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I have bought a City Bike Elops Speed 900 a year ago. I noticed that the disk brake cables wear out way too often. It happens sometimes only after a few hundred kilometers of use.

They are torn at the "front" edge of the metal holder (with the screw fixing it - sorry, I don't know the terminology).

This wearing out seems to be better or worse each time the bike shop replaces the cable. My naive guess is if they screw it too tightly, the metal holder sort of clips the brake cable (Bowden).

I asked the shop, but they said it's expected with disk brakes. I have a hard time believing this. Can I protect the cable somehow, by wrapping it with something protective? (There is no sharp edge on the holder, but it still feels like it's essentially clipping the cable.)

I only have an image of the new cables, but I indicate where the tear happens.

Point of tearing on front wheel

Point of tearing on back wheel

Thanks a lot for your time reading!

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    looks like you might have applied too much torque to the bolts
    – Paul H
    May 9 at 16:49
  • Are they actually breaking over time? On rim brakes I’ve never seen this kind of failure, except maybe a single strand breaking.
    – Michael
    May 10 at 11:52
  • Thank you so much to everyone for the detailed answers! You are super helpful guys!
    – bud.dugong
    May 11 at 6:16
  • Yes, I see some threads being "cut" over time, but so far I did not check it so often to say more. I do not brake sharply, in general.
    – bud.dugong
    May 11 at 6:31
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    Do not wrap the cable in anything, it may only hide the fact that some strands are broken, so at simple inspection it may look like the cable is good but it may have as little as one single strand holding.
    – Jahaziel
    May 12 at 19:51

4 Answers 4

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I think this is a design failure for this particular brake model.

Many of the mechanical brakes I've used have a sort of rounded "landing" surface for the cable, and the cable is rolled into it as the brake releases. When you apply the brakes, the cable sort of unrolls from it without flexing at the anchor point.

With normal use, the cable is flexed just a little bit and into a gentle curve, so no problem is caused.

On the brakes on your picture, however, it's apparent that the cable is flexed right at the anchor point. As you repeatedly apply the brakes, the cables are repeatedly flexing at this sharp point and the strands are broken by fatigue. (You can cut heavy gauge wire by sharply bending it back and forth)

Another observation is that with other type of cable anchoring, the cable always exits the adjusting barrel at the same angle, no matter to what degree the brakes are being applied, with the design on this type of brakes, the exit angle of the cable changes, and at some points it rubs against the inner part of the adjuster, which may also contribute to cable wear and may make feel the brake less smooth than it can be.

Hand drawing showing different cable anchoring methods

Here I show an example of a caliper that has this round part where the cable lands. Notice how the cable wont flex right at the bolt. (It may flex down where it leaves the receiver channel, but it won't be a sharp bend)

Example of caliper that does not flex the cable right at the anchor bolt

In my opinion, it is worth upgrading from these calipers. You may be able to find better mechanical ones, or even upgrade to hydraulic if budget allows.

I think there is nothing inherently wrong with good quality, well designed cable operated disk brakes. I used to ride Downhill on a bike equipped with mechanical disc brakes, despite all my peers "harassing" me into upgrading to hydraulic. I did never had a problem with the cable system, so I know good calipers exists. Hydraulic brakes are more expensive but can be virtually maintenance free (you'll only need to change brake pads when they wear out).

Do not skimp on brakes, as an accident derived from brake failure may end being way more costly.

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    Probably because the classic BB5 has a curved cable support and everyone copies that. Starting from cheap cable brakes my upgrade would be to BB5s or Spyres (I have the latter on a tandem, the former on my tourer) rather than having to replace the levers etc. to go hydraulic
    – Chris H
    May 9 at 20:53
  • BB5 are the way to go as far as quality and bang for buck. Apparently they are onlu $20-something bucks now. BB7 are about twice that. Jumping up to hydraulics would be $$$. MT200 shimano brakes can be had for about $100/set if ordered from overseas. I wouldn't mess with anything cheaper than those (e.g. Clarks).
    – shox
    May 10 at 0:55
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    @shox I put MT200s on my MTB. They're good. I get different pricing to you - I can't get BB5s that cheap but paid a little less for MT200s
    – Chris H
    May 10 at 5:53
  • Can't go wrong with MT200s. I'd take those over any mechanical brakes.
    – shox
    May 10 at 19:06
  • Thank you @Jahaziel, very clear explanation!
    – bud.dugong
    May 11 at 6:19
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Next time you replace the cables, try and increase the twist rate just before you clamp down the pinch bolt.

