When I moved to Germany for a year, I picked up a used mountain bike with Shimano Deore DX equipment. After a few weeks, the front shifter started misbehaving (it wouldn't hold on upshifts, insisting on returning to the smallest chainwheel).
As an old-timer who believes that stuff should keep working, and as a confirmed cheapskate, I wasn't about to pay over €100 for a new shifter on a bike I got for free and was going to give away in a year. So I took it apart. Then I ran into trouble and searched the Web for repair instructions.
The results were depressing. Everybody agreed that you can't repair Shimano indexed shifters. One guy said:
Not a lot to add here, but it does make me chuckle thinking of my misguided attempt to rebuild a rapidfire shifter. MyFirst Law of Do It Yourselfis that if someone put it together in the first place, I can take it apart and put it back together again.
I've concluded that the theory doesn't apply to rapidfire shifters. These were clearly assembled by Swiss watchmaker using alchemy, witchcraft and liberal dose of unicorn blood.
This brings me to mySecond Law of Do it Yourself: all mechanical items are over-engineered, so that if you have parts left over after reassembly, it will still be within normal operating tolerances.
My advice: buy a new shifter.
My own first conclusion (which I still cling to) was that indexed shifters aren't worth the hassle. If you're a racer with a Shimano sponsorship, sure: An indexed shifter can mean the difference between a win and 15th place. If you're a crappy weekend cyclist, then indexing can save you from your lack of experience. But as a skilled rider, I can hit a shift every time using my creaky old Campy bar-ends. The human nervous system is a wonderful thing.
Unfortunately, those creaky bar-ends were safely stored in my garage, about 8000 miles from where the freebie Deore DX was misbehaving. So I still needed to fix my shifting problem, or ride for a year on the small chainring—especially because at this point the shifter was in pieces, so coaxing it back to good behavior wasn't an option.
To make an already-long story shorter, Man battled Shifter and Man won. To my wife's great amusement, I carefully took photos along the way. I've annotated the photos to produce step-by-step instructions.
I rebuilt a left (i.e., front) shifter. I believe that the rear shifter is similar, but haven't disassembled it since mine works.
(Note: click on any photo to see a bigger version. You can click more than once to keep zooming in.)
Update Oct. 29, 2004: Depressing news. My shifter has broken again. I don't have the time right now to take it apart and find out what's wrong. The good news is that I now know how to do it. The bad news is that maybe it really is impossible to rebuild a Shimano shifter and have it work.
Update May 28, 2008: As it turned out, I went through the remainder of my German year with a broken front shifter. However, since then a number of people have written me to report that they had successful repair efforts. So don't be discouraged. Remember, the worst that can happen is that you destroy it, which only leaves you where you were before!
Getting the shifter apart is much easier than putting it back together. Whenever I disassemble complex equipment, I spread out paper towels or newspaper, and lay the parts on the paper from left to right so that I can remember the order in which I did things. To remove the shifter from the handlebars, look on the back side, where you will find a medium-sized Allen-head mounting screw. Unscrew it and the shifter will come away, supported only by the shift cable. Disconnect the cable from the derailleur, pull it through whatever tubing you have, and take the whole shebang inside the house. (You will probably wind up discarding the cable. Fortunately, a new cable costs only about €1,50.)
Once you are indoors, set up a comfortable workspace where you won't lose small parts. Don't try to cheat (as I did) and work outdoors or (as I did) save the cable. You cannot rebuild the shifter without removing the cable. Cables are cheap. So find a warm, quiet place with good light.
It is a very good idea to wear eye protection during disassembly and reassembly. There are several small springs that are fond of suddenly popping into the air, and you don't want one of them to pop into your eyeball. A trip to the emergency room will definitely slow your project down.
To remove the cable, there is a small cover on the side of the shifter housing, which is held on by a Phillips-head screw. It isn't identified it in the parts photo because I foolishly tried to leave the cable attached while I rebuilt the shifter. Remove the screw and the cover, and then push the cable through the shifter and set it aside (or discard it).
After the cable is gone, take the shifter cover off by removing the
small Phillips screw on the perimeter (
Cover anti rotation screw
in the photograph) and the larger Phillips-head center cover screw.
When you lift the cover off, the upshift lever return spring may
decide to pop out, so be ready to catch it in the palm of your hand.
If you're lucky and it stays put, remove it using a needle-nose pliers.
Then lift off the upshift lever and its two copper bushings.
Most of the rest of the shifter is held in place by the top plate. You will need a small jeweler's screwdriver (Phillips size 0) to remove it. When the top plate comes off, you'll be able to remove the downshift lever return spring and the holding pawl spring. The remaining parts can then be pulled out one by one.
