Brakes - Are disc brakes better? and why?

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  • springtide9
    springtide9 Posts: 1,731
    There are a lot of unknowns with adding disc brakes to road bikes in terms of stresses, but to find out what are real and what are imaginary, you can't just stick your finger in the air and take a best guess.
    Talking about a fork bending under stress from a brake is complete nonsense as a best guess - to find out whether this really is an issue depends on many many factors, and you need to run a full suite of computer simulations to find out the potential forces involved.
    Forks are pretty strong, so strong in fact that they are capable of regularly coping with hitting a pothole at 30+mph, so is this type of stress more of less than braking?

    The argument about why disc brakes are only now starting to be talked about on road bikes is not because it's technically not possible, but mainly down to weight. Technology has moved on a lot over the last 10 years of disc brakes. I must admit the 'post' about having to get the discs hot before the brakes work made me chuckle... :lol:
    Full on downhill MTB brakes are now lighter than the superlight XC brakes of yesteryear. And superlight XC brakes today, offer more power and control than downhill brakes of the past.

    To answer the question of whether this is technically possible or not - you have your answer. SRAM (who are very talented with disc brakes on the MTB scene), have taken the idea from a concept into a product. SRAM also make wheels, so are very aware of what is needed to build a strong wheel with a disc. Cyclocross wheels also need to do this, and they seem to be pretty strong (and also have carbon forks that are not stupidly heavy)
    Not only that, but as part of that product release, they have a stop gap for the intermediate timeline where frames don't have bosses for the disc mount.

    Whether this ever becomes a mainstream product we will have to wait and see. All I can say is that having better brakes on a road bike for a little extra weight sounds more beneficial than having electronic gears.

    And this...
    Il Principe wrote:
    MattC59 wrote:
    If you're comparing the current crop of MTB dick brakes
    :D Says it all really.

    I think this is the biggest reason some roadies are outraged. How dare the road scene take technology developed on the much hated MTB scene. Makes me laugh really. Seems that the people who have regularly ridden both MTB's and Roadies over the years, and have been part of the technology enhancements on both sides are pleased discs are coming to road bikes (at last!).... and it seems that it's only the 'pure roadies' that are taking an exception to the idea (and a number of these appear 'clueless' of disc brakes - i.e. they need to be hot to work?? lol). I don't get it. What is wrong with road bikes getting better brakes? It's made a huge difference to descending on an MTB in terms of speed, so why wouldn't you want this on a road bike. It seems to me that if someone thinks that their calliper brakes are amazing in all weather conditions, they need to 'man up' and descend a little faster.
    Simon
  • rake
    rake Posts: 3,204
    springtide9 wrote:
    Talking about a fork bending under stress from a brake is complete nonsense as a best guess
    Forks are pretty strong, so strong in fact that they are capable of regularly coping with hitting a pothole at 30+mph, so is this type of stress more of less than braking?

    I must admit the 'post' about having to get the discs hot before the brakes work made me chuckle... :lol:


    (and a number of these appear 'clueless' of disc brakes - i.e. they need to be hot to work?? lol).

    have you read this.
    http://www.bikerumor.com/2012/02/14/roa ... they-work/
    it answers your questions. frame and fork at least 500g heavier, it talks about the assymetrical torque from the brake, not nonsense. a pothole is different type of loading.
    the article talked about metalized pads to cope better with the temperature, think it was magura that said they work better when warmed up. look at the heat discolouration of the disk in the picture and tell me it didnt get hot.
    thats magura who are clueless then?
    a lot of folks think all this crap and expense isnt worth it, i can ride well enough to use calipers.
  • ddraver
    ddraver Posts: 26,661
    FFS rake, we ve been through this on the last page....You can't just bring it up with someone else and pretend it's all new again.

