Why have disc brakes become so popular?

General cycling advice ( NOT technical ! )
Brucey
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Re: Why have disc brakes become so popular?

Post by Brucey »

Peter W wrote:There still hasn't been a convincing explanation of how Formula 1 braking systems can continue to work reliably (non fade or fail) while the discs are glowing red hot. Stating that cooling ducts, and high speed air flow misses the obvious point that neither PREVENTS the discs, and presumably the pads and callipers and brake fluid itself, from 'boiling up' and glowing red hot from heavy braking. (We see it for ourselves on T.V.) The fact that the ducts and airflow cool things AFTER the heating is not the point. The systems are built to work at red hot temperatures. (Indeed, they don't work properly when cold.)

If our present bike hydraulics are unable to work properly if overheated by fast descents then what is needed is a 'half way house' between the two, with cold working as well as hot, and reasonable durability and serviceability as a requirement. I can't believe that won't be possible with continuing development.


I think you don't understand how the braking system is designed and the constraints around it, in either the F1 case or bicyce brakes. You could have fantastic cooling on bike brakes but they would be very non-aero. A ducting that moved out into the breeze when the brake was applied would be an improvement.

cheers
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amediasatex
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Re: Why have disc brakes become so popular?

Post by amediasatex »

On the regulation front:

There is no such regulation that says rims must not overheat, and they can...

Things are designed for normal service loads, and then with an additional margin for abnormal situations.
You can argue about where the 'normal' line gets drawn till you're blue in the face but I think you'd be terrified at just how low the bar is set in terms of what is considered an acceptable brake (or any type) as far as the laws and regulations as they currently exist are concerned, discs certainly exceed them, as do all properly adjusted rim brakes.

If you want to draw up new regulations for braking then crack on, they'd need to be applied to all brake types (and tested, and enforced), and I think you'd find it somewhat trickier to balance all the elements than you think.

There are heavier duty options available for scenarios that require them, perhaps not enough to please everyone but there are some. If everyone was forced to accept brakes that are acceptable for say, a loaded tandem with trailer down the alps, that would be a bit of an over-reaction and unlikely to meet with much approval for people wanting a lightweight road bike or for an urban runabout.
Peter W
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Re: Why have disc brakes become so popular?

Post by Peter W »

What standard should be set?

An average weight rider, on an average weight solo bike,descending an average long steep twisty hill, involving fairly heavy braking over a longish while. Wasn't something like that already a design brief in putting hydraulic disc brakes on road bikes? Don't manufacturers work that-a-way?

All I'm saying is, in the light of many folks experience of the joy of using those wonderful disc brakes to their full potential, (can't resist -feel soooo nice), that design brief now needs 'beefing up' a bit more!
Brucey
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Re: Why have disc brakes become so popular?

Post by Brucey »

lovely brakes? Hmmm.

When suggesting brakes for other folk, I couldn't give monkey's how lovely they feel if they are not reliable. I don't know anyone who has used disc brakes for any length of time who hasn't worn pads out frighteningly quickly and/or run out of pads unexpectedly (using a self-adjusting system).

cheers
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amediasatex
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Re: Why have disc brakes become so popular?

Post by amediasatex »

Peter W wrote:What standard should be set?

An average weight rider, on an average weight solo bike,descending an average long steep twisty hill, involving fairly heavy braking over a longish while. Wasn't something like that already a design brief in putting hydraulic disc brakes on road bikes? Don't manufacturers work that-a-way?

All I'm saying is, in the light of many folks experience of the joy of using those wonderful disc brakes to their full potential, (can't resist -feel soooo nice), that design brief now needs 'beefing up' a bit more!


Have you looked up the relevant deceleration requirements to pass the current laws and standards?

And what makes you think that disc brakes in general don’t already meet your ‘averages’ situation above?

The failure cases we are talking about are still edge cases, in the same way that people who blow tyres off due to overheating rims are edge cases.

Just because there are some scenarios where certain brakes are lacking doesn’t mean that they not fit for normal use. Don’t get me wrong I’m no disc evangelist I just think that sometimes people pick on one or two aspects as downers while ignoring that other brakes also have downsides at times, I’m very much in the ‘pick the right brakes for the use case’ camp, and sometimes that means upgrades or unusal setups for unusual use cases.
Peter W
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Re: Why have disc brakes become so popular?

Post by Peter W »

I think that we are at cross purposes Amediasterix. Disc brakes DO meet 'my' average situation by intentional design and build, on THAT basis.

All I am suggesting is that users are now 'pushing' that a bit harder, which is probably beyond what the manufacturers envisioned. (i,e. the average, plus a little safety factor.) I think the main reason why we 'hammer' discs more is because they are so finger light and responsive to apply (no artificial feel or effort factor built in) that one tends to lose sense of the energy (heat) being created. Thus it is easy to exceed their limitations. With rim brakes, stopping quickly from runaway speed down a steep hill, you are in little doubt (lever force necessary) of the work and force involved.

Therefore, either a 'feel' factor should be added, or, preferably, they should be built to withstand as much heat necessary for many fast (normal) riders.
amediasatex
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Re: Why have disc brakes become so popular?

Post by amediasatex »

I dunno, despite what many may think I don’t think discs are causing people to really ride any faster or harder, the hills are as steep as they ever were, humans are as fit as they ever were and generally speaking it’s peoples courage that limits their descending.

I think you might be into something though with people braking harder with less perceived effort, but that’s actually one of the best ways to prevent discs (or any brake) overheating, hard stops/deceleration with intervening cooling periods, it’s prolonged dragging that kills brakes as they never have he chance to cool. Obviously light deceleration with cooling is better but if you have a big hill to get down brake-release-repeat is going to be better for your brakes than dragging so a brake that can do the decelerating quicker and with less effort is not necessarily a bad thing there...

