Ultegra 6800 long cage rear derailleur indexing issues

Discuss light weight issues concerning road bikes & parts.
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Joined: Mon Aug 29, 2016 11:19 am

by alcatraz

Hi WW's...

A friend is having some trouble indexing gears. He is heavier, has above average power, wearing out chains pretty fast like a few months. His bike has done maybe 10kkm but the derailleur is only about 4000km.

In any case I'm having trouble getting the 3rd and 10th cog on the cassette to index correctly. Seems there is always a compromise between the two.

I did put a sram cassette on his bike because shimano didnt have any with the gearing of his taste. He used to use ultegra cassette and chain and it worked well back then however the stuff was newer and in better shape. I wouldn't call it end of life at all as it is now. Should be plenty of km left in the stuff and yet still this problem. Cable was changed recently by a shop, maybe erroneously. (Bike is a trek domane, full 6800 ultegra, internal cable routing)

There is a slight indexing difference shifting up compared to shifting down but I wouldn't call it huge.

One thing that surprised me is that when running low gears the cable makes an almost 90 degree turn coming out of the barrel adjuster. This apparently is normal (although to me seems like a design flaw). There is a short tube/lining just at the exit point that has come off. I wonder if this could have impact on indexing and if anyone has a good idea how to make/find a working replacement.

When the derailleur is in the high gears (small cogs) the cable exists the adjuster almost straight (no sharp turns). Seems to me that low gears will be impossible to index when the cable exit point gets worn because it only affects low gears, not all gears equally.

Does anyone understand what I mean? Got any tips?

Thank you for reading and any comment! /a


by Weenie

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Joined: Wed Jan 10, 2007 10:56 pm
Location: Canada

by goodboyr

Check rear hanger alignment and ensure attachment screws are tight.

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Joined: Tue Feb 05, 2013 2:46 pm

by WinterRider

The cable is clean.. no oil, grease, dirt inside the rear cable? Observed some issues a few times.. not a likely candidate. Thoroughly degrease the wire and cable inside going to rear de.

How many wire tension adjusters in the routing.. 2.. 3? Observed high tension on one in the line giving issue.

Me .. I'd make sure the line not fouled.. drop all tension down same at adjusters (not zero just enough to have small amount)... adjust the rear de to just quiet prior to climbing onto the 2nd cog.. and gradually increase wire tension if needed. Wire angle.. can be factor where it attaches to rear de.. make sure it's right in that groove w the securing plate placed correctly.

Length of rear wire into de... sometimes a wider hoop works.

Wire quality could be poor.. stretch. First step after replacing wire is to work it manually.. seating all the adjoining surfaces. Being a replacement at shop.. often not done.

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