    So you don't want disks, fine we don't care,no one is forcing you. Leave the rest of us alone so we can talk about the future...
    We're in danger of confusing passion with incompetence
    - @ddraver
  • rake
    rake Posts: 3,204
    your just sore because you dont like the facts. youve gone off topic. :mrgreen:
  • ddraver
    ddraver Posts: 26,661
    h'okay little buddy....
    We're in danger of confusing passion with incompetence
    - @ddraver
  • rake
    rake Posts: 3,204
    ddraver wrote:
    h'okay little buddy....
    im not little :wink:
  • ddraver
    ddraver Posts: 26,661
    well, it's even more important you have disk brakes then...
    We're in danger of confusing passion with incompetence
    - @ddraver
  • rake
    rake Posts: 3,204
    they wouldnt hold me. :lol:
  • andrewjoseph
    andrewjoseph Posts: 2,165
    rake wrote:
    ...
    have you read this.
    http://www.bikerumor.com/2012/02/14/roa ... they-work/
    ...

    The writer of the piece doesn't seem to know how to use brakes properly, (drag braking on a long descent), states incorrectly that small rotors are needed for better cooling, was not the only one using disk brakes on that descent but was the only one who had problems.

    So, after reading most of it, I come to the conclusion it was rider error. He didn't brake properly.

    My wife and I have come down long steep descents on fully loaded bikes with cable disk brakes with 160mm rotors. No brake fade but hot rotors.

    Tandem bikes have had rear disk brake for years with a 'drag brake' to reduce speed build up. It is a proven method for heavily laden bikes. Disk brakes are a proven system for competition mountain bikes, weekend riding and anything in between.

    From what I understand, a big worry amongst roadies is rim heating/expansion/glue melting on a long downhill, causing tub roll off or rim explosion. I don't know the figures, but this has also caused a number off accidents. If I find some information about one incident supposedly causing a crash, would this prove that all rim brakes are flawed?
    --
    Burls Ti Tourer for Tarmac, Saracen aluminium full suss for trails
  • ddraver
    ddraver Posts: 26,661
    andrewjoseph wrote:
    From what I understand, a big worry amongst roadies is rim heating/expansion/glue melting on a long downhill, causing tub roll off or rim explosion. I don't know the figures, but this has also caused a number off accidents. If I find some information about one incident supposedly causing a crash, would this prove that all rim brakes are flawed?

    Hee Hee, you mean like this? http://www.youtube.com/watch?v=h_8m5-sR6I4
    We're in danger of confusing passion with incompetence
    - @ddraver
  • MattC59
    MattC59 Posts: 5,408
    Rake; Whilst some of the points you makes are valid, they're non arguments. All issues can be over come and not with the penalties that he describes.
    The requirement for a larger disk to combat overheating is utter tripe.
    The need for brakes to heat up before they work properly is also tripe (in this application), especially with the forces concerned.
    And I believe the word that you're looking for is sintered, not metalized, but you're an engineer, so of course, you know that.

    It would appear that this is a classic case of reading, but not understanding.
    Science adjusts it’s beliefs based on what’s observed.
    Faith is the denial of observation so that Belief can be preserved
  • andrewjoseph
    andrewjoseph Posts: 2,165
    ddraver wrote:
    andrewjoseph wrote:
    From what I understand, a big worry amongst roadies is rim heating/expansion/glue melting on a long downhill, causing tub roll off or rim explosion. I don't know the figures, but this has also caused a number off accidents. If I find some information about one incident supposedly causing a crash, would this prove that all rim brakes are flawed?

    Hee Hee, you mean like this? http://www.youtube.com/watch?v=h_8m5-sR6I4

    makes me cringe every time, but you're right. I don't understand why rim brakes are still used really. :twisted:
    --
    Burls Ti Tourer for Tarmac, Saracen aluminium full suss for trails
  • springtide9
    springtide9 Posts: 1,731
    andrewjoseph wrote:
    makes me cringe every time, but you're right. I don't understand why rim brakes are still used really. :twisted:

    People are afraid of change, especially when they have no first hand experience of what is being proposed.

    If you look at the comments on 'bikerumour", the replies are very similar to on this forum. Anyone who has extensive experience with disc brakes over the years, all have the same positive opinion; the sceptics are the people with very little experience. No real surprises I guess.

