Dangerous Disc Brakes???

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Disc brakes are back in the headlines.  The UCI decided to allow their use again this year. Marcel Kittel and Tom Boonen were two of the most prominent riders using them so far.  Then Kittle got caught up in a crash with Owain Doull, Team Sky, and Doull claimed he was sliced, at least his shoe was sliced, by Kittel’s disc rotor.  I think he was wrong.

SInce then, the CPA has called for them to be disallowed.  And lots of websites have done experimental videos showing if a disc rotor can cut things.  Velonews did a couple videos that showed, if someone is powering the wheel, then it could possible cut through a cycling shoe.

The only problem with that experiment is that when someone has their cycling shoe up against someone’s brake rotor, no one is pedaling that bike.  That bike is most likely going to hit the ground very soon, riderless.  And the time they held the pig’s skin and shoes against the rotor was so much longer than a person could ever be touching a brake disc in a crash scenario.

I very much doubt that brake disc rotors are dangerous.  Just because they are rotating doesn’t make them into meat cutting blades.  They are pretty dull and I’ve never come close to being cut by one.  And I’ve fallen a fair amount of times on bikes with disc brakes.  And I’ve been run over by a fair amount of times by guys riding disc brakes.

Think how many crashes, mass pile ups have been at the start of MTB races since discs have been used.  I’ve never heard of anyone getting sliced by a rotor.  Add cross races too, now that disc brakes are becoming commonplace.  I’ve never seen someone in MTB or cross cut by a disc rotor.

I’m not big on the disc brake switch.  It is a huge change and makes exchanging equipment, especially on the road, very difficult.  When the manufacturers get their shit together and make the calipers more adjustable, maybe make the pads retract further, then the wheels might be interchanged much quicker.   Until then, maybe they are only good for individual racers where riders have their own equipment, in pits, available.

If you gave me a choice between touching a rotating brake rotor or having a guy run into me with a chainring, I’d take the rotor everytime.  I’ve been hit by chainless chainrings and those things are very dangerous.  An exposed chainring is so much more dangerous than a brake disc connected to a hub.   I very much doubt the CPA is lobbying to get rid of those.

***Okay, I just went out to my garage and spun a MTB rear wheel up to speed.  I could stop it very easily with my thumb.  I do realize that hand skin is tougher than other skin on a human’s body.  I’d think if a leg or arm came in contact with a rotor, from the top, where it would cut you, then the same leg or arm would make contact with the spokes of the wheel too, so it would not only be the rotor stopping the wheel.


35 thoughts on “Dangerous Disc Brakes???

  1. SB

    right… and nobody ever mentions that every racing wheel now has “bladed” spokes – where’s the VeloNews video of a guy sticking his finger into the spokes at speed?

  2. Mark

    I love disc brakes. Have them on my mountain bike (couldn’t imagine riding without) and my Cyclocross bike. That said, while working on centering a caliper on another rider’s ‘cross bike I managed to slice my finger all the way to the nail bed on the rotor. ER visit. Anecdotal? Yes. Painful? Yes.

  3. ScottO

    I’m not taking a side here, but what you wrote here is not going to be the solution:
    “When the manufacturers get their shit together and make the calipers more adjustable, maybe make the pads retract further, then the wheels might be interchanged much quicker. ”

    Motorized applications for disc brake on the planet tolerates pads dragging on the discs. Bike industry didn’t develop this tech, it trickled down via motorsports. I think the future of road racing w/discs lies with standardized spacing/tolerances so wheels can be switched reliably and quickly on the road.

  4. LD

    “The only problem with that experiment is that when someone has their cycling shoe up against someone’s brake rotor, no one is pedaling that bike.” True, unless the hidden motor is still running. Oh wait, that’s cheating, nobody would do that.

  5. Steve Tilford Post author

    ScottO-It seems to be 142 spacing is the number. I’ve seen blow outs on frames with 135. But even the same. Ike with duplicate wheels have issues. There is so little tolerance for being off just a tad. I can’t imagine a wheel change working correctly in a road race situation.

  6. El Tejan

    The rotors currently used for road applications (e.g. UCI road races) _are_ rounded off.

  7. Bolas Azules

    What a bunch of lads that came out of the soccer culture of Europe, suck it up boys this is bike racing.

    So these boys who almost unanimously elect to ingest a laundry list of drugs, shoot-up micro-doses as well as ‘maxro-doses’ of things they have no way of understanding , insert suppositories to make them faster & feel less pain, pack blood back into their bodies after it sat in a ‘fridge for months and about 10-15 other things that might just kill them prematurely or at least cause themselves some ailments and diseases like cancer to the point where they don’t even know what all of these things will do to their offspring and thay are worried about disk brakes being dangerous???

    A hilarious topic to take the high road on you bunch of namby pambies. Shut-up and race.

