Ultegra RD-R8000 derailleur chewing up shifter cable - WTH?!
 

I have an Ultegra RD-R8000 (GS cage) that has chewed up multiple shifter cables (Dura Ace and Jagwire) at the cable bolt. Seems that when in a high gear (11t chainring) the cable bends over the clamp edge and starts to fray there. Have any of you all found a fix for this? I really don't like replacing cables every 2000 miles. What the heck kind of bad design is this?!

I have a good photo but can't post it bc I'm a newbie :(

Thanks all!

Welcome to bike forums.
Yep no posting pictures until 10 posts.

But if you upload one into your gallery, we can post it for you.
Just let us know it’s there.

Barry

Are you over torqueing tightening the clamp bolt. Or, are you sure the cable is being installed properly. I have a 7000 GS and have never had that problem. I have thousands of miles on it, still the original cables from when I built the bike. I did have to realign how the cable was clamped at the clamp bolt due to having it at the wrong angle and causing difficulty with the lever pull, too much pressure to actuate the lever.

https://bikeforums.net/g/picture/25261382

https://cimg8.ibsrv.net/gimg/bikefor...b3f513936a.jpg

I don't know much about Shimano but before I put a new cable on I'd check for extra friction/tension:

Pivot spring
Cage spring
Pulley wheels

If all you're doing is replacing the inner cable each time it breaks, it's time for new housing front to back. Something is creating tension that increases at the end point.

This seems like an unfortunate side effect of the geometry of that cable mounting approach, doesn't it? When pulled taught (in the largest sprocket), the cable angle between where it exits the cable stop and where it enters that anchor is basically 0 degrees -- straight in. But when fully loose (in the smallest sprocket, and as pictured above), it's pulled that cable angle over to something like 60 degrees. That anchor doesn't pivot on its own, so it's just continually bending that cable. And these Shadow style derailers generally have pretty stiff springs as well, which probably just increases the force on the cable at that delicate point.

The fact that others don't seem to have problems with it suggests there may be other factors at play. But it sure doesn't look like a very forgiving design, does it?

To help narrow it down.
A bad cable housing will effect the felt force at the shifter, but not the tension at that point of the cable.
I wonder if the “L” limit screw is set too tight. This would make getting into the largest cassette cog difficult and cause you to use excessive force at the shifter??

Barry

Seeing how there is an even cut at the cable, kinda, sorta, suggests to me that the clamp may be too tight. Hard to say for sure though. I installed some of these "Alligator, 31 strand Superior Shine" for my 6600 shifters which usually fray at the shifter. They use more but thinner strands than Shimano or Jagwire and are compatible with both housings and cheaper too. I'm hoping that the thinner strands make them less prone to break from the constant bending at the shifter drum and maybe better for the OP's derailleur situation. I only have about 2K miles on them so far and the Shimano and Jagwire's best cables would usually last around 4-6K miles so can't yet say if they're actually better but worth a try in your case. ALLIGATOR 31-STRAND INNER CABLE (alligatorcables.com) I found the best prices were on Ebay.

From the picture, it looks like the cable is not installed properly. I think it should not have that big curve in it. I believe the end section of the cable coming out of the clamp should be routed through the channel at the back end, and coming out almost straight back from there. The way it is curving is causing friction at the clamp, causing fraying, over tightening could also be an issue. The only contact should be right where the cable goes into the clamp.

https://attachment.outlook.live.net/...animation=true

Correct - the cable is at a bent angle when shifted onto the smallest cog so it rubs over the corner of the derailleur and frays. I don't want to alter the der but I wondered about using a dremel to smooth out that edge or carving a small channel? Or what about adding a ferrule of some sort? Looking at the Shimano install instructions there is not normally a ferrule there (sorry, again, as a newb I can't post the Shimano link but you can google Shimano R-8000 dealers manual pdf and look at page 17.

Pretty sure the install of the cable in the groove is correct based on the R-8000 dealer's install manual pdf (google that since I can't post a link as a newb). Over tightening may be an issue, however?

I uploaded a second photo with a better angle of the clamp bolt showing the channel and cable. I'm 99% it's all installed correctly. Maybe the admin can link to my pic in the album (thanks!). Ignore the bit of road goop partially obscuring the channel.