You'll note, by the way, that I didn't actually strip things to the bone. It was clear how to take apart the upshift pawl, but it wasn't the source of my problem. The same was true for the holding pawl assembly.
I'm a big believer in cleaning mechanical parts. Dirt causes friction, and friction is my dastardly personal enemy. So wipe off the old grease, soak things in kerosene, do whatever is necessary to make those pieces SHINE.
When you put it all back together, use a light waterproof grease for lubrication. Remember that your shifter was supposed to last forever (or at least until Shimano needed to squeeze some more money out of you). Stick to a light coating, though. Too much grease will gum it up and make it misbehave.
Now we get to the fun part. Just so you don't get discouraged, it took me the better part of a week to get my shifter back together. But a lot of that was false starts and learning curve. The whole point of this Web page is to let you get back on your bike after a single evening's work.
I'm going to assume that you didn't take the upshift pawl or the holding pawl assembly apart. If you did, you're on your own to put them back together (but I don't think it should be too difficult).
- Insert the shift cam return spring into the shift cam. Be sure that the spring tab is securely in the small hole in the cam.
- Insert the cam into the shifter body. While doing so, be sure that the cam return spring does not disconnect from the small hole in the cam.
- Turn the cam clockwise as far as possible. In the photos, I am holding the shifter body so that the adjusting barrel points to the top of the picture; in that position the tab on the shift cam return spring should be in roughly the 8 o'clock position.
- Assemble the downshift lever onto the cam pivot. Place the lower (hat-shaped) bushing on the pivot, then the lever, and then the upper bushing. (Note: you may wish to practice the following step before you include the downshift lever in the assembly.)
- Install the cam pivot. Find the slot on the bottom of the pivot, and insert it so that the slot engages the tab on the cam return spring. Then twist the pivot slightly clockwise while pushing down, until the pivot snaps into place in the star-shaped slots on the bottom of the housing. Check your work by holding things together with your thumb while you look at the bottom of the shifter to be sure that the pivot is seated in the star slots.
- Install the downshift lever return spring. Catch the lower loop on the edge of the downshift lever.
- Install the top plate. This involves simply setting the plate into position. Note that the photograph shows the holding pawl return spring already in position. However, it is easier to leave it off until the top plate is in place.
- Install the holding pawl return spring. This is a bit of a tricky step. With the shifter assembly in your left hand, tilt the top plate so that there is a gap between it and the holding pawl pivot. You can then push the spring in from the side and slide it down over the pivot. If you do it right (as shown in the photograph), the upper spring loop will catch the tab on the top plate as you push the spring in. At the same time, the lower tab on the spring will engage the holding pawl. Push sideways with your right index finger, then slide the spring down over the pivot while lowering the top plate. Voila! The spring is in position and the top plate is ready to be attached.
- Install the top plate screw through the hole in the top plate and into the holding pawl pivot. But don't tighten it yet! You need some freedom of movement in the top plate for the next step.
- You now need to put the downshift lever into final position. This is easy: while pushing down hard on the top plate, rotate the downshift lever to the right (counterclockwise) until the top plate snaps downward into place. At the same time, the downshift lever will pick up the loop on the return spring. When you have gotten the top plate to snap down, tighten the top plate screw until it is just snug. Don't over-tighten it yet.
- The downshift lever return spring may be slightly out of place, preventing the top plate from getting into exactly the right position. Push down on the top plate, while using a flat-bladed screwdriver to push the copper-colored spring to the side. You will probably have to push in several places. Each time you feel the top plate move down a little further, tighten the top plate screw more. When you can't make the top plate move any lower, finishing tightening the top plate screw.
- Congratulations! You have finished the downshift assembly. Take a break and pat yourself on the back. Spend a few minutes with your family—but remember to wipe the grease off your hands first!
- Now it's upshift time. Start by repositioning things to make room for the upshift pawl. Using a flat-bladed screwdriver, rotate the shift cam counterclockwise. The holding pawl will cause it to stay in position. (If you're curious, like me, operate the downshift lever and see how the cam snaps back into place. Check out how there are two downshift levels, and how cleverly they are arranged so that pushing the lever farther gets you all the way back to the inner chainring.)
- Before you install the upshift lever, put on the downshift lever weather seal. This is easy; just slide it over the lever and wiggle it into place. Remember to make the "U"-shaped slot face upwards.
- Put the lower (hat-shaped) upshift lever bushing on the pivot.
