5-19 Rehabilitating Shimano STI Integral Brake/Shift Levers

If you have a jammed Shimano STI shifter, you cannot go into the mechanism and replace parts because Shimano doesn’t sell the internal parts separately. Beyond that, opening the mechanism voids the warranty.

In the 5th edition of Zinn & the Art of Road Bike Maintenance, I advise trying an injection of aerosol chain lube to free up a sticky mechanism (pages 93–94). If that does not work, you can replace the entire shifter unit of two blades and internal ratchet (Fig. 5.38). Note that this approach may be false economy; you save the lever base, rubber hood, and band clamp, but you generally pay more than half the cost of a pair of levers for a single blade assembly. But if you find a bargain somewhere, here’s the procedure:

1. Remove the shift and brake cables and the brake-cable hook from its notches.

2. With a 2mm hex key, remove the setscrew holding the pivot axle (Fig. 5.38) in place under the lever. Expect it to make noise while being unscrewed and for it to be hard to remove. There is a lot of threadlock compound on it to keep it from vibrating loose.

3. Push out the axle with a blunt nail struck by a hammer, and catch the spring.

4. Pull off the old blade assembly and insert the new blade assembly.

NOTE: If you have a lever that is Flight Deck–computer compatible, you will need to unscrew the cover on the inboard side of the lever under the gum hood and push the end of the wiring harness up through the lever as you pull off the blade. Fish the wires of the new blade back in the same way, and replace the cover to hold the little rubber part and the four terminals in place.

5. Replace the return spring and axle. The return-spring hook goes in the hole adjacent to the cable-hook notches, and its other end must sit on the shelf adjacent to the setscrew, not down in the wide notch in the lever body. Line up the rounded groove in the axle with the setscrew.

6. Put some threadlock compound on the setscrew and screw it back into place.

7. Replace the cable hook into its notches.