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The pizza cutter strikes again

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Road Cycling “It is by riding a bicycle that you learn the contours of a country best, since you have to sweat up the hills and coast down them. Thus you remember them as they actually are, while in a motor car only a high hill impresses you, and you have no such accurate remembrance of country you have driven through as you gain by riding a bicycle.” -- Ernest Hemingway

The pizza cutter strikes again

Old 04-13-22, 11:01 AM
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popeye
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The pizza cutter strikes again

Hugo Hofstetter left with huge cut in ear after dramatic crash at Circuit de la Sarthe, questions safety of disc brakes.

https://www.velonews.com/news/road/f...th-disc-brake/
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Old 04-13-22, 11:06 AM
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Brakes at all are dangerous, what we need are rocket boosters, fixies, and some PBR!
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Old 04-13-22, 11:17 AM
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keep a safe personal space distance from all crashes.
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Old 04-13-22, 11:52 AM
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How does a rotor cause a small puncture like the one that's in line with the gash? I guess I can't tell if that's a ridge or a valley between the two.


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Old 04-13-22, 12:27 PM
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Originally Posted by WhyFi View Post
How does a rotor cause a small puncture like the one that's in line with the gash? I guess I can't tell if that's a ridge or a valley between the two.



It doesn’t
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Old 04-13-22, 12:35 PM
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Dumb question... I don't have a lot of experience with discs, but how does a 2mm thick rotor become "razor-sharp"? I do have some experience with razors, and they are quite thin.

Wouldn't rounding the outer edge a bit keep it from getting sharp during a reasonable service life?
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Old 04-13-22, 12:40 PM
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Originally Posted by ThermionicScott View Post
Dumb question... I don't have a lot of experience with discs, but how does a 2mm thick rotor become "razor-sharp"? I do have some experience with razors, and they are quite thin.

Wouldn't rounding the outer edge a bit keep it from getting sharp during a reasonable service life?
not sure, but I'd be concerned of the barbed wire that the cables could transform into during a race.
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Old 04-13-22, 12:47 PM
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Originally Posted by ThermionicScott View Post
Dumb question... I don't have a lot of experience with discs, but how does a 2mm thick rotor become "razor-sharp"? I do have some experience with razors, and they are quite thin.

Wouldn't rounding the outer edge a bit keep it from getting sharp during a reasonable service life?
Yeah, they're not razor sharp unless describing then as such is useful for a narrative. Shimano are certainly blunted, as are SRAM. I don't know about Campagnolo, but I would assume that they are, too. Of course, detractors will say that rotors cut better than you'd think because they're super-heated. Yeah, that one doesn't make a lot of sense to me, either.

FWIW you *can* get an extremely sharp edge out a nominal 90° angle, but it takes some work teasing out and burnishing that edge (which is how woodworking cabinet/card scrapers work). The rounding off that the manufacturers do should prevent anything near that level of sharpness for the lifespan of the rotor.
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Old 04-13-22, 12:53 PM
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Originally Posted by ThermionicScott View Post
Dumb question... I don't have a lot of experience with discs, but how does a 2mm thick rotor become "razor-sharp"?
It's about as sharp as a razor scooter
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Old 04-13-22, 12:58 PM
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Originally Posted by ThermionicScott View Post
Dumb question... I don't have a lot of experience with discs, but how does a 2mm thick rotor become "razor-sharp"? I do have some experience with razors, and they are quite thin.

Wouldn't rounding the outer edge a bit keep it from getting sharp during a reasonable service life?
It doesn't, but if you spin it fast enough it will cut or tear through soft tissue.
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Old 04-13-22, 12:59 PM
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Some questioned the propriety of some riders using fast-stopping discs while others were managing the different deceleration offered by rim brakes.
hahaha emphasis mine
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Old 04-13-22, 01:00 PM
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Originally Posted by Mojo31 View Post
It doesn't, but if you spin it fast enough it will cut or tear through soft tissue.
How fast do you imagine it's spinning?
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Old 04-13-22, 01:14 PM
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Originally Posted by Darth Lefty View Post
How fast do you imagine it's spinning?
Don't know. Put your bike on a stand and start spinning the rear wheel. Put your finger on the edge and see what happens. If no cut, increase the speed of the wheel and try again. Eventually, you'll find out what it takes.

Or, maybe he didn't get "cut." Maybe his ear got caught in something around the area of the disc and was torn in the melee. The article did not really say what specific injury he had. In lay usage, the word "cut" can mean a lot of different things.
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Old 04-13-22, 01:56 PM
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Perhaps we need safety razor discs with 5 blades
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Old 04-13-22, 02:00 PM
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I think the OP's point is that racing is dangerous and Big Bike should stop forcing it on us.
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Old 04-13-22, 03:09 PM
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I don't think there's any way that a disc brake rotor could damage a helmet like that unless it was removed from the hub and thrown by a ninja.
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Old 04-13-22, 03:18 PM
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Originally Posted by tomato coupe View Post
I don't think there's any way that a disc brake rotor could damage a helmet like that unless it was removed from the hub and thrown by a ninja.
The new Shimano Shuriken™ rotors have awesome stopping power.
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Old 04-13-22, 04:47 PM
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Old 04-13-22, 04:50 PM
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Damn, bruv, brave move!
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Old 04-13-22, 04:52 PM
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If the discs are good and hot, they’ll self-cauterize the wound, making extensive debridement necessary, but preventing potential exsanguination.
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Old 04-13-22, 06:52 PM
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I have a chainring scar on my left leg from falling off of my mtb. Let's get rid of those dangerous chainrings.
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Old 04-13-22, 07:34 PM
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Originally Posted by big john View Post
I have a chainring scar on my left leg from falling off of my mtb. Let's get rid of those dangerous chainrings.
They are like buzz saws!
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Old 04-13-22, 07:38 PM
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You guys should see my legs after an hour with kittens!
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Old 04-13-22, 07:56 PM
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Originally Posted by big john View Post
I have a chainring scar on my left leg from falling off of my mtb. Let's get rid of those dangerous chainrings.
I concur that chainrings, especially the biggest chainring on 2 or 3x is far more dangerous than disc brakes.

It's one reason I went 1x. No more exposed teeth from the chainring because the chain shrouds them at all times and 1x chainring tend to have more dull/wider teeth, less likely to cut even if exposed.
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Old 04-13-22, 09:17 PM
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The real danger is hitting the tarmac at 30 mph in a virtual bathing suit and an eggshell. - Happens in almost every pro road race. Blaming the brake discs is a red herring.
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