Muddymoles mountain biking in the Surrey Hills and Mole Valley

Hydraulic disc brakes – the future for road bikes?

Posted by Matt | January 31, 2012 | 18 comments so far

Disc brake on a cyclocross frame

If you ask any mountain biker to name the single most effective development in their riding career, the chances are that they will say – with very little hesitation – that making the switch to hydraulic disc brakes was the best thing they have ever done.

We all know the fear which comes with knowing you are not going to be able to stop in time. An obstacle appears, the trail tightens unexpectedly or someone slows in front of you, requiring a panic-y grab at the brakes.

Then there’s those other occasions when you’re riding downhill and slowly – but surely – the momentum starts to build. What starts as a steady descent becomes increasingly wayward until you are just hanging in there for dear life with your backside way off the back of the bike.

Well, hydraulic disc brakes won’t stop any of that happening. Those scenarios can happen whatever brakes you are using. Physics is physics at the end of the day as many of us have discovered the hard way after putting too much faith in our skills and equipment.

But without doubt, disc brakes provide a much, much wider performance envelope in which to operate. This is a truism that every mountain biker knows but it wasn’t always so. In the early days of disc braking there were many who doubted it would ever have a value beyond downhill racing with many XC riders clinging to their V-brakes for years after most ‘normal’ riders had made the switch.

Now it’s the turn of road riders to have the same debate.

There’s quite a rumpus going on at the moment in the world of road cycling over the possibility that there may be a move to disc brakes for road bikes, despite no manufacturer actually having a disc brake set up to sell. What’s so striking to me is that all the arguments against are pretty much identical to the arguments made against disc brakes on mountain bikes over ten years ago.

Up to now, the issue just hasn’t been there. Pro road cycling, governed by strict rules on the type of equipment allowed for racing has banned disc brakes; so no disc brakes, or rather, they’ve never been explicitly authorised. Added to which the technology just hasn’t been there to build a lightweight hydraulic setup into the cramped confines of road ‘brifters’ (combined brake and shifter units).

With manufacturers gaining expertise – and following a relaxing of the disc ban on cyclocross racing – UCI (the sport’s governing body) have let it be known the only reason discs are banned is because no-one has seriously petitioned them to lift the ban. So the stage is set for disc brakes on road bikes.

Manufacturers are making noises about developing hydraulic disc brake models for road bikes (expected to be for the 2013 model year), with SRAM and Shimano’s braking expertise looking to be a strong advantage. Campagnolo certainly lack this at the moment but interestingly Magura have just launched a hydraulic rim brake for the new Cervelo P5 time trial bike. Quite an investment unless you have long term plans in this market.

For the benefit of the roadies then (who may have stumbled across this article), what are the benefits of hydraulic disc brakes?

Arguments for hydraulic road disc brakes

  1. Power. Much, much greater power than you can ever generate using a cable set up which will stretch and absorb more of your braking input. But we all know that anyway.
  2. Modulation – hydraulic brakes are very responsive and provide great feel through the lever, meaning you can finesse your braking efforts very accurately. The combination of increased power and greater delicacy allows a rider to brake much later into turns and carry more speed through to the next straight.
  3. Consistency. The performance remains pretty much constant whether it’s wet or dry or anything in between. It is possible to boil the fluid on long off-road descents but that is now increasingly rare on MTBs and road bikes will unlikely put anywhere near those levels of heat into the system. Compare that to over-heated, sticky, grabby brake pads on rim brakes.
  4. Weight. Yes, really. A complete top end Magura MT8 disc brake for MTBs is 310g including a 160mm rotor and fluid, whereas Shimano Dura-Ace road brakes come in at 285g plus the shifter/brake units of 366g. When you’ve averaged it all out there would be little difference between the two systems I’d predict. And throw into the mix the opportunity to save weight off the wheels, which don’t need braking surfaces at the rim – for example, a relatively low cost, everyday, aluminium MTB wheelset can easily weigh under 1650g these days and that’s not without turning to carbon technology which saves even more weight.
  5. Reliability. Disc brakes rarely go wrong. OK, so the odd fluid bleed from time to time to keep them working at their best but that’s once in a blue moon stuff. I’ve had brakes that I haven’t touched for years at a time. As for pad wear, properly bedded in brake pads will last for many, many miles.

I’m sure I could go on but you get the picture. Disc brakes are a mainstream technology for MTBs and no-one I know would ever seriously argue against them – be they professional racer or the proverbial weekend warrior.

Looking at discussions on road oriented websites though you’d think it was 1999 all over again as in the face of all these benefits people are variously arguing that.

