Why have disc brakes become so popular?

[reohn2]

Brucey
I've never claimed disc brakes are a magic fixall braking system.
What I have claimed is all up thread for those who care to read.
But to sumerise; IME their performance is predictable and reliable in all conditions,and where that is best appreciated,which is considerable,is in bad/wet/mucky conditions when their modulation and power are consistent with their dry weather performance,and is a boon for those who ride in UK winter weather.
They also need less maintenance,don't wear through rims and keep the bike cleaner in those bad winter conditions.
I have extensive experience of both rim and disc brakes and it is from that experience I draw my conclusions.
TBH I get slightly irritated by those who claim a good brake is really a bad brake and a bad brake is a good one,by spurious opinions of risk compensation and that those who rides disc brakes suddenly turn into a reactive idiot relying on their reflexes alone

[Brucey]

I would suggest that you try actually measuring your stopping distances and try to imagine what will happen when someone steps/pulls out in front of you before you start to describe other folk as 'reactive idiots'.

cheers

[Cugel]

Brucey
I've never claimed disc brakes are a magic fixall braking system.
What I have claimed is all up thread for those who care to read.
But to sumerise; IME their performance is predictable and reliable in all conditions,and where that is best appreciated,which is considerable,is in bad/wet/mucky conditions when their modulation and power are consistent with their dry weather performance,and is a boon for those who ride in UK winter weather.
They also need less maintenance,don't wear through rims and keep the bike cleaner in those bad winter conditions.
I have extensive experience of both rim and disc brakes and it is from that experience I draw my conclusions.
TBH I get slightly irritated by those who claim a good brake is really a bad brake and a bad brake is a good one,by spurious opinions of risk compensation and that those who rides disc brakes suddenly turn into a reactive idiot relying on their reflexes alone

All current bike brake designs have advantages and disadvantages. All have some limitations to their function. Some lads here seem content to emphasise the disadvantages and limitations of disc brakes whilst neglecting to compare them with the disadvantages and limitations of other brake designs.

For example, good rim brakes can throw you over the handlebars just as easily as can disc brakes, if they're good quality and you grab the levers very hard at speed in an emergency. It ain't just disc brakes that do this. However, although a poor brake might stop you skidding or going over the bars in an emergency stop, it might instead allow you to continue your plunge under the lorry or over the cliff edge. To argue that the dangers of an emergency stop require poor brakes is a somewhat paradoxical stance, I feel.

But let some clever chap come up with effective ABS for (already good) bicycle brakes, by all means.

Another example of parity between disc & rim brakes .... the very good rim brakes currently available give the unthinking just as much overconfidence as good disc brakes, so risk compensation will still occur if the user is unaware of this syndrome but is impressed by the excellent braking power they posses, however it's rendered at the hand.

In practice, disc brakes can also lend a better (not over) confidence to the riding style as the user knows they will be easy to apply & modulate; and more likely to work well in adverse conditions that might overwhelm rim brake function (in the wet; with carbon rims; with weak hand grip). I personally find this, whilst studiously avoiding the overconfidence generated by risk compensation. Let those who can't properly assess risk learn how to do it. It's not hard .... unless you don't like thinking employing the associated theoretical considerations, on top of the experiential.

Rim brakes are just as hard to maintain and set up as disc brakes if one is unfamiliar with their designs. Once you've become familiar and generally adept at the necessary procedures, neither is difficult to deal with. (Of course, some people never learn to mend a puncture; or even to blow their nose without making a mess). If you can easily deal with rim brakes now, then you can learn to easily deal with disc brakes in the future (about an hour into the future is all it takes).

****
Personally I'm inclined to the conservative (not the political party type but the notion that tried & tested is better than mad new notions). Nevertheless, even a conservative disposition needs to be able to recognise the difference between real innovation/improvement and mad, spurious, ineffective, fashion-driven notions. Disc brakes on bikes seem to be in the former category whilst L-shaped cranks or magnesium frames might be considered in the latter.

Cugel, seeing at least 256 shades of grey.

[Peter W]

Yes, you could do as you suggest Mick, but you don't get maximum retardation with a locked wheel. For that, the flexible tyre needs to 'lock' into the rough road surface (think rack and pinion effect) just at the point of slipping. That would give the shortest stopping distance, but it requires a very skillful touch.

