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How to service a Shimano TZ rear mech?

I’m trying to swap out the top jockey wheel on a rear shifter mechanism.

The bottom jockey wheel simply unbolted as expected but the top one seems to share a shaft with the main spring rather than having its own bolt.

I can twist one of the cage plates a complete turn but it doesn’t unthread anything.

I can see a steel nubbin through a small slot, but its not shaped like a bolt head.

Is this Unserviceable?

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Bicycles Asked by Criggie on December 31, 2020

3 Answers

3 Answers

These units are simply not meant to be serviced. The end of the bolt looks stamped like a rivet anyhow.

It may be a bit short as an answer but it's the (bitter) reality.

Correct answer by Carel on December 31, 2020

I cleaned my Shimano Tourney TZ today and i had the same problem (that's why i'm here). I cleaned the bottom wheel and it was clogged with dirt and hairs .I cleaned the top wheel the best i could because i can't remove it. It now moves good enough without having to struggle and breaking the derailleur.

This answer confirms that the top jockey wheel is not removable in another Tourney rear derailleur.

Answered by Bruce on December 31, 2020

Removing the top jockey wheel is simple.

Because the derailleur is budget the shaft for the top jockey wheel is riveted.

The photo also shows that there is a screwhead at the top. It will be necessary to remove this by first taking off the plastic cover, then cutting off the screw head.

This allows the shaft to be removed.

This shaft is then replaced with a standard bolt and nut on the outside, having serviced the jockey wheel.

There is rarely a component that is not serviceable. Manufacturers are relying on you not being able to work it out, or as in this case replace a riveted shaft with a standard bolt. A bolt cost a whole lot less than a replacement derailleur.

Answered by johnggold on December 31, 2020

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