Arguments against hydraulic road disc brakes

  • I’m not putting ugly discs on MY road bike. They’re a hideous abomination against the purity of the traditional road bike. Nasty. And I bet they’re not aero-dynamic!! (Hmmm, I guess. Never seen an ugly fast bike though…)
  • They will make it slower to change wheels in a race as nothing can be as fast as rim brakes to change (would that be rim brakes which require the new wheel/tyre to be deflated BEFORE inserting it into the dropouts? Versus drop in and go?)
  • Don’t want the weight penalty (neither do I and I doubt there will be one)
  • I’ve never needed more power from my cable rim brakes (well maybe, but power is nothing without control)

And so on. You can read a representative discussion on the website where they were discussing Dura-Ace rumours recently. Obviously I’ve paraphrased for effect – I apologise for mocking – but really these arguments are nearly identical to everything we’ve heard before.

It works both ways of course (not every mountain biker is convinced by carbon for off-road bikes) but I can’t help feeling disc brakes are the way forward for roadies, especially when they see how much time they will save on those Alpine passes.

What do our readers think I wonder?

Filed under Mutterings, Trends in January 2012


About the author

Matt is one of the founding Molefathers of the Muddymoles, and is the designer and main administrator of the website.

Having ridden a 2007 Orange Five for many years then a 2016 YT Industries Jeffsy 29er, he now rocks a Bird Aether 9 and a Pace RC-627.

An early On-One Inbred still lurks in the back of the stable as a reminder of how things have moved on. You can even find him on road bikes - currently a 2019 Cannondale Topstone 105 SE, a much-used 2011 Specialized Secteur and very niche belt drive Trek District 1.

If you've ever wondered how we got into mountain biking and how the MuddyMoles started, well wonder no more.

There are 18 comments on ‘Hydraulic disc brakes – the future for road bikes?’

We love to get comments from our readers - if you've spent a few moments to comment, thank-you.

If you haven't had a chance yet, jump to our comments form if you have something to say.

  1. tony says:

    Hi Matt

    Interesting post.

    There are other advantages of disc brakes that you didn’t mention.

    1. With disc brakes you aren’t solely dependent on rim trueness for braking quality.
    2. You don’t wear out rims (kinda obvious really but useful for commuters etc….).
    3. It’s hard to rim brake a carbon rim.
    4. For Alpine racers rim heating can be a problem – remember the crash that caused Lance Armstrong to go into cyclco cross mode – that was caused by a tub rolling off.
    5. Rims don’t need a braking surface so that you can make the strongest/lightest/aero rim according to function not braking requirements. Stan’s rims for MTBs spring to mind at this point.

    There are disc brake disadvantages that you haven’t mentioned.

    1. Weight. Dura ace isn’t that light for a rim brake and you will still need a gear lever. Hence the weight disadvantage will be there.
    2. Forks – you have to build these substanially more robustly for disc brakes which adds to weight and to the detriment of ride quality.

    Overall I can absolutely see the advantages for CX and communters. However many of the disc brake advantages for MTBs (lack of maintainence requirements, improved modulation, power in all conditions) etc are MTB specific. A really good dual pivot rim brake provides all the power you need on a road bike (anyone fancy locking up a front wheel on a road bike), lots of modulation and very little maintainence. The case is much weaker for disc brakes on racing road bikes.

    • Matt says:

      Tony you’re teasing me!

      So you don’t think being able to build a more aero, lighter rim (less mass at the rim is a big advantage), that doesn’t overheat and de-laminate the braking surface or soften the tubs’ glue at speed (read ‘long descents’), while having more power, control and independence from weather conditions is beneficial to road bikes then? For a likely similar overall weight?

      Locking a wheel on a road bike has the same unfortunate consequences as on an MTB and is something every rider has been able to do in the modern era regardless of braking tech or style of bike. It’s always been about controlling your braking efforts.

      Thanks for the additional advantages and disadvantages though, all valid especially the wheel trueness issue, less rim wear but also the possibility of a heavier/stiffer fork.

      It’s going to be one of those things that will need to be tried but don’t forget people’s resistance to 29ers initially. People thought they didn’t handle or were too heavy, now you are at a disadvantage if you’re racing on 26ers… and that’s just XC racing!

      • tony says:

        To paraphase the pythons
        “So what have disc brakes ever done for us?”
        “well there is the lighter rims…”
        “well apart from the lighter rims….”

        Point taken Matt. But, but, but they look horrible on the clean lines of a road bike.

    • MuddyDave says:

      I’m also not so sure about the fork weight issue. On-One 29er Race fork is 550g according to their website. I can’t imagine a road fork is much lighter than that? Even if it is I’m sure the engineers will soon sort it out.

      Overall weight is also going to depend on whether it’s cable or hydraulic. Currently there is no way for STI levers to work directly with hydraulic but, again, only a matter of time before it get sorted. Go the cable route and without the need for a braking surface on the rim the wheel gets lighter to offset the rotor weight.

  2. Gordon says:

    I upgraded my mtb this summer from cable to hydraulic and the result is amazing. I would love to have that braking power on my road bike. I’m now running Crud mudguards on the road bike so it does come out when its wet, and to have the reassurance of greater stopping ability would outweigh any of the disadvantages I can foresee.

