TKJava

I took my bike in to the LBS yesterday to discuss getting the derailleurs adjusted as I am getting some chain rub on the inside of the front derailleur cage. Basically my chain rubs when I press hard with the left foot. This as I understand it can be a simple adjustment of how far the cage moves to the outside when shifting into the large chain ring. I also mentioned some less than smooth shifting in the rear. After about 15 seconds of shifting the bike the LBS mechanic says "you need to replace the shifter cable from the hoods to the rear derailleur, these often get twisted inside the tubing" (I have internal cables). He also said that over time the end of the cable can simply break off inside the hood when they are "too old". This sounds a bit flaky to me. Under what circumstances can a cable a) get twisted and b) why would replacing it cure that?

I wanted to add that my bike is 4 years old and is well taken care of e.g. I don't ride in the rain, it's cleaned, dried etc.

ridelikeaturtle

I've seen cables fray, due to water ingress and corrosion, in very old cables with deteriorated housings, and yeah everything needed to be replaced.

But twisted in the housings? Ehhhh... I'd get a second opinion.

Kapusta

While the issue you are having may or may not have to do with the condition of your cables/housing, the mechanic may have determined that the condition was poor and dis not want to get into trying to tune a bike with bad cables.

Although a simple cable tension adjustment might have been all thats needed for the front, the rear may have required more work.

Or maybe his rent was coming due and things were slow at the shop.

DrIsotope

I'm going to give the guy at the LBS the benefit of the doubt, and assume that when he said twisted he meant crossed-over. When fishing the cables through the downtube, it's pretty easy to cross the FD and RD cables over one another, so they would be rubbing, and result in poor shifting. It's not entirely uncommon for pre-built bikes to come from the mfr. this way.

As to the cables breaking off at the hood, unless you have older Shimano levers (like say 5700/6700,) or haven't changed the cables in a decade, it's not much of an issue.

kingston 

Replacing the cables on a 4 year old bike sounds reasonable to me. I typically replace my cables more often than that as preventative maintenance. Seems to me there are two reasonable approaches. Take your bike to the shop and let them do what they do and charge what they charge, or learn to work on your bike yourself. Adjusting the FD is a 30 second fix with a phillips screwdriver. Hard to charge someone for 30 seconds of labor. When I worked as a mechanic as a teenager in the 80's, we were encouraged to replace consumables as preventative maintenance when people brought their bikes in for service. I assume that hasn't changed.

_ForceD_

I concur with kingston above. If the cables are only four years old they don't necessarily need replaced...unless you keep the bike outside. Some of my bikes have cables much older than that and work just fine. Like he said, the FD adjustment is pretty easy with just the Philips screwdriver. And, the rear derailleur adjustment is just about as easy, and probably no tools need for that. There are plenty of videos on the internet that can show you exactly how to do it. Just Google what you're looking for and give it a try.

Dan

Wilfred Laurier

Cables are a wear item. The LBS guy gets to feel the shifting action on brand new bikes every day, and possibly felt an obvious decrease in performance/increase in friction on the 4 year old bike - a change that might be very difficult to perceive if it happened gradually over the course of 4 years.

I have no experience with twisted cables, but my career in bike shops was after the early era of internal cable routing (~late 1980/early '90s) and before the current era of internal cables.

There are many reports of cable heads breaking off inside shifters, Specifically Shimano shifters of the past ~15 years. I don't know if they made changed for newer bikes such as yours, but it is not something the LBS guy made up. It can also sometimes be a major headache to get the broken cable head unstuck from the shifter.

cyccommute 

I wouldn't be so quite to dismiss the mechanics assessment. If you look at the cable housing on the left shifter in this picture, you can see a bit of a twist in it.

noodles small by Stuart Black, on Flickr

It started to shift poorly and when I took it apart, the rods inside the outer plastic sheathing had broken loose. The ends of the rods will come out of the ferrule and cause the cable to jam. This isn't the same housing but it's the same problem

IMG_1361 by Stuart Black, on Flickr

This is what it looks like without the ferrule

IMG_1362 by Stuart Black, on Flickr

The housing in both cases had an odd "twist" to the housing.

dedhed

Cables are cheap and do make a difference in shifting quality.