    There are a lot of flaws in the 'bikerumour" post, or should I say rant, as he crashed, but can only assume this was user error (or those brakes he tested were really, really rubbish). I have come close to ''cooking' my Hope C2's (10 years old) in the past, but it wasn't exactly a surprise; the 'smell' as well as the feel on the lever was the give away, and all that was needed was to 'back off' to get the temperatures down.
    For any roadies I have just scared talking about 'cooking brakes', the C2's are/were 10 years old - my Formula RX's are 200g lighter than the C2's, and never come close to overheating. Interestingly, they use the same size rotors, which is odd as 'bikerumour" post implies that all brakes of a specific disc size are created equal lol
    Simon
  • MattC59
    MattC59 Posts: 5,408
    Reading the Bikerumour article is like reading the Daily Mail !!! Half the facts and an opinionated author.
    Science adjusts it’s beliefs based on what’s observed.
    Faith is the denial of observation so that Belief can be preserved
  • andrewjoseph
    andrewjoseph Posts: 2,165
    When I had our Burls touring frames designed, I wanted the disk brake mounts of the right fork for mechanical reasons*. Justin Burls (the designer) got in touch with the russian frame fabricators and was assured that the fork would take the stresses with no additional strengthening.

    but I did ask him to make the frame strong and not worry too much about weight.

    * I should have said on the front of the right fork.
    --
    Burls Ti Tourer for Tarmac, Saracen aluminium full suss for trails
  • springtide9
    springtide9 Posts: 1,731
    andrewjoseph wrote:
    When I had our Burls touring frames designed, I wanted the disk brake mounts of the right fork for mechanical reasons*. Justin Burls (the designer) got in touch with the russian frame fabricators and was assured that the fork would take the stresses with no additional strengthening.

    but I did ask him to make the frame strong and not worry too much about weight.

    * I should have said on the front of the right fork.

    Just from an interest point of view, looking at the weights between Cyclocross forks, disc specific vs standard, there doesn't appear to be much weight penalty for disc version:

    http://www.3tcycling.com/products.aspx?p=Luteus
    http://www.eastoncycling.com/en-us/road ... ace/ec90-x

    3T state the fork is strengthened for the disc mount, but actually comes out slightly lighter than the Easton. Obviously standard road forks are lighter than cross, so will probably need additional material compared to a cross which is designed stiffer in the first place; I guess we'll have to wait and see rather than 'finger in the air' speculation of the additional weight for the disc mount on a disc specific road fork.
    Simon
  • MattC59
    MattC59 Posts: 5,408
    springtide9 wrote:
    3T state the fork is strengthened for the disc mount, but actually comes out slightly lighter than the Easton. Obviously standard road forks are lighter than cross, so will probably need additional material compared to a cross which is designed stiffer in the first place; I guess we'll have to wait and see rather than 'finger in the air' speculation of the additional weight for the disc mount on a disc specific road fork.

    Exactly, adding strength doesn't necessarily mean adding weight, especially with carbon fibre.
    Science adjusts it’s beliefs based on what’s observed.
    Faith is the denial of observation so that Belief can be preserved
  • andrewjoseph
    andrewjoseph Posts: 2,165
    I think it's on the wheels where most weight will be gained, beefed up hub, rotor and bolts (could manage 3 or 4 bolts?), perhaps 20-26 spoke,3 cross on disk side, maybe 2 cross on opposite side, (I don't know if this possible?).

    Weight saving from rim as braking surface not needed? Could make this more aero with the much touted 'toroidal' shape?

    Thinking about it, those 4 'spoke' TT wheels may be fine, are they heavier than normal wheels?

    All in all, with the fact that teams have to add weight to the bikes to keep within the UCI limit now, I don't feel that the extra weight of disks will hold back bike makers.
    --
    Burls Ti Tourer for Tarmac, Saracen aluminium full suss for trails
  • ddraver
    ddraver Posts: 26,661
    Hope already have their integrated disks and hubs which are lighter than 6 bolt and centerlock... Again with Mtbs increasingly moving toward thru-axles, there is no reason for roadies to stick with what is available now...
    We're in danger of confusing passion with incompetence
    - @ddraver
  • andrewjoseph
    andrewjoseph Posts: 2,165
    ddraver wrote:
    Hope already have their integrated disks and hubs which are lighter than 6 bolt and centerlock... Again with Mtbs increasingly moving toward thru-axles, there is no reason for roadies to stick with what is available now...

