Brakes - Are disc brakes better? and why?

King Large

Is there any evidence out there to suggest that disc brakes are better than standard brakes? and can you change any bike to have disc brakes?

thank you

campbellrae1

Disc brakes have a lot more power and are less effected by the weather(e.g. if it's raining they still work very well), however they are heavier than standard road brakes. Not all bikes can be fitted with them, there have to be mounts on the frame and forks, as well as disc specific hubs.

Personally, if you are on a standard road bike, with 23-25mm tyres for example, the power of discs will very quickly over-whelm the grip of the tyre(especially in the rain), and you end up locking wheels a lot, so they aren't really worth the hassle as when the tyre is skidding your braking force is greatly reduced. However on a hybrid style bike with larger tyres they can make sense!

It's all a we bit confusing really!

MattC59

If you're comparing the current crop of MTB dick brakes to road brakes, then yes they're massively more powerful, however.........

These aren't used (generally) on road bikes. Cable operated disk brakes for the road have less power than their MTB equivelant, ave a look at the Avid cable disks, for example. The hydraulic disk brakes creeping into the market, and being released have smaller cylingers and pistons, giving lower power than their MTB equivalents.

As campbellrae1 mentioned, the power of a disc brake would quickly overcome the grip that a road tyre offers, however, that's not the case if you use road bike specific disk brakes. You're not after a huge increase in power, but more, the better modulation and control of the power on offer, which is generally something that a disk brake will offer.

You also don't have the issue of brakes binding if you manage to bend your rim, and you don't have the issue of rims overheating on long (Alpine etc) descents. They're barely effected by weather and they would negate the issue of poor or grabby braking on carbon rims.

Of course, there's the weight issue, but as a result of taking the braking away from the rim, you can redesign the rim with out a braking surface and save rotating weight there.

You've probably opened a huge can of worms here, so no doubt someone will be along in a minute to tell you that they're a complete waste of time.

m00nd0g

I think disc brakes have got a place, however I do not use them.
I understand that much work in cycle workshops is disc brake related.
My road bike is fitted with Koolstop pads and stop me when I apply the brakes.
My mtb does not have discs, I would have them if I was racing reguarly.

SaintMark

I started using discs on my MTB for mud clearance. By not using the rim for braking you can ride in deep mud with a buckled wheel and still make progress on a wet muddy ride. Gone are the days of stopping and getting a stick to poke mud out of your brakes. Not a problem on a road bike of course, rim brakes are powerful enough for most people's needs and weigh nowhere near as much as a disc setup, so discs would be overkill for most riders. I am sure there are some who regularly ride up and down the Alps who would disagree.

You need a frame and fork with disc mounts so it's not possible to add discs to a bike that wasn't designed to take them. Such bikes seem to be quite rare at the moment and aimed at the cyclocross/tour/crossover market.

Road bikes use rim brakes because pro race bikes are restricted by UCI regulations meaning they can only use certain designs, and of course the technology trickles down to us so we use them too. Modern rim brakes are also very efficient when set up properly, especially in terms of power to weight, that is one of the reasons they remain the best choice on road bikes.

bus_ter

From this season UCI have permitted disc brakes for cyclocross. As such you should start to see more and more that will fit road bikes. However as already stated, you simply don't need them on regular road brakes and they add unnessasary weight.

MichaelW

Disc brakes redistribute the braking forces around the bike. They put more stress on the fork and possibly the spokes (???) and they change the angle of forces acting on the hub. Rim brakes force the hub into the dropouts, disc brakes force them out. If you use std road axles, dropouts without lawyer lips and a lightweight, external cam skewer, it may be possible to pull the axle right out of the fork during braking. You should be able to swap the forks to a disc-compatible version. Rear braking is much less important when you are trying to stop.

My cable discs have the same kind of power as my caliper brakes but the performance is constant in all conditions.

nicklouse

m00nd0g wrote:

I understand that much work in cycle workshops is disc brake related.

less than work on Canti or V brakes.

MichaelW wrote:

, disc brakes force them out. If you use std road axles, dropouts without lawyer lips and a lightweight, external cam skewer, it may be possible to pull the axle right out of the fork during braking.

very generalised and mostly incorrect.

rolf_f

A good idea on bikes with mudguards!

scarthie99

i wish had disc brakes on my super six the lot better the rim brakes+the disc brake work better in wet not rim brakes.the should start put on road bike lot better stop power the rim brakes in wet+any weather.have use rim brakes in wet the a night mare when try to stop at lights.that why the have mountain bikes, down hill bikes+don.t have to buy new wheels rims

MattC59

nicklouse wrote:

m00nd0g wrote:

I understand that much work in cycle workshops is disc brake related.

less than work on Canti or V brakes.

