Why have disc brakes become so popular?

[reohn2]

….As an aside, I've been surprised just how many disc-brakes bikes have been used in the TdF this year on the flatter stages but not by Sky as has been pointed out.

some folk are surprised the other way, i.e. they predicted that 'everyone in the peloton would use discs as soon as they were allowed to'.

I'm on record on the forum of forecasting the opposite and that the pro peloton would only use discs for some races.

In the giro there was (IIRC) one team that used disc brakes exclusively and one or two others that had them as an option (rider choice)

The Giro is a case in point,the weather in Italy can be unpredictable at that time of year in(we've been in Tuscany in mid June and experienced some very changeable weather conditions),even in the south of the country so maybe some teams put their eggs in the disc basket as CF rims and DP calipers aren't the best match in wet weather?
Whereas the TdeF is more likely to be better weather overall being in France July.
The pro peloton is a very different world,where mariginal gains mean money in the bank,than the one everyday cyclists encounter where a more all round approach is needed,especially where differing road and weather conditions in the same day may be encountered.
Just some thoughts on the pro peloton's possible position on the subject of disc brake selection

[Peter W]

Indeed so, Alan O! I can quite believe my father (ex 8th Army Desert Rat) who would probably have used his bayonet to remove a bothersome appendix would have agreed. Though I suspect Mr utility confines his wrath to cyclists who he believes jump on the disc brake Band Wagon. But hey, I can quite forgive anyone can skillfully bring Brexit, and the 'porkies' into a disc brake discussion.

By the way Brucey, I've checked the discs (Roubaix) after yesterday's ride when it was preying a bit on my mind, (Down Hawes side of the Buttertubs, and back to Reeth via the Redmire pass and couple of mile steep fast twisty belt back down to Grinton which has to be one the best descents in the Dales), and they appear to be a smooth and consistent 1.7 mm after a year and a half use, so big relief.

[Brucey]

By the way Brucey, I've checked the discs (Roubaix) after yesterday's ride when it was preying a bit on my mind, (Down Hawes side of the Buttertubs, and back to Reeth via the Redmire pass and couple of mile steep fast twisty belt back down to Grinton which has to be one the best descents in the Dales), and they appear to be a smooth and consistent 1.7 mm after a year and a half use, so big relief.

that is good to hear; you should get a fair amount more use out of them. I've seen them knackered in a similar length of time, despite a lot fewer hills. I have no idea what they do with them. Maybe the pad type (there are several offered by shimano) makes more of a difference than is usually supposed.

To be specific,what makes better brakes worse?

There are multiple qualities of a brake:
- Max friction
- Modulation
- Weight
- Pad wear
- Braking surface wear
- Reliability
- Workshop maintainability
- Roadside maintainability


You can easily have a brake which improves on some yet is detrimental for others...

to which I'd add
- friction coefficient variation with weather (wet)
- friction coefficient variation with temperature
- wear rate variation with conditions
- heat soak/cooling characteristics
- adjustment protocol (e.g. most hydraulic discs self adjust)
- inspection protocol (e.g. most hydraulic discs self adjust; you can run out of brake pads without knowing, unless you make a point of inspecting them)
- knock-ons in terms of the rest of the bike; e.g. wheel strength varies with brake type
- knock ons for the rest of the bike; e.g. frame weight and stiffness varies for disc vs rim brakes
- interchangeability (eg of wheels)
- availability of spare parts
- special tools that may be required for maintaining different systems
- cost of consumables
- compatibility (with different types of bike/other systems on the bike)
- possible safety implications (both in normal use and when not in use)


how these things are prioritised will vary in a subjective fashion; some aspects will be show-stoppers (or alternatively must-haves) for some folk, but merely mild inconveniences ( or alternatively modest gains) for others. The subjective issues will vary with intended use and perceived possible consequences in the event of problems.

cheers

[Cyril Haearn]

Rims can get very hot so tyres explode (happened to me), does the wind cool them down?
Going downhill in the TdF disks must get very hot, can they distort? How long do they last?

[LollyKat]

I don't think anyone has mentioned comfort - Brucey, maybe? IME disc brakes need a beefier fork which for a given tyre gives a harsher ride. Personally I'd like a cable disc on the rear and a caliper/cantilever/v-brake on the the front, thus getting the best of both worlds / hedging my bets / saving my rear rim.

[horizon]

why?
Telling people they are a must have, telling porkies about the advantages (a bit like the porkies over remaining n the EU) promoting the heck out of them with those well known web sites/income based on how well we can promote products organisations promoting them, getting professional teams/riders to use them (on the back of pushing their new product) so if the pros are using them then they must be good/right, right?
Oh and reducing the line up/availability of non disc bikes/frames.
Because it dumbs things down, there's no skill or ability to concern yourself with ... apparently :roll

Funny how in the wet at high speed in the pro ranks it's not the brakes ability to work that is the problem, it's the tyres grip, poor line, poor decision making that is the deciding factor as to why they crash, that in turn is dictated in part by helmet wearing, it's not about modulation or ultimate braking power.