    The success of the design will all come down to the cost and the market desire. The top road bikes may not be the early adopters,due to weight and forks…. but I expect there to be an appetite in the mid range.

    –Thanks for the great article, really enjoyed reading it.

  3. Baz says:

    Hi Matt
    quite interesting point, but i am with tony with this one for the points raised, for the time being anyway………… but i am up for new technology that will solve the old concealed rim getting too hot on those decents!!!!!

  4. Jem says:

    Interesting debate Matt, Are you just warming us up for Friday evening??

    Although I am not riding a road bike these days, I used to back in the day.
    I agree with Tony mostly, although with a lot of R&D it could work.

    As far as modulation of disc brakes goes, yes on a mountain bike descending you are usually slower than on a road bike and the contact patch with the ground is also far greater with tyres that are knobbly and running at much reduced pressures.
    When you brake hard on a mtb the tyre will deform and squash into the terrain. That would not happen on a road bike.
    I certainly would not want to lock up a road wheel on a descent, this I feel would be far easier with a disc brake.
    Perhaps hydraulic rim brakes could work, as there would be no cable stretch and maybe more feel for the rider.

    Aesthetically, disc bakes, would it look right??

    I am certainly up for new technology, but sometimes I feel things work well enough as they are.
    Maybe I will have to eat my words!!

  5. Tim says:

    So, um yea. It exists and I want one. One of these in fact:

    Volagi Liscio Ultegra

    Granted, it is mechanical BB7’s but I’d imagine where there’s a will there’s a way to switch it to hydraulic.

  6. paul901 says:

    In my all-time top 10 and even top 3 cycling things I reckon the hydraulic disc brakes on my humble Whyte have to be in there and that’s from someone who hardly gets on the trails. As someone who for 40 years rode only cantilever, side pull and dual pivot brakes and did not ride motorbikes they were an astonishing experience, truly.

    On the road though? Hmm, I have no technical argument against any of the points made and I like the article and the debate but I am cynical. Like all things cycling it will be marketing and boutique led for quite some time so quite simply we will pay stupidly (and unecessarily) for the privilege until trickle-down reaches the value groupsets. Was it ever thus.

    But in the 21st century things are changing and why not? Pretty soon a desirable Cervelo, Van Nicholas, Colnago, Ridley et al will look shaped, mean, Di2 or Campag/SRAM equivalent equipped and disc-brakes adorned and the next generation of cyclists will lust after them even if this generation manages to hold out.

  7. tony says:

    From today. Well it looks like we’re not going to have to wait too much longer for high end road disc brakes

    “SRAM said, “It’s been rumored that SRAM is developing RED level hydraulic brakes. We want to confirm this and let you know that we are currently working on a hydraulic disc brake and a hydraulic rim brake. Information on pricing will come at a later date and no photos are currently available.”

    Matt did you have some insider knowledge??

    • Matt says:

      LOL Timing is everything!

      It’s going to be fascinating to see how this all pans out in the long run; nobody really knows what a properly designed hydraulic system is going to be like until we get our hands on one.

      There is a big chunk of marketing involved in all this but there are also likely to be benefits too. Anyone who bases a ‘nay’ argument around the ‘too much power’ issue is missing the point though.

  8. paul901 says:

    Agreed Matt, having ridden down Whitedown on road bike and dual pivots and then on the Whyte and its Hydraulic discs the only time I have felt safe is with the latter. I will be intrigued to see if we can avoid skidding on our smooth road tyres though.

  9. J-Sub says:

    I’m all for hydraulics on road bikes, so much so that I didn’t feel like waiting around for them. I made my own conversion using all off the shelf parts. I used to have cable actuated cyclecross disc brakes and I hated the weight, the constant cable stretch and the horrible modulation. Now my road bike has super strong hydraulics on it and performs the way it should. My website above has pictures and how to’s if anyone is curious. Enjoy.

  10. J-Sub says:

    Hmm, the website field wasn’t displayed. It’s in case anyone is interested. The how to section is what you’ll want to look at.

  11. jens says:

    From my point of view the argument for or against disc brakes is very much in favour. Shortly after I bought a hybrid with hope discs I did my usual 65 mile route and the difference between the hybrid and road bike was a mere ¼mph – road only slightly faster. As for confidence on a 1 in 4 I know which option will give consistent braking power – even only using 2 fingers. I remember coming down past Dent Station and struggling to brake and the levers were just about touching the handlebars and I was waiting for the brakes to fail!

    I’ll chose disc brakes everytime and remember no amount of rain will reduce braking power.

Leave a comment…

Have your say – we'd love to hear what you think.

If you have something to add, just complete this comment form (we will not publish your email address).

*Required information.

This site uses Akismet to reduce spam. Learn how your comment data is processed.