Just got my bike back from LBS with new shifter cables put in. When I got it home my Ultegra R8000 front der indexing is off and the barrel won't get it there, so I decided to tighten the cable.

I loosened the cable tightening bolt and it looked frayed. Could it possibly be frayed already just from its initial installation? (I haven't even ridden it yet). Or could the LBS have somehow "forgotten" to put the new cable in?

Even weirder, now the tightening bolt won't tighten. It just keeps spinning. I don't understand how I could have stripped it just by loosening it. And it was tight enough to shift before I started working on it. Could I have disengaged it from an underlying mounting nut somehow that now I'll have to fish out to re-engage the bolt?

Sorry the picture isn't better—this is the best I could get after 20 minutes of trying, and I have to get to bed for a race in the morning (guess I'll be racing my training bike). Many thanks for any advice!

Yes it can. A good shop would have spotted that, thrown it out & put in another at no extra cost to you. Sometimes it’s the angle you cut the cable at, or simple “ham fistedness”.

Yes, it can. Some cable anchor designs are more prone to this than others, the "hole through the bolt" design especially.

Cables "generally" won't do that unless there is a burr at the end of the cable housing. In my years of working in bike shops years ago and the hundreds of cables I replaced I don't recall more than a handful were defective out of the bag; however, I often encountered cable housing with a burr on the end from a previous person not cutting it correctly. A burr will do that to a cable in short order depending on how sharp it is and if it's burred to the inside (cable runs directly against the burr).

I agree with Velocivixen, a good shop should have caught that. You wouldn't have stripped it by loosening it. It may have been over-tightened in the shop and only had a couple of threads left and your tightening it back may have stripped it the rest of the way. Those bolts are easy to strip if you don't work with them all of the time and get a "feel" for them. Luckily replacements are either cheap or free at a shop.

Are you sure this is metal that is fraying? Looks to me as a cable coating that is abrading off. Some "low friction coated" cables are known for this. Andy

I think that a cable job should include getting the shifter dialed in, is that unreasonable? If you are trying to decide whether to complain to the shop I would say you should on principle, I don't know what your relationship or the general competence of the shop though, it could also be better to just go somewhere else

Andy's got a good point there. Are the individual strands of wire broken and fraying or just the cable coating? Either way, the shop should check out the cable housing.

+1 and coated cables can tend to slip under the clamp nut which might explain why the derailleur was out of adjustment. Some of us scrape off the coating where the cables get clamped for this reason. This is just a guess though but something worth checking and you should take it back to the shop and let them try to fix the issue.

This is all incredibly helpful everyone, thank you.

I’m definitely taking it back to the shop. The most important thing to understand was whether this could be an innocent problem or if it was definitely a case of didn’t-replace-the-cable.

Sounds like there isn’t enough evidence to conclude bad intent, which is the outcome I was hoping for. I’m also glad to hear I can’t conclude he stripped the bolt. More likely I screwed it up at some point and the additional wrenching at the shop didn’t help.

Amazingly this isn’t the first time I got a bike back with poor indexing. Scarily, it’s still probably the best shop in the area. It’s why I’m learning to do more and more of my own work, and will probably be hanging out here a lot.

I really appreciate it again everyone!

As Andrew R Stewart said it is probably the coating coming off. It certainly looks like a coated cable.

In terms of bolts they can be easily stripped using poor tools and poor hands. Always use high quality hex wrenches and as gentle of a touch as possible and if it is an aluminum bolt or cheap steel or something just be extra extra careful with it or replace it with a good stainless steel bolt or if you need to save the weight forged titanium.

Take it back see what they say but more than likely that is coating. If they didn't replace housing and bar tape that should be done but if they offered and you refused that is bad. Anytime I am replacing cables I want to replace the housing and I want to replace the bar tape with regularity. It soaks up your sweat and since it goes down and down is your bars and your bars are hidden under the tape you have zero idea what is going on. In terms of housing it collects all the grit and grime or coating from cables and get gummed up and leave you with poorer performance or premature wear on cables. You can flush it and maybe get more time with it but honestly I would just replace it. Jagwire makes some excellent kits the Elite link being my favorite and cheaper in the long term as the "beads" (the linked housing) will last forever basically and you just replace the inner liner which is cheap and the cables and it works a treat and looks nice as well.

Looking more closely it does look like something viscous. Slide your bare fingers over it and if you get the sh*t poked out of the end of your finger - it’s a frayed wire.