So to conclude for now;
1) I'll try using a Jagwire non teflon-coated cable to reduce friction.
2) Will also check the torque on the bolt in case it's too tight.

THANK YOU ALL for your sage advice. Really appreciate it.

If you want to keep chewing up and replacing cables, stick with how you are doing it. If you look at the clamps in your picture and mine, they look identical. I watched a video, I believe Parktool.com, that of an actual mechanic doing the installation because the way I was doing it, by the directions, was not working. Once I switched the routing to the same as seen in the video, it all worked. You may want to at least try it. Trying to help.

From the tech manual for this derailer (https://si.shimano.com/api/publish/s...001-04-ENG.pdf), it looks like the cable is installed correctly. bchains has curled the untensioned end of the cable back towards the outside, but I don't think that untensioned end would impact what happens on the tensioned side of the anchor bolt, would it? The tech manual shows, down on pages 17 and 18, what the derailer looks like in low gear (tensioned with no cable angle going on).

delbiker1 could you post a picture of exactly how your cable is routed, and how it looks with the derailer shifted into the smallest sprocket, so bchains could see exactly what differs and make his or hers match yours? It sounds like you've found the by-the-book method not to work as well as what you currently have.

what is the length of the cable housing from stop to derailler. IIRC needs to be something like 240mm?

of interest as I will be putting one of these on a build soon

Something looks a bit odd but getting 2000 miles on a rear shifter cable is not that horrible. They don't last for ever as the rear is shifter the most. I would guess I replace mine twice a year but I do ride a lot. I don't seem to have this problem and I upgraded by 6800 rear derailleur to r8000 because I like the angle of the derailleur better. Bike shifts perfect.

As I stated in an earlier post, when I installed the derailleur according to the instructions, I could not get it to work properly, too hard to push the lever to make the shift. The video I watched, pretty sure it was Park tool, showed the routing as I now have it. What I know for sure, when I rerouted the cable as it was in the video, it all worked properly. I have the same cables on the bike now, over 2 years and somewhere in the 4,000 to 5,000 mile range. The housing from the front of the cable stop to the interior of the derailleur attachment is right at 200mm, 54 cm frame and IIRC, 42cm stays. I had more of a loop, someone suggested a smaller loop would improve the shifting, it did make it a bit quicker. Here are some pictures.

https://attachment.outlook.live.net/...animation=true

https://attachment.outlook.live.net/...animation=true

https://attachment.outlook.live.net/...animation=true

https://attachment.outlook.live.net/...animation=true

https://attachment.outlook.live.net/...animation=true

Sorry, no pictures attached

I have the same derailleur but I question whether you have an 11T chainring - just shifted to all the combinations - I can cross shift to all but the smallest 3 cogs - and in no combination is there even the slightest possibility of cable schred - if I were you I'd take it to a reputable shop and have them set up a new cable .

From what I see the cable is routed the same as the way I route them and I have not had any breakage where the OP is getting breakage. It looks like there is some teflon on the cable where it goes through the pinch bolt. My recommendation is to strip that off the cable at that point so the pinch bolt does not need to be over-tightened to compensate for the teflon coating.

Well guys, just to close the loop on this I emailed Shimano customer service and sent very close up photos of the derailleur. They responded:

"After reviewing your case with our QA team we have found there may be an issue with your pinch bolt and that it may getting over torqued due to a bad plate. Manufacturing side not user caused. We will be sending you a new chain, derailleur, and a cable set kit."

I had heard about this design issue and that there was a correction of sorts on another forum and it seems that it is true. Hopefully anyone else with a similar issue can obtain this same level of service and support from Shimano.

Thank you all for your input and help with this.

Wow -- great customer service from Shimano! "Over torqued due to a bad plate." Interesting. I'd certainly be interested to know if you can tell any difference, visually, between the new derailer and your existing one when you receive it.

Save the old one for pulley wheels etc

When indexing first came out (around 1984, of course this statement disregards history before I was alive when other indexed systems were offered) Shimano suggested a replacement rear shift cable every 1000 miles or so was the maintenance schedule. Now nearly no one I know of does that. Instead most all will replace the cable after it has started to fray, often after it broke. After the first broken cable many riders start to pay more attention to their cables and some replace them before they fray to insure best riding performance. After all the cost of a cable is pretty minor. Andy

+1 and bchains, please post a photo of the differences between the two. I always am curious about these things.