Disc road bikes - your opinion

Discussion in 'Road Cycling' started by AyeYo, May 2, 2014.

  1. swampy1970

    swampy1970 Well-Known Member

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    The biggest performance most drivers can make is upgrading the nut that holds on the wheel.
     


  2. Froze

    Froze Well-Known Member

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    I agree. In the long run disk brakes will be much more expensive than rim brakes. The world has used rim brakes for years, even the pros, even heavy ladened touring bikes, even tandems, and there was never any real issue with them, people weren't hurling off cliffs, or blowing stop signs and colliding with cars because they couldn't stop, but now the industry wants you think you can't stop without them. Nonsense. The industry wants you to use disk brakes because they know they will cost a lot more to maintain and thus more money in their pocket. If you will be riding in mud and snow then get disk otherwise don't bother.
     
  3. swampy1970

    swampy1970 Well-Known Member

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    I've seen tandems having braking issues under very hard use with combined cantilever and hub brakes. If you have two lads intent on booking it down a hill at a great rate of knots then you can make just canti's pretty much next to useless on a tandem fairly easily. Even with an added third brake you can still pop a tire off the rim. Disks eliminate that - especially a large diameter disk with an hydraulic system. Count the cost of abrasion on a carbon rim over many seasons of use - ie you need a new rim eventually - and all of a sudden you may find that running disks ain't anymore expensive. If you wanted a really fun "bad road" bike I couldn't imagine anything better that zipp303s with disk brakes - ace ride with monster stopping power and great modulation in all weather. The aero of the rims would be completely negated by the disk brake setup but the really wide rims would provide a nice ride with something like a 25 or 28mm tire.
     
  4. juanpelota

    juanpelota New Member

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    I think everyone is missing the point here, it has been said that the cycling industry is conditioned to accept imperfection and that is exactly what caliper brakes are.

    The technology is old, has poor performance and extremely non aero, yes I actually prefer the look of calipers and no you don't need to innovate but why the hell not.

    Caliper or even rim brakes cant keep up with advancements in wheel technology! This is why braking performance on high end wheels is absolutely terrible.

    The main reasons wheel rims are made from carbon are that weight, stiffness and aerodynamics can be optimised. This is then completely compromised by needing to use the rim surface for braking leaving you with a heavier less aero rim than could be produced.

    We should bare in mind that the total weight of bike is not the be all and end all in cycling. The specific weight of certain components are far more significant

    The rotational weight of a rim for example if one of the most significant factors for performance in climbing and by enabling a lighter rim with disc brakes, even at the cost of a few more grams, you would have a higher performance product added to which the braking performance on the following descent would be far improved.
     
  5. juanpelota

    juanpelota New Member

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    As for any concerns for heat dispersion, have you never seen a blow out from a rim getting to hot, or tub glue melting and a tyre rolling because of the heat accumilation?

    Come on this is like arguing that computers should have never been invented because the abacus was all we ever needed!
     
  6. OldTimer79

    OldTimer79 New Member

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    Someone actually makes shifters that use batteries? Are you freaking kidding me?
     
  7. new_rider

    new_rider New Member

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    Common sense FTW. :)

    The level of hyperbole is getting insane. Disc brakes are to rim brakes what the computer is to an abacus?!? Some of you guys are getting really desperate. :)
     
  8. swampy1970

    swampy1970 Well-Known Member

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    Some of us "old" guys have braked from 180mph to very slow in a damn short space of time on good disk brakes on a 400lb motorcycle. Rim brakes would never ever provide that level of performance. The hyperbole is real - disk brakes beat the shit out of rim brakes. Period, end of story. All that is needed is for a common standard (disk size, caliper mounting location etc) to be set and let the real fun begin. Just don't expect this to be on bikes where aero is important though... Everywhere else - there's no contest.
     
  9. CAMPYBOB

    CAMPYBOB Well-Known Member

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    I descended several Alpine passes with a steel touring bike loaded with about 45-50 pounds of gear with cheap Weinmann 999 centerpulls and clinchers with no problems. I came off too many Rocky Mountain descents to recall while using sew-ups and never had a tire/glue issue. Ambient air temperatures during some of those Arizona blitzes off various climbs exceeded 100°.

    Quote by juanpelota:
    "As for any concerns for heat dispersion, have you never seen a blow out from a rim getting to hot, or tub glue melting and a tyre rolling because of the heat accumilation?"

    In 42 seasons of cycling I've never witnessed a clincher pop a bead from heat build-up. At least none that I can recall that caused anything significant enough to generate a memory of such an incident. The only sew-ups I've seen roll were in races and NOT due to a glue heating problem. Poor gluing, dried out glue, cornering on deflating tires, exceeding the grip of the glue...sure.