MichaelW wrote:

, disc brakes force them out. If you use std road axles, dropouts without lawyer lips and a lightweight, external cam skewer, it may be possible to pull the axle right out of the fork during braking.

very generalised and mostly incorrect.

I'm glad you said that, as I was going to pile in with my usual response of "Utter horse sh*t !!"

Monty Dog

MichaelW wrote:

If you use std road axles, dropouts without lawyer lips and a lightweight, external cam skewer, it may be possible to pull the axle right out of the fork during braking.

Been running cable discs on my titanium CX bike for 6 years, no lawyer lips plus external cam QRs and never had any problems - if folks aren't competent enough to be able to fit a wheel to a bike securely, using lawsuits to seek redress, then there's not a lot of hope for them.

neeb

It looks like hydraulic disk brakes will be the next big marketing thing on road bikes after everyone has got electronic shifting... I can see the advantages, e.g. full carbon wheels that don't need a rim braking surface so can be lighter and also not suffer from the performance issues of carbon rim braking, better, more modulated braking that will give you more confidence on descents, etc. However it's pretty obvious that it will work best as a complete package, i.e. dedicated disk brake wheels, disk specific frames and forks. So it's probably a whole-new-bike thing in 3 or 4 years time rather than a sensible upgrade on a current road bike.

pdw

Monty Dog wrote:

Been running cable discs on my titanium CX bike for 6 years, no lawyer lips plus external cam QRs and never had any problems - if folks aren't competent enough to be able to fit a wheel to a bike securely, using lawsuits to seek redress, then there's not a lot of hope for them.

Actually there is a real concern here. The ISO standard for quick releases only requires QRs to withstand a direct pull of 2300N, or 1150N per drop-out. This can be fairly easily exceeded with a disc brake mounted such that the reaction force is inline with the drop out, so I don't think it's really fair to suggest that wheel ejection requires incompetence on the part of the user.

Although manufacturers have never conceded that there's a problem here, with the one case that got to court being settled out of court, I assume that they have been quietly beefing up QRs so that they are well in excess of the ISO minimum, and of course, high end MTBs have all moved over to bolt through designs.

Contrary to some of the comments above, slick rubber on tarmac, even with thin tyres, is pretty much the best combination for grip that you'll see on a bike so there's potential for generating even greater braking forces than you'd see on a MTB.

I've got QRs + discs on both my mountain bike and my commuter and have never had a problem, but then I always ensure that the front QRs are done up very tight.

NickintheLakes

neeb wrote:

It looks like hydraulic disk brakes will be the next big marketing thing on road bikes after everyone has got electronic shifting... I can see the advantages, e.g. full carbon wheels that don't need a rim braking surface so can be lighter and also not suffer from the performance issues of carbon rim braking, better, more modulated braking that will give you more confidence on descents, etc. However it's pretty obvious that it will work best as a complete package, i.e. dedicated disk brake wheels, disk specific frames and forks. So it's probably a whole-new-bike thing in 3 or 4 years time rather than a sensible upgrade on a current road bike.

That's a sensible post.

It seems strange that braking development for road bikes is hindered (if indeed they are) by a set of regulations that apply to race bikes. At the end of the day maybe a squillionth of a percent of all bikes built that are termed road bikes ever get used under UCI juristiction.

Having used discs (Hope) and canti's (Ritchey) on an MTB there really is no comparism in terms of one being truly confidence inspiring and the other not - esp' in wet road conditions.

As for the fact that skinny tyres are easily sent into skid mode due to their tiny contact area then maybe for most users these tyres are really too skinny?

Maybe the 99.9% of road bike riders who are not competitive cyclists would be better off with some decent disks and some fatter rubber and hence being able to stop a good deal quicker.

pdw

NickintheLakes wrote:

It seems strange that braking development for road bikes is hindered (if indeed they are) by a set of regulations that apply to race bikes. At the end of the day maybe a squillionth of a percent of all bikes built that are termed road bikes ever get used under UCI juristiction.

True, but people who ride road bikes like to ride bikes that look like what the pros race on.

As for the fact that skinny tyres are easily sent into skid mode due to their tiny contact area then maybe for most users these tyres are really too skinny?

