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I have a Dawes Discovery 401 hybrid bike that was fitted with QuadQMD-6 mechanical disc brakes.

I like the bike but the brakes are beginning to show signs of wear and direct replacements are not available. So I was thinking of replacing the calipers with hydraulic ones and converting the cable-operated system to a hydraulic one.

I'm pretty handy with a spanner and would like to try this myself.

Is it easy to convert from cable to hydraulic and what bits would I need for adapting the cable runs? Is there anything else I need to consider?

I don't want to spend a fortune but would like a decent set. Rotors: 160mm Mount: post.

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    If you filter the shopping there is a good question hidden in here around "Whats the possible issues with replacing mechanical with hydraulic brakes"
    – mattnz
    Commented Jun 30, 2017 at 20:10
  • While direct replacement pads may not be available replacement pads may be available. Remove your pads take them to your local bike shop and see if they can match them to a brand name pads. Many pads fit more than one brand. If they are physically the same size they should work.
    – mikes
    Commented Jun 30, 2017 at 22:37
  • @mattnz Question is edited as per your suggestion.
    – Criggie ♦
    Commented Jul 1, 2017 at 7:39
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    @RoboKaren question is tweaked to be more general "replacing cable disk brakes with hydraulics" rather than shopping.
    – Criggie ♦
    Commented Jul 1, 2017 at 7:40
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    Deleted my objection. I still think replacing with a set of BB7s is a much better solution, but some people have much money to spend and it supports the bike industry, so I shouldn't complain.
    – RoboKaren
    Commented Jul 2, 2017 at 5:45

3 Answers 3

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If the brake lever is integrated with the shiftier, you will need a new shifter.

Cable run for Hydraulic will be continuous, and you wont have C-Clip mounts. You will need to use zip ties to hold the cable to the frame. Functionally there is no problem with this, how you feel about this depends entirely on if you prefer form or function.

MTB Caliper mounts have been standard for 15 years or so (Road has a different standard introduced by shimano in 2010 ). In most cases you will be able to unbolt the mechanical calipers and bolt on the new ones, however some calipers are aimed as a different minimum rotor size. This means you may need a new adapter depending what you have and what you get. As long as the new caliper minimum rotor size is not larger than the rotor you have, you can get an adapter to fit.

I would think about installing new rotors (although $$ is a consideration). The old brakes were not expensive, so the rotor won't be the best quality, new rotor would keep everything matching. It may make no difference but might help with longevity and reliability (e.g. if they are warped).

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    Agreed on the new rotors. If you're being frugal then replace just the front caliper/lever system and fit a new rotor. I like how this answer addresses the underlying considerations and doesn't quote brands.
    – Criggie ♦
    Commented Jul 1, 2017 at 7:37
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All hydrauluc disc brakesets come pre-bled, so if you're not fussed about the excess hose lengths then fitting hydraulic brakes over mechanical brakes has fewer steps.

I mention the excess hydraulic hose because brakes typically ship with 1000mm and 1700mm long hoses for front and rear brakes. In my experience very few bikes really need hoses this long and if you're not cutting them down to a more suitable length then the excess hose will form large loops out from the handlebars.

If you'd like to shorten the hydraulic hoses then you'll need some specialist tools, at the minimum a hydraulic hose cutter and a bleed kit for the specific brakes. This is where fitting hydraulic brakes differs hugely from mechanical brakes.

Depending on how well finished your caliper mounts are, it may also be worth having these faced by a local bike shop to ensure the calipers align perfectly with the rotors.

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  • Better to be slightly too long than slightly too short !
    – Criggie ♦
    Commented Jul 3, 2017 at 1:49
  • Haha! Always @Criggie! I only mentioned it because some of the small and extra small bikes we get in for PDI are fitting with the same length hoses as the L and XL frame sizes and it just looks poor IMO :p
    – Ryan Flaherty
    Commented Jul 3, 2017 at 7:51
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Your bike might have braze-on fittings for holding the current cables in place. These won't fit the hydraulic line because the opening will be too small, and the braze-ons won't be wide enough to accept the line through the wire-slot. And you can't generally disconnect the hydraulic line to feed through the braze-on anyway.

There's nothing wrong with using cable ties to fasten down the hose/pipe instead, and you can run the new line beside your braze-ons for some support.

On the other hand you might wish to grind off the braze-ons for a more streamlined look. Bad idea on carbon and even aluminium I'd not do it. But a steel frame is easy to work on. Just touch up the bare metal after to avoid rust.

Internally routed cables suffer the same problem as braze-ons. The entry/exit holes are generally too small, and you have to disconnect the hose anyway to get in them,

But you might want something that looks better.

Option 1. http://problemsolversbike.com/products/brakes/clamp_on_cable_guides_-_27723 From the above website

These are intended for top tubes but may fit your fork.

Option 2. Stick-on cable guides http://jagwire.com/files/product/DCA056.jpg

There's a bunch of different brands and styles, these are Alloy ones.

enter image description here

And these are plastic ones. You'd have to clean the frame really well to ensure a good adhesion, but there's fairly low forces acting on the tube while braking - all the pressure is internalised.

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