How soon will disk brakes be used on road racing cycles?

Discussion in 'Cycling Equipment' started by doiturself, Jul 7, 2011.

  1. doiturself

    doiturself Member

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    /img/vbsmilies/smilies/ROTF.gifLove it, very good!

    I just checked out the Magura MT8 mountain bike hydraulic setup and it is incredibly light. The master cylinder is made from some kind of Carbotech composite, it's insanely light. The whole thing, brake hose, master, and caliper was very petite. For road bikes it could be much lighter.

    http://www.mission-performance.com/en/products/mt8.html

     


  2. Eichers

    Eichers New Member

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    Hi doiturself, will these disc brakes fit to 130mm rear hubs?

    The reason I ask is that I think this is necessary to ensure a narrow/small Crankset Q (thread) :)

    What is your opinion about this?
     
  3. tafi

    tafi Member

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    Given no-one is complaining about any lack of control or consistency of current rim brakes, and I've certainly never felt brake fade, what is the reason to change?

    Because this is where bike companies make their money. You call it "consumer grade" yourself, presumably for this reason. If it can't be done on a decent budget, no-one except wankers with fat wallets will buy it, and there is no point in catering to that rather small corner of the market (in terms of volume or turnover). Look at Di2. that is not a money making exercise by any stretch; it was a good marketing strategy. Shimano are only now about to make money on it as they start rolling out the Ultegra version (which people can afford). So far no-one has been able to meet both price and quality criteria on the disc brakes currently available.

    That's nice, but I don't recall this being a discussion about motor bikes. A bicycle disc brake has a very flimsy disc less than 1/16" thick and a single piston caliper. Rather a different kettle of fish. A bike wheel change also needs to be made by any old hubbard, not an experienced pit crew.

    Wheel changes with rim brakes will average out shorter than the equivalent changes with disc brakes, simply becasue the disc caliper is harder to aim at (obviously). You were able to install your wheel today quickly because it was the exact same wheel which came out of the fork. Take any other spare wheel and you'll find that this will not be the case without the brake rubbing. I work in a bike shop and regularly perform wheel changes as part of services. I have yet to find a caliper which does not need to be realigned for a wheel change. Since you don't want to talk about "consumer grade" brakes you obviously mean that this technology ought to be applied to racing. I don't know how much bike racing you watch but I can assure you that wheel changes are common. Call me picky but I think that it would wear pretty bloody thin if the team mech had to perform brake realignments at the roadside.

    The statement you make about design and adjustment is true, but unfortunately very few current bike disc brakes are well designed, and most require adjustment far too often (as per my point above).
    As mentioned above a typical bike disc is less than 1/16" thick (1.5mm for those of us who use real units). That is pretty flimsy and much more prone to warping than thicker moto or auto discs which are at least 5mm, and often several cm, thick. The single most popular MTB repair we do is correcting brake disc rub, straightening rotors and correcting squealing. To use a thicker sturdier (and heavier) disc on a road bike would be out of the question, so your disc brake with a few thousands clearance would be impossible in a sport where any rub is significant lost power.
    Preventing rim brake rub is pretty easy as all it needs is a moderately true wheel (and road wheels must be pretty true to avoid contact with the frame anyway).

    So, unlike ALL the current bicycle disc brake experience to date then...

    MTB rims are a lot wider. Take a look at an MTB rim and you'll find that the spoke bed is no narrower than a current road rim spoke bed. Road rims will not be able to get narrower in this area than they already are (eyelets and nipples have to fit somewhere). The material in the brake track is largely already there to contain tyre pressure anyway so not much material removal is possible. Furthermore MTB wheels don't need to be designed with aerodynamics in mind. Road race wheels do. They have deep faired sections which blend into the tyre side wall. For aerodynamic reasons this rim shape will not change and to add the brake track requires very little extra mass. A disc-only road rim won't save any more than a few grammes over an equivalent rim brake version. In contrast, the wheel will be handicapped by a heavier hub body with a steel rotor attached to it.

