I have bought some generic cable housing without paying attention to the specification (https://www.bricklanebikes.co.uk/blb-brake-cable-outer-housing-black). It comes with a set of ferrules and I didn't know those have a size as well (mines are 5mm according to the link above). The ferrule fits very well into my lever (a bar short-pull straight bar lever), but it doesn't fit on the brake housing slot (see picture below). The brake is a Shimano 105 5800, but I can't find anywhere a mention of the size of the housing slot. (I tried to look even in the dealer's manual.)

What's the standard size for the cable housing slot of modern road caliper brakes?

If I go with a cable housing (and ferrules) with smaller diameter, am I going to have issue on the lever side? (It fits perfectly now).

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  • I'm guessing it varies based on road vs mountain vs whatever, but I've definitely seen both 5mm and 4 .5mm ferrules. Oct 16, 2017 at 11:25

1 Answer 1


Many road calipers don't have you use a ferrule at the brake end. That's the intent here. If you want to anyway or if you must due to using a braided/compressionless brake housing, the solution is to use stepped ferrules such as Jagwire POP ferrules, which are long and have an opening for 5mm housing on one end and reduce back down to 5mm OD on the other end.

  • I am very happy to not use (look for) a ferrule at the brake end, if that works well. It's the first time I assemble a brake, so I don't know what's best :) Is there any non-negligible advantage of using a stepped ferrule over not using any ferrule at all? What do you mean by "reduce back down to 5mm OD"? Did you mean to write a smaller measure? Oct 16, 2017 at 16:12
  • 2
    Yep, it's fine, not using anything is standard on brakes like this. If you're using compressionless brake housing (made of braided wires instead of thick steel coil) you must use some kind of thick-ended ferrule to keep the housing from failing, and that's the reason stepped ferrules exist. And to the second point, no, 5mm is the outside diameter of brake housing. Stepped ferrules mimic that diameter on their stepped end. Oct 16, 2017 at 16:55
  • Ah, I see what you mean now with 5mm OD, thanks for the explanation! The only question left is whether I use compressionless brake housing or not. Oct 16, 2017 at 20:08
  • I accepted the answer. Both the explanation on and the recommendation of using POP ferrules are really appreciated. Thanks! Oct 17, 2017 at 12:47

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