    One solution to heat and sew-ups was just to stop using glues that are so affected by heat and using shellac. There were several base tapes that acted as insulators to prevent heat transfer into the tire. I haven't seen these in decades though.

    Several studies are available on the net showing caliper brakes on long descents only cause a tire pressure increase of about 10-15 PSI IIRC (1 PSI increase for every 10° F temp rise...again, going from memory) and this is normally not enough to cause deflation issues. Heat buildup may cause the rubber in the clinch to get more slippery and the bead to come un-hooked. As noted, the primary type of bike that suffers this failure most often is the tandem.

    That said, even disregarding the heat issue, the hydraulic disc (or even a good mechanical disc) is going to offer superior braking properties when the descents are long and require repeated applications of the brakes. They will also excel in wet conditions.

    If I were building a racing tandem today...even for flat land racing...there is no way I would go without a pair of disc brakes as the primary braking system. Beef up the fork and wheels a bit more more than tandem standards and let 'er rip.

    So far in this year's Giro I've seen zero tires blow off or rolled while descending.

    I'll see if I can dig up one of those rim brake heat studies.
     
  10. AyeYo

    AyeYo Member

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    That's just part of the issue. I don't think anyone (even new_rider) is contesting the superior braking ability of properly sized disc brakes. The problem is focusing solely on that one aspect of superiority while ignoring the laundry list of drawbacks. Full size sport bike racing slicks would certianly corner better than 700x25 bicycle tires and a frame made out of rubber and Jello would certainly ride smoother than one made of out carbon, but those single aspects of superiority aren't reason enough to start adopting those items.

    Likewise, the repeated tangets about tandem bikes and cross bikes are missing the point of the thread. This is about disc brakes on road bikes, racing and touring oriented road bikes in particular. I see this as a pointless push aimed at putting more money in manufacturer's pockets and not improving bike performance. Disc brakes make sense on muddy mountain bikes where their cons are outweighted by their pros, speeds are slower so heat is lower, and weight is less of an issue so rotors can be larger - likewise with CX bikes that race in messy conditions. Maybe they even make sense on big tandems if you use rotors off a truck. However, in order to make a road disc with the thermal capacity to not boil fluid on long, fast downhills, you're introducing a large set of compromises to fix stopping power and modulation problems that don't even exist with milled aluminum braking surfaces. This makes no sense to me.

    The only angle I can see this making sense from is to fix the poor braking of full carbon rims. However, as I previously mentioned, you're now shelling out a ton of money on aerodynamic rims that can't stop, so you have to shell out a half ton more money on disc brakes to help them stop... and those discs totally negate (and likely even drop you in the negative) the aero benefit of the wheels you spent so much money on. Now you're back to square one and the only thing you've accomplished is lightening your wallet... which is exactly what the component manufacturers want.
     
  11. CAMPYBOB

    CAMPYBOB Well-Known Member

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    http://www.johnforester.com/Articles/BicycleEng/safe_brakes_that_burn_up.htm
     
  12. swampy1970

    swampy1970 Well-Known Member

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    It's just like anything else - a lot of people want the latest stuff and it doesn't matter what it is or how much it is. Most guys that race would be just as well off on 9 speed as they are on 11 and spending a bit of time working on their flexibility to get better aero than spending thousands on fancy frames and wheels. For a fun fast training or touring bike it's a done deal - hydraulic disk brakes. For road racing at amateur level, I'd say disk brakes would be a good way to go. If you have to rely on that small difference in aero to get you from Cat 4 to Cat 3 then you're never getting past Cat 3 anyway. I can't believe the number of dunderheaded f**ktards that can't brake worth a damn in road races and the only reason I can attribute this too is carbon rims and the wrong brake blocks (listening to tribal wisdom rather than the instruction sheet) or riders are just brain dead lemmings. I never had a problem getting my front wheel out of my motorcycle - can't see why it would be an issue on a bicycle. If I ever decide to change a frame in future I'd be definitely giving disk brakes a look.
     
  13. AyeYo

    AyeYo Member

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    Basically confirms what I said about fixing issues that don't exist. You could throw a 200mm rotor on the bike and it's not going to have more heat dissipating and absorption ability than a 700c aluminum rim, especially these new wider, deeper rims. Talking about tiny disc brakes having better heat dissipation is lunacy.

    I have a 1000ft, ~12% average grade hill by me that I like to us for hill climb practice, I'm 175lbs. After decending that hill on a road bike at 25-30mph (can't go too fast because the road is in terrible condition), the rims and pads are barely above ambient temperature. After decending that hill on my hydro disc hybrid (something I'll never do again after actually researching disc brakes), the discs are so hot that they will vaporize drops of cold water dripped on them.
     