Maybe the 99.9% of road bike riders who are not competitive cyclists would be better off with some decent disks and some fatter rubber and hence being able to stop a good deal quicker.

It's more that the idea that skinny tyres don't have much grip is nonsense. On a dry road, you'll go over the handlebars before you manage to lock and skid the front tyre.

If you don't believe that skinny tyres have plenty of grip, just look at the kind of angles the pros lean their bikes to when cornering. Contact area isn't a particularly important factor in determining grip.

NickintheLakes

True, but people who ride road bikes like to ride bikes that look like what the pros race on.

Some might but I bet most couldn't give a fig. I would hazard a guess that most people who ride road bikes would struggle to name a pro (apart from maybe one or two global superstars) let alone know what bike they ride and then want one that looks the same.

Contact area isn't a particularly important factor in determining grip.

I think I know what you are saying but everything else being equal a greater contact area is surely more useful under braking conditions - notwithstanding aquaplaning issues.

springtide9

Yes they are better (much more control/feedback as well as power), but are generally heaver... hence why they haven't been used on the road yet.

Things have moved on massively on disc brakes over the years. I recently switched my old disc brakes for much more modern discs recently on the MTB; I saved something like 800g in weight, and the brakes leaps and bounds better in terms of power and modulation. I had Hope discs on my MTB for 6 years, and all I ever did in terms of maintenance was change the pads.

SRAM are bringing out the first road specific disc brakes for their red range:
http://road.cc/content/news/52299-sram- ... shots-land
I guess this will be the start of many disc systems appearing on road bikes. It can't be soon enough for me, as there is so little 'feel' of braking compared on my roadie compared to the MTB; I think the lack of power is less of an issue
But like everything, you get used to it and adapt.

rake

disk will lead to many more broken hip recovery posts and i just had my first crash. i dont want discs. heavy, much more cost and not needed. the line about saving weight on rims is pants, youl need a thicker spoke bed.
why do i want brakes to grip as well in the wet, the tyres wont.

MattC59

rake wrote:

disk will lead to many more broken hip recovery posts and i just had my first crash. i dont want discs. heavy, much more cost and not needed. the line about saving weight on rims is pants, youl need a thicker spoke bed.
why do i want brakes to grip as well in the wet, the tyres wont.

Why more broken hips ? If you're applying sufficient brake force to lose the front or rear wheel, then it doesn't matter what type of brake you have, you need to learn to use the brakes you have and to brake properly.

A set of road disk brakes aren't going to be hugely heavier than calipers, yes, you need a disk, but not of the diameter (and possibly thickness) of an MTB disk, so you can recover some, if not all of this weight in the rim design. As for the cost, have you seen the cost of DA, Red or Super Record calipers ?

Why would you need a thicker spoke bed ? Admittedly, the distribution of forces wil lbe different, but you'll not start ripping spokes out of the bed. Oh, and the comment about being able to lose weight from rims was following a conversation with a Shimano development engineer. His words, not mine, but being an engineer, I can understand his comments.

As for the comment about braking in the wet......... really, you didn't think that through did you........

ps, hope your crash wasn't too bad.

rake

MattC59 wrote:

rake wrote:

disk will lead to many more broken hip recovery posts and i just had my first crash. i dont want discs. heavy, much more cost and not needed. the line about saving weight on rims is pants, youl need a thicker spoke bed.
why do i want brakes to grip as well in the wet, the tyres wont.

Why more broken hips ? If you're applying sufficient brake force to lose the front or rear wheel, then it doesn't matter what type of brake you have, you need to learn to use the brakes you have and to brake properly.

Why would you need a thicker spoke bed ? Admittedly, the distribution of forces wil lbe different, but you'll not start ripping spokes out of the bed. Oh, and the comment about being able to lose weight from rims was following a conversation with a Shimano development engineer. His words, not mine, but being an engineer, I can understand his comments.

As for the comment about braking in the wet......... really, you didn't think that through did you........

ps, hope your crash wasn't too bad.

i have yet to come off a road bike but thanks for your concern.
if i can lock the wheels in the wet, why need more braking. dont give me any crap about modulation unless you need to learn how to press a lever.
being an engineer then does it not concern you about the leverage ratio using a smaller disc.

MattC59

rake wrote:

MattC59 wrote:

rake wrote:

disk will lead to many more broken hip recovery posts and i just had my first crash. i dont want discs. heavy, much more cost and not needed. the line about saving weight on rims is pants, youl need a thicker spoke bed.
why do i want brakes to grip as well in the wet, the tyres wont.

