Ultegra 6800 rear s...
 

Ultegra 6800 rear shifter fix

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Twice last winter I had issues with this not engaging when shifting - nothing a good blast of GT85 wouldn’t fix. Same issue again but GT85 does nothing this time rendering the ‘winter’ bike unusable. What’s the most cost-effective fix as I can’t really afford a new set of integrated brake/gear levers. Taking them apart looks like a disaster waiting to happen with so many intricate bits. Anyone had this issue and how did you resolve it? Don’t really want to get the ‘nice’ bike shit up every time I fancy a road spin.

 
Posted : 06/01/2024 5:51 pm
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My 6800 shifter had a problem where the small button would fail to release cable. I sprayed a load of disc brake cleaner into the shifter body and then followed that with silicone spray (fork juice). It seems to be fine now.

 
Posted : 06/01/2024 6:07 pm
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Cheers ac282 - what small button? The brake levers and shifters are integrated. I’ll persevere with spray for the time being

 
Posted : 06/01/2024 6:10 pm
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Is it a 6800 shifter or a hydro unit? If it’s 6800 you can replace the main lever with the shifter mechanism for around £100 if yours is dead.

part no Y00E98010

 
Posted : 06/01/2024 6:13 pm
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silly - it’s a calliper brake unit - cheers

 
Posted : 06/01/2024 6:14 pm
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Tried a new cable ?

 
Posted : 06/01/2024 6:24 pm
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fossy - not yet!

 
Posted : 06/01/2024 6:26 pm
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If you have the super dooper shimano cables they can go fluffy and bung it all up.

 
Posted : 06/01/2024 6:35 pm
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If you have not changed the cable then do that before you do anything else.

You'll remove the cable and you'll find it all. Freyed behind the cable head. These shifters are notorious for it due to the sharp bend on the inner entering the outer in order for the cable to run along the bar.

This stops the cable releasing when you push the button and release the ratchet.

 
Posted : 06/01/2024 6:39 pm
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You’ll remove the cable and you’ll find it all. Freyed behind the cable head

This!

Thought mine were goosed, was shocked when I opened them up to inspect. Summer bike which shifted perfectly until suddenly it didn't, cable was frayed almost all the way through.

New cable sorted it.

 
Posted : 06/01/2024 7:03 pm
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Same as tail rat, mine used to do it, started like the indexing was slightly out and then when completely to pot.

But for the last two years owning mine, every now and then shifting down the cassette just didn't work randomly!

 
Posted : 06/01/2024 7:08 pm
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Yep, this. Same on several other Shimano shifters. Design fault I would say.

 
Posted : 06/01/2024 7:10 pm
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Cheers all - new cable it is then!

 
Posted : 06/01/2024 8:32 pm
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+1 cable, had some 105s which did that.

 
Posted : 06/01/2024 8:36 pm
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@rascal if it was one of the coated cables they shed their skin like a snake. This can clog the shifter and the outer cable. Clean with compressed air and a light lube, firing it down the inside of the shifter and cable but beware, it sometimes pops out with some force. Replace with a good quality stainless inner from Shimano or Jagwire - without any fancy coating! Hope this helps.

 
Posted : 06/01/2024 9:05 pm
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The Optislick cables seem better in that respect than the Polymer coated cables.

 
Posted : 06/01/2024 9:17 pm
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Ps stop spraying solvent based lube into your shifter all you have done is wash out the useful grease

 
Posted : 06/01/2024 9:29 pm
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OP here. Pulled the gear cable out and had a play. Turns out there’s a really thin length of housing just under the hood that the cable slides though. The cable was fine but the housing was chewed up so I cut 20mm off and reinstalled the cable. Job jobbed.

 
Posted : 09/01/2024 12:06 am
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Put a new full cable in. Might as well. Bit late now though. 

 
Posted : 09/01/2024 12:15 am