  8. John Gretzinger

    I do have one story of a friend being cut by a disc brake. She is a very experienced cyclist and mechanic. She was preparing to ride a mountain bike and was mounting her front wheel to the fork when the bike fell over and her finger became pinched between the disc brake and the frame. She suffered a deep cut, lost a lot of blood and required several stitches. I was not with her at the time but she could not drive to get medical help but a person who had just finished riding at the trail system gave her a ride to the ER and picked her up several hours later to return to her car. Just my one story, not saying they are good or bad, just sharing a story.

  9. Larry T

    1st The bike biz salivates over the idea of getting the entire pro peloton on disc brakes. What better way to instantly make all those $10K+ bikes we (well, you) ride obsolete? They know from history (SPINACI) that the punters will attach stuff to their bicycle if the pros have it, whether it’s actually useful to them or not and yank it off just as fast when the pros are no longer using it, whatever the reason. 2nd The pros don’t much like to be told what to do. They didn’t want to wear crash hats, pee in cups or answer the door to give blood samples while at home with the wife and kids. 3rd This pissing contest will end soon enough with discs taking over, though the days of swapping a wheel out in case of a flat tire might go away in favor of bike swaps unless the bike makers come up with some ghastly “Cannondale Lefty” type frames and forks so wheels can be swapped F1 style without disturbing the brakes. All of this is ugly and silly, but so many things like these are described as “progress” or “evolution” rather than just another way to get money out of the wallets of trendy consumers. Same as it ever was.

  10. CSPAN Caller # 5

    Real men don’t need brakes. They descend and corner with complete abandon.

  11. Jmal

    I’ve been sliced by a rotor while working on my mtb. It didn’t take much at all to end up with a pretty deep cut on my finger. You must have thumbs of steel if you dragged them on the rotors while they were rotating at speed. I still agree with you about them otherwise.

  12. Randy Legeai

    “Following extensive examination of the equipment and a detailed safety report, it has been agreed with manufacturers that the trial will restart on January 1st 2017 exclusively with discs which should be modified to ensure the perimeter edge of the brake rotor does not contain any 90 degree edges but are smoothed or chamfered.”

  13. Steve Tilford Post author

    Jmal – I saw a couple guys on Facebook, at a shop, do the exact same thing, stopping a wheel with a thumb. It might depend on the specific rotor. I’ve never been cut by a rotor. All the rotors on my bikes have dull edges, as the UCI has mandated. Still, in the whole scheme of things, this isn’t close to the biggest danger involved in our sport. There are lots of other things that could use our attention before this stupid rotor issue.

  14. Jeremy

    I did the same thing. Adjusting calipers and sliced through my fingernail into my fingertip. Ouch.

  15. JV

    Ben Hur sliced up O’ Douell’s cycling shoe poor lad. Its All Marketing they know We will buy anything new that they throw at us. A touch of Disk Brakes in a leadout train heck they better move the 3k rule back to 5k! You might ask yourself My Gawd what have I Done!

  16. conrad

    There are plenty of legit reasons not to use disc brakes on a road bike- but safety isn’t one them. I think all the vehicles amongst the race are a much bigger safety issue.

  17. conrad

    Except for wrenching on the fixed gear bike. Stick a finger in the spokes and it’s gone!

  18. Barb

    If they’re motor doping/cheating and get cut by a spinning rotor when no one is pedaling, does the falling tree in the forest still make a sound?

  19. Barb

    I’ve been mountain biking for over 15 years, 12 of which I’ve used disk brakes on my bikes. And we all know especially during the learning curve, mountain biking is like motorcycles. It’s not if you crash, but when. I’ve crashed a lot, and have gotten my shins chewed up by chainrings, handlebar perforated here and there, sprains, so many injuries. But not once did I ever even come close to being cut with a rotor. I think the issue with road racing is the proximity of other riders increases the risk exponentially. Because when one person crashes, usually others go down too and often they’re on top of each other in a chain reaction.

  20. Mark

    Everyone has done that one ONCE. Then you learn the tricks on how to center them without the wheel spinning and without having to move the caliper with your fingers.

  21. Lowell Premer

    It’s not the edge of the disc that cuts you, it’s the holes in the sides of the disc. Early designs had NO finish machining of the edges of these holes/spaces/whatever, and they were REALLY sharp. The mass of the rotating wheel on a workstand would slice into any digit or soft tissue that found its way into one of those holes, let alone what a rolling bike with a rider on it could do to someone who got up against the side of the disc. I understand there’s been some effort made to round off those edges here lately; the disc shown in the pic at the end of the article looks like it might be safer than the old ones.

  22. CSPAN Caller # 8

    Those holes make a wonderful Parmesan cheese grater. But soft cheeses tend to gum up the works.

  23. Franz

    A guy I work with sliced a centimeter off one of his fingers working on his bike with disc wheels. Turned the crank, wheel was spinning, stuck his finger in the rotor and sliced it off. Now his middle finger is shorter than his index finger. I definitely see the potential


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