Discs are a step too far (I've explained previously why) unless you're bothered about rim wear, in which case more fool you because you just spent a shed load of money on a new bike and all your existing wheels are utterly useless for your new mchine so you have to spend even more money on new swap out wheels or simply get a new stable throughout.
Modulation, learn how to brake properly, learn how to anticipate/read the road and stop going too fast, travel at a speed you can stop well within the distance you can see to be clear, stop expecting to have things dumbed down, discs devolves skill/thinking ... it's exactly the same as motorvehicles/motorists.

While I wouldn't say I'm in agreement with you on many of those points, I do appreciate a well-crafted rant, and I salute you for it

Nicely put Alan O. There is a lot of disagreement on this thread but lots of passionate argument. At least everyone here seems to care (and strongly) about cycling even if their views differ.

[Marcus Aurelius]

I do have a slight issue with disc brakes on road bikes in the mainstream. It boils down the the disparity in performance between discs and rims. I often lead group rides and recently I had 2 bikes with discs and 5 with rims. The disc brakes bikes stopped way quicker than the rim brakes bikes. Cue lots of swearing and swerving.

[Cugel]

I don't think anyone has mentioned comfort - Brucey, maybe? IME disc brakes need a beefier fork which for a given tyre gives a harsher ride. Personally I'd like a cable disc on the rear and a caliper/cantilever/v-brake on the the front, thus getting the best of both worlds / hedging my bets / saving my rear rim.

One very significant advantage of disc brakes is that fat tyres can be mounted, assuming the frame is designed to provide the necessary gaps. Rim brakes themselves tend to be the limiting factor to the width of tyre that can be fitted to a rim brake frame.

Fat tyres, especially the efficiently-rolling modern variety, add a huge amount of comfort and may actually be faster of themselves, as well as keeping you more inclined to pedal hard because you're not fatigued by the punishment that hard narrow tyres can impart over the miles.

Cugel

[Cugel]

I do have a slight issue with disc brakes on road bikes in the mainstream. It boils down the the disparity in performance between discs and rims. I often lead group rides and recently I had 2 bikes with discs and 5 with rims. The disc brakes bikes stopped way quicker than the rim brakes bikes. Cue lots of swearing and swerving.

Hmmmm. The limiting factor to emergency braking tends to be the grip of tyre on road - or, rather, the breakaway point at which a skid starts. The brake technology that brings this about is not really relevant, assuming all such technologies can apply enough brake pad grip to cause the skid.

On the other hand, you could argue that the better modulation opportunities of disc brakes mean the rider is less likely to induce such a skid, even in an emergency stop. In addition, if the disc brakes have allowed the rider to also mount fat and softer tyres, this too improves road grip during an emergency stop. These factors argue for disc brakes and against rim brakes, so perhaps all your group riders should all be required to go-disc?

Cugel

[reohn2]

I don't think anyone has mentioned comfort - Brucey, maybe? IME disc brakes need a beefier fork which for a given tyre gives a harsher ride. Personally I'd like a cable disc on the rear and a caliper/cantilever/v-brake on the the front, thus getting the best of both worlds / hedging my bets / saving my rear rim.

Whilst I agree in theory,in practice most MTB's have a suspension fork or big get section tyres and most road bikes sold today don't have a particularly complianrt fork,most being CF and the vast majority of which are solid stiff forks whether made for rim or disc.
The Surly LHT touring bike is one of the most popular and I'm convinced surly spec the same fork for both LHR and Disc Trucker.I have a Genesis Longitude and a Salsa Vaya,and have owned a Cannondale Road tandem for a number of years both selling it to a forum member's friend,all three bikes are very comfortable machines to ride,and I'm a pretty beat up old and Arthritic individual.

All that said there aren't many modern steel bikes with a compliant fork such in days of yore,I think Thorn were the last makers of a truly compliment "hockystick bend" in their Renolds 531 forks.Also tyres are the first defence against road buzz and taking shock out of road deformations,which there are many on UK roads.

Fora truly compliant fork take a look at this article:- https://janheine.wordpress.com/2017/05/ ... eel-bikes/

[reohn2]

I do have a slight issue with disc brakes on road bikes in the mainstream. It boils down the the disparity in performance between discs and rims. I often lead group rides and recently I had 2 bikes with discs and 5 with rims. The disc brakes bikes stopped way quicker than the rim brakes bikes. Cue lots of swearing and swerving.