    Wasn't aware of that, thanks.
    --
    Burls Ti Tourer for Tarmac, Saracen aluminium full suss for trails
  • rake
    rake Posts: 3,204
    andrewjoseph wrote:
    I think it's on the wheels where most weight will be gained, beefed up hub, rotor and bolts (could manage 3 or 4 bolts?), perhaps 20-26 spoke,3 cross on disk side, maybe 2 cross on opposite side, (I don't know if this possible?).

    Weight saving from rim as braking surface not needed? Could make this more aero with the much touted 'toroidal' shape?
    .
    the shimano design man thinks you cant remove the brake surface as the rims will be too fragile. think how side walls can blow out already from worn brake surfaces. he said at least 40G weight added to the rim needing to be stiffer because of the dish. they concured that they are less aerodynamic as they the brake system is bigger and doesnt fit the contour of the frame.
  • ddraver
    ddraver Posts: 26,661
    If nothing else, I admire your devotion to that article.

    Andrew - see here, http://www.hopegb.com/voir_whspxc3.html
    We're in danger of confusing passion with incompetence
    - @ddraver
  • MattC59
    MattC59 Posts: 5,408
    ddraver wrote:
    If nothing else, I admire your devotion to that article.

    Andrew - see here, http://www.hopegb.com/voir_whspxc3.html

    :lol:
    Science adjusts it’s beliefs based on what’s observed.
    Faith is the denial of observation so that Belief can be preserved
  • rake
    rake Posts: 3,204
    of course they wont fit a road frame as the rear axle is 135mm.
  • MattC59
    MattC59 Posts: 5,408
    rake wrote:
    of course they wont fit a road frame as the rear axle is 135mm.

    :roll:
    Science adjusts it’s beliefs based on what’s observed.
    Faith is the denial of observation so that Belief can be preserved
  • ddraver
    ddraver Posts: 26,661
    MattC59 wrote:
    rake wrote:
    of course they wont fit a road frame as the rear axle is 135mm.

    :roll:

    :lol::lol::lol:

    Oh this is so much fun!

    :lol::lol::lol:
    We're in danger of confusing passion with incompetence
    - @ddraver
  • springtide9
    springtide9 Posts: 1,731
    rake wrote:
    andrewjoseph wrote:
    I think it's on the wheels where most weight will be gained, beefed up hub, rotor and bolts (could manage 3 or 4 bolts?), perhaps 20-26 spoke,3 cross on disk side, maybe 2 cross on opposite side, (I don't know if this possible?).

    Weight saving from rim as braking surface not needed? Could make this more aero with the much touted 'toroidal' shape?
    .
    the shimano design man thinks you cant remove the brake surface as the rims will be too fragile. think how side walls can blow out already from worn brake surfaces. he said at least 40G weight added to the rim needing to be stiffer because of the dish. they concured that they are less aerodynamic as they the brake system is bigger and doesnt fit the contour of the frame.

    The Shimano man obviously knows nothing!
    Mavic 717 Rims come in both disc specific as well as with a brake surface. 717 disc rims are 25g lighter. MTBers will also tell you that disc specific rims are also stronger as they don't have the design constraints that a braking surface adds.
    Please no more quotes from that article.. it's complete nonsense from some who is very 'bitter and twisted' for obvious reasons.
    Simon
  • rake
    rake Posts: 3,204
    some say the 717 rim has terrible durability. buckling, welds cracking and dents. you can built anything light :wink:
  • ddraver
    ddraver Posts: 26,661
    who?

    A vast majority of people say they re one of the best XC rims available...
    We're in danger of confusing passion with incompetence
    - @ddraver
  • springtide9
    springtide9 Posts: 1,731
    rake wrote:
    some say the 717 rim has terrible durability. buckling, welds cracking and dents. you can built anything light :wink:
    If 'some' people are trashing 717's riding XC, then these 'some' people need to loose a lot of weight or learn to ride ;)
    Mine are as true as I got them, and have been ridden hard over rock gardens, trail centers, etc even when I was 110+kg.

    But it's off topic... regardless of the rim, the equivalent disc specific rim is lighter and stronger. You won't find a disc specific rim with a similar profile to one with a brake surface, and that's because the profile of a rim with a brake surface is far from ideal.
    Simon

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