upperbackside of the levers that can be replaced,and there is a return spring that can be replaced.

By no user serviceable parts, do you mean that they are plastic parts that have deteriorated and broken?

If anyone breaks a lever, I'd pay for the shipping if they are getting rid of it. I'd like to take them apart, photograph the parts and try to see what it is that goes wrong with them. Let me know if anyone is willing to donate a lever or two for science!

Also, if people could describe the difficulties they ran into dissassembling the levers, I'd like to know.

BungedUP said:

Also, if people could describe the difficulties they ran into dissassembling the levers, I'd like to know.

No problem with Disassembly. A MORON could do it!! Worse than a Rubics Cube to get back together. Some claim to have done it.Wouldn't waste my time and you cannnot get internal repair parts even if you do findg something that has gone TU.

boudreaux said:

No problem with Disassembly. A MORON could do it!! Worse than a Rubics Cube to get back together. Some claim to have done it.Wouldn't waste my time and you cannnot get internal repair parts even if you do findg something that has gone TU.

There's one common problem that can be fixed that not many people realise; well, at least on the older models. If the down-shifter (the smaller lever) starts to miss, it's often because the grease that Shimano put in there becomes "clagged up" in the spring, which can be fixed removing the cover, and giving it a good clean.

As Boudreaux has realized, I'm a "backyarder", and I've done this several times 😄

BungedUP said:

By no user serviceable parts, do you mean that they are plastic parts that have deteriorated and broken?

Yes, there are plastic parts inside. And as boudreaux mentioned, there are spare parts you can order (screws, springs, etc...) - check the exploded views (in PDF) from the Shimano website. These are all 'non-sensitive' parts (brake lever, mounting)

As far as I know, there are no spare parts for the shifter mechanisms.

nutbag said:

There's one common problem that can be fixed that not many people realise; well, at least on the older models. If the down-shifter (the smaller lever) starts to miss, it's often because the grease that Shimano put in there becomes "clagged up" in the spring, which can be fixed removing the cover, and giving it a good clean.

As Boudreaux has realized, I'm a "backyarder", and I've done this several times 😄

Hmm - interesting. Do you know if there is a common part failure if the lever will not upshift? I hear what people are saying regarding the difficulty to repair and find parts, but I am still interested in the precise mechanics of it all (if anyone has any ideas anyway). I have to admit that I am naive as to the true horrendousness of STI lever repair - I have been a long standing holdout against the STI road levers due to their complexity and fragility. However I am intensely curious about the things, and recently bought a new one (right side - which works just fine so I don't want to take it apart until its not functioning working properly). Thanks for humoring me!

BungedUP said:

Hmm - interesting. Do you know if there is a common part failure if the lever will not upshift? I hear what people are saying regarding the difficulty to repair and find parts, but I am still interested in the precise mechanics of it all (if anyone has any ideas anyway). I have to admit that I am naive as to the true horrendousness of STI lever repair - I have been a long standing holdout against the STI road levers due to their complexity and fragility. However I am intensely curious about the things, and recently bought a new one (right side - which works just fine so I don't want to take it apart until its not functioning working properly). Thanks for humoring me!

YIKES!!! :eek: Whatever you do, don't pull apart a fully functioning lever. :eek:

It's hard enough getting the cap and cover back on, but if you start to pull the mechanism to bits it could cost you a bucket to get it back together.

It's my understanding (but I could be wrong) that a "buggered up" up-shift is a bit more serious than a dodgey
down-shift. But then if the the down-shifter gets to the stage where it only works when you hold it forward when you switch, then that is even more serious?!?! 🙂 I dunno, I'm just a backyarder with about 6 sets of mid 1990s 8 and 7 speed shifters.

I definitely wouldn't say that they are fragile, especially the first generation models (I have two pairs of 1993 8 speed Shimano 105s which are just starting to die, with over 30,000 miles on them), but they are ridiculously expensive, particularly here in Australia. The cheapest (by a mile) pair of 9 speed Dura-Ace levers I've seen here in Melbouren were $370 US!! At one stage they were retailing for $500US!! So, I would say that the complexity and occasional fragility of them only relates to whatever you pay....obviously. 🙂

I consider myself a retro guy (i still ride steel....well, mostly), who's a bit reluctant to try new stuff, but as soon as I could afford STIs in the early nineties, I jumped at them. Best thing since lycra!! 😄

If you're that curious about the mechanics of them, I'm sure your local bike shop will have some "dead" ones that they are keeping for parts, and they might give you one to play around with.

I suggest that you read this article Campy vs. Shimano, especially the part about the shifters. Got that from the thread with the same title 🙂

BungedUP said:

Hmm - interesting. Do you know if there is a common part failure if the lever will not upshift?

The shifter cable goes through a cog/ratchet assemby inside the lever. Moving the BIG lever (upshift) rotates this cog and pulls the cable, thereby pulling the rear deraileur's arm towards the bigger sprockets. A pawl arm catches the ratchet to lock the cog in place. Pushing the small lever (downshift) releases (lifts) the pawl, which slackens the cable. The rear deraileur's tension spring then pulls the cable, at the same time swings out towards the smaller sprockets. A reverse ratchet/pawl assembly prevents a continuous downshift.

So, if the cog inside the lever breaks, there's no way to pull the cable to move the RD inward. Most of the time, it breaks due to misuse (trying to shift even when there's no more sprockets to shift to), or it just gets brittle with age.

Tried to patch a broken "shifter cog" once, but the stress was too great once I tried shifting to the higher gears - the thing broke again...

AHA! This is exactly the kind of info I'm interested in! Very interesting, and I'll check the thread more closely. I perused that thread a bit, but it seemed a bit superficial at times. I wonder if the cog is something that is very complex in shape? Is it merely a gear, or does it have odd protrusions, etc. I am wondering as to the ability to fab one out of aluminum or steel. I realize again that it might not be worth the effort.

Good idea about checking LBS for dead ones. I'll do that. And again, if anyone has any they want to get rid of, let me know.

Quoted post said:

I am wondering as to the ability to fab one out of aluminum or steel.

Got a CNC machine? Well good luck! 😄

It's a gear alright, but not the simple, common type like the ones in your sprocket cluster.

The gear has an eyelet that portrudes along the circumference where you insert the cable with a groove along the circumference which holds/guides the cable on the gear. This portrusion is also the one that pulls at the cable end.

Since there's a ratchet/pawl system that controls/locks both the upshift and downshift, both faces of the gear have slots where it catches the pawl - one side controls the upshift, the other the downshift. The slots are on opposing directions to each other.

To make sure that the gear has enough tension and snaps quickly to position during a shift procedure, a helical spring is used connecting the cog with the lever frame.

Still think you can fab one? 😄

BTW, Shimano uses basically the same technology on both road and MTB STI levers. The road levers are more delicate with closer tolerances than their MTB versions.

Cheers!