Will disc brakes will help you get from A to B quicker than a classic caliper set-up?

Despite the UCI giving the green light to disc brakes in the peloton, one of the most successful Classics riders of all time, Fabian Cancellara, has decided to stick to caliper brakes for his final pro season. “I don’t think they [disc brakes] make me go faster, or slower. It’s a technical and personal decision,” he said.

Like Cancellara many of the road riding community have been asking ‘are disc brakes necessary on a road bike?’ Ultimately cyclists will choose what gets them from A to B in the shortest amount of time, so perhaps the question we should be asking is ‘will disc brakes make me faster?’ For both caliper and disc brake wheels ‘faster’ means considering the same metrics: aerodynamics, weight and braking.

Aero factor

The focus has shifted evermore towards aerodynamics. It plays an important part in your speed on all but the steepest hills. No one wants to waste watts.

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Head-on there is a little difference between a caliper and disc brake set-up from an aero perspective. “With a direct head or tailwind (zero degrees yaw) and travelling at 40kph, the difference is about 0.5-1.5 watts, or four seconds over 40km,” says Dr Chris Yu, aero and racing R&D lead at Specialized.

Storck Aernario Disc G1

However, due to the larger surface area of a disc rotor, in crosswinds they can have a negative effect. “In crosswinds the difference begins to increase and become more noticeable, around two to three watts or 10 to 12 seconds over 40km.”

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Michael Adomeit, product development engineer at Canyon, compared a standard Canyon Ultimate with caliper brakes to a prototype Ultimate with hydraulic disc brakes and found even greater discrepancies between the set-ups. “On average, a disc brake set-up is three watts slower when travelling at 45kph, but at high yaw angles, which are less likely, the difference is as much as five watts.”

Lighter rims

As well as not slicing through the wind as efficiently, disc-equipped bikes are generally around 300g to 400g heavier. However, Chris Boardman, founder of Boardman Bikes, believes the weight penalty is negligible. “As a percentage of the rider/bike package and as a percentage of performance impact, [the additional weight is] way too small to measure,” he says. “Also, there could be a small rotational weight saving at the rim.”

Jonathan Day, owner and director of Strada Hand Built Wheels, agrees that due to the lack of a rim-braking surface there is the possibility of reducing the rim weight: “Due to no braking/friction surface, the rim can be made lighter by removing some material.

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A lighter rim means the rotating mass of the wheel is reduced, allowing it to spin up quicker in acceleration, and will also be noticed when going uphill. Yes, there is a weight gain as a rotor is fitted, but it is at the hub and is centralised so the effect is reduced,” he said.

Better braking

The main argument for adopting disc brakes is the purported superior braking power along with the greater feel and modulation. In theory the consistent all-weather braking provided by disc brakes could improve a rider’s confidence, resulting in later braking into corners meaning speed can be held for longer. “Disc brakes certainly offer a better braking performance and that will also help save time,” said Adomeit.

Are you braking bad?

Our Take

From an overall performance perspective it is very difficult to split disc and caliper brakes. Currently road bikes are using disc brakes modelled almost exclusively on mountain bike set-ups, which comes with aerodynamic and weight penalties. However, the marriage between disc brakes and road bikes is largely in its infancy. As companies invest more time and money in R&D it is inevitable the performance of disc brakes and disc-equipped bikes will improve. Disc-brake bikes are already fast, and are only going to get quicker.

Are disc brake bikes faster?

Disc brakes

Disc brakes

Yes Chris Boardman, founder of Boardman bikes

In isolation discs are slightly less aero than rim brakes, but in my experience, better, more reliable braking instils confidence, allowing you to brake later and less often. This far offsets any aero small losses. The weight penalty is negligible — you are into the 0.08% range. When you factor in the option for reducing rotational weight (lighter rims) giving better acceleration, I’d say your performance is far more likely to improve.

No, Dr Chris Yu, aero and racing R&D lead at Specialized

Although disc brakes aren’t always the slowest option, from a pure speed and aerodynamic perspective caliper brakes are faster. At zero degrees yaw there isn’t much difference. However, with disc brakes a large portion of the aero drag comes when the rotor is exposed to crosswinds. On a completely flat time trial, or a race with little extreme braking, disc brakes are currently slower.

  • llos25

    They are brand new and the best shimano make they are useless a manufacturer produced non event to make money.