    At the very least, one half of the wheel will need a crossed spoke pattern. Otherwise spoke life will be significantly shortened by fatigue.

    You have not understood what I said (like many of my points). I know discs are consistent between wet and dry. However, grip is not. A disc brake will much more easily overwealm the tyres in the wet.

    At the end of the day the rim brake is still more reliable, less maintenance intensive, lighter, cheaper, and certainly no slower than discs. This being the case, there is nothing about discs which would see Cadel Evans or Andy Schleck riding with them any time soon (and Cadel has won two MTB world cups:)).
     
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  4. doiturself

    doiturself Member

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    The reason no one is complaining about lack of control or consistency is very simple, it is a hard truth, but very few road cyclists have any idea of what it is like to use top quality disk brakes on a single track vehicle. They are used to chuck wagon brakes. That is because they have not ridden high-performance motorcycles and lack the experience and skill of being able to really utilize the power and control of a disk brake system. I sure as heck am complaining about it; I just put some cyclocross tires on my 2011 Camber Elite MTB and the thing now descends like a rocket on pavement; it has hydraulic disk brakes and compared to any of my other road cycles, it is far and away superior at every aspect of braking. On the same fast descents I can brake much later and compress the amount of time spent braking into less distance with much more control and safety, and this is with a bike fully ten pounds heavier than my lightest road bike. I know what I am talking about as I have ridden high-performance motorcycles for almost 30 years, I raced mc's, I instructed at a high-performance riding school, etc.

    Re: another post, if someone doesn't want to experience an "I told you so" then the best policy is at least acknowledge there might be some advantage to disk brakes. The "ITYS" is coming along with the disk brakes.

     
  5. tafi

    tafi Member

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    And this is just my point. The fact you can brake later has nothing to do with control or modulation, and everything to do with sheer power. Discs will only be of benefit if they allow later braking. You can only brake later if the brakes are more powerful and the tyres have the grip to match. If you increase the grip, you must also increase the rolling resistance. Which brings me back to point (1) above: no roadie will suffer the increased rolling resistance that comes with the required extra grip.

    I think you assume that we ride road bikes like you ride a moto. Unfortunately that's not the case. The speeds are lower and the time spent braking is significantly less in proportion to total ride time. Moreover, part of the skill of riding a roadie is to brake less and scrub off the bare minimum of speed (any braking has to be compensated by more acceleration later on so the less you use the brakes, the better). Any increase in braking performance would be negligible in the context of a race. We also spend a lot more time under power (mainly becasue there is a lot less of it) and any increase in rolling resistance is now big gobs of wasted energy. So the answer to the question: "Will they make me faster?" must be "no".

    If instead we choose to use discs with less power, then all we are doing is increasing stopping distances and adding weight, and I don't think a roadie would pay good money for that either.

    I think you also assume that technology from motorbikes will simply transfer across to road bicycles without any compromises in the way that they function and without introducing other compromises to the design, operation, or servicing of bikes. It is an assumption you have made without explaining how it could technologically be achieved. In order to be adopted by racing teams, your super-dooper brakes will need to:
    • have very thin and light rotors which can stay magically straight even whilst bouncing around in the back of a team car (current 1.5mm thick discs, made of steel, are not capable)
    • have no rubbing at all (most current MTB discs can't even acheive that with ~1mm of clearance, much less your "few thou")
    • hubs with extremely tight tolerances for disc mountings to avoid brake realignment after every wheel change (a different cone adjustment is all you need to put that out)
    • Somehow integrate as cleanly as current brakes with the aerodynamics of the bike (this is a biggie, particularly for TTs)
    • require beefier brake mountings than current brakes without adding weight to frames (yeah right)
    • result in, at most, no gain in weight to the bike (certainly can't happen with current brakes)

    So do I. I know that a set of six pot Brembos are a thing of engineering beauty because I have a Mechanical Engineering degree (now doing a PhD). But my experience of ten years racing and working on bikes also tells me that you have little chance of seeing a better brake on a road bike than what we currently use. All the technical leaps above will have to be made before they can be adopted. If discs were so good wouldn't you think we'd already have them?
     
