Opinion: How the UCI and manufacturers collectively bungled the disc brake trial

by James Huang


There’s been no shortage of controversy when it comes to disc brakes and professional road racing. After a long, drawn-out deliberation on whether the technology would be considered at the highest level of the sport, the sport’s governing body, the UCI, finally settled on a trial period during which the merits of disc brakes would be evaluated. That trial period was abruptly halted after an alleged incident at Paris-Roubaix. Whether discs should or shouldn’t be allowed is a complex issue. But what’s clear is that the process designed to answer that question has been fundamentally flawed.


It’s been a long time since the needs and wants of everyday cyclists closely overlapped with those of top-level professional riders. Whether it’s gear ratios, rim and tire choice, or overall bike weight, the ideal bike for one group is often not well-suited for the other.

While disc brakes offer tangible benefits to everyday road riders — and professional cyclocross, cross-country and downhill racers — professional road cyclists have approached the technology more cautiously.

“The CPA [Cyclistes Professionnels Associés] emphasises that it is not at all hostile to any technological development in cycling, as it has already been shown in many occasions,” said the racers’ union on April 15, one day after the UCI announced it was suspending the trial period for discs in road racing. “Certainly our sport is also a mechanical sport, but so far, research and innovation should not be implemented without considering the priority concerns of the riders, especially in terms of security.”

Professional road racers have a long history of resisting change, and safety hasn’t always been a paramount concern; many riders opposed helmets before the UCI mandated their use in 2003. However, incorporating disc brakes into the pro peloton introduces a wealth of questions. How quickly could disc-equipped wheels be swapped during a race? How would neutral support work? Would there be any problems with a mixed peloton — some on discs, some on rim brakes — in critical situations like foul weather or highly technical descents?

Shimano and SRAM are the two dominant suppliers of road disc brakes at the moment. Both currently use disc rotors with edges that are sharper than they need to be, which is something the UCI could have addressed before starting the competition trials.
Shimano and SRAM are the two dominant suppliers of road disc brakes at the moment. Both currently use disc rotors with edges that are sharper than they need to be, which is something the UCI could have addressed before starting the competition trials.

All of those are valid issues that can only be fully addressed in a real-world setting. In the long and arduous lead-up to the full implementation of discs in racing, the UCI wisely embarked on a trial period to help answer those questions. Sponsors prepared by developing and supplying thousands of dollars worth of equipment; riders test rode the bikes beforehand, to become accustomed to their different braking characteristics; team mechanics laboured for days and weeks.

The ban was temporarily lifted in August and September 2015, and in November 2015, it was official. The decision to allow the trial of disc brakes to continue in 2016 had been made, UCI spokesman Louis Chenaille explained, “following a period of due diligence where all represented parties were consulted via their individual bodies, and where riders and organisers’ concerns were reviewed and addressed.”

Among issues that were reviewed and addressed were the risk of contact burns from hot rotors, the potential for lacerations caused by the rotors’ sharp edges, and a potential loss of braking ability due to hydraulic failure.

By all accounts, it seemed that the floodgates had finally opened.

However, it now appears that all may have been for naught, because one major issue wasn’t properly addressed to the satisfaction of the group that cares about it most.

The CPA’s biggest concern, in terms of injuries associated with disc brakes, relates to the potential for lacerations from the rotors’ sharp edges in a mass pileup. This is precisely what Movistar’s Francisco Ventoso claims happened to him — and what he alleges happened to Nicolas Maes (Etixx-QuickStep) — at Paris-Roubaix.

Rotors may not quite be the "spinning knives" some have made them out to be but they certainly could be a little more dull.
Rotors may not quite be the “spinning knives” some have made them out to be but they certainly could be a little more dull.

A secondary concern is the less likely possibility that riders could burned by hot rotors in the event of a group crash on a long Alpine descent, where mass pileups rarely happen.

The UCI says that safety concerns such as contact burns, lacerations, and loss of braking ability were “addressed and reviewed through research,” but that doesn’t seem to be the case.

I remain doubtful about the risk of contact burns for several reasons. First, seasoned pros don’t commonly drag their brakes on descents long enough to generate excessive rotor heat. Second, mass pileups tend to occur not on downhill sections but on fast, flat sections where brakes aren’t used much. Moreover, carbon tubular rims can already heat up well in excess of boiling temperatures — more than enough for a serious singe.

Nevertheless, the issue of lacerations was, and is, valid. Cast aside conspiracy theories for a moment on whether or not Ventoso or Maes really did get slashed by discs during Paris-Roubaix. Ultimately, it doesn’t matter — the fact that it was even possible is a problem in and of itself. Simply put, disc rotors, as they are currently manufactured, can be very sharp and there is the potential for rider injury in a mass pileup.