As regards a necessary maximum braking force any bike should need, it MUST be sufficient to safely and relatively easily, decelerate and bring to a halt a bike and heavy(ish) rider who is riding down a 1 in 3 hill. (Rosedale Chimney for example which has a less steep run in from the top, but which quickly ramps up to a real 1in3 section before a very steep right angled corner.)

Such a minimum requirement braking system, of what ever type (rim or disc) would be more than powerful enough to hurl a rider over the bars in ordinary use in a panic stop emergency. But how can you make it less powerful without making it dangerous (likely to get out of hand and run away with the rider) down steep hills! (In such a case, the manufacturer would have to put a giant sticker on the bike saying 'Not to be ridden down steep hills.'

Some progress, methinks!!

[reohn2]

I would suggest that you try actually measuring your stopping distances and try to imagine what will happen when someone steps/pulls out in front of you before you start to describe other folk as 'reactive idiots'.

cheers

I suggest you read what I've posted and compare it with what TUC has posted about disc brakes,in that anyone using discs will automatically have a tendency to brake later and fall into some self made trap of believing because their brakes are better they won't need to take as much care in their's and or others' safety,but rely totally on their better brakes.
Neither do I claim discs will stop me any quicker in wet and mucky conditions only that their modulation and power are the same as in the dry.The one thing that changes between wet/mucky and dry road conditions is the road,and two wheel riders more than any other should bear in mind that there is more chance of skidding and falling in the wet and muck.
To have a brake that is reliable in modulation and power in such conditions than a brake that is unpredictable,which rim brakes can be in such adverse conditions,is a help to the rider not a hindrance.
To claim that anyone who uses a predictably good and reliable braking system such as discs will crash soon or later because of it is bonkers of course,unless the rider in question is an idiot,which drew me to the conclusion I did,and the post I made.
YVMV mine won't.

NOTE:-- I've rewritten this post for clarity

[tim-b]

Hi

I can't see the need for Anti-lock Braking Systems (ABS) on a bike unless you include Electronic Brake force Distribution (EBD). You don't need to lock a wheel up to head over the bars, whereas EBD would detect your weight distribution and apportion braking force most appropriately

IF such a system could be developed for a bike then hydraulics is the way forward with current tech, and discs lend themselves most readily to the systems for detecting a locked wheel

As the owner of an hydraulic disc-braked bike I can understand their advantages, but I still think that they are unnecessarily heavy and complex as compared to rim brakes, and electronic systems will only make this worse

Regards
tim-b

[busb]

I've had a couple of conversations with other cyclists regarding the differences between rim & disc brakes where they have stated that they could easily lock up their rim brakes. My reply was that that the ability to lock up brakes is a poor measure of their effectiveness. The point that many don't seem to understand until they experience decent disc brakes for themselves is that they are less like to "grab" hence lock up.

Although I managed to lock up my disc brakes last March as reported on this forum - to the extent I came off & hurt one wrist on a very greasy surface, I've crashed far more often over the years on bikes with rim brakes. I can only re-iterate that the power of disc brakes is only half their advantage - their "feel" being equally important. If disc brakes didn't have that "feel", they would perhaps indeed be "too powerful" as some have suggested. However, my personal experience of cable disc brake on 3 hire bikes that had them was far worse than all the rim braked bikes I've ever ridden! So when I talk of my preference of disc brakes I mean hydraulic!

Both my current bikes have hydro disc brakes. the ones on my 15 month old Defy have remained absolutely consistant but the front pads were worn out when I checked them after a free "service" - I had a spare pair that took me about 10 mins to fit - no re-alignment was needed, just had to use a plastic tyre lever to fully open the pistons so the rotor would fit. Once the levers had been operated several times, the original travel was restored.

The front disc brake on my nearly 5 yr old hybrid did cease to work as effectively as expected until I replaced the pads with Shimano resin ones rather than generic ones. I suspect that the 3-layer Shimano rotors are fussier than average regarding pads (compress just ever so slightly more than solid S Steel ones?)

