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What is the difference between brake cables and derailleur/shift cables? When I look online for replacement cables I see "brake cables" and "shift cables."

Brake CablesShift Cables

From the images they all look the same.

Furthermore, what is the difference between mountain bike specific cables and road bike specific cables?

  • 3
    The biggest difference is the ends. – Daniel R Hicks Oct 27 '16 at 20:58
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Cables:

The main difference that I am aware of is the diameter of the cable. Most brake cables are 1.5 or 1.6mm in diameter. Most shift cables are 1.1 or 1.2mm, galvanized shifter cables are 1.3mm.

I'm sure that there is a lot of science behind the difference but I'll leave that to someone else.

One major difference in MTB vs road BRAKE cable is the different sizes and styles of head: road cables have mushroom like ends where as MTB brake cables have barrel like ends.

Shifter cable ends are the same. Although nowadays many cables come with both ends, one on each end, and you can cut off the one you're not using.

There are two basic types of cables; brake and shifter. Brake cables are thicker, typically 1.5/1.6mm in diameter. Brake cables come with a choice of three different heads - one for mountain/flat bar brake levers, one for Shimano road/drop bar brake levers (compatible with most non-Shimano levers), and one for Campagnolo road/drop bar brake levers. A Shimano cable head is slightly larger than a Campy head so it may not fit into a Campy road brake.

Five different cable end styles, labelled A-E

A. Shimano Brake Cable
B. Campagnolo Brake Cable
C. MountainBrake Cable
D. Shimano Shifter Cable
E. Campagnolo Shifter Cable

Derailleur cables are thinner, 1.1/1.2mm in diameter. There are two heads available on derailleur cables - Shimano and Campagnolo. A Shimano cable head is slightly larger than a Campy head so it may not fit into a Campy shifter.

From Bikeman

Housing:

Just like with cables, housing comes in two different types: brake and shifter. From the outside they may look the same - but they are in fact very different.

Brake housing is built around a wire that coils down the length of the cable. This structure gives the great strength needed for the power generated by the brake lever.

Coil in brake cable housingStraight-wired shifter cable housing

Shifter cables see different forces so the housing is built differently. Shifter housing is built around many length-wise running cables that make the housing 'compressionless' which aids in the crisp feel of shifting - especially needed on today's 8/9/10/11 speed cassettes.

4mm and 5mm shifter housing, with plastic and metal ferrules

Shifter housing also comes in two different outside diameters, 4mm and 5mm. New bikes and shifter sets typically come with 4mm housing. Most 4mm housing will have plastic ferrules at the ends while 5mm housing uses metal ferrules. Here at Bikeman we recommend using 5mm shift housing.

Other variations of housing include housing made from many aluminum segments, like Nokon housing. On the positive side the aluminum housing is stiff, lightweight, and reusable. On the negative side there is a lot more set up time, cost, and care must be taken to be sure that the frame is protected as aluminum housing will rub paint off where it contacts the frame.

Please Note: Due to their construction, brake housing should always be used with brakes and shifter housing should always be used with shifters. Shifter housing could fail if used on a brake (not good when you want to stop), brake housing could make that shifter feel a little dead.

  • The other thing is that the housings are in general different. Not all shift housings are suitable for brakes. – Batman Oct 27 '16 at 15:49
  • @Batman a good point, i have editted in some information from the same site regarding housing differences. Thanks for mentioning that. – Nate W Oct 27 '16 at 16:29
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    "I'm sure that there is a lot of science behind the difference" Not much: brake cables are bulkier because they need to transmit much higher forces and it's really important that they don't snap. – David Richerby Oct 27 '16 at 17:51
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    I realize that much, i just wasn't about to delve into the physics behind it : P – Nate W Oct 27 '16 at 18:17
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    @DavidRicherby conversely brake cables can deform, slip, stretch a tiny bit without any real performance drop. However shifter cables will misalign if any of those occur. Really at the end of the day they are designed for very different things. Brake cables are designed to transmit force. Shifter cables are designed to transmit a (precise) 'movement'. – Aron Oct 28 '16 at 3:11
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Well here is one, you can't use brake cables to shift with or shift cables to brake with, the ends are wrong.

If you ever shorten your shifter housing you will find the difference. One you can cut, one you have to have a real good set of cutters.

I just replaced all my cables the other day, what an improvement.

  • 2
    This is true, but it adds nothing to the existing answers. They already say that the ends are different and that brake cables are thicker. And, please, don't just say "one you can cut, one [you can't, easily]" -- say which is which. You're writing for people who don't know which is which. – David Richerby Apr 26 at 9:24
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    You're completely correct, but "the ends are different" was said in the accepted answer dating from 2016. Instead of repeating, its much better to give the good answers an upvote. Do please take a moment to read the tour page, which will show you how Stackexchange is organised. Specifically its a Q&A format, and the best answers get upvotes. Normally I'd delete dupe answers, but yours shows promise. Have a go at other questions, and see how you go. – Criggie Apr 26 at 10:27
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Minor point that others have overlooked - your images show a brake and a gear cable set.

These will hold two inner cables, enough outer to do an entire bike, and the ferrules to suit that cable.

Those ferrules will be the right size to go in the frame stops, and into the mechanism endpoints.

  • If you try to use a brake ferrule in a gear mech, it won't go in.
  • If you use a gear ferrule on a brake, it will be very sloppy fitting and will pop out easily.

Also, for metal ferrules (common in brake kits but not gear) then the hole in the middle is sized for brake inners. Try putting a brake inner through a gear ferrule and it will have added friction, which can help lift the ferrule out of the cable stop.

Also, a kit will have end-caps to stop your wire fraying. 3 or 4 are common. The end caps will be sized for the thickness of wire in the kit.

Kits often come with tiny rubber doughnuts to protect the frame from rub, because cables can get quite slack.

Sometimes brake cable kits for V brakes come with a pair of rubber boots and two noodles, but these tend to be the higher priced kits, and its more practical to buy a cheaper kit with noodles separately if you need them.

tl;dr, a kit for brakes is for brakes, and a kit for gears is for gears. There's no good reason to mix these up.

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Ive interchanged before on older bikes - but the key difference is gear cables must be prestretched, and less prone to subsequent stretching because of the indexing tolerances on STI or similar systems

Gear cables also tend to be a bit thicker with less cables included, and are a bit shorter

  • 6
    Arguably, the most important distinction is that brake cables are stronger. They have to support greater tension and their integrity is critical to the rider's safety. – Will Vousden Oct 27 '16 at 14:55
  • All inner cables are supplied overlength and trimmed to fit the bike. Its not like you can extend them. – Criggie Oct 27 '16 at 19:01
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    Also "Gear cables also tend to be a bit thicker with less cables included, " gear cable inners are thinner than brake cables, about 1.1mm v 1.5mm, and have fewer strands – Criggie Oct 27 '16 at 19:02
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    Just because you can interchange them, doesn't mean you should. – altomnr Oct 27 '16 at 21:40
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    I rarely downvote an answer. However, this is very bad advice. Brake cables have too much elasticity to make good derailleur cables. And using derailleur cables for your brakes is incredibly dangerous. The greater thickness and elasticity of brake cables makes them much less likely to fail than derailleur cables. – jimchristie Oct 28 '16 at 18:41

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