Why more broken hips ? If you're applying sufficient brake force to lose the front or rear wheel, then it doesn't matter what type of brake you have, you need to learn to use the brakes you have and to brake properly.

Why would you need a thicker spoke bed ? Admittedly, the distribution of forces wil lbe different, but you'll not start ripping spokes out of the bed. Oh, and the comment about being able to lose weight from rims was following a conversation with a Shimano development engineer. His words, not mine, but being an engineer, I can understand his comments.

As for the comment about braking in the wet......... really, you didn't think that through did you........

ps, hope your crash wasn't too bad.

i have yet to come off a road bike but thanks for your concern.
if i can lock the wheels in the wet, why need more braking. dont give me any crap about modulation unless you need to learn how to press a lever.
being an engineer then does it not concern you about the leverage ratio using a smaller disc.

My mistake, I thought you had said in your previous post that you had:

rake wrote:

....and i just had my first crash.

I'm not going to give you any crap about modulation, I'll just refer you to all of the brake manufacturers and let them tell you how important it is. You need a combination of power and modulation, simple as that (and knowing that braking isn't just down to pulling a lever.)

When you mention leverage ratios, are you talking about the ratios applied at the lever and thus hte brake on the wheel, or those transmitted through the disk to the fork due to the rotation of the wheel ? Either way, not particularly. Or are you talking about the leverage the rotating wheel has over the smaller disk, thus reducing it's braking performance ? If this is the case, this is why you have a smaller disk, because you don't need the same braking force as you get using a 160mm or 180mm MTB disk.

pdw

I think the comment about spokes refers to the fact that you can't use radial spokes on a disc front.

The reason that discs are better in the wet is not because they can lock the wheels more easily in the wet, but because they are more reliable. If you get rim brakes properly soaked, they'll do one or two rotations with the brakes applied before they do anything useful, whereas discs grip immediately and predictably. I switched to commuting with discs a year ago, and it certainly makes cycling in traffic in wet a more predictable business.

MichaelW

I'e mentioned before that the riders who can benefit most from disc brakes are not professional racers but commuters, winter trainers, tourists and tandem riders.
The first road disc brake system is going to be the pro-grade SRAM Red, way too expensive for any everyday rider to use. There is a real danger that the riders who can afford it wont see any benefit so SRAM will deduce that there is no need to trickle down the technology to affordable groupsets. There could be a big demand for an affordable road disk brake system outside of racing.

ddraver

I ve said this a few times on here now but I think electronic shifting and hydraulic brakes are the future. I would go as far as to say that in 10 years, very GBP1000, 105 equivalent bike will have them.

With regard to hydraulic rim brakes, every MTBer wanted the Magura hydraulic rim brakes when they were out because they were recognised as being so much better than cable brakes. I'm surprised SRAM has made these rim brakes and I think they could be a very interesting avenue

NickintheLakes

ddraver wrote:

I ve said this a few times on here now but I think electronic shifting and hydraulic brakes are the future. I would go as far as to say that in 10 years, very GBP1000, 105 equivalent bike will have them.

I'd say you are probably right there.

NickintheLakes

Just a thought but if say hydraulic disc brakes 'took off', would they be able to be retro-fitted to bikes with internal cable routing?

ddraver

NickintheLakes wrote:

Just a thought but if say hydraulic disc brakes 'took off', would they be able to be retro-fitted to bikes with internal cable routing?

I'd guess that's where SRAM are going with the rim brakes...

NickintheLakes

ddraver wrote:

NickintheLakes wrote:

Just a thought but if say hydraulic disc brakes 'took off', would they be able to be retro-fitted to bikes with internal cable routing?

I'd guess that's where SRAM are going with the rim brakes...

Ooooops! I mean't to say hyrdraulic rim brakes! Was wondering whether they would go through the frame holes and/or cope with the bends.

ddraver

Apparently, hydraulic hoses cope much better with bends (there is no difference in drag for a start), and the hoses on my MTB are no thicker than my road bike brake cables - Is there a standard size for brake/gear cables or hoses anyway?

jthef

Been thinking about this for a while but my next winter/commuting bike will have disks brakes.
Reason too many time had trouble stopping in a rush when wet, roundabouts, going down hilland prople pulling out etc. As for the summer bike (when I get one that is ) not as bothered as would be ridden mainly in the dry.