So, Chris Froome has tossed a hand grenade into the disc brake debate. In what was – accidentally or through exceptional guile – a spectacularly effective boost to his fledgling YouTube channel, Froome delivered a scathing rebuke of road disc brakes. And I agree. [Keep your eyes peeled for our counter-argument, next week.]
I’m not anti-disc brakes; it isn’t a tribal thing. I don’t find them ugly and I’ve no traditionalist sensibilities to offend. I’ve spent over 20 years reviewing bikes and products, so I weigh everything up and speak as I find. If I thought disc brakes were entirely better, I’d say so, and I’d ride them myself. But I don’t want to, at least not yet. They’re simply not ready.
I’m fortunate enough to live in the Pyrenees running a guest house (ahem, Escape to the Pyrenees) and ride rim brakes exclusively on my own bikes. I never wish for more power or wet bite or anything else. However, I am always glad not to be carrying an extra kilo of bike (and no, I don’t really have a kilo to lose), glad not to have the embarrassing squealing that plagues even many pros’ disc brakes, and glad not to have the soul-crushing tish-tish-tish of brake rub. Disc brakes should have solved rubbing, not made it worse.
Ineos is one team that has stuck to rim brakes (Photo credit: Simon Wilkinson/SWpix.com)
Sure, Canyon now has a 6kg disc brake bike, but the rim brake version is 5kg and its THM brakes are brilliant. Don’t think that matters? Take away the UCI weight limit and watch every team switch back to rim brakes.
Despite the widespread adoption of disc brakes in the peloton, in 2020 all three Grand Tours were, yet again, won by riders on rim brakes: Tadej Pogacar, Colnago V3Rs, Tour de France; Tao Geoghegan Hart, Pinarello Dogma F12, Giro d’Italia; Primoz Roglic, Bianchi Oltre XR4, Vuelta a España. Given that none of their bikes are among the lightest in the bunch, it appears all three judged the weight saving to be more important than any advantages that disc brakes might offer.
So, what carnage ensued with the peloton on mixed braking systems? None. Differing rates of retardation into corners have caused no crashes. What’s more, no rider on rim brakes has ever been gapped on a descent by a rider on disc brakes because he/she lacked braking power. Skill has been the differentiator, proven by riders on rim brakes sometimes being the ones to open a gap.
Amateur pelotons now include many disc brake bikes, but in my own racing I’ve never felt that I was at a disadvantage. I’ve wished for electronic rather than my mechanical Dura-Ace for more accurate shifts when sprinting (I’m still stewing over a 1cm loss after a missed gear last season), but I’ve never wished for disc brakes.
Perhaps what annoys me most in this debate is how the case for disc brakes is so often misrepresented. Most of the real advantages are ignored in favour of other points that are, at best, overblown, yet they keep getting repeated. It’s become a meme.
Modulation – This term has been hijacked to mean reduced effort at the lever for a given brake force. Modulation really means fine control over the progression of the braking power you’re applying, and this requires maximum power to come from a greater lever force, not less. The more effortless the power, the harder it is to control it precisely. The strongest disc brakes I’ve ridden have made me nervous in the wet. Fine control is essential, and discs aren’t there yet.
Power – Yes, there’s a big difference compared to bad rim brakes on bad wheels, but not against a good set-up. There are some hugely powerful disc brakes and some rather weak ones (140mm front discs are a joke, as I discovered on the Col du Tourmalet one sketchy day last summer), with a typical good set-up about on par with high-end rim calipers biting on textured brake tracks. What really matters, though, is usable power and if you’re still riding the same size tyres at the same pressures then your limiting factor is likely to be grip, not brake power. If you can already lock your tires, or lift the rear wheel, what’s the point in having more power?
Brands like Shimano, ENVE and Mavic offer carbon rim treatments that hugely improve braking performance (Photo credit: Simon Wilkinson/SWpix.com)
Wet braking – Against most carbon wheels? Certainly. Against the best? Nope. A few wheel brands have continued pushing rim brake technology to improve performance in the wet. I’m fortunate to have both ENVE and Mavic wheels in my garage, with brake tracks that feature moulded and machined textures respectively.
They eliminate the heart-stopping delay long associated with most carbon fibre wheels and deliver near identical power in the wet as in the dry. Even when I’ve been riding discs for a while on a test bike, I never feel wanting for wet braking performance when I return to my own bikes. Paired with advanced calipers, such as Cane Creek eeBrakes, I’d wager most riders in a blindfolded test would guess they were riding discs. If they hadn’t crashed owing to being blindfolded, that is [NB, to reiterate: do not try this at home]. Imagine how good rim brakes could become if such development both continued and trickled down.
Maintenance – While you can go months without touching them, hydraulic disc brakes are far harder to set up and it doesn’t take much to contaminate a set of pads. I also know a few riders who have had problems with air entering the system when flying with their bike or even storing it vertically.
I’ll be balanced, though. Some of the arguments against disc brakes are nonsense, too, especially the myth that they’re like saw blades when spinning. YouTube’s ‘RJ The Bike Guy’ disproved it by stopping a spinning wheel using his hand on the disc (https://www.youtube.com/watch?v=vBeSDCHhAPk). Yes, it’s possible to injure yourself on a disc, if you’re unlucky. But your chainrings are nastier and nothing on a bike is going to be pleasant to land on in a pile-up, so trying to label discs as dangerous is ridiculous. If that were the case, every CX and MTB race event would look like a Game of Thrones battle scene…
Tadej Pogacar won the Tour de France in 2020 on rim brakes (Photo credit: Alex Broadway/ASO)
I’ll also grant that there are some really good reasons for disc brakes that don’t get talked of enough.
Rim weights are reduced, as a brake track requires a lot of extra material. Because this is rotating weight at the outer edge, the inertia reduction is significant, so you really feel it. Eliminating rim wear and cable degradation are obviously huge benefits, too.
Tyre clearance is the big one. Wider tires are catching on fast but dual-pivot rim brakes are a limiting factor on road bikes. Bigger tyres increase comfort and, crucially, grip, allowing riders to use extra braking power.
Heat safety is also significant, especially in mountains. I never worry about riding rim brakes here in the Pyrenees, but I still recommend disc brakes for guests because the loads can be extreme and rider ability is a highly influential variable. A rider without good knowledge of the roads might drag the brakes a little more, and that rider could also weigh 95kg. That’s a lot of kinetic energy to turn into heat and dissipate. The best carbon wheels have all but solved the problem for regular use cases, but they’re expensive and still not infallible. Disc brakes remove the issue of rim or inner tube heat failure altogether, and the fade that Froome describes is very unusual.
I know disc domination is inevitable. Heck, I’ve almost convinced myself while writing this. Disc brakes are already the clear choice for everything off-road, for commuters, bike-packers, and for endurance road bikes needing bigger tyres. However, high performance race bikes are the last outpost and right now the rubbing, squealing, feel and weight of disc brakes are deal-breakers for me. Call me when they’re finished.
Title photo by Paolo Martelli