  14. new_rider

    new_rider New Member

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    Only someone as perpetually confused as you are would ever compare the brakes required on a FOUR HUNDRED POUND motorcycle versus the braking needs of a TWENTY POUND BICYCLE.


    Quote:
    Originally Posted by swampy1970 .

    Some of us "old" guys have braked from 180mph to very slow in a damn short space of time on good disk brakes on a 400lb motorcycle. Rim brakes would never ever provide that level of performance.

    The hyperbole is real - disk brakes beat the shit out of rim brakes. Period, end of story. All that is needed is for a common standard (disk size, caliper mounting location etc) to be set and let the real fun begin.

    Just don't expect this to be on bikes where aero is important though... Everywhere else - there's no contest.
     
  15. new_rider

    new_rider New Member

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    Dual pivots and v brakes work very well on bicycles.

    The techno weenies will never admit this, as they have an axe to grind and their egos are heavily invested in new gadgetry. It's like trying to convince a crackhead that they can live without drugs. No rational debate is possible with those people. At some point, people are too far gone to recognize new =/= better. Better = better.
     
  16. OldTimer79

    OldTimer79 New Member

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    I will repeat my earlier comment. When comparing the Trek 7.3 to the disk brake version, the 7.3 that I ended up buying stopped as well as the disk bike plus was lighter and those disk brakes were noisy!
     
  17. new_rider

    new_rider New Member

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    I was actually quite curious in a positive way about disc brakes 10 years ago. I've test ridden bikes with mechanical discs periodically over the years. I've been disappointed each time in the sense that I have not perceived a bump up in either braking power or modulation. Perhaps this is due to poor bike setup; many test ride bikes aren't adjusted optimally. But I've never come close to being 'wow-ed' or even strongly impressed.

    I'm very happy with dual pivots and v brakes.
     
  18. swampy1970

    swampy1970 Well-Known Member

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    I'm not confused. As with other comments in this and other threads, you bring the fail.

    I've ridden both. I was a 1st Cat road guy back in the day, have ridden very fast motorcycles and raced, and won at regional level, cars. The traction circle is a common feature amongst all those. You have a certain level of grip available - go beyond that and you're on a fun trip across asphalt. It doesn't matter what the vehicle is - the principles are the same, the needs are the same. Exceed the limits of grip on a two wheel vehicle, the odds of being on your ass at speed increase exponentially.

    Riding a sports bike (motorcycle) and a road racing bicycle downhill are very similar. The only thing lacking is the ability to accelerate fairly hard whilst leaning over on a bicycle. The concepts of braking points, laying off the brakes mid corner and "tip and lean" are all the same. Having "more brake" with good modulation is always a good thing. If on a long fairly steep descent, with a good number of corners, you're not getting the rims hot enough to the point where they're too hot too touch then you need to stop descending like a pussy, harden the f**k up and go faster. At those speeds you can grab more anchor and not worry too much about locking up the brakes on a bike with alloy braking surfaces. Even with very clean rims, clean pads and Dura Ace 7900 brakes, there's still room for more stopping power.

    If you're talking about grandma Jane riding her 86 year old bike to the shops - as I suspect you are - then any brake will do. Fred Flintstone has a pair of high friction soled shoes for grandma.... Personally, I'm talking about either racing or fun rides in the mountains - something like the Alta Alpina Challenge where you're hitting ~60mph after 14 hours and 180 miles in the high mountains with another 20 to go. Situations where you really appreciate a damn good set of brakes, especially when you're tired and your hands even more so.

    Disks are cheap and very effective. I'd rather pay $50 for a replacement top of the line XTR quality disk than have to replace a rim... I'm not sure I could even buy a rim for $50.
     
  19. swampy1970

    swampy1970 Well-Known Member

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    No ego boost from me with regards to bikes. When I was a kid I wanted to be a Pro. I raced, I got to 1st Cat and that was it. Essentially, I had many good times but I ultimately failed. Now I ride for fun. Depending on the mood, I also drink copious amounts of beer.

    That's all that matters to you? So, you really don't care about discussing brakes or whatever topic you hijack with your "view from the armchair."
     
  20. jpr95

    jpr95 Active Member

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    Analysis fail.

    You have to look at bike PLUS rider. So, yeah, a motorcycle and its rider will need to stop 600 lbs. A bike and its rider come in at about 200 lbs. That's a factor of 3, not 20.

    What I'll stipulate is that a motorcycle needs better brakes due to the speeds. Kinetic energy is half of mass times velocity squared, so if you double the speed, you quadruple the amount of heat energy you need to dissipate in the braking system. But, stopping the above examples from 80MPH and 40MPH, respectively, results in needing 12 times the braking power (for the same stopping distance) for the motorcycle and rider over the bicycle and rider. Still not 20 times.
     
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