Bicycle Mechanics - Carbon Fiber Brake Cables

Seems sensible--no stretching, would probably weigh less than a steel cable (not that it would make a difference).

What's the problem? Difficult to cut, low tensile strength, cost, excessive friction with housing, gets kinked easily?

Or does it exist any my cursory Google search just didn't turn it up?

Probably snap at the pinch bolt which would crush it,and "carbon fibre" is actually a composite of the carbon fibres and (usually) an epoxy resin.Hardened epoxy resin certainly isn't flexible enough to be used as a cable.
Kevlar,on the other hand...

no point.

It's a safety issue. There's marginal weight savings and the risk of sudden unpredictable failure is too high.

Someone brought out both brake and gear wires with lots of fanfare a few years ago, and the consensus was OK for gears but not brakes, though I don't think either is made anymore.

Some of the aramids like Spectra, Kevlar, Dyneema and Amsteel Blue would seem like they'd be naturals for the application. Spectra, for example, has a one-time, 3% stretch and then that's all it ever stretches until it breaks. But they are all difficult to cut, and they are all difficult to tie knots in. They are very slick, you see, and any knot placed under load tends to just creep on out. Sleeving the line solves this problem but adds others. Honestly, it's more hassle than it's worth.

Need a budget like a Formula One race car team, for a starter..
note the competition between the Italian and the Japanese manufacturers
in electronic shifters.

A number if years ago Magura Made a Hydraulic Road bike caliper to bolt on,
in place of the typical road side pull caliper .

A clever bit of engineering, a double piston spreads a lever on each side ,
above a pivot, which forces the brake pads to squeeze the rim.

but the scheme was not weightless..

They have continued making a hydraulic rim brake, that goes on V brake posts,
now in 20th year of production.
Hydro-stop, HS33 is a very good brake set, I have them on a Trekking bike,
I bought a few years ago..

hose is plastic, so that part is lighter than a steel cable and steel housing.

CF cables??? I wouldn't have imagined that CF would work eventually work it's way into our cables too........thought the stuff wouldn't be able to stand any laterat bending forces that our cables go through as it makes thos tight turns towards our dreailleurs and in our brake lever assemblies.
Manufacturers seem to sprinkle CF on many compnents these days to give it a sort of "fairy dust effect" to attract the techy gear heads amongst us.
Never really thought that the steel or SS cables we've been using kept us from cycling as fast and braking as well as we can with our sidepull brakes, so once again this looks like mostly a solution looking for a problem. Frankly, I'd rather see them develop more lightweight hydraulic disc brakes for road/race bikes to get rid of the cables all together, once and for all......:rolleyes:
............Dang!!, when's that aluminum cased CLB brake cable set that I just ordered come in??:rolleyes::D

Chombi

They are called Power Cordz

They are called Power Cordz

I don't see anywhere where they say this


Power Cordz™ utilize a synthetic fiber called Zylon HM or PBO. It’s stronger than steel and twice as strong as Kevlar. PBO is a rigid-rod isotropic crystal polymer that has superior tensile strength and modulus of elasticity. Simply stated - Zylon is very stiff and strong, it’s superior cable material. A slick nylon protective coating encases around 10,000 PBO fibers. The cord is then bonded (using a top-secret patented process) to a high quality anodized anchor. The bond has a breaking strength of over 600lbs which is the same as steel at 25% the weight of steel.

http://www.powercordz.com/catalog/

The actual fibers that are carbon wear quickly and easily from abrasion. It's only when they are bound in a matrix as we usually see them that it is strong stuff. So carbon cables is pretty much a non starter as ideas go. Kevlar fibers are themselves fairly abrasive and would cut into the inner liner of the housings. I know this because I've actually used loose kevlar tow in my model airplanes. If I draw the fibers over the balsa under tension they cut into the wood quite alarmingly. So carbon or kevlar would both need to be jacketed with something such as nylon or some other protective layer. In the one case to protect the inner fibers and in the other to avoid the fiber cutting into the housing liner. Then factor in the difficulties of clamping them at the brake caliper and you have a number of good reasons for sticking with stainless cable.

What's wrong with good old stainless steel? Lasts longer than the cable housing and doesn't cost an arm and a leg or the servitude of your first-born.

What's wrong with good old stainless steel? .......and doesn't cost an arm and a leg or the servitude of your first-born.
That's the same type of argument I've used to defend standard high-grade steel ball bearings against the latest high-zoot ceramics and you've seen how much heated controversy that's caused. :)

What's wrong with good old stainless steel?

Nothing, really...I mean, nothing significant.

It just struck me that carbon fiber is being used for many different bike parts these days, and I was curious about its utility in a currently carbon-free application.

Some of the aramids like Spectra, Kevlar, Dyneema and Amsteel Blue would seem like they'd be naturals for the application. Spectra, for example, has a one-time, 3% stretch and then that's all it ever stretches until it breaks. But they are all difficult to cut, and they are all difficult to tie knots in. They are very slick, you see, and any knot placed under load tends to just creep on out. Sleeving the line solves this problem but adds others. Honestly, it's more hassle than it's worth.

Kevlar is only slick if it's been wax coated. Otherwise it's pretty abrasive. Has a habit of cutting through other types of thread in knots.

A replica of an old British roadster with rod brakes, all done in Carbon fiber might work.

substituting the rigid carbon fiber composite, for rigid metal could work.

That is how it is generally used, it seems, so far.

Kevlar,on the other hand...

...has issues with UV radiation. And I don't know that the fibers would like the pinch bolt any more than carbon would.

Some of the aramids like Spectra, Kevlar, Dyneema and Amsteel Blue would seem like they'd be naturals for the application. Spectra, for example, has a one-time, 3% stretch and then that's all it ever stretches until it breaks. But they are all difficult to cut, and they are all difficult to tie knots in. They are very slick, you see, and any knot placed under load tends to just creep on out. Sleeving the line solves this problem but adds others. Honestly, it's more hassle than it's worth.

Spectra, Dyneema and Amsteel blue aren't aramids. They are ultra-high densitiy polyethylene. Very strong but UDP has no cut or abrasion resistance. In kite applications, you have to keep Spectra lines away from Kevlar...knife/butter:eek: I've bumped my Spectra lines against abrasive stuff while flying and the line just melts.

I don't see anywhere where they say this



http://www.powercordz.com/catalog/

It has other problems that make it a poor candidate for brake cables. From here (http://en.wikipedia.org/wiki/Zylon)


Poly(p-phenylene-2,6-benzobisoxazole (PBO) fiber degrade by UV and visible light, seawater and chafing and is therefore protected by a synthetic melted-on jacket.

If you want to save weight on cables, you could try using a shift cable for your rear brake...

or just get rid of the freewheel. although then hipsters will sneer because it's not SS, and conventional roadies will just be baffled.

on other hand, CF brake cable would be a perfect match for CF socks or CF spoke nipples.

Steel is a wonderful material. There's nothing wrong with it, and it doesn't need replacement.