As has been pointed out - no braking system is without certain disadvantages so anyone so-minded can perhaps over-state their flaws. I can only say from my own experience on both a hybrid & drop-bar bike that despite the weight penalty disc brake have - I'd be very, very reluctant to return to rim brakes. Apart from their consistant operation in the wet or dry, the minimal maintanence has been a big bonus, once I'd correctly matched the pads, I've experienced little rubbing, squealing or fading.

[Brucey]

modulation is great (please tell me where I have said otherwise....) but it counts for precisely nothing in an emergency stop situation from normal speeds; you simply don't have time to exploit any modulation. You should be aiming to stop in about 1s or so, which is not enough time to control your braking force accurately. If your brakes are powerful enough to throw you over the handlebars then they are arguably a positive hinderance to stopping safely in the shortest possible time.

The reasons for this are down to very simple physics and biomechanics, yet some folk still seem to believe that 'more is always better'. Well it isn't; anyone who has thought about it for more than five minutes should come to that conclusion, and anyone who has seen first hand the consequences of having 'too much brake' in an emergency would know it too.

You can of course have too much power with any brake (it was a rim brake that did for a chum of mine; if he'd asked my advice beforehand I'd have suggested a different setup BTW) and some drum brakes are too powerful too (for an unladen solo) but by far the biggest offenders are disc brakes; very many are powerful enough to do stoppies, and that is arguably 'too powerful'.

If you have such brakes then very simply, in an emergency stop from about 20mph (lasting about 1s like it should) you will either

a) throw yourself over the handlebars or
b) fail to stop as quickly as you should.

Frankly anyone who believes otherwise is either terminally arrogant (and thinks they have abilities that no mortal does) or doesn't really understand the nature of the problem.

IF YOU DON'T BELIEVE ME THEN DO SOME MEASUREMENTS/TESTS LIKE I HAVE

BTW to be safer, there isn't necessarily a need for a lot of extra weight, electronics or complexity; you can

a) simply have brakes that cannot generate enough torque for a stoppie and/or
b) there has been at least one system that uses the braking torque of the rear wheel to actuate a powerful front brake. This arrangement means that you can't do a stoppie; the moment the rear wheel starts to lift, the front brake ceases to be actuated in the same way. The result could/should be a safer stop in an emergency, i.e. a consistent retardation of (say) 0.8 or 0.9G or whatever the system is set up to generate. I think that, with development, this sort of system could be a real (rather than an illusory) improvement in safety without huge downsides.

cheers

[Peter W]

''Terminally arrogant.'

' Doesn't really understand the nature of the problem.'

'Simply have brakes that CANNOT GENERATE ENOUGH TORQUE FOR A STOPPER,'

Really!!! What's the old saying about having put yourself in a hole, stop digging!

[Brucey]

''Terminally arrogant.'

' Doesn't really understand the nature of the problem.'

'Simply have brakes that CANNOT GENERATE ENOUGH TORQUE FOR A STOPPER,'

Really!!! What's the old saying about having put yourself in a hole, stop digging!

I said " simply have brakes that cannot generate enough torque for a stoppie'.

Not 'stopper'.

Maybe you didn't bother reading what I wrote, in which case I suggest you put down your shovel and have another go.

[Peter W]

Stopper/stoppie, an obvious careless typo with words of similar sound, but your perverse and persistently repeated mantra is perfectly clear to me; that a bike which is unable to generate the force necessary to put one over the bars is safer in an emergency situation than one which can. ( You should avoid descending any very steep hills at anything greater than walking pace if you indeed practice what you preach.)

You are entitled to your opinion which you hold against any or all opposition, but to blame those who do not accept your premise of 'terminal arrogance' and 'doesn't really understand the nature of the problem' is outstandingly ironic!

But hey, have a nice day, and probably the last word. I'm up early and looking forward to a 'nice' ride on my disc equipped Roubaix. It will include a descent of Limber hill (Yorkshire Moors - Egton to foot of Glaisdale) which is approached at the top by a sharp right hand corner, and progressively steepens to 1 in 4 at the bottom before a sharp left corner. It is one of those tricky hills to judge your speed on as you let the bike fly at the top before progressively pulling on the brakes as it steepens, but it is the perfect hill to highlight the difference between disc and rim brakes.