  6. doiturself

    doiturself Member

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    Well, I can only say that you have an impressive pedigree but all the reasons you give are utterly contrary to my personal experience so we must leave it at that. In the meanwhile, Team Radio Shack's manager is already pushing for disk brakes -- see the link below for details (pullquote follows).

    In offering one possible solution to the problem, Bruyneel said, “I think it’s time to start to consider some different equipment. If you look at the bikes, they’ve become lighter and lighter, so why not consider disc brakes? They’re heavier, but I think it would be perfectly possible. And discs definitely brake a lot better. I think with the light equipment and carbon rims (regular brakes) are sometimes a problem in the rain.”

    On top of this, the midrange Volagi bike weighs only 17 pounds with a full disk system and it would be obviously easy to shave another two pounds from that; I don't know what their top-of-the-line Dura-Ace weighs but I soon will as I intend to own one in the near future.

    I wish now I had not been so eager to buy my Litespeed but it will take its place in my garage among the other antiques, I suppose.

    This "debate" hinges far more on traditionalism than any kind of logic; to introduce disks would be to introduce an entirely new skill set into the mix and a different group of riders would then have a tremendous advantage. It reminds me of when Kenny Roberts and Freddie Spencer came to Europe and crushed the motorcycle Grand Prix competition, because they had grown up racing dirt track. The Americans dominated in Formula One GP (now Moto GP) until the dirt-tracking Euro riders (Doohan, etc.) got into the fray.

    The wine-and-espresso-sipping set don't want the last bastion of European tradition wrecked by a bunch of uncouth mountain-bikers, the way I see it./img/vbsmilies/smilies/ROTF.gif/img/vbsmilies/smilies/duck.gif

    http://velonews.competitor.com/2011/07/news/inside-the-tour-with-john-wilcockson-what-caused-the-crashes_183602
     
  7. danfoz

    danfoz Well-Known Member

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    This is a good point. Although many including myself feel their current brakes adequate under the circumstances, no one would argue against better brakes. If only the aethetics of disc brakes on a road bike didn't hurt my eyes /img/vbsmilies/smilies/wink.gif
     
  8. finnrambo

    finnrambo New Member

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    hate to point this out but my 105 brakes with kool-stop pads stop me just as adequately as my 4-piston shimano saints....... why are 300-400 dollar top of the line heavy disks just as powerful as 100 dollar entry level brakes? dh disk rotors are larger than xc rotors to gain leverage, now look at the leverage of a road wheel. dh racers use disks because 10 foot drops warp your rim (I go through a Singletrack rim every 2 races on average) magura mt8's are for flat bars only, i broke my set because one hit a tree going less than 10km/h and the other cracked when i was racing xc not dh in 32 degrees celsius something like 110 fahrenheit and cracked in a rock garden when i used one finger to hit the brake. disk brakes are a faulty design almost the second coming of rod brakes (any senior cyclists care to share a storie?), when your in the rain just etch your metal training rim like the barloworld mechanics do if you are lacking that much confidence on a bike in the rain, bottom line: rim brakes work perfectly as good as a disk brake 5 pounds more and 3-4 times the price, I should know I ride xc, race downhill and have done more road racing in the rain than in the dry (vancouver.....)
     
  9. doiturself

    doiturself Member

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    I can't argue with another's personal impression about rubber pads on rims vs. disk brakes; apparently there are some riders who really do believe that they work just as well and for those riders disks are a non-starter. (One wonders why jets, racing cars, racing motorcycles, cars, trucks, and all other moving and motorized vehicles have transitioned to disk brakes but that is a discussion for another venue. However I will say that based on the style of riding, a bicycle will not be pushed anywhere near what is actually possible in terms of hard braking when equipped with rubber pads, thus, this seems to explain comments such as "I have never experienced fade with pads" or the one below. Cyclists have simply adapted to the stone-age performance and think that is the high water mark for brakes.)

