Why have disc brakes become so popular?

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

Postby horizon » 17 Jul 2018, 10:03am

Disc brakes were invented in 1902, hydraulic brakes in 1918. They are only now de rigueur on bicycles. This question isn't about rims versus discs so the answer to the question isn't because they are better. My question is why now? What has happened to make disc brakes (hydraulic or mechanical) suddenly (you can question that) so popular?
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hamster
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Re: Why have disc brakes become so popular?

Postby hamster » 17 Jul 2018, 10:17am

Marketing and trying to give the upgrade cycle another whirl...

Brucey
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Re: Why have disc brakes become so popular?

Postby Brucey » 17 Jul 2018, 10:27am

most folk assume that they are newer and better; some folk just like the look of them. in some respects they can be an improvement, but it is a bit of a curate's egg when you look deeper into it.

The thing that has changed is that you can buy half-decent bicycle specific disc brakes now. For many years there was nothing available and then there were brakes that were meant for MTBs that were very expensive. Only latterly has it been possible to equip a road-going bike with vaguely sensible disc brake equipment at some sensible cost.


Personally for any given on-road application I think there are other brakes that make as much (or more) sense. But since when did sense have much bearing on the buying habits of the headless chicken that is the average consumer?

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Airsporter1st
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Re: Why have disc brakes become so popular?

Postby Airsporter1st » 17 Jul 2018, 10:29am

horizon wrote:Disc brakes were invented in 1902, hydraulic brakes in 1918. They are only now de rigueur on bicycles. This question isn't about rims versus discs so the answer to the question isn't because they are better. My question is why now? What has happened to make disc brakes (hydraulic or mechanical) suddenly (you can question that) so popular?


Disc brakes were never fitted to mainstream cars until the 60's/70's when they "suddenly" became standard. I wonder whether that was linked to improvements in tyres - no point locking the wheels if the tyres won't grip.

On bikes, certainly fashion plays a big part, but also economies of scale in manufacturing making them competitive price-wise with rim brakes?

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Si
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Re: Why have disc brakes become so popular?

Postby Si » 17 Jul 2018, 10:35am

IMHO:

Disc brakes make a lot of sense on MTBs when everything stays wet for much of a ride and your rims are covered in grinding paste. MTBs haven't been around that long, and it took a while for cycle-appropriate discs to be built for MTBs.

Many people who started with MTBs have moved to road bikes and want to continue to use the brakes that they know and trust rather than those weird rim things that don't work as well in the wet.

You've also got things like gravel bikes appearing where people prefer discs because they are used off road, and because it allows you to swap wheel sizes easily (which, apparently, is becoming popular for some reason)

And, of course, not everyone had hands that can crush coconuts, some people find that operating a drop bar lever from the brake hood is much less powerful than doing it it from the drop (where they don't want to be riding all of the time as its not as comfie). whereas when they have a good disc brake they can get the bike to stop really well from the hoods.

Oh, and marketing, keeping up with the jones's, etc but that's true of many innovations whether they are good or not.

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horizon
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Re: Why have disc brakes become so popular?

Postby horizon » 17 Jul 2018, 10:57am

Si wrote:IMHO:

Disc brakes make a lot of sense on MTBs when everything stays wet for much of a ride and your rims are covered in grinding paste. MTBs haven't been around that long, and it took a while for cycle-appropriate discs to be built for MTBs.



That sounds quite convincing, that discs have been driven by MTBing where they are (I presume because I don't know) a real advantage. MTBs presumably also suffer less from the fork weight/stiffness issue because they're already heavy and stiff - for MTBing. It wouldn't be a huge step then to translate that technical development and general learning/accustomisation to heavier touring and commuter bikes, gravel bikes etc.

I think this matters because it's saying that there has been a step change in disc brakes (even if that is just common usage and common knowledge) driven in this case by a new sport. While I'm not currently in the market for discs, it makes them appear a bit more than just fashion and marketing (even if that drives them too).

It would be interesting to know if there have been specific developments in disc brake design or whether it has just been incremental improvements and economies of scale over the last twenty years or so.
I have two doctors, my left leg and my right leg. (G. M. Trevelyan)
PS I always wondered why the YHA HQ was called Trevelyan House. :)

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100%JR
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Re: Why have disc brakes become so popular?

Postby 100%JR » 17 Jul 2018, 11:08am

I had my first Disc brakes on my MTB in 2002 I'm just surprised it's taken as long as it has to cross over!
I don't however see the point on Road bikes,Cross bikes yes but I personally think that hydraulic discs are just too powerful for skinny tyres even with small(by MTB standards) 140mm rotors that seem to be the standard.
Mechanical discs offer no improvement in performance over rim brakes IMO.I have Mechanical discs on my CX bike(160mm rotors) and they aren't particularly good TBH.
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Re: Why have disc brakes become so popular?

Postby Cugel » 17 Jul 2018, 11:10am

Brucey wrote:......

Personally for any given on-road application I think there are other brakes that make as much (or more) sense. But since when did sense have much bearing on the buying habits of the headless chicken that is the average consumer?

cheers


Being conservative in nature, I used to agree with this .... until I decided to allow experience to replace mere opinion by getting & using a disc brake-equipped winter bike.

I tried mechanical, hybrid (cabled lever, hydro calliper) and eventually full hydro disc brakes. The first two were not a lot better than rim brakes except for the absence of wear to the rims. The full hydro brakes are far, far better than any rim brakes I've used for bad winter conditions. They work without grinding dirt into the rims and pads but, most importantly, with much more controllable modulation thus avoiding skids in wet slime.

I now wince as I ride in winter with the club and listen to the awful graunch and grind of their rim brakes on dirty wet rims, hoping any need for a quick stop doesn't result in them making a brake-grab, delay then a skid, slide and fall right in front of me, as their brakes take their own good time to bite the dirty wet rim then suddenly grab it.

