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A question about cable stretch.
Cables don't stretch :)
Well, they do on overload, but the elongation which happens early in the life of a new cable is bedding-in. The thin wires have a small bearing area on one another, and tension tries to straighten the helical winding, generating radial pressure between the wires. The small bearing area means that this pressure exceeds the elastic limit of the wires, causing deformation which reduces the cable diameter. This reduction in diameter allows the helix angle to be permanently changed, so wires which haven't actually changed length become a cable which has. Good quality cables should be pre-bedded. In an actuating cable which moves, especially if it bends, inter-wire wear causes reduced wire diameter and consequent cable elongation for the same reason. Compared with these two effects, cold relaxation is trivial. TL;DR Static cables at room temperature and under stress well below their elastic limit do not elongate significantly after the initial bedding-in period.
Hydraulics have their own problems, which are different depending on whether they are open or closed systems. Anything with plastic hoses will exhibit creep if pressurised for a long time, but probably not enough to worry about. That's the end of the story with closed systems. Open systems may leak fluid back past the master cylinder seals into the reservoir, so it may be necessary to pump the brakes to restore the normal engagement point if they have been stored under pressure for a long time.
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gbj_tester
A question about cable stretch.
We have all ability cycles with a hand break that we can stick on which holds the brake lever in the locked position tensioning the cable.
Colleagues have suggested that we shouldn't leave the cycle with the handbrake locked on when the cycle is parked for the night/week as it stretches the cable.
So my question: Is it good to stretch the cable using by doing this so long as we compensate and tighten the brakes each time until it has completely stretched. And when its stretched does it matter if we leave the handbrake on for long periods as it is unlikely to stretch any more?
Is there a difference if the brakes are hydraulic? Most of them are cable disk brakes