Racing Dan

The added weight of discs equates to less than 1% of total weight. Im sure the acceleration/speed penalty is way below treshold of human perception. Brake performance how ever is not.

Bob Dopolina 

Why are you jamming on your brakes in a group? Rim or disc, people are going down.

You will learn, very quickly, how to modulate your disc brakes. It's not rocket surgery.

Complete falacy.

Racing Dan

Its silly arguing over theoretical "risks" related to discs brakes when every single stage of TDF and any other road bike race involves crash after crash and riders seriously injured from hitting the tarmac a high speeds. Its not the brakes, its the inability to stay on the bikes thats the problem, combined with zero protective gear besides the helmet.

RJM

Both of these show the hand (or orange) being placed on the rotating disk and that one video with the hand the dude looks to be gently placing his hand on it. This wouldn't happen in a crash so they videos aren't testing anywhere near the same conditions or with the same forces that would happen in a road bike collision. Slam the orange (or hand) with the same force as a body slamming into the spinning disk and then the test might make more sense.

redfooj

Maybe he's trying to say, when he grabs his rim brakes in a group, the calipers wont bite

WhyFi

The discs still aren't "slicing" anything - we're talking about a blunted, 1.5mm thick (at a minimum) "blade." If the disc weren't there, we'd be talking about slamming [your body part of choice] in to the spokes/dropout, instead; if you're going to ask for volunteers to slam a hand on to a disc, I'll be happy to right after you slam your hand in to the spinning spokes/hub/dropout.

Racing Dan

Bladed or slim spokes seem like a much more likely offender than discs, yet they are off the hook.

RJM

Hey man, if there is no danger why are you scared to do it?


Besides, I didn't put a supposed test up on youtube that shows how safe discs are, and that is what I'm commenting on. There are ways to test to see how dangerous discs would be in the event that a body part comes into contact with a spinning disk at speed during a crash, but these two videos did not show that. I can think of a few good ways that involve pork shoulders, a two by 4, and another person to spin the rear wheel on my cross bike but I'm not motivated enough to do it. Besides, we all know what will happen when you slam some flesh into a spinning disc during a crash and I would bet it wouldn't be pleasant.

WhyFi

Why are you scared to slam your hand in to the spokes or even just punching the dropout? Besides, I'm not saying that there's no danger, I'm saying that there's probably not an appreciable increase in danger.


Are you under the impression that centrifugal force of spinning a blunted 1.5mm thick "blade" will somehow stretch the outer "edge" of the disc in to a finely-honed Ginsu? Sweet.

RJM

Congratulations on the dumbest thing I've read this past week.

WhyFi

Exactly. I'm glad that the ridiculousness of your comment is not lost on you.

Doge

For that reason they don't want discs. Given the choice of 15lbs with disc or 14lbs without by people trying not to brake at all - the 14lbs bike will normally be preferred. There is a very large segment of the Road Cycling market that rides on dry paved roads where they rarely use brakes, and also want lightest they can get (for the money etc.) "racing" bike, whether they race or not. I think that will remain the largest segment.

Road Cycling is not by definition the most efficient or practical way to transport, or even has transport as the primary purpose. It is recreation, and that drive all kinds of products, colors, feelings. Making the argument that discs stop better is one few care about, and I have not seen anyone disagree with, just rim brakes are good enough for most Road Riding.

RJM

Dude, if you think hitting a spinning disc at force with your leg is the same as resting your hand on one, it doesn't leave much room for intelligent discussion. Like I said, there are ways to test it, but we all know the outcome.

dabac

The rotor sits at about the same place as q/r levers have been sitting for decades.
If impacting rotors are a valid concern, I'd expect to have seen or heard about at least some people being gouged by or impaled on q/r levers by now.
But I haven't.

So yeah, it's a fairly narrow edge. Rotating or not, falling on it might do some new damage. Eventually, it'll happen to someone.
But is it overall a valid concern, I think not.

RJM

I'm not even making the argument that it is a valid concern...all I'm doing is saying those two videos suck for testing the theory.

dabac

Ah, gotcha.

WhyFi

I don't think that. I think that hitting a spinning blunted disc at force is not significantly more dangerous than hitting a non-spinning blunted disc at force. Do you think that sawing really quickly with the back edge of a kitchen knife is going to carve a ham? Hint: it's not.

We await enlightenment.

RJM

Looks like a proper test is in order and until then we will agree to disagree. I think it will show significant damage and you don't. I can say that laying your hand on a spinning disc brake isn't going to cause the same damage as smacking that hand into it with force.


For instance, I have a cleaver used to chop up meat. I can rest that cleaver on my hand and nothing will happen but if I slam it into my hand with force it will cut my hand off. I'm sure there is enough internet engineering in this forum that we can delve deeply into why that is for a few pages, but I will leave it at that.

WhyFi

Wait - I thought you already knew the outcome? Enlighten us.

NSS.

Not with the back edge, bro.

RJM

With enough force it will.


Have you ever seen someone accidentally amputated at a jobsite? It's usually not done with a ginsu knife.

Athens80

With enough force ... Hurricane Andrew drove a 1x4 through a palm tree: AccuWeather.

Racing Dan

"Good enough" is not exactly high praise. Sure latest 105 and Ultegra calipers are good and riders in that segment may not want or need anything else. Lots of bikes, how ever, comes with inferior brakes. For instance my 2015 Defy 1 came with noname caliper brakes and it was terrible. Compared to that, even the cheapest Tektro hydro disc is vastly superior. In the road bike market hydro haven't really trickled down yet, but Im betting it will, like in mtb, and riders will embrace it because its simply better.

WhyFi

NSS, but the force required would make anything harmful. Are we getting the picture yet?

And it's usually not done with the kind of force generated by a flailing body part of a 150lb person falling from a couple feet.

RJM

Like I said, it's probably worth testing and we will agree to disagree until it is. You can't know what force is required to cause a problem because I think it is clear that you haven't tested it. Neither have I, but I can say that a fall into the disc in a road ride would create more force than just laying your hand on a spinning disc.




Are we going to go on and on about that for longer?


btw, how old are you? I haven't heard NSS since grade school.

Doge

It is not high praise, but good enough keeps folks from buying something else where there is other compromise to be had. And especially for the paved dry Road Cycling application, there are many good enough rim brakes.

To the OP - the question/answer is a marketing one, not a performance one. Better is not as big a driver as being sufficient and the biggest driver is what the racers are using.

Road Bikes are performance bikes of the types people compete on. As long as most competition is on paved, dry roads, my guess is discs will never get over the 50% attachment on mass start race legal road bikes.