A bunch of strands twisted together has more strength and flexibility than the same number of identical strands all separated.

Wrapping the wire in heatshrink tubing might help, but it also provides squish space which will allow movement, which is bad in a brake cable.

Personally, I wouldn't mess around. Instead I would either replace the whole caliper with something better, or swap in a complete pre-bled shimano hydraulic system. The rotor doesn't need to be altered. Brakes are the one area I don't cut corners.

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    I also think that the last paragraph is the best solution: hydraulic brakes are not expensive, and are huge boost in safety and consistency (safety because of auto-adjustment).
    – Renaud
    May 10 at 11:22
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    @Renaud "safety because of auto adjustment"? Adjusting the brakes for wear is trivial and it is actually easier to get rid of brake rub by adjusting the pistons while with hydros you have to readjust the calipers with very high precision.
    – Vladimir F Героям слава
    May 10 at 17:10
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    @VladimirFГероямслава for bikes used in an utility purpose, it's common to postpone some basic maintenance tasks, even if it's just adjusting a brake cable (not saying to the point doesn't brake at all, but enough for normal use, but not for emergency use). So auto-adjustment is a huge plus to my opinion. As for my experience with hydraulic calipers adjustments, I've done it when I unmounted the calipers (fork overhaul), but they otherwise stay in place.
    – Renaud
    May 10 at 17:25
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    Thank you it makes a lot of sense, and I agree: brakes are not the things to be stingy with :-D!
    – bud.dugong
    May 11 at 6:21
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    @Renaud consistency yes, safety no. On my cable discs I can feel when they need adjusting, do so, and if there's little or no adjustment left I replace the pads. Auto-adjusting hydraulic calipers need at least the wheel to be removed and maybe the pads to check the remaining pad thickness. Even commuting (15km with 120m descent per day) can eat pads when there's mucky water around, and my riding conditions are too diverse to replace pads on a schedule.
    – Chris H
    May 11 at 13:26
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I wouldn't risk wrapping it in anything, but I would look for any rough edges on the cable clamp, and lightly file them. Even a slight smoothing of the problem edge, no more than 1mm affected, would help quite a bit.

This isn't normal. In 45 000 km on my tourer, 2 sets of brakes, and probably 15 sets of pads, I've only ever replaced brake cables as a precaution or because they were running stiffly, never for fraying.

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  • It absolutely is no normal if the clamping is done right. If it is done improperly (like I myself did the last time on my front derailleur), then anything can happen. I ended up riding for some time with the whole end of the derailleur cable fallen of.
    – Vladimir F Героям слава
    May 10 at 17:12
  • @VladimirFГероямслава derailleur cables being thinner and less safety-critical are a little more likely to fail.
    – Chris H
    May 10 at 17:41
  • Thank you! I think I will replace the caliper or the entire system depending on the offer I get!
    – bud.dugong
    May 11 at 6:29
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I asked the shop, but they said it's expected with disk brakes. I have a hard time believing this.

Me too. I've had a catastrophic failure of the sort and it was scary. The failure mode is "they fail when you need them(when you squeeze them hard)". The root cause was me screwing the fixing bolt too hard.

My naive guess is if they screw it too tightly, the metal holder sort of clips the brake cable

Exactly my experience. Overtighten and it looks fine until you really need them.

Can I protect the cable somehow

You can do anything conceivable but the answer to the should question is NO. The system is designed to work in some way and slapping some duct tape is not acceptable when loss of life is a possibility. Any non-standard additions will only conceal the root cause of the problem.

upgrade to hydraulic - by Jahaziel

This is a no-brainer. A pair of pre-bled* Shimano BR-3whatever is 60 EUR. Modulation and power are on another level**; the bleed scare is false***.

* - includes calipers, shifters, hoses, oil inside them
** - compared to SRAM BB5
*** - even those bottom tier devices hold for at least 3 years with zero maintenance as long as you don't use them for extreme mountain biking

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