    Here again, why present the notion that disk brakes are "five pounds heavier" or that the Magura are for "flat bars only"? Makes no sense as it is patently obvious that first of all, no disk brake system is even close to being five pounds heavier than a pad brake arrangement (note the 17-pound weight cited for the disk-equipped Volagi), and of course any system designed for a road racing cycle is going to be specifically designed for that application.

    The title of this thread was not "What Kind of Objections Does Everyone Have to Disk Brakes?" It was and remains "When Will Disk Brakes be Used on Road Racing Bicycles?"

    It is a given; the question was "When" not "If".

    Forward thinkers like Team Radio Shack's manager and many others already know it and are working on it. It is probably no coincidence that Team Radio Shack's management has made such statements given that Levi Leipheimer, who spends a lot of time in Northern California and is part of Team Radio Shack, seems to be in close proximity to Volagi, also in Sonoma County.

    I seem to recall that some other innovators, like Gary Fisher, Tom Ritchey, Keith Bontrager, and a few other names are all from Northern California. It seems to be no coincidence, either, that many of these early MTB innovators either came from a motocross background or had a good deal of contact with motorcycling.

    Northern California is back on the map with the first all-disk lineup of road cycles and this will be the shot heard around the world. As I asked, "When" not "If". Perhaps the thread would take on more significance if that question was answered instead of becoming a repository for objections to what is destined to be a fait accompli.

     
  10. finnrambo

    finnrambo New Member

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    all of those vehicles have wide tires high in rolling resistance to cope with the force of disk brakes if they didnt the tires would brake contact with the ground, they will eventually be used but theyre a passing fad like scandium bikes, who here has a scandium frame?
     
  11. dhk2

    dhk2 Active Member

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    "When" is when a huckster can convince enough suckers that the extra weight and cost of a disc brake system will actually save them time on a road stage, ie, they will gain more on the descent than they lose on the climb due to the extra weight. And there is no doubt about the extra weight; it's a function of the mechanics and forces involved in shifting from the very-efficient rim caliper braking to disc hub braking. You've heard that from several of us, but don't appear even vaguely interested in understanding why that is.

    Actually, these are discussion forums; anything you post is subject to questions, discussion and outright rejection. That's how forums work. You can't start a thread based on a personal opinion without any supporting evidence and not expect questions or challenge, regardless of how cleverly you word the subject line. EG, if I start a thread "When will 2+2=5?" , what sort of responses should I expect to get?
     
  12. ambal

    ambal Active Member

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    Wheel changes in races would require a standardized disk size, I can't see that happening between the big 3 component makers. Apologies if its been mentioned already.
     
  13. cheetahmk7

    cheetahmk7 Well-Known Member

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    My historic Formula 2 racing car is one very fast car with excellent disc brakes. It has 265kW and weighs 480kg including the driver. The front wheels are 9" wide and pushed to the ground with the aid of wings and ground effect side pods. On the other hand my racing bicycle has 300W and weighs 80 kg including the rider. The wheels are just over 1/2" wide.


    Racing car power to rate ratio: 552 W/kg
    Racing bicycle power to rate ratio: 3.75 W/kg

    Now if you know much about automotive brakes, you would know that there is a degree of pads rubbing the discs, and that lateral run out of the discs is what forces the pads/pistons away from the discs. This drag is easy to feel when you apply and then release the brakes and then turn the discs by hand. The drag from this isn't a problem when you have a power to weight ratio of 552 W/kg, but when you have a paltry 3.75 W/kg every bit of drag is extremely significant. The discs on a mountain bike are slightly different in that they have spreader spring, but it isn't strong enough to overcome the friction of the pistons in the bores, so MTB discs are predominately reliant on using lateral run out to force the pads away from the discs.

