sjanzeir

Hello everyone,

For a possible upgrade to a better mechanical or even a hydraulic disk brake system on a folding bike, how well do compressionless cable housings or hydraulic lines play with tight bends? I do fold the bike in question occasionally, but not often. Thanks!

Geepig

Not well if they are inside the tube or clamped close to the fold, as they need a certain amount of freedom. If the hinge is on the right, they need to be on the left and allowed to turn through an easy curve. Really it is not a lot different to the situation up on the handlebars, where they need enough free movement to survive turning hard to the left to turning hard to the right.

Barry2 

Given that it is a brake upgrade you are looking for, I'd suggest a brake block replacement.
There are better blocks available and it is a lot less trouble and money.

Take a look at Kool Stop

Barry

sjanzeir

Hi Barry! I was referring to my first and only disk brake bike. The rim brakes on my other bikes still perform just fine on their factory blocks, so no issues there.

Back to Geepig's point, here's what the standard coil housings look like at the frame hinge:




The more sharply looped of the two is the rear brake housing. My hand is there for reference, and I've got tiny hands! And that does not look to me like the kind of bend that a compressionless housing - or a hydraulic line, for that matter - could handle and stay intact for long.

Troul 

I'd give it a wider radius & make sure any connecting points are far away from the bending area.

Racing Dan

In my experience they are VERY stiff and tricky to install under bar tape. They are like very thick gear cable. I'm not so sure they would work well in your application.

sjanzeir

Dan, are you talking about compressionless housings or hydraulic lines?

Geepig

If those are round tubes you might be able to find some cable clamps so that you can run the cables/pipes together down the same side, with the clamps further from the hinge. You could experiment by taping a spare compressionless cable to the frame to find the optimal clamping points to get a good turn without risking damage when the bike is folded (like catching the cable on something in the trunk of your car...).

One of my folders has plastic clamps with the same kind of flexibility as a zip tie to hold the cables, allowing me to run the cables somewhere that they do not get hooked up when folded or eaten by the chainwheel while I am riding.

Racing Dan

Compressionless housing. Shimano hydraulic brake hose is more compliant.

HillRider

Compressionless brake housing is quite stiff and doesn't tolerate tight bends very well. TRP recommends using it for their mechanical disc brakes (Spyres) with drop bars but also recommends use of a short section (4-5") of standard spiral wound housing to go from the brake lever or brifter around the tight bend from the lever to the straight section of the bar. Then they recommend adding a double end ferrule and using compressionless housing from there to the brake caliper where the bends are wider.

base2 

In my experience with compressionless housing, the tight bend such as under the bar tape really only affect how easily the inner cable slides. With the tight bend, the compressionless housing squishes to an oval shape & pinches the inner cable. The coiled shortie sections made by Jagwire are a good solution if this proves itself a problem for your particular installation.

For short sections such as the top tube cable stop to the rear brake, I find that most often it will ovalize & pinch as above, gumming up the release action of the brake spring. But, with a few firm brake applications, the short section of housing can then be removed & the ends of the cable can then be trimmed up square. (The inside & outside of the radius are different lengths. It takes a firm pressure to move & equalize the individual linear strands.) After the additional rework, the housing & brakes work as expected.

For a folding bike, just keep your cable radiuses large at the fold & don't expect the brakes to release well while riding it in the folded configuration.

You'll be fine.

veganbikes

Use the Jagwire Elite Link housing and you will do well.

Crankycrank

There are also screw-together cable splitters. Here are two examples. Cable splitters for S&S Coupled travel bikes (sandsmachine.com) Just install at the bend and no problem folding the bike up. Also for hydraulics I know you can get leakproof splitter couplings for motorcycles but not sure if they're available for bicycle sized tubing.

sjanzeir

Touché!

My concern was that given their structure, compressionless housings or hydraulic lines might sustain damage after multiple folding and unfolding cycles.

cpach

From the looks of your picture, hydraulic line will probably be just fine.