- Install the upshift lever. Hold the upshift lever in roughly its final position, not quite centered over the pivot. This will allow you to insert the upshift pawl into the space you made for it next to the shift cam. Slide the upshift lever onto the pivot.
- You are now almost there—you have only one more tricky
step. But it's the step that took me several days to solve.
You need to install the upshift lever return spring. The
lower tab on the spring fits into a small hole inside the
pivot. The upper tab goes in a slot on the upshift lever.
The problem I had is that every time I installed the spring, it popped right back out. After a lot of attempts (including a trip to the bike shop to see if I could buy a new spring, or get the cover screw apart—no on both counts) I decided that I needed to bend the tabs. The photographs show how I gently tweaked the two spring tabs so that the spring would stay in place. Then I inserted the lower tab in the hole and used a screwdriver to push the upper one into place.
Note added 7 April, 2008: Ryan Shepherd offers an alternative (and, if you can pull it off, far superior) method of doing this step. He writes:
You mentioned that the last step with the upshift lever return spring was near-impossible until you bent the spring. As I was reassembling mine, I came across a method that worked for me without bending the spring, perhaps it may work for you as well as other readers of your page. I didn't think to take any pictures at the time, but hopefully I can describe it adequately.Note added 26 May, 2008: Ian Graeme has further hints:
- I placed the spring into the pivot, inserting the tab into the slot.
- Next, I used the side of a thin flathead screwdriver to slide the upper tab into place and at the same time held the tip of the screwdriver over the spring in the pivot, holding it in place.
- While holding the spring down, I put the top cover in place and started the screw, tightening it until it was against the screwdriver.
- Then I would slide the screwdriver out just a little bit, followed by slightly tightening the top cover screw some more. Make sure the shaft of the screwdriver is still over the upper tab in the upshift lever. Repeat this step until you are forced to pull the screwdriver out. By this point, the cover should be holding the spring in place.
Regarding step 17, the biggest problem I had was getting the final copper bushing to sit still while I installed and tightened the top cover. I found that disassembling the plastic cover from the cover screw made the whole procedure a lot easier. With the plastic cap removed you can actually monitor that wretched spring and the bushing as you re-install the cover screw. I used a set of good quality needle-nosed vise-grips to hold the threaded spindle of the cover screw and then backed out the Phillips screw from the spindle (standard anti-clockwise thread). It came apart quite readily although it's very important that your use a correctly sized Phillips head or you'll strip the head of the screw. Some penetrating oil might be a good idea too. So picking up from Ryan Sheperd's approach to step 17, I then proceeded as follows:Note added 27 Jun, 2009: Manuel Guzman writes:
- Place spring into the pivot, inserting tab into the slot
- Use a flathead screwdriver to slide the upper tab into place, while firmly maintaining pressure on the tab and the spring with the flat part of the blade (I actually used an old feeler gauge to hold everything down—it's thinner than a screw driver blade but nice and wide—enough to cover the entire spring and the tab)
- Slip the copper upshift lever bushing into place. Proceed slowly while maintaining pressure with the flat head of the screw-driver (or in my case the feeler gauge)
- Now insert the threaded spindle (the part that was unscrewed from the center cover screw) into the slot and using a 10mm socket, slowly tighten the spindle all the time checking the location of the copper bushing and the pesky return spring. As you continue to tighten, slowly back out the feeler gauge (or screwdriver blade if that's what you are using). Make sure the copper bushing is lined up nicely then tighten it the rest of the way
- Install the plastic cover and secure with the center cover screw and the anti-rotation screw I've attached a poor quality photo of the disassembled cover/cover screw.
When inserting that last spring the bottom side goes into the hole and the top part goes into the slot for the larger shifter. You just lay it in there and put everything back together. Now this will not look right becuase the shifters will be so far apart but all you do is start clicking back in place and there's no need for any special handling. I wish I would have taken pictures but I already put it back together.
- All done! Put the upper bushing over the pivot and put the top cover on the shifter. Do it quickly before the stupid spring pops back out. :-)
When you put the shifter back on your bike, two bits of advice. First, note that the shifter has some nubs that fit into the handlebar mount; you can choose one of three positions so that the shift levers are where you like them. Second, when you install the shift cable, don't install it as tightly as possible. Instead, leave a very small amount of slack (I suggest about 2-4 mm) that you can take up by turning the adjusting barrel. (You did remember to screw the adjusting barrel all the way in, right?) That will give you a way to adjust the exact position of the derailleur over the chainwheels. That's very important on an indexed shifter; it's how you keep the cage from rubbing.
That's all I have on the subject. Good luck, and may the wind always be at your back.