    Warping is another difference between bicycle discs and the discs on a car. I can spot the warping on my MTB discs with my naked eye, but the warping on the discs on my cars isn't actually warping at all but an uneven transfer of pad material onto the disc. This warping just makes the brake drag worse.


    Racing car weight to rim width ratio: 53.3 kg/inch
    Racing bicycle weight to rim ratio: 160 kg/inch

    No surprise to see that the bicycle has a third of the relative tyre width compared to the car (and that is before taking into account that the car has wings and sticky rubber). If the racing car only had 3" rims, I would expect that drum brakes would be perfectly adequate as it would take two thirds of five eighths of stuff all to lock up the tyres. Like so many people have said before, as long as the brakes have the ability to lock up the tyre , then the tyre is the limiting factor when it comes to braking . Any more braking ability will not make a vehicle stop faster, in fact the extra weight will decrease the braking ability.
     
  14. Moto700

    Moto700 Member

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    I have mechanical disc on my Motobecane and don't see a whole lot of difference between disc and rim, IMHO. In fact I get occasional rubbing of the rotor from time to time. I know that has to be wearing the pads but even when the bike was new I didn't see a lot of difference.
     
  15. cloudhead

    cloudhead New Member

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    I was at my LBS today and brought up this debate over disc brakes and asked again their opinions on the Volagi bikes. I spoke to the owner and master mechanic, both well-respected in their jobs and opinions.

    The owner doesn't believe Volagi bikes are made for flat-out racing, but for long-distance high-speed riding, such as a brevet, with the disc brakes allowing for less fatigue when braking down that mountain--after already putting in 200+km on the ride.

    The master mechanic brought up a point that the bikes are not good for larger/heavier riders (are any CF bikes?), because they stop so hard that the front fork flexes. Rear is fine. He thinks they should thicken the carbon in the fork, or create an asymmetrical fork with more reinforcement on the disc side.

    Neither believe that there is any hinderance in speed of replacing a wheel due to the disc mechanism.

    My own opinion on changing the wheel with sidepulls: Long-distance rides often call for wider tires, and most racing sidepulls don't open wide enough to allow the wheel and inflated tire to pass through. I've been riding on Challenge Parigi-Roubaix tires that have to be partially deflated if I remove the wheel. I have Shimano 105 sidepulls, and am assuming Ultegra and Dura Ace are the same.

    I agree with the owner, that the Volagi's are not touring, not racing, but are a serious long-distance bike for an experienced rider. Perhaps someone will ride one in the upcoming 1200km Paris Brest Paris.
     
  16. doiturself

    doiturself Member

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    You are talking good sense. In fact the designers of Volagi bikes specifically state they are endurance bikes and the owners themselves are accomplished endurance racers. One of the owners did indeed compete in and finish the 1200km Paris-Brest-Paris. http://volagi.com/about-volagi

    Another interesting point regarding Volagi, they are in Sonoma County, also home to Levi Leipheimer's Gran Fondo. Radio Shack is the main corporate sponsor for that event. Team Radio Shack's manager is on record as endorsing a change to disk brakes for road racing cycles (see link in my earlier post). Sonoma County has some of the best roads in the world (read: toughest) when it comes to road cycling.

    None of the objections I have read here hold water; standardizing a disk size is child's play with a $25 part like a brake disk. A well-adjusted disk will not rub but if for some reason it does begin to warp due to heat from hard descents during a single stage, this would be no more likely than having a pad rub the rim, and probably far less likely. In any event both pads and disks would be replaced each night between stages of a race like the Tour de France. All wheels for any given competitor's cycles would be identical, of course, so no adjustment would be needed if swapping wheels due to a puncture or other reason.

    Right now Volagi is running a 160/140 front/rear disk size, as compared to a 185 front for most MTBs. As you mentioned, disks allow any tire size, the caliper spread is no longer an issue, and of course there is no reason to open the calipers with the quick-release as none is needed (and thus no chance of forgetting to close the QR after installing the new wheel -- but that never happens, right?!?)