Yet it doesn’t have to be that way, and this is where the UCI’s Equipment Commission has failed its mandate.

Disc rotors are approximately 1.8-2.0mm in thickness (when new). With a properly rounded edge, they'd be no more dangerous than a common 14g round spoke.
Disc rotors are approximately 1.8-2.0mm in thickness (when new). With a properly rounded edge, they’d be no more dangerous than a common 14g round spoke.

Disc brake rotors are made with stainless steel brake tracks measuring 1.8-2.0mm in thickness. That’s more than enough material to create a blunted edge with a 0.9-1.0mm radius — exactly the same as common 14-gauge spokes, which aren’t exactly widely perceived as meat slicers on wheels.

For comparison, DT Swiss Aerolite and Sapim CX-Ray spokes — far and away the most commonly used bladed spokes in modern aero wheelsets — are not only half the thickness, but as pointed out elsewhere, more numerous and faster-moving (albeit somewhat sheltered by the rim and comparatively prone to breakage when an obstacle is introduced).

That disc rotors are sharp shouldn’t come as a surprise to anyone, and certainly not the UCI’s technical commission.

According to the CPA, a letter was sent to the UCI in January 2016, which “warns again about the security risks for the riders using disc brakes and notes that the riders were not consulted about the decision of testing them. At this time, the CPA requested to have a representative in the Equipment Commission. The UCI responds diplomatically taking note of the letters and accepts that a member of the CPA could be part of the Equipment Commission as an observer.”

Read into that as you will, but it does come across as disappointingly dismissive.

Within modern professional cycling exists an inseparable partnership between athletes and equipment suppliers, and the UCI is to be respected for at least trying to work more closely with both entities.

However, the UCI’s Equipment Commission should have determined that current rotors were dangerously sharp, and insisted that brake companies incorporate modifications such as blunted edges, modified rotor arm shapes, or potentially even some sort of disc cover to temper rider worries, costs and engineering challenges be damned. Even if the laceration risks weren’t as threatening as the CPA contended, such an action likely would have gone a long way toward tempering concerns.

A stock Shimano rotor (left) has edges that are quite sharp. After a bit of filing and sanding, the one at right has a much blunter edge.
A stock Shimano rotor (left) has edges that are quite sharp. After a bit of filing and sanding, the one at right has a much blunter edge.

Worth note: Several members of the UCI Equipment Commission, including Rolf Aldag, Bobbie Traksel, and Pascal Chanteur, are former professional road racers, while commission member Robbert de Kock is Secretary General of the World Federation of the Sporting Goods Industry (WFSGI).

Regardless, not all the burden falls on the UCI and its Equipment Commission; disc manufacturers should share some of the blame, which is ironic given their vested interest in seeing the trial go smoothly.

“Safety is always a primary concern,” said SRAM brake product manager James Alberts. “Obviously, we feel disc brakes offer added safety in terms of stopping power, modulation, and control. Beyond that, we are constantly looking at new ways to make our products safer and, along with a multitude of other considerations, rounded edges on rotors are a part of our internal discussion. We are engaged with the UCI and the WFSGI, and will provide any recommendations for improved safety as they might require.”

In other words, disc rotors can be blunted, but most manufacturers don’t currently do so.

According to Lance Larrabee of TRP — whose rotors are impressively blunted straight from the factory — grinding an even-safer chamfer or radius into the edge of disc rotors would require an additional manufacturing process and, thus, additional expense.

Whatever that cost might be, I’d guess it pales in comparison to what neglecting to do so in the first place has cost disc brake proponents now.

Tektro/TRP rotors, however, are impressively blunted straight from the factory.
Tektro/TRP rotors, however, are impressively blunted straight from the factory.

And yes, some blame also falls on the cycling media — myself included — for being so enamored by the performance benefits of disc brakes that we didn’t investigate the purported risks ourselves. The UCI may ultimately be responsible, but so are we, and I’ll admit I didn’t view the topic as critically and objectively as I should have. As always, hindsight is 20/20.

I still believe that disc brakes are superior to rim brakes. Then again, I’m not hurtling myself through the countryside at breakneck speeds in shared quarters with 200 riders all vying for the same piece of real estate. The kind of riding I do rarely, if ever, results in a mass pileup. (Knock wood.)

So what now? Is there a place for disc brakes in professional road cycling? I believe so. Bicycle technology should, and will, advance. And the sport’s governing body must adapt to it. But there is a smart, safe way to do this, and there is a sloppy, dangerous way to do this — and what we’ve seen thus far certainly feels like the latter.

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