I think I've set something up wrong

[Peter Salt]

Alright, so I've put this bike together from scratch with used parts. Did an 80k ride on Saturday and  something isn't entirely right with the rear derailleur, I think.

Based on below, does this look/sound right to you?

Biggie-small, line through axle and pulleys not 90° to the ground but not miles off:







Small-biggie, guide pulley very close to big sprocket (2-3mm) but shifting fine up and down:





Cross-chain positions (if you want to see them):





Chainring: 50/34
Cassette: 11-32
Chainstay length: 16 inches
Chain length: 54 links

Short cage derailleur, according to the manual, suitable up to 33t sprocket. 'B' adjustment screw in max position.

Any advice welcome.

 

[Cycleops]

You might like to check the chain length. Remove the chain and run it big front to big rear ( not through the derailleur) and add two links.
I would think that derailleur might be struggling but if you say it’s within spec…..

 

[Sittingduck]

IMO take one link out and don’t run 32 largest sprocket on an SS caged mech, regardless of what the manual says. I wouldn’t go more than 30 likely 28 on an SS, just my opinion.

 

[Peter Salt]

You might like to check the chain length. Remove the chain and run it big front to big rear ( not through the derailleur) and add two links.
I would think that derailleur might be struggling but if you say it’s within spec…..

Yeah, I do have a 53 link chain somewhere, will see how that looks. Just double-checked the documentation and the spec says max 28t, oopsie.

IMO take one link out and don’t run 32 largest sprocket on an SS caged mech, regardless of what the manual says. I wouldn’t go more than 30 likely 28 on an SS, just my opinion.

As above, it actually says max 28t. Will try and find the mid cage somewhere as that accepts 32t. Correct me if I'm wrong, the difference between a short and mid cage is literally just the plates that hold the pulley wheels, right?

 

[Ming the Merciless]

What is the capacity of the derailleur?

 

[Ian H]

It's the difference between the chainrings which is the problem for your rear mech.

 

[I like Skol]

You are exceeding the max chain wrap of your derailleur.
11-32 = 21
50-34 = 16
Both added together is 37, so you need a mech with at least a 37 tooth capacity. This is NOT the same as max sprocket size!

 

[Peter Salt]

Cheers everyone. Looking for the mid cage plates on the Interwebs as we speak... Don't suppose anyone has a pair laying around?

 

[Peter Salt]

I'm not familiar with this retailer, but they do seem to have what I need in stock:

https://www.sjscycles.co.uk/gear-sp...er-plate-plate-stopper-pin-gs-type-y5yc98080/

https://www.sjscycles.co.uk/gear-spares/shimano-ultegra-rd6800-inner-plate-gs-type-y5yc25000/

I think that's all I need?

 

[alicat]

SJS are a solid bet for anything out of the ordinary.

 

[TTSS]

Given the prices good quality used parts are going for, it might be worth buying a new one and selling your old one, I bet there's not much in it tbh.

 

[si_c]

To be honest I wouldn't go faffing around trying to change the plates on a SS series derailleur with those from a GS. It wouldn't surprise me if that was the only difference, but I wouldn't want to try and find out either.

My suggestion would be to get a 105 R7000 or Ultegra R8000 derailleur and put it on in place of the current Ultegra 6800 - you'll get a number of benefits by doing that, not least of which is greatly increased capacity and the option of running a larger 34t cassette if desired, plus you'd still have the old 6800 to either resell and offset costs or act as a backup. The plates alone are about £30 including shipping, with a new GS derailleur costing £56 from wiggle.

 

[Peter Salt]

Given the prices good quality used parts are going for, it might be worth buying a new one and selling your old one, I bet there's not much in it tbh.

This particular derailleur has actually been through a flood, actually. I've completely disassembled, cleaned, greased and reassembled before putting it on the bike. Works perfect, I just misread the manual and thought the short cage will manage a 32 tooth. Amateur mistake.

Reached out to LBS and asked if they have the plates by any chance, even used, or if not if they can source them for me - prefer to support the brick and mortar shop before buying online.

For the time being, the bike runs alright on a 53 link (slightly shorter) chain up to the 28 tooth sprocket so I'm just treating it as a 11-28 10-speed.

To be honest I wouldn't go faffing around trying to change the plates on a SS series derailleur with those from a GS. It wouldn't surprise me if that was the only difference, but I wouldn't want to try and find out either.

My suggestion would be to get a 105 R7000 or Ultegra R8000 derailleur and put it on in place of the current Ultegra 6800 - you'll get a number of benefits by doing that, not least of which is greatly increased capacity and the option of running a larger 34t cassette if desired, plus you'd still have the old 6800 to either resell and offset costs or act as a backup. The plates alone are about £30 including shipping, with a new GS derailleur costing £56 from wiggle.

Yeah, the R8000 swap sounds sensible. If I can't get the plates for a reasonable price ( say, £15) I might just do that.

 

[Peter Salt]

An update on my predicament:

Ended up buying a new R8000 mid-cage RD. This is because the plates alone for the 6800 were about £30, an entirely new 6800 for £60 and a new R8000 for £90. Somehow, in my mind, the latter appeared as the best deal.

Got it two weeks ago but decided to wait with the fitting as I had two events coming up and figured I'm better off with a RD that works but technically is 10-speed then swapping just before the events and risking some sort of catastrophic failure.

Really wished I had something bigger then the 28-tooth during the Sportive

All fitted now, looks good with the original 54-link chain, no slack even in small-small (biggie-small on pic).



Thanks for the help, Everyone

 

[si_c]

An update on my predicament:

Ended up buying a new R8000 mid-cage RD. This is because the plates alone for the 6800 were about £30, an entirely new 6800 for £60 and a new R8000 for £90. Somehow, in my mind, the latter appeared as the best deal.

Got it two weeks ago but decided to wait with the fitting as I had two events coming up and figured I'm better off with a RD that works but technically is 10-speed then swapping just before the events and risking some sort of catastrophic failure.

Really wished I had something bigger then the 28-tooth during the Sportive

All fitted now, looks good with the original 54-link chain, no slack even in small-small (biggie-small on pic).

View attachment 644304

Thanks for the help, Everyone

The new derailleurs also sit further inward towards the wheel and in my experience have a lighter action than the old 6800 series derailleurs. That and the 34t max sprocket should make life easier!