    I would expect the disk sizing on a road racing cycle to be somewhere in the 125 mm range for the front and 110 for the rear, with comparably sized calipers, hoses, and levers.

    The entire system, comprised of complete wheels, disks, hubs, hoses, calipers, and mounting hardware, would weigh no more than any current Dura-Ace or other high-end braking system but would be more...

    -Efficient
    -Durable
    -Effective

    ...which of course leads to better racing times = winning.
     
  17. danfoz

    danfoz Well-Known Member

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    A factor which is then rendered moot if everyone is using them.

    Also, there may be more to descending speed than just braking - Look at Sean Kelly dropping the field on the descent down the Poggio to catch up to and eventually beat Argentin in 92. Granted it's more technical and downhill speeds didn't reach Alpine extremes, and acceleration out of the corners was a big factor but fast descending is more a psychological skillset than any other. The argument that better braking would improve on that may be flawed as in today's world of even keels, some descenders are still faster than others.

    Many of the negative factors pointed out can be adressed by good technology i.e. weight, quick wheel changes, etc., except the power vs. traction point noted by cheetah - it's a legitimate issue and one for which this thread has no answers yet.
     
  18. cloudhead

    cloudhead New Member

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    what if the Thread question was re-worded to:

    "How soon will disk brakes be used on endurance racing cycles?" Bikes designed for Paris-Brest-Paris, California Triple Crown, etc.

    I looked at the about pages for Volagi and the three designers and they seem to know what they're doing, and it seems they designed this bike for the endurance races that they ride. But the debate so far has been over weather they are more mechanically efficient, lighter, etc. But I haven't seen much in regards to the rider that is burned out and in that alternate state of mind, after being up riding competitively all night long and napping on checkpoint floors. Would disc brakes serve a better purpose than sidepulls at this point?
     
  19. doiturself

    doiturself Member

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    I was discussing this with a buddy of mine who was a pro downhill mtb racer and he pointed out that with a top-flight disk system (which he had on his bikes), arm pump was greatly reduced or eliminated altogether. So yes, of course, physical effort decreases, physical problems for the rider are mitigated, and performance is increased all in one fell swoop using better technology. That is why the point is not moot; yes, if the rules were the same as in 1950, all riders would be on a level playing field but of course that is not the way sports work.

    There was a time when no one thought it possible for a man to run a mile in less than four minutes.

    These systems will simply increase what a rider can do overall; their suitability for descents is well-known in MTB and now Cyclocross circles. Bring them into road bike racing and the times for completion of various events will decrease accordingly, as will rider effort, and safety will be enhanced as well.

    I replaced a set of chuck wagon rubber pads on one of my road bikes today and got to thinking about what a small area of the pad actually contacts the rim and how much dirt and debris gets caught between the pad and rim because it's so close to the road surface. With a disk brake the entire pad is contacting the disk but this is rarely the case with rubber pads on rim brakes. Also the velocity is much higher at the rim so heat builds up much more quickly and a rubber pad is not particularly capable of handling high levels of heat, nor is a tubular tire. Disks, properly designed of high-tech alloys, can withstand tremendous amounts of heat (enough to sear and brand your skin) and still remain unwarped and effective. Shimano is using ceramics and all kinds of proprietary compounds in its pads and other disk system components as are Magura and other manufacturers, and far from this being a problem for the makers, they are assuredly pushing very hard to see their products on new model bicycles of every type. They are in fact the engine driving this change, not an impediment to it.

     
  20. doiturself

    doiturself Member

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    I just got another tidbit from Volagi.

    Their high-end E7 wheelset for disks weighs the same as a Dura-Ace setup for rim brakes. We are looking at a bicycle here with a weight of around 16 pounds in their high-end model with the wheelset upgrade. Pretty darn light.
     
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