Derailleur pivot point frozen

[mrcharly-YHT]

The pivot point (where the bolt goes through to the hanger) on my derailleur is almost jammed solid (Shimano Tiagra 4600 I think).

Took whole derailleur off bike, and needed leverage of long allen key just to get it to pivot. Tried to work some oil in there and it just about moves, but not decently.

Seems that the internal gubbins are held in place by a circlip (blasted pingfuggits).

Any suggestions?

also, would a GRX long cage rear be compatible with Tiagra shifters?

[Hot Flatus]

Had same on di2 6800. I replaced the pivot assembly (was about £16 on ebay).  If its Tiagra and its that old I probably wouldn't bother.

[mrcharly-YHT]

Seems not compatible with GRX (only 4700 will work).

Very hard working out what I have, I think it must be 4600 since it is 10 speed (why don't shimano clearly put the damn model number on the shifters?).

[JonBuoy]

I have stripped, cleaned, regreased and rebuilt the pivot assembly before now on Shimano rear mechs - I assume that they are all similar.  It involved a bit of swearing to get the spring to re-engage properly but no special tools.

[Hot Flatus]

You have to loctite the pivot bolt, but not do it up stupidity tight or it impedes the pivoting.

[rr]

I took the circlip off, pushed/tapped the bolt out and cleaned and regreased the pivot. I remember running my demelalike through it with one of those bullet shaped polishing pads on it. The spring was a brief pain, during reassembly but not a hard job.

[Feanor]

Those pivots come apart fairly readily.
There's a little peg you can unscrew to allow the sproing to un-tension before you unmantle it.

Re-assembling them can be a bit tricksy, getting the legs of the torsion sproing into the right holes, and then holding it all together as you wind the pre-load into the sproing and try to hold it there whilst screwing in the little peg wot stops it un-winding.  Can nip at you a bit.

As an alternative, dunk the whole thing in diseasel overnight.
Then work the pivot by hand vigorously.
Repeat.

This will usually free them off after a few repeats.

[mrcharly-YHT]

I slackened off the bolt last night. That freed it a bit.

Dunking in diesel seems a viable solution. Don't have a tub to hand, must source some.

[Hot Flatus]

All sorts of grimy shit gets in there

[bobb]

If loosening/dieseling doesn't work and you want to take it apart there are lots of vids on YouTube. I think it was this one I watched last year before tackling a very stuck XT mech.

You will wish you were inbred and had three hands, but with a bit of swearing it's pretty straight forward.

[JefO]

.... also, would a GRX long cage rear be compatible with Tiagra shifters?

Yes

[Lightning Phil]

Pretty easy to service, just a spring in there with the end slotting in one of two holes at the back.  They simply get gunked up.  Clean, fresh grease then reassemble. Remembering to wind beyond the stop before finally tightening up, so you get the tension.