the first level of disassembly of the left (rear) shifter. · 2010. 1. 27. · shimano shifters....

Shimano shifters

The bar-end shifter for my rear derailleur suddenly jammed. I could use the upper three or four ratios, but couldn’t shift down. The sales slip was dated 2000, so it’s not likely I could have claimed warranty (July, 2007).

They are sold only in sets – $80 – so I got new bits and pieces that I didn’t really need. Here’s the old kit… let’s take it apart.

The pieces in the lower center take up cable slack. The plastic cover is essentially a lock nut.

The first level of disassembly of the left (rear) shifter.

It clamps into the handlebar through an expander, three sections of a cylinder loosely bound together with a weak spring. The expander bolt has a hex recess in the threaded end, so it can be tightened from the shifter body.

Does that soft rubber finger grip slide off? Yes.

That looked like a washer, and indeed it is.

The total rotational travel of the lever is limited by tab A running in slot B.

Tab A

Slot B

Turning the lever over, we see a collection of metal bits, one of which looks like it may be a press- fit lock washer. We pry it up….

I wasn’t sure what the remaining bits of metal were, but I thought it would become apparent if I removed the plastic shell. Obviously not the correct sequence for disassembly – I destroyed it to get it off.

But what remains is clearly a slotted nut. The tips of my long-nose pliers fit into the slots and extracted the nut.

Notice also the warped washer constraining two balls that roll on a ridged ring. It holds the lever where you put it. On this (old) shifter, the action is smooth because the ridges are worn into a groove. On the new one, I could feel the ball rolling over the ridges as I shifted.

Plastic shell

Slotted nut

Warped washer

With the slotted nut removed, the remnant of the plastic cover comes right off, and we get a better view of the warped washer and how it locks onto the threaded hub.

Flipping the warped washer over…

The groove worn by the balls in the ridged ring is clearly apparent here.

The core extracted from the other side

And taken apart…

The other side

The complete set of bits and pieces of the left shifter. This is the simple one, since it doesn’t have indexing. I continue to be impressed by the complexity of things that seem very simple from the outside.

Imagine planning, designing, manufacturing, inventorying, coordinating and assembling all these components. And $80 is the retail price for Dura-Ace, the high-end product line. The same thing, more or less, sells for a lot less in the other Shimano lines.

The right shifter, for the rear derailleur. I had the impression that it was good for 9 and 10 speed cassettes, but I see here that it’s 8 and 9 instead. Well, 9 is what I have. I guess if I ever go to 10, I’ll have to get yet another shifter assembly.

The first step of disassembly.

As with the left shifter, the cable wraps around in the groove of the handle as it rotates.

Cable channel

This time we know immediately to remove the lock ring and then the slotted nut. It’s a little different on the inside because it can be switched between friction and indexed shifting modes.

Removing the slotted nut to expose the next layer

This ring is responsible for the function of switching between friction and indexed mode. Under control of the external ring (with the heavy wire handle), the variable radius slots relocate the balls so they either fall into the index stops or rotate freely at a smaller radius in friction mode.

Taking apart the rest of the assembly. This time, the balls are constrained by two warped washers, and a dented ring defines the index stops. Notice that the index spacing is not the same between each pair of adjacent stops. This fine detail is why you can’t just randomly mix this shifter with any arbitrary rear derailleur and cluster.

Variable radius slots

The upper warped ring constrains the balls, as we saw on the left-side shifter. I’m not sure where the second warped ring rides. The ring with variable radius slots surrounds the balls.

The various components spread out for inspection, including the smaller-radius ridged ring for friction mode. By comparison to the same component on the other shifter, you can tell that this shifter got no friction-mode usage.

Something in this picture probably explains why the shifter failed, but my uneducated eye cannot pick it out.

The other side

Even this side has a certain amount of complexity.

Yes, the piece that looks like a ball- bearing race is exactly that.

One more piece to remove from the top side

The complete kit

The bike, new shifters in place