That would seem to illustrate that those using rim brakes don't know how to ride in a group
Whereas someone on this thread claims the exact opposite

[reohn2]

I don't think anyone has mentioned comfort - Brucey, maybe? IME disc brakes need a beefier fork which for a given tyre gives a harsher ride. Personally I'd like a cable disc on the rear and a caliper/cantilever/v-brake on the the front, thus getting the best of both worlds / hedging my bets / saving my rear rim.

One very significant advantage of disc brakes is that fat tyres can be mounted, assuming the frame is designed to provide the necessary gaps. Rim brakes themselves tend to be the limiting factor to the width of tyre that can be fitted to a rim brake frame.

Fat tyres, especially the efficiently-rolling modern variety, add a huge amount of comfort and may actually be faster of themselves, as well as keeping you more inclined to pedal hard because you're not fatigued by the punishment that hard narrow tyres can impart over the miles.

Cugel

I'd agree with that generally,though V brakes overcome such a problem.
Some years ago after getting big rubber dialled in and sorted,I also found I could descend far faster.On a particular twisty bumpy descent I ride often àlmost 10mph faster, due to the lower TP's and complience of the bigger tyre which are more secure and planted,only my lack of courage stops me from pushing the envelope further.

[rmurphy195]

I don't think anyone has mentioned comfort - Brucey, maybe? IME disc brakes need a beefier fork which for a given tyre gives a harsher ride. Personally I'd like a cable disc on the rear and a caliper/cantilever/v-brake on the the front, thus getting the best of both worlds / hedging my bets / saving my rear rim.

One very significant advantage of disc brakes is that fat tyres can be mounted, assuming the frame is designed to provide the necessary gaps. Rim brakes themselves tend to be the limiting factor to the width of tyre that can be fitted to a rim brake frame.

Fat tyres, especially the efficiently-rolling modern variety, add a huge amount of comfort and may actually be faster of themselves, as well as keeping you more inclined to pedal hard because you're not fatigued by the punishment that hard narrow tyres can impart over the miles.

Cugel

Totally agree - Well spotted!

[Brucey]

Re group riding. if you were to design a brake that impressed on a test ride, it would have a very high MA and be easy to use. A side-effect of this might then be that even in casual use, certainly until you got used to it, your 'normal retardation' might be a lot greater than with brakes that have a lower MA.

I think that folk buy bikes with disc brakes because they do have a high MA and then they do tend to ride them in exactly that fashion. Note that hydro discs may modulate beautifully across most of the speed range (but not all, depending on the pads used) but that mechanical discs may not modulate terribly well (depending on pads and cables). I use hydro discs on my MTB because they modulate better.

The crazy thing is that in an emergency, a good rim brake will stop you pretty much as quickly as a disc brake will, yet in 'normal slowing down' there may be a difference, especially if the riders of such bikes are not terribly experienced. This difference can indeed be a problem in a group; I would suggest that if certain riders tend to slow down abruptly - for whatever reason- then they should perhaps be asked to ride at the back of a group, in the same way as a slow rider is not 'left behind'; it is all part of group etiquette.

Note that in most forms of close group riding, the last thing anyone should do is use the brakes appreciably without warning. On the track you are not allowed to even have brakes, for that very reason. Learning to ride smoothly in a group is a skill just like any other; if there are relatively inexperienced disc brake users that are causing problems then maybe they need a bit more practice at group riding and braking smoothly; if nothing else, they are less likely to skid on a slippery road.

Re Surly LHT forks. I think that, now, you do get basically the same fork with and without disc tabs, but that you used not to, and the 'old' rim brake fork was lighter and more compliant (perhaps not by much because the fork is a fairly heavy duty one anyway; there would be bigger differences in other cases I am sure). I also think that differences in fork compliance have long been apparent and have been significant factors in myself and other's choice of bikes to ride. Putting up with a stiff fork and hoping it will be alright because fatter tyres are used is (to my mind) a fairly crude way of improving an otherwise unsatisfactory situation.

It took many decades to engineer forks that were nice and compliant whilst also being strong enough, and arguably we are blithely throwing that all away just to have brakes that offer some marginal advantage for a tiny fraction of the time, and hoping that fat tyres will paper over the cracks. Well, if fat tyres were such a great idea, we could have had them decades ago; 650B was a well-established size for decades in France, but it never caught on over here. However one thing that did catch on in France was lovely 531 Forks; much better than a lot of domestic offerings, they sold very well. Should this be telling us something...?

cheers

[Marcus Aurelius]

The problem with getting people with discs in a group to stay at the back, is getting them to actually do so. In my experience they will try to get to the front ( particularly on descents ) because they can brake better, right? That’s what causes the issues.