Debunking the Disc Brake Rotor Fiasco.

Posted: 13 April 2016 in Uncategorized

I don’t know what the whole fuss about the dangers of disc brake rotors in pro road racing is all about. I may not be the fastest road racer on the planet, but I’ve had my fair share of experience in a road racing field and same goes for disc brake use.

It blows my mind how little these pros actually know about disc brakes, pros/cons, or how to even use them properly.  I guarantee you more than half of the pro peloton at this year’s Paris Roubaix probably have never used a disc equipped bike in their life time.  Especially the ones who remember racing on bikes that only had 3 gears…

To clarify, I really feel bad about those riders who were injured during this years Paris Roubaix, and I wish them a very speedy recovery.  Yes, road racing has it’s dangers.  I’ve crashed on the road more than I care to admit, and crashing at speed makes it even worse.  Throw in some cobbles, 200 of some of the strongest cyclists in the world, and a pretty big trophy at the end of the race, and you end up with these dangers compounded.

This year is the first full year (or was until about 3 hrs ago) where at least the pro peloton had the ability to ride a disc brake equipped road bike in any UCI sanctioned road event.  Yet you can easily get away with racing an old school cantilever equipped CX bike with carbon rims in a rainy road race no problem, but that’s another story.  Honestly, I cannot tell you what the solution to this whole debacle is, I’m just here to point out some VERY obvious facts.

What actually happened?

First off:  If you read Ventoso’s word for word account of what happened, his recount of the crash goes something like this:

Let me take you to 130km into the race: into a cobbled section, a pile-up splits the field, with riders falling everywhere. I’ve got to break [brake] but I can’t avoid crashing against the rider in front of me, who was also trying not to hit the ones ahead. I didn’t actually fall down: it was only my leg touching the back of his bike. I keep riding. But shortly afterwards, I have a glance at that leg: it doesn’t hurt, there’s not a lot of blood covering it, but I can clearly see part of the periosteum, the membrane or surface that covers my tibia. I get off my bike, throw myself against the right-hand side of the road over the grass, cover my face with my hands in shock and disbelief, start to feel sick… I could only wait for my team car and the ambulance, while a lot of things come through my mind.”

Ok, so he remembers his leg ‘touching’ the back side of the bike of the rider in front.  I have a hard time believing that he himself remembers exactly what his knee touched.  But regardless, lets move onto some other alarming facts.  Did he ever mention anything about spokes?

Ventoso goes on to talk about the number of disc brake rotors present in the peloton for this years Paris Roubaix, 32.  Meaning 2 full teams of 8 all had disc brake bikes.  8 x 2 (wheels per bike) x 2 (# of teams) = 32.

Disc Brake Rotors:

Only those who have used disc brakes a lot would understand the true dangers and/or subtleties of riding with disc brakes.  For example, if you are riding down the Stelvio, or a MTB trail descent next to the Stelvio, your rotors will heat up like no body’s business by the end of the downhill, so you better stay away.  Yet if you are on a long road ride where you only use your brakes (lightly I might add) to take a 90 deg corner every 5 mins, it will be highly unlikely that your rotors will heat up hot enough for the hot rotors to be any help in cutting through your skin.

Bladed Spokes:

So how many bladed spokes do you think were present in this year’s Paris Roubaix Peloton?  Of all the bikes I could see from photos of the race, and the status of the types of wheels in the current pro peloton, I imagine EVERY team had aero wheels with bladed spokes (as flat box regular spokes are essentially a thing of the past), but just for safety sake lets say 5% of the wheels out there used normal non-bladed spokes.  As most wheels are carbon, this allows less number of spokes per wheel, but lets assume that the average number of spokes for a wheel is 20 (a far cry from the 32 on some wheelsets, so this ends up being a very safe estimate).  So the total number of bladed spokes in the peloton would have been about 200 (# of riders) *2 (wheels per rider) *20 (average # of spokes per wheel) = 8000 (factoring in the 5%) = 7600 bladed spokes.  A whole lot more than 32, or am I wrong?  That’s over 200 times more likely to come in contact with a more dangerous spoke than a rotor.  ***My initial math was of by one whole digit.  Which further makes the case.  Thanks to Gary for pointing this out!

Spokes vs. Rotors:

Bladed spokes are always more narrow than rotors further adding to the danger of the bladed spoke.  Most bladed spokes (and even rotors for that matter) are measured in units smaller than mm’s but lets say for the public sake that an average bladed spoke ends up being around 1mm wide.  When the average rotor comes in around double that at 2mm’s.  Adding to the fact that bladed spokes are called ‘BLADED spokes’ for a reason (meant to be as aerodynamic as possible in order to cut through the wind with minimal resistance like a blade) I don’t know of any rotors that are designed with this in mind.  Most of them are all flat at the end further reducing their ability to cut through skin.