Frayed at the head is a common enough issue on Shimano brifters that I change mine every year.

https://www.bikeforums.net/bicycle-m...5-shifter.html

WizardOfBoz

If the LBS said, "You know, this is a four year old bike, and the brake and shifting action are ok but probably will be better if we replace and relube cables. More reliable, too - brifter cables really take a beating" I'd be ok. But the "Cables twisting" is a red flag for me.

That said, four years IS a good time to replace cables and if done competently should make your bike work (shift, brake) better. IIRC, (per dedhed's note) Shimano recommends replacing brifter cables every year. They are a hassle if they brake when you're riding. After one episode of that, I do change mine out regularly.

shelbyfv

Yep. Seems pointless to question the mechanic's assessment w/o some basic knowledge of your own. As mentioned, cables are consumable and it's hard to predict when they will let go. Probably he noticed the shifting wasn't responding predictably to barrel adjustment which can indicate a binding (for whatever reason) cable.

Mad Honk 

So did anyone in this discussion hear that the the rub occurs when pushing down on the left pedal? I would look to a miss adjustment of the BB, or some looseness there. Cables will wear out and do so often in four years of riding, but a bottom bracket will wear in that time as well if not kept in proper adjustment. Before I start to replace cables and such I would look to the BB adjustment and play in the bearings. JMO, MH

em_525

Based off what you're saying about the issue happening when you pedal on the left, to me, that indicates either a bottom bracket lacking torque, your crankset being a bit loose, chainring bolts perhaps slightly loose, or your derailleur just needs brought in a hair more. Of course, at 4 years, changing cables isn't really unreasonable(I change mine once a year on all bikes). So, if you want, have the cables done, but inquire about the other potential issues as well. In sum though, it doesn't sound like a red flag, just an odd choice of words.

cpach

Shimano road shifters really are prone to breaking cables in the shifter and should be replaced periodically even when they shift well--for a frequently ridden bike annually is more than reasonable. It can be potentially really annoying to fish out the broken cable head. Cable friction has a significant effect on shift quality and it should be replaced frequently. It is more than possible on a frame with internal cable runs for the cable to get routed wrong so that it rubs on another cable, housing or something else significantly decreasing shift quality. So not BS. Shop mechanic probably just noticed your shifting was observably worse than it should be. You should probably replace your cables/housing if you ride regularly. You can get used to mediocre performance if it degrades slowly--the difference is often pretty dramatic.

Cable friction isn't related to your FD cage rub though.

TKJava

Regarding questioning the mechanic without basic knowledge... I agree ergo the a question to a bike repair forum on the web. I'm inclined to give someone the benefit of the doubt however one wants to mitigate doubt.

headasunder

four years on the same rear cable is pushing it, the tighter routing of the gear cables in the generation of shifters where the cables are buried makes for a lot of friction and fraying of the cable in the shifter is a common issue. After a close call I now change the rear cable at least yearly to be on the safe side. Buy a cable or let the lbs at it

Wilfred Laurier

Re: Asking a shop for help

Further to al the above comments, some LBSs might be perfectly happy doing a half-arsed repair, get it 'good enough' to put you back on the road... the downside to trying to be helpful is that the customer might forget they have been told that the repair was not a permanent one or not a perfect repair, then be frustrated when the thing goes wrong again in a month.. or the customer might take it to another shop and say 'this cable should have been replaced long ago', to which the customer forgetfully replies 'I had it fixed at LBSX and they said this was good enough', which then gets LBSX a bad reputation for doing half-arsed work.

When I was running my own business, every customer was told that they were probably getting a new set of cables, and new brake pads... I didn't change every cable or brake pad (only charged for it when I did, obv) but I didn't want to ever stall or delay the work because I didn't know if the customer would be happy if the final price was ~$10-20 more than I originally quoted them.

The same goes got chain and cog replacements. If you want to pay me to adjust your shifters and/or derailleurs, then I am not going to take a chance on telling the customer the bike is 'perfect' when I left a worn part on that might make it much less so.

It is possible that the tech could have put the bike up on the stand and adjusted the front derailleur to stop rubbing in less than a minute, but if they suspected that wear items might have needed to be replaced and this could have affected the customer's satisfaction, then they probably didn't want to take the chance.