An earth-shattering rumble was heard in Europe last week, as the Everesting record was shattered by a relative unknown, taken by 23 minutes, and an up-and-coming star stormed to a comfortable solo victory at Strade Bianche, both utilizing cutting-edge technology.
The stopping system aboard both bikes is simpler, removing redundant components and expensive fittings, more robust, as it can more easily tolerate misalignment and mismanagement and abuse, and can be more easily worked on with fewer tools, lighter, reducing rotating weight as well as frame weight. It’s a system that’s more flexible, with components more easily interchanged. It’s even cheaper.
The radical technology incorporates the already existing, and necessary, rims into the system, making a separate rotor unnecessary. Owing to the fact that the rotor rim is huge, 622mm in diameter, the system has more leverage and is more easily cooled, reducing the need for cooling elements.
The technology is known as: cable-actuated rim-disc caliper braking. Shorthand is: “rim brakes.”
Yes, rim brakes crushed the Everesting record and the newest WorldTour classic. Both conditions arguably called for the alleged greater stopping power of separated rotor discs.
Everesting is seen as a climbing contest. While that’s true, the elite racers who are undertaking record attempts have generally chosen short, steep hills on which to make their attempts. Hills that are two kilometers long or less and featuring a fairly straight roadway and grades of 10% or more. It is correct that on grades that steep, weight matters while going up. But it is also correct that descending steep hills and stopping fast and hard calls for good braking.
Ronan McLaughlin, the guy who shattered Alberto Contador’s Everesting record, who himself beat WorldTour rider Lachlan Morton’s record, is a pretty good racer. And a bit of a specialist at hill climbing events. That written, he’s not a WorldTour racer. He’s currently an amateur racer who is also working a full-time job.
According to Strava, McLaughlin’s fastest descent of the half-mile grade he used was 34 seconds. That means he basically went from walking pace at the top to average 52.94mph on the descent, before heading back up. According to Strava, his max speed was 53.7mph. Those speeds are pretty high; he hit them on light carbon-fiber Shimano Dura-Ace C35 wheels, not noted for their braking prowess, with a direct-mount Tri-Rig Omega X brake in front (for aerodynamics) and a Campagnolo direct-mount brake (his standard equipment) in back. (To be fair, there is now some debate about whether or not rotating weight matters, though overall weight is lower with rim brakes, too.)
And the roads were wet, for at least some of the attempt. It rained at some point. And the assumption is that wet carbon rims can, at least, somewhat compromise braking.
Strade Bianche, the classic that takes in Tuscany’s loose-gravel white roads, was won on a solo escape by Wout van Aert of the Jumbo-Visma team. Van Aert is a world-champion cyclocrosser who successfully crossed-over to road racing. He also happened to take his first cyclocross World Championship victory in a wet, muddy race, also on rim brakes. That race, despite the fact that cantilever rim brakes were more successful than rotor discs, was pretty much the last gasp of rim brakes in world-class cyclocross racing.
Van Aert’s choice of ride was his team sponsor’s top race bike, the rim-brake Bianchi Oltre XR4, with Shimano shallow-section carbon-fiber rims (probably the same as what McLaughlin was running), oversized tubular tires, and Shimano’s Dura-Ace Direct Mount brake calipers. Bianchi does make a disc-brake version, and it appears that at least some members of the team ride the disc-brake version, so it’s hard to tell if the choice was van Aert’s or the team’s.
Furthermore, the defending champion of Strade Bianche, Julian Alaphilippe, was taken out of contention by six flat tires. Pre-race favorite Mathieu Van der Poel was also felled by at least one flat. While flat tires aren’t caused by disc brakes, it’s fair to wonder if the inability to change wheels, or change them quickly, is what ended the race for these competitors. Most disc-brake bikes have thru-axles that are worked by Allen keys. Decunick-Quick Step, Alaphilippe’s team, taped wrenches to team bike seat posts at Paris-Roubaix in 2019 to speed up wheel changes. No evidence that that did this for Strade. Nor, does it appear, was the question even asked. Racers ride what the sponsors tell them to do; the advertising value is what matters, not the victory.
So, these events beg the question we have been asking for years.
When we tried writing about it in 2016, one industry insider told us the “debate” was over; rotor discs had already won. It took four years for this to become obvious, though this insider suggested that if the UCI dropped their 6.9kg minimum weight requirement to something lower, or nothing at all, no pro would want to race a rotor disc bike.
The system is more expensive ($$$), more complex (hydraulic fluid, heat dissipation, more bolts, more parts, tighter tolerances, easy-to-bend rotors), less durable (pads don’t last as long and contaminate more easily), less flexible (harder remove wheels, swap wheels, rotor sizes, multiple thru-axle options), heavier, and, even according to many proponents, the bikes don’t handle as well.
This last one is something that gets hinted at in various forums. I’ve heard it from experienced cyclists, who find the ride quality of rotor disc-brake road bikes wanting compared to rim brake. There’s a column in which Lennard Zinn explains that it’s easier to notice differences in a frame’s vertical compliance with narrow tires, because the necessary higher tire pressure means the tires deflect less. My thinking is that rotor disc braking possibly calls for significantly stiffer forks and stays, which might get noticed in terms of reduced vertical compliance in both, and possibly weight at the fork. I don’t know if there’s that much difference, and even if there is, if it can be noticed. But this possible drawback might be blunted by the wider tires. At what point wide tires slow someone down is up to debate, but there’s at least some evidence that possibly up to 31mm is still faster than smaller tires on all but the smoothest surfaces. And now that rims are being designed with certain sized tires in mind to maximize aerodynamics, it’s hard to find an ideal size unless working with a specific rim; so 25, 26, 27mm etc. could be fastest, depending.
Part of me feels uncomfortable questioning disc brakes. It makes me feel like an outlier, like Quixote tilting at a windmill that can only crush him. The invisible hand has done its thing and everyone should respect that. As was pointed out earlier, there was evidence that, for unknown reasons, disc brakes won out in the bike industry some time ago. It’s hard to pinpoint what did it, but it feels like the media followed the industry’s lead and decided, on very little evidence, of what was best; editorial decisions followed, as did marketing decisions, and presto-change-o, the decision was made. All the same, considering how we’ve experienced the spread of misinformation in the recent past, it almost feels as if people are afraid to question even this most basic of question. The buying public feels that the industry decided, the media feels the manufacturers decided, and the manufacturers feel the buying public decided.
I’d like to believe I’m open-minded, that evidence could convince me.
I still feel that evidence is lacking. I’m still troubled that the primary benefit of rotor disc braking is supposed to be better stopping performance, but there is almost no serious analysis going on to prove that contention; I wonder if magazines don’t have the resources to test, and are afraid of scaring advertisers. Global Cycling Network did a fun, unscientific test with two riders, then more recently did a more scientific descending test. The first one is fun, but poorly controlled. The second one is far more controlled, though hardly perfect, and the result is that rim brakes did a little better in the dry and discs did better by a bit more in the wet. At the same time, the differences are hardly dramatic—enough to wonder if the time “saved” going down could be lost on the climbing–and could be chalked up to the abstract issues of “feel” and “confidence” rather than a quantitative mechanical improvement. There’s also a question of how often most cyclists encounter such conditions. And if it is a quantitative improvement, is it worth the other hassles that go with? Toasters are still going strong, and the tech is pretty old.
Maybe the differences would be more obvious with bigger tires and more dramatically changed designs. Maybe the differences would be smaller with better controls and a better selection of components. I don’t know.
That we’re collectively betting so much on something that hasn’t been answered feels wrong. Something that could hurt cycling in the long run. And that bugs me most of all.