So for the longest time I've had quite a few issues with not being able to drop out of the biggest cog on the cassette. I've had the cassette checked, tried new chains, messed around with adjustments, had the (seriously furred) cabled replaced... etc etc etc, nothing fixes it.

I was just about to try replacing the spring when I noticed that there's a HUGE difference in how easy it is to change gears when the clutch is enabled. I'm assuming all the BB200 drownings have helped to screw it up, and I'm wondering if there's a way to bring it back to life (bearing in mind last time I messed with one of these things I destroyed it accidentally).

I'm still not entirely convinced it'll fix the gear change issue (I don't have time to take it for a ride right now), but something's definitely not right with it. Hugely draggy, and definitely messing with the gear change.

I found this... possibly a good place to start? https://www.velonews.com/gear/tech-wear ... erailleur/

I had exactly the same Richard. You need to clean the mechanism and especially the axle/Bush it rotates on. Remove mech. Remove the stopper that stops it rotating too far. Spin the cage around to release spring tension. Remove the cover over the clutch housing. Dismantle, clean and grease. I found the maintenance guide pdf from Shimano most useful.
Mine was failing to tension the chain too.
https://si.shimano.com/en/pdfs/dm/RD000 ... 09-ENG.pdf - page 23ish

I had similar issues with a new grx mech. I adjusted the clutch to reduce the tension a bit and it's fine now.

Johnallan wrote: ↑Tue Oct 25, 2022 6:21 pm I had similar issues with a new grx mech. I adjusted the clutch to reduce the tension a bit and it's fine now.

Try this first, though if it worked initially, it's probably time for the surgical option.

Last time I took one apart I ended up snapping it in two. Bolt failed despite still being under the recommended torque (page 25 on that guide).

Resulted in a drive across the country to get a replacement as I was off to the US for a race two days later.

Take the three bolt cover off and flush it with WD40/GT85 then

boxelder wrote: ↑Tue Oct 25, 2022 6:51 pm Take the three bolt cover off and flush it with WD40/GT85 then

Aye. Hoping I don't make it worse though.

Richard G wrote: ↑Tue Oct 25, 2022 7:05 pm

boxelder wrote: ↑Tue Oct 25, 2022 6:51 pm Take the three bolt cover off and flush it with WD40/GT85 then

Aye. Hoping I don't make it worse though.

Thats what I did. Or use brake cleaner for a bit more skoosh. I've taken them to bits, cleaned and re-greased too but its a bit of a fiddle

BB200 killed my clutch too. Disassembled and cleaned up as per this video.

https://youtu.be/X_aQxSQahrA

Ugh, the inner plate thing came off when I was cleaning it. Am bricking trying to get it back on now as I know what happened last time.

Edit - Interesting that literally the first thing in that vid is what was happening to me, yet three different bike shops failed to diagnose.

Hmm, turns out I don't have any lightweight grease. I guess normal bearing grease will do for maybe 20 hours of riding right?

I can replace it when I get back.