Not sure, maybe you’re onto something, maybe not, dare I say it’s perhaps it’s a change in behaviour relating to ‘new’ riders having less mechanical sympathy than in days gone by? I certainly see that with the way many crunch and force their gear shifts under high loads, but that’s another discussion ;-)
Last edited by amediasatex on 14 Aug 2018, 8:43pm, edited 1 time in total.
amediasatex
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Re: Why have disc brakes become so popular?

Post by amediasatex »

Peter W wrote:or, preferably, they should be built to withstand as much heat necessary for many fast (normal) riders.


I think they already can for ‘normal’ riders, cases of boiling up and overheating are normally down to uses right at the end of the bell curve, or a result of an issue or under-specced system from the start, ie: gummy fluid, discs too small for alpine brake draggers or heavy loads, but a simple bleed, or change to bigger discs or different pads would often fix it. I agree that’s a failing of the bike companies (or shop to advis) to spec things but it’s not an inherent failure of discs as they can be altered to suit, just the same as OEM 24spoke wheels being a bad idea for heavy uses, or gear ranges being too small, it doesn’t mean ‘wheels’ are in adequate or ‘X/Y gears’ are inadequate, it’s a case of spec for the use.
Jezrant
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Re: Why have disc brakes become so popular?

Post by Jezrant »

Brucey wrote:I don't know anyone who has used disc brakes for any length of time who hasn't worn pads out frighteningly quickly and/or run out of pads unexpectedly (using a self-adjusting system).

cheers


I haven't worn out pads frighteningly quickly nor run out of pads unexpectedly in the past eight years that I've been using disc brakes.
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RickH
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Re: Why have disc brakes become so popular?

Post by RickH »

Brucey wrote:I don't know anyone who has used disc brakes for any length of time who hasn't worn pads out frighteningly quickly and/or run out of pads unexpectedly (using a self-adjusting system).

I was a bit disappointed to feel the need to change the OEM organic pads on my current bike after around 500 or so miles (I could probably have left them a while longer but wanted to make sure I had decent pads for a short tour), the replacements lasted around 2000 before I changed them.

Twice I've "run out of pads" once on a bike with V brakes & once with discs. Entirely user error in both instances. The Vs were frighteningly ineffective all of a sudden (fortunately I was on a canal towpath ride when I discovered this). The discs worked surprisingly well, albeit rather noisily, in the few subsequent instances when I felt the need to use both brakes on the rest of the ride.
Former member of the Cult of the Polystyrene Head Carbuncle.
Jezrant
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Re: Why have disc brakes become so popular?

Post by Jezrant »

I always inspect the pads before I set off on a ride, and I have a good idea of the brakes' limitations. I have yet to be caught out. If Brucey quantified these last couple of warnings rather than relying on scare tactics, the argument would be stronger. Sorry if this point has been made before in this thread -- all 31 pages of it so far -- riding through gritty mud will of course wear out disc pads fast but grit in rim brake pads will also wear out rims pretty fast. This is hardly surprising.
Last edited by Jezrant on 14 Aug 2018, 11:54pm, edited 1 time in total.
Airsporter1st
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Re: Why have disc brakes become so popular?

Post by Airsporter1st »

Jezrant wrote:I always inspect the pads before I set off on a ride, and I have a good idea of the brakes' limitations. I have yet to be caught out. If Brucey quantified these last couple of warnings rather than relying on scare tactics, the argument would be stronger.


Well I'm now scared stiff to go out on my disc-braked bike; if I don't die by flying over the handlebars, it will be while descending a hill with brake fluid boiling and pads worn down to the pistons.
Jezrant
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Re: Why have disc brakes become so popular?

Post by Jezrant »

Don't brake. :lol:
Airsporter1st
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Re: Why have disc brakes become so popular?

Post by Airsporter1st »

Jezrant wrote:Don't brake. :lol:


I'm thinking of some sort of anchor and chain fastened to the downtube, with a quick release button on the bars, to take care of both the emergency stops and downhill disc brake failure. Its either that or sell my bike and buy a decent pair of walking shoes.
Brucey
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Re: Why have disc brakes become so popular?

Post by Brucey »

Jezrant wrote:
Brucey wrote:I don't know anyone who has used disc brakes for any length of time who hasn't worn pads out frighteningly quickly and/or run out of pads unexpectedly (using a self-adjusting system).

cheers


I haven't worn out pads frighteningly quickly nor run out of pads unexpectedly in the past eight years that I've been using disc brakes.


Maybe you keep a more careful eye on the brakes than most folk. I've gone through a set of pads in a day's riding which I think is unacceptable. I think it would be very easy to design brake calipers and brake pads so that there is an inbuilt wear indicator; for example the 'tangs' on top of most pads could be bent inwards so that once the linings are worn, they touch or overlap or something. You would then be able to see at a glance if the pads were worn that way.

Different pads can cure the fast wear but the hard-wearing pads also conduct more heat into the hydraulic system, so the brakes may be less suitable for long downhills. Swings and roundabouts. On my first hydro system (the thick end of twenty years ago now) it was a 'closed' system so I was happy to take the risk re overheating; with that system the brakes are not self-adjusting and in the event of an imminent boil-up the brakes come on and start dragging, which is inherently 'safe' (if annoying) vs an 'open' self adjusting system.

Good disc brakes (and some others) can feel great in normal use, such that you feel pretty invincible really, maybe out of all proportion to their actual effectiveness. I am sure that is likely to make some riders take a few more risks than they might otherwise. Understanding that

a) your brakes (of whatever type) might have limitations and
b) where they might lie

is useful, nay essential information. To call such information 'scare tactics' is just daft.

cheers
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