Just over a year ago I got it wrong on the rim braked Roubaix in wet conditions, when the wet delay in the rim brakes biting allowed the bike to gain runaway speed. The difficulty in then hauling hard on those levers and trying to modulate the force without sliding off was the closest I've come to a really bad accident. I don't need anyone to lecture me on what they imagine I do or do not understand. Experience has taught me that the consistent and progressive modulation of hydraulic disc brakes is safest, in ALL situations I've encountered!

[Cugel]

Stopper/stoppie, an obvious careless typo with words of similar sound, but your perverse and persistently repeated mantra is perfectly clear to me; that a bike which is unable to generate the force necessary to put one over the bars is safer in an emergency situation than one which can. ( You should avoid descending any very steep hills at anything greater than walking pace if you indeed practice what you preach.)

You are entitled to your opinion which you hold against any or all opposition, but to blame those who do not accept your premise of 'terminal arrogance' and 'doesn't really understand the nature of the problem' is outstandingly ironic!

But hey, have a nice day, and probably the last word. I'm up early and looking forward to a 'nice' ride on my disc equipped Roubaix. It will include a descent of Limber hill (Yorkshire Moors - Egton to foot of Glaisdale) which is approached at the top by a sharp right hand corner, and progressively steepens to 1 in 4 at the bottom before a sharp left corner. It is one of those tricky hills to judge your speed on as you let the bike fly at the top before progressively pulling on the brakes as it steepens, but it is the perfect hill to highlight the difference between disc and rim brakes.

Just over a year ago I got it wrong on the rim braked Roubaix in wet conditions, when the wet delay in the rim brakes biting allowed the bike to gain runaway speed. The difficulty in then hauling hard on those levers and trying to modulate the force without sliding off was the closest I've come to a really bad accident. I don't need anyone to lecture me on what they imagine I do or do not understand. Experience has taught me that the consistent and progressive modulation of hydraulic disc brakes is safest, in ALL situations I've encountered!

Brucey does not like to be thought wrong or unknowing, which is a peculiar and paradoxical state of mind for one who has obviously learnt a great deal. so must have been at least unknowing, and likely wrong, at many previous moments in his life.

In this case he is not wrong or unknowing but, rather strangely, fixated on emergency stops as some sort of minus for disc brakes - even though they are a minus also for rim, canti and even hub brakes (wot those) if the brakes actually work.

Like a dawg with a bone! Grrrr..rrr..rrr.

Cugel

[Brucey]

hey we can all overestimate our ability and/or brakes (of any sort) and have some iffy moments, but

a) you are talking about a planned braking manoeuvre which lasts for maybe tens of seconds (which has precious little bearing on what happen during an emergency stop which might last 1s, which is what I'm talking about and you are ignoring) and
b) you need to be extra careful on steep descent because the force required to send you over the bars is less than on the flat.

Regarding the latter point, if you can normally manage a ~1G stop, when you are on a 45 degree slope, you can't use the brakes at all without going over the bars, not unless you radically redistribute your weight. Thus if you had brakes that (say) only ever pulled a 0.9G stop on the flat, but modulated well, you would be no worse off on a steep descent during planned braking.


As I have repeatedly said, I like brakes that modulate well; I choose to use these over other brakes in some situations, and in some of these situations there is no such thing as 'too much power' because nearly all braking is planned and takes several seconds to accomplish as intended. However I'm not delusional enough to believe that they are 'the best brakes for all circumstances' or somesuch. If a given rider (as many people do) rides much in an urban/semi-urban environment, where the chances of having to pull up sharply are greatly increased, very powerful brakes are not an asset, but a liability; any lovely modulation counts for nowt if you are hoping to pull up in ~1s, you simply can't use it. It doesn't matter a fig if the brakes feel lovely at other times, if they are very powerful then they will cause as many accidents as they help avoid when folk have to pull up sharply.