Do rotors heat up when braking and cut through skin when red hot?  I don’t know if you’ve seen the recent GCN episode talking about the differences between disc brakes and canti’s but for shits and giggles, it’s a must watch.  Make sure you get to the middle part when they use a sausage to show you the dangers of the rotors, er… I mean bladed spokes…

Not only are bladed spokes more dangerous when comparing directly to disc rotors, you need to keep in mind that spokes are travelling at nearly twice the speed of the rotor and are always moving.  Lets use this image from to show what I’m talking about.

If the bike ends up moving at 40km/hr (v) which is roughly the speed of the rotor given how small it is and close to the hub, then the part of the spoke that is closest to the rim end up moving at almost double this speed, or 80km/hr (2v)  I don’t know about you, but this trend is getting a bit alarming for me…


Ok, now taking all this into mind, on top of the fact that Ventoso doesn’t recall exactly what he ran into, nor doe they say anything about the details of his Etixx- QuickStep buddies incident, who’s to say his knee didn’t ‘touch’ a spoke.  The dangers in the peloton are real, yes, but the inexperience (when related to disc brakes) of the majority of these pros is portraying a very twisted view on what the dangers truly are.

If the majority of the people involved in cycling at this higher level are really just worried about the compatibility problems, and the fact that they know they will have to wait longer for a wheel than if they just stick with the tried and true rim brake wheels, then why are they shooting technology advancement in the foot by playing the safety game.  Or is cycling the next soccer (or football for those outside of North America) and we are just looking for the next thing to blame in order reduce the amount of suffering we have to go through to win a bike race.  Hey what do I know, I’m just a cyclocrosser in the ‘off-season’ who’s 2 beers into the night…


  1. BM says:

    The thing that bothers me the most about the argument from Ventoso is that it takes people to get hurt for riders to be heard. How many high speed descents have resulted in serious injuries? Could this risk be mitigated some by adding a reliable braking method to road bikes? In the end cycling is a stubborn sport with a culture that resists change, I think this is more the origin of the disc injury blame game.

  2. DF says:

    Funny how they all seem to be in awe looking at Peter Sagan’s skill that – by the way the FB comment box argument goes, should stay on MTB – has avoided him of serious crashes. Yet, instead of the pro riding peloton investing time on developing the skills they just scream sorcery. Another funny and ironic thing, is that the same conservative backwards mentality that took decades to adopt the helmet, now is all of a sudden so worried about injuries.

  3. John says:

    Complete rubbisch… A spoke does not stick out in any way. Even a turd could see that… Hé ran into the back of anonther bicycle so in that direction the spokes could never ever cause that kind of injury…. Only somthing like a derailer or a disk. But Who cares! You Just can’t getoond rid of the dangers during cycling! Unless you pack youself in armor and use a fullface helmet. So grow some balls and quit whining because you lost a race and your sponsor die not gave you 2016 equipment….

  4. Lars says:

    As someone who slices open his skin with metal on a regular basis let me just add my two cents. Neither heat nor rotation is needed to produce an injury. A sharp edge ( as may occur on the edge of discs) or blunt force can produce all sorts of nasty cuts. While a cut from a disc is certainly possible, blunt force trauma is handed out by the basketful in peloton pile ups . Skewer ends,sprockets, derailleurs and pedals all have sufficiently sharp edged parts that can produce nasty gouges. If discs are deemed a problem, manufacturers could easily produce rounded outer edges that would reduce danger without effecting stopping power.

  5. ajmacdonaldjr says:

    They should ban motos instead of disk brakes, because motos are a real danger.

  6. Brian says:

    I will assume you’ve never worked at a deli. The rotating blade of a slicer will cut so smoothly that you’d never notice your fingertips missing until you saw the blood on the next slice of balogna. A brake rotor at any speed above a crawl will act similarly. Rotor edges are not rounded, they are as-cut and sharp. The rotor does not need to be hot to slice. I have personally trapped my ungloved hand between the backside of the fork and the rotating blades spokes of the front wheel and ended up with deep red compression lines across the back of my hand befor the spokes were pulled out of the carbon. No blood. 28 mph. Hard head-first ends, but no cut from the wicked wicked blades.

    • B says:

      auto-correct got me – “hard head-first endo” is the correct result for my hand-in-fork error.

  7. Bob says:

    The analysis of the physics here could not be more wrong.

  8. “So the total number of bladed spokes in the peloton would have been about 200 (# of riders) *2 (wheels per rider) *20 (average # of spokes per wheel) = 800 (factoring in the 5%) = 760 bladed spokes. A whole lot more than 32, or am I wrong?

    YES, yes you are, as 200 x 2 x 20 = 8000!

  9. […] 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 […]

  10. […] 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 […]

  11. davy says:

    How is it even possible to run into a bike and touch a disc with left leg?.As discs are on left ventoso bike would have to be on right side of bike he hit and his left leg on opposite side of bike he hit seems virtually impossible. From what I remember of cut it seemed to be in perfect alignment to shin bone blunt force trauma on thin skin with bone behind results in bone deep cuts.

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