Jim’s Tech Talk
By Jim Langley
Before we get to the shift cable question, I want to share one more comment about e-bike battery safety, which we were discussing last week. If you have a battery bike and you missed the article, you should read it and the comments because there are a lot of good tips.
The comment I’m sharing is from Bevan Quinn whose dad Neil Quinn founded West Hill Shop in Vermont where I worked in the late 70s (Bevan worked there too). Bevan said,
“As a state fire academy instructor I have learned information for teaching firefighters how to deal with lithium-ion battery fires, which can help consumers learn to protect themselves. (Although a former shop guy, I’m not knowledgeable about their use in bicycles, specifically.) As noted, the FDNY is a leader in dealing with battery fires because they have seen a large number of them.
Some points to consider;
- only use the correct batteries for your device
- only use the correct battery charger for your device.
- do not use aftermarket parts as they may not be rated correctly
- do not charge batteries unattended
- unplug and remove batteries when charged
- do not leave it plugged in until the next time you’ll use it
- also – and this is a big problem in high-rise and multi-apartment buildings – do not leave or charge bikes in the entry to your apartment. If it catches fire you have blocked your exit
Watch some of the videos to see what happens to Li-ion batteries when thermal runaway takes effect — it’s scary! Keep in mind the material in Li-ion batteries contain oxide, i.e., they have their own oxygen and will not stop burning until spent or cooled. An ABC fire extinguisher will not put them out. They need to either burn out or be cooled and monitored until the thermal effects are gone. The info from Human Powered Solutions provided by Bicycle Retailer is excellent for e-bike retail and can be applied on a smaller scale. Here’s that link: https://www.bicycleretailer.com/sites/default/files/downloads/article/battery-protocols-v1.6.pdf.”
Assessing Shift Cables
Today’s question is from my buddy and Spokesman Bicycles teammate Mike Andalora. Though we haven’t ridden together in awhile, I still can’t have him missing shifts from cable issues. So I want to help him out straight away. Feel free to share your tips for Mike in a comment. He asked,
“I’ve had some questions lately about when shift cables give out, or can they be stretched out? I know that when I have to click my shifter twice to get the derailleur to shift that it might be time for a new cable but I’m not sure if I can just tighten the cable and readjust it? How do I know for sure that a shift cable is done and needs replacing?”
I wish I had an easy answer for you Mike, but the only way to “know for sure” is to inspect the cable. Which is not easy on most modern road bikes. Because to inspect the cable thoroughly you need to look at the entire cable, from its head that’s inside the shift lever all the way down the cable. And most newer bikes have internal cable routing.
When you pull out the cable what you’re looking for is any fraying, sharp bends, corrosion or signs of weakness. Cables often break at the head so be sure to look very closely at that for any signs of wear and tear.
How Long do Cables Last?
Since inspecting the cable involves removing it, it’s usually best, rather than going to that trouble, to just replace the cable at regular intervals. Modern cables are high-quality and assuming they were installed correctly, they should last for 2 to 3 years, maybe twice that. But how you ride, where you ride and the conditions you ride in all affect wear and tear on cables and the rest of the bike too.
Do they Get Ruined by Stretching?
Cables do stretch but it usually happens when the cables are new and then the cables don’t stretch a lot more after that. Instead what makes it seem like the cable is stretching more is that the housing sections that the cable runs through compress. FYI: “housing” is also called “casing.”
The housing has a major impact on how long shift cables last. Housing installation errors can cause cables to break. And even if the housing is installed perfectly the housing will wear over time. That’s how compression happens, which essentially makes the shift cables longer creating slack in the cables and hesitation when changing gears.
Fixing Hesitation Shifting into Easier Gears
To fix hesitation, usually you can simply turn the cable tension adjustment barrel on the back of the rear derailleur to remove cable slack and restore the shifting. When viewed from behind the bike, turn the barrel counterclockwise in half-turn increments, one half turn at a time and keep testing the shifting until each lever click hits the gear.
Park Tool has an excellent short video showing how this is done:
Signs that Cables are Ready to Fail
Needing to adjust the cable tension repeatedly
If you need to use the adjustment barrel again and again over a short period of time, there’s likely something wrong. The most common issue is that the cable is fraying inside the shift lever. If you recently worked on your rear derailleur, another issue that would let the cable slip is if you didn’t sufficiently tighten the derailleur cable anchor bolt.
It can be very difficult to get broken cable heads out of shift levers so ideally you’ll identify a bad cable that’s failing there and get it out before it breaks.
Signs of fraying or corrosion
If you can see the cables on your bike, look all along them for any signs of fraying and corrosion both mean you should replace the cable(s).
If you have cables that run inside the frame, you have to remove the cables to look at them. If you have cables that run through housing sections that run alongside the frame, you might be able to look at most of the cable to inspect it and get an idea of its condition.
Fraying at the very end of cables doesn’t mean they’ll break. You can usually either trim off the frayed part with cable cutters and install a cable end. Or if the cable is frayed such that you can’t get an end on, try carefully rewinding the strands with a pair of pliers. This takes a little care and patience but you can usually get it back in order enough to get a cable end on.
Quality modern shift cables and housings when properly installed should work trouble-free for at least several years assuming they’re not subjected to crashes, constant bad weather, outside storage and so on. If you can avoid those things, shift cables could keep working fine for a lot longer.
If you’re not using quality cables or if the cables and housing sections weren’t installed correctly that can cause problems leading to cable issues and possibly breakage too. For replacing cables I recommend using the cables and housing made by the manufacturer of your components, usually Campagnolo, Shimano and SRAM. In last week’s comments readers also recommended Yokozuna cables.
With internal housing and cables it can be a big job replacing the housing. It may be routed inside the handlebars for example. But one of the advantages of internal cables is that they’re better protected inside the frame. So hopefully you won’t need to replace the housing and can just remove the shift cable itself.
Jim Langley is RBR’s Technical Editor. A pro mechanic & cycling writer for more than 40 years, he’s the author of Your Home Bicycle Workshop in the RBR eBookstore. Tune in to Jim’s popular YouTube channel for wheel building & bike repair how-to’s. Jim’s also known for his cycling streak that ended in February 2022 with a total of 10,269 consecutive daily rides (28 years, 1 month and 11 days of never missing a ride). Click to read Jim’s full bio.