If there is a debate to be had, it is where the best tradeoff might be for an average rider, if you have a choice between a brake that modulates well, but is very powerful, and one that it less powerful and maybe modulates less well too. I'd argue that if you might think you would ever need to pull up sharply (as described), you might be better off with the latter type of brake. I don't think there is any pattern of road riding where this is never going to happen at all and for some riders it is likely to be a common event. This being the case maybe there is no place at all for super-powerful brakes on the road, no matter how well they modulate.

I expect my chum would agree (now) and fortunately he doesn't have lasting brain damage as a result of believing the other view. I'm trying to do my best to ensure that other folk don't make the same mistake; if I need to get your attention by pointing out that you are either
a) subject to normal, delusional human thinking in believing that you can modulate a powerful brake under all circumstances, or
b) you don't understand the nature of the problem

then I think this is fair game.

Frankly it would be an awful lot easier just to say 'enjoy your time in hospital' but I'm not like that.

Very powerful brakes, under manual control, merely give an illusion of safety, which is why they are accompanied by ABS on other vehicles, without which they just cause worse accidents in many types of emergency situation.


There is nothing particularly complicated about any of this, it is widely accepted by the motor industry (and the bicycle industry too, for example shimano have for years gone out their way to ensure that urban/utility bikes are unlikely to cause this kind of accident). In fact it is worse in the case of a bicycle because the duration of a well-executed emergency stop is usually much less (thus giving less time to manually modulate the brakes)... but more recently powerful disc brakes have migrated onto road bikes and they are being used in conditions were you are likely to have to do an emergency stop and when that happens they are not an asset but a liability, not likely to save your bacon so much as cook it.

I'm hearing a chorus of " I'm so personally invested in these shiny new brakes I've just bought and love that I am prepared to argue that they are lovely under all conditions and without any sensible or scientific basis ". If that sounds like you, try and have another think about it.

[Cugel]

........ Very powerful brakes, under manual control, merely give an illusion of safety, which is why they are accompanied by ABS on other vehicles, without which they just cause worse accidents in many types of emergency situation.


....... but more recently powerful disc brakes have migrated onto road bikes and they are being used in conditions were you are likely to have to do an emergency stop and when that happens they are not an asset but a liability, not likely to save your bacon so much as cook it.

The rim brakes on my nice summer bike seem very "powerful" to me - as good as the disc brakes on the winter bike in terms of their ability to slow & stop the wheels rotating in normal conditions. Were I to foolishly attempt the "emergency stop" with the rim brakes, I doubt if I would be less likely to be deposited over the handlebars than if I were to grab at the levers on the disc braked bike.

Why do you say that disc brakes are "more powerful" than rim brakes? Most modern rim brakes are just as "powerful" unless of poor quality (in which case they may be dangerous in many other, more common, braking scenarios).

Your argument is one against giving "powerful" brakes to the untutored (at bike braking) not an argument against disc brakes. Or an argument for ABS et al, on both rim and disc brakes.

****

Disc brakes do have advantages - the better modulation possible with the hydro versions; the room for bigger tyres; the ease of brake shoe changing; etc.. They have some disadvantages, notably cost. Being "powerful" is not a disadvantage or advantage over good rim brakes.

*****
And this "emergency stop" thing is all a bit strange. In 60 years of cycling I've only ever done the over-the-bars scenario when a novice of 10 years old. One soon learns that there are better reactions to things suddenly appearing in front of you. I have often laid the bike down and slid, gone for the infinitesimal gap or simply accepted the coming smack. For the very reasons you describe (over the bars) and others (e.g. skid inducement) its best to learn never to grab at the brakes in "an emergency".

Novices and the untutored will instinctively grab at the brakes. Can one learn not to, in such "emergencies"? I believe one can because I have.

Cugel

[iandriver]

I'm going back a while to my old Kawasaki 305. Essentially a bored out lightweight 250. It had twin disks of the front and was terrifyingly easy to lock up the front end. I've not ridden the current crop of hydro discs on a road bike, only on 37+ tyres.

The concept that at some point you can over brake a two wheeled machine sounds quite plausible to me, Kawasaki managed it. The big point some one made, to my mind, is quality brakes should be less likely to grab and be harder to lock up. Though agreed, in an emergency, a handful is the norm. I've never used any wheeled machine without ABS that I couldn't lock up in the right conditions.