I'm cutting brake and derailleur cables and housing for a new build and trying to figure out the optimal housing lengths.
Park Tools writes:
The less the drag on the cables, the better for the shifting and braking. Too short of housing will cause it to kink and bind, making even more friction. As a rule of thumb, try to size the housing so it is as short as possible but it still enters the stops and barrel adjusters in a straight approach. For the rear derailleur housing, note especially how the housing enters the barrel adjuster.
Sheldon Brown writes:
The Four Commandments of Cable Routing:
1. The handlebars must be able to turn as far as they can in both directions without being limited by a cable pulling taut. Instead, the turning limit must be set by the handlebar bumping into the top tube or by the brake arm or reflector bracket bumping into the down tube.
2. No wrong direction bends (For example: as the rear brake cable leaves the top tube and makes the bend down toward the caliper, it should make a smooth transition from parallel to the top tube to parallel to the seat stays. If the cable bends up from the top tube before bending down toward the seat stays, it is probably too long. If the cable curves out past the caliper, then bends back at an angle more vertical than the seat stays, it is certainly too long.
3. The bends that cannot be avoided should be made as wide (gradual) as possible,
4. Cable housings should be as short as they can be without violating the above rules.
They're suggesting similar lengths, but why is Sheldon focused on leaving so much cable that the bars bump the frame? I think the extra rear brake cable housing I've got might be causing mushy braking (everything is brand new - cables, housing, shifters, calipers), but if I cut it shorter it might stop the bar just before it would hit the top tube.
Park Tools writes:
The less the drag on the cables, the better for the shifting and braking. Too short of housing will cause it to kink and bind, making even more friction. As a rule of thumb, try to size the housing so it is as short as possible but it still enters the stops and barrel adjusters in a straight approach. For the rear derailleur housing, note especially how the housing enters the barrel adjuster.
Sheldon Brown writes:
The Four Commandments of Cable Routing:
1. The handlebars must be able to turn as far as they can in both directions without being limited by a cable pulling taut. Instead, the turning limit must be set by the handlebar bumping into the top tube or by the brake arm or reflector bracket bumping into the down tube.
2. No wrong direction bends (For example: as the rear brake cable leaves the top tube and makes the bend down toward the caliper, it should make a smooth transition from parallel to the top tube to parallel to the seat stays. If the cable bends up from the top tube before bending down toward the seat stays, it is probably too long. If the cable curves out past the caliper, then bends back at an angle more vertical than the seat stays, it is certainly too long.
3. The bends that cannot be avoided should be made as wide (gradual) as possible,
4. Cable housings should be as short as they can be without violating the above rules.
They're suggesting similar lengths, but why is Sheldon focused on leaving so much cable that the bars bump the frame? I think the extra rear brake cable housing I've got might be causing mushy braking (everything is brand new - cables, housing, shifters, calipers), but if I cut it shorter it might stop the bar just before it would hit the top tube.