  • Don’t forget the extra ability to lightly modulated the brakes to perform emergency stop on steep grades make a massive difference to keeping your hand feeling fresh (as I’ve found out with such joy on the Tourmalet.

  • 28mm let alone 25mm barely cope with the quiet but rough road of the South Down, either that or I’m heavily spoiled by riding slick 42mm like the old Frenchie did in the past.

  • They are ugly, but if you don’t find them working for you, then your brakes is fucked mate.

    Even cable pull BB7 + Yokozuna Reaction bite as sharply as dual pivot calipers.

    Just need to take it to a reputable LBS to get it properly sorted out, even the Shimano hydro in our shop isn’t great out of the box and need setting up properly to make it feel amazing.

  • llos25

    Never worn a rim out yet and I have done many thousands of miles over many years but that I suppose is down to how you use your brakes .I would agree that riding through slush and snow with carbon wheels is stupid but that is why most sensible riders have a winter bike with cheapish alloy wheels.

  • llos25

    What about the condition of the road gravel etc ,having a disc braked bike on test I find that they are ugly and do not work for me in any conditions better than rim brakes they are very expensive to buy and to maintain ,I was glad to return to rim brakes.

  • seattleben

    On descents with steep turns, assuming you do need to brake, disc brakes gives you better control and shaves seconds off your time. The less familiar you are with the route, if there is any length of downhill that is not completely straight, the ability to brake later gives you the extra confidence to ride faster.

    If you have to pay for your own wheels, there is no question that the disc aero carbons are going to last much longer than the rim brake option, and if you do away with the rim brake track, you can still shave some weight off as the article pointed out. This is a big deal because nothing hurts more than discarding a $3000 carbon wheel with a worn out rim.

    On flats and climbs, they do nothing, and when its all dry, they do nothing. But now you can ride your fancy aero carbon wheels even through some slushy winter rides without fear of brake failure or destroying your wheels. That’s worth something to people who ride in days when the roads are not completely dry.

  • Noriner

    Probably means incessant brake rub resulting from tiny pad-rotor clearance blunting speed

  • Tony Short

    Well I ride 25s myself but each to their own, my point being that the wider, treaded tyres on mountain bikes and cyclocrossers that can shift water are better suited to the braking forces a disc set up can put through them in the wet than skinny racing slicks can. In any case, I haven’t made a scientific study of this but I imagine that for most of the people, most of the time, the amount of time spent on long technical descents where discs might present a small advantage over rim brakes is a tiny fraction of any journey or race. Hey, I don’t have a problem with people who want discs on their bikes, but I do question the motives of manufacturers who are always looking to find a new niche and maximise their profits.

  • With calipers brakes, you need to worry about the braking limitation, but with disc calipers, you’ll only need to worry about the tyres limitation.

    The latters is a much better trade off once you stop worrying about being able to stop quickly in any circumstance.

    Secondly, who ride on 23mm nowadays? go for a nice fat 28mm GP 4000sII/Corsa G+/etc. and you’ll be right as rain.

  • Tony Short

    It’s a given that disc brakes out perform rim brakes in terms of stopping distances, especially in the wet. However in the dry, because modern rim brakes are actually quite close in performance terms – certainly for the 99.99999% of us who don’t make a living racing bikes, and because in the wet the other limiting factor is the grip available from a slick 23 or 25mm wide tyre, then I’m struggling to see how disc brakes will be a worthwhile investment on road bikes.

  • blemcooper

    What is a “turgid ride” in the context of a road bike?! Is it more about appearances or ride quality?

  • Simon Barnes

    I have really enjoyed Focus road bikes in the last few years. Therefore I purchased the “disc bike of the year” the izalco max disc. It is in my view a massive, terrible and expensive disappointment. If you are happy with 1% of your ride being great (the braking) and you feel this can outshine the remaining 99% of the turgid ride….then disc brakes are for you.

  • Altimis Nuel

    For lazy reading (and probably rush to conclusion)

    Nope, Disc is not faster than Rim brake in good-dry-weather condition

    Just go find youtube about Disc vs Rim aero test by wintunnel (Specialized) and Braking power Disc vs Rim (GCN)

    You will understand why. But if racing on bad weather/descent/muddy/gravel road, Disc proved to be **better** (not implied its faster yet) than Rim Brake in all aspects.

    For now, Disc is not faster but future? maybe.