On Monday, April 30, 2018 at 9:24:31 AM UTC-7, Joerg wrote:
On 2018-04-30 08:19, jbeattie wrote:
On Monday, April 30, 2018 at 7:22:35 AM UTC-7, Joerg wrote:
On 2018-04-28 18:34, John B. wrote:

[...]


With all your cable problems I'd think that a "dead weight"
cable tester would be to your advantage. Simple to build and
simple to operate it would ensure that your cables met the
necessary strength requirements.


It won't help. At least mine didn't fail during emergency hard-pul
situations. I have learned early on not to lock up my brakes,
whether on bikes or in cars, unless it is advantageous and even
then you don't need much force. They just ... failed, out of the
blue. For example, when I cam home from school I approached the
last traffic light 1/2mi from our house. It was red, so I applied
front and read brake. Front cable snapped and the bumper of a BMW
helped me to come to a stop. The driver got out but when he saw the
cable jacket flopping around in the air he said "Oh, yes, that
happens", got back in and drove off. I guess he was a cyclist and
it seemed like he also had that happen.

Where did your cables snap? Did the heads pull off?


Yes, in all cases.


... Did you change the housing after the failures?


No, though I did smooth the channels a little with fine-grit sandpaper
and polishing paste. Couldn't help much though because the heads simply
pulled out of the cables.

Besides, why do we as end users a.k.a. consumers have to correct design
mistakes on bicycles so often?

Most cable failures occur over time and involve breaking of individual strands -- which should be noticed with routine maintenance. There are housing, lever, adjuster and ferrule designs/installations that can hasten cable failure, but a catastrophic failure probably means a defective cable. IIRC, Shimano did recall some cables 10+ years ago because of ends popping off. And most of the "design" problems with other brake parts usually result in symptoms long before the failure, like brakes that are stiff, sticky, etc. These are usually symptoms of a cheap bike, too.

More curious tech problems: I currently have an Avid BB7 rear cable disc on my commuter that is in housing all the way from the lever to the caliper. I expect drag, and the return springs on the Avid brakes are not great -- better than the first generation BB7, but still not great. So, I expect cable drag from the housing and even some pad drag caused by the weak return spring.

What I didn't expect is that the brakes would self-tighten. It's the oddest thing. The brakes just tighten up, and the torque arm is fully retracted -- so its not a stuck cable. In some instances, I think it is because the rear axle has smooth faces, and the wheel can get cocked under load (and with a tight QR), but I've even had the brake drag after dropping the wheel to make sure it is straight. It's like I have a haunted rear brake caliper.

-- Jay Beattie.