The only winter rim brakes I ever found nearly as good as hydro discs were standard short calliper brakes of beefy arms and soft pads employed agin' Mavic ceramic rims. These worked well and immediately in wet-nasty, with no rim wear albeit fast pad wear. They didn't have the degree of modulation that hydro brakes have, simply because Bowden cables are less effective at transmitting force and the associated feedback to/from the brake pads. But at least they didn't not-work for half a second then grab.

But here's an interesting blog-thing on the "cycling myths" theme from that Jan Heine:

https://janheine.wordpress.com/2018/07/ ... im-brakes/

I agree with his basic notion that good quality rim brakes on a racing bike used in dry conditions are more than adequate.

Cugel

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Re: Why have disc brakes become so popular?

Postby Brucey » 17 Jul 2018, 11:17am

in the late 1970s shimano offered mechanical disc brakes but they were horribly heavy and didn't catch on outside of cruiser type bikes. They were so heavy that they didn't even appeal to MTBers that mainly rode downhill.

Hope and a few others showed that you could make a half-decent hydraulic disc brake for MTBing and then others showed that you could make a functional mechanical disc brake which opened up the possibilities considerably. One of the first good mechanical disc brakes was the 'Avid BB'; this brake cost about £100 a wheel BITD, but sold well enough and worked well enough that SRAM bought Avid out and continue to this day to make a very similar brake; the current BB5 is almost identical to the Avid BB model from ~20 years ago.

FWIW I have used disc brakes for about twenty years on various bikes and I'm still not at all tempted to use them on a road bike. I use ordinary rims and (between choice of parts and technique) I don't wear out rims within 20K miles very often. [FWIW I have at least one rim brake rim that has done over 60K miles and that isn't a very heavy one.]

Apologies if this is b-obvious but regarding technique, the thing that makes the biggest difference is dabbing the brakes a few times before you apply them fully; this cleans the muck off the rims and prevents most rim wear.

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horizon
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Re: Why have disc brakes become so popular?

Postby horizon » 17 Jul 2018, 11:19am

Cugel wrote:Being conservative in nature, I used to agree with this .... until I decided to allow experience to replace mere opinion by getting & using a disc brake-equipped winter bike.



This seems to suggest that disc brakes are an idea whose time has come, when enough people start using them and reporting back on their experience to convince others - critical mass. So that's an answer to why now. As I said in my OP I'm not concerned in this thread which is the better brake, just why discs have quite suddenly (IMV) taken off. You didn't mention that disc brakes got better, just that you decided to give them a go.
I have two doctors, my left leg and my right leg. (G. M. Trevelyan)
PS I always wondered why the YHA HQ was called Trevelyan House. :)

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Re: Why have disc brakes become so popular?

Postby scottg » 17 Jul 2018, 1:39pm

horizon wrote:My question is why now? What has happened to make disc brakes (hydraulic or mechanical) suddenly (you can question that) so popular?



Carbon clincher rims, for a long time carbon clinchers would fail on long steep descents, so much so
they were banned from use in some US Grand Fondo events. Rainy days the braking was poor,
hot days the rims would come apart.
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Re: Why have disc brakes become so popular?

Postby pwa » 17 Jul 2018, 1:54pm

Disc brakes have a few advantages:

New and funky, so appeal to people who assume what works on a car must be the best on a bicycle.

Work well in the wet.

Remove the problem of wheel rim wear. This would make me consider them on a bike to be used for commuting in all weathers.

But they add weight, they make maintenance more complicated, and they require a sturdier and probably less springy fork.

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Re: Why have disc brakes become so popular?

Postby brynpoeth » 17 Jul 2018, 1:58pm

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Re: Why have disc brakes become so popular?

Postby random37 » 17 Jul 2018, 2:17pm

Having been looking at my first bikes in about 10 years, I think they look like a solution to a problem that doesn't exist. But if people like them, they're good.

Personally, I wonder why drums never caught on. Thousands of miles on a single set of pads. They need not have been so heavy, that was just an engineering problem. Same as the lacklustre braking.

I suppose you could make a very light fork for a drum brake, depending on the length of the reaction arm.

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Re: Why have disc brakes become so popular?

Postby Brucey » 17 Jul 2018, 2:20pm

Cugel wrote: …..I tried mechanical, hybrid (cabled lever, hydro calliper) and eventually full hydro disc brakes. The first two were not a lot better than rim brakes except for the absence of wear to the rims. The full hydro brakes are far, far better than any rim brakes I've used for bad winter conditions. They work without grinding dirt into the rims and pads but, most importantly, with much more controllable modulation thus avoiding skids in wet slime....


My most used MTB has had hydro disc brakes on it for about twenty years for exactly those reasons. I think there are times when I'd value better modulation on the road too. However there are some wrinkles:


1) when it is really raining, there is a short delay before (properly wet) disc brakes work properly. Drum brakes suffer no such issue, and since I have no urge to skittle some hapless idiot who staggers off the pavement in front of me, I think that drum brakes are better for commuting.

2) Drum brakes require less maintenance, can be fitted to a wider variety of frames and (in the context of steel framed 'winter machines' that you might cobble together), don't incur a meaningful weight penalty vs discs.

3) Hydro discs that see winter weather (in training and/or commuting uses) seem to be prone to corrosion-related leaks that limit their service life. Some users report multiple failures of this type (which I have done my best to investigate in a separate thread).

4) Hydro discs with dropped bars presently works out complicated and/or expensive; both features that I try and avoid on a winter/commuting bike, if I can do.


So as with most things, it is swings and roundabouts; which is 'best' depends on your priorities I suppose, and it would be a rather dull old world if we all made the same choices.

cheers
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