Brake cable / gear cable sleeves - why the difference - ?

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simongt

Guru
Location
Norwich
I know that gear and brake cable sleeves can't be interchanged, but can it be explained why and what is the difference between what APPEARS to be two things that serve much the same function - !
Ta - ! :thumbsup:
 

Joffey

Big Dosser
Location
Yorkshire
Gear cable pre-stretched and brake cable not? So indexing keeps accurate and your brake cable doesn't snap?
 

raleighnut

Legendary Member
It's down to dimensional stability vs strength

The force put through gear outer is far less so the linear construction is able to cope but as the casing strands are only held together by the plastic outer braking effort would cause the outer to split.
 

I like Skol

A Minging Manc...
Of course in the old days of friction gear shifting, the casing for brakes and gears was constructed in the same way. It was the greater accuracy required for the indexed shifting that led to the introduction of the weaker, longitudinally stranded sis cable casing as it is much more compression resistant than the spiral wound coil type used in braking (upto a point, whereupon it explodes/collapses!).
 
Brake cables need to withstand a greater force so are 1.5-1.6 mm in diameter.
As less force is needed to shift gears they are only 1.1-1.2 mm in diameter.
Outer sleeves are sized to fit inner cables.
 

Ajax Bay

Guru
Location
East Devon
gear and brake cable sleeves can't be interchanged, but can it be explained why and what is the difference between what APPEARS to be two things that serve much the same function

AASHTA - recommend a read of this link for a complete answer.

Types of Cable Housing
Conventional Helical Housing
Cable housing (outer) is made of steel; a tightly-wrapped helix of steel wire: the plastic is a covering to protect it and the bike. It has no particular strength in tension but it cannot be compressed because the coils of wire are tight against one another.

Compressionless "Index-compatible" Housing
With the advent of indexed shifting Shimano introduced "S.I.S." housing, now widely copied by other manufacturers. This type of housing does not consist of a single helical-wound wire, but instead, it has a bundle of wires running pretty much straight along parallel to the housing, held in place by being sandwiched between the plastic housing liner and the plastic outer covering. "Compressionless" housing doesn't change length significantly as it is flexed, so the indexed shifter is able to communicate the correct setting to the derailleur.
 
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