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  1. #1
    Senior Member Seattle Forrest's Avatar
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    Anyone in here ever have problems with the brakes heating up...?

    I'll probably ask in the road forum as well, but I thought I'd start here, because Cs & As tend to have a lot of inertia for the brakes to overcome. I know I'm not the only person in here who rides in the mountains, at least sometimes.

    The reason I ask is that I'll probably be getting a set of wheels in the next couple months, and I'd like to learn what I can before I decide which ones. Disc brakes aren't an option. I've heard horror stories about long descents, and it's never happened to me.

    If it's happened to you, what did it take?

    Don't believe everything you think.

  2. #2
    Gears? CliftonGK1's Avatar
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    I haven't encountered any long descents around here where I felt it necessary to ride the brakes. At the 7% grade for most of the pass roads I've been pretty comfortable with a 45 - 48mph downhill coast for 12 miles. (Think: SR-2 coming off Stevens Pass headed west.)

    Hard braking on shorter, steeper descents heats up the rims, I'm sure; but not to the extent that I've suffered problems. My daily commute has me hard braking on a 10% downhill grade from keeping up with 40mph traffic to making a 90-degree right at a light. No rim failures so far.
    "I feel like my world was classier before I found cyclocross."
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  3. #3
    Senior Member Mithrandir's Avatar
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    I imagine my rims heat up significantly sometimes, but I've never had a blowout, and I try to avoid descents that are either too curvy or end in stop signs/lights. Added to the fact that I haven't really done any descents that most cyclists would consider "large".

    Regardless, I attempt to alternate brake levers at regular intervals when I'm descending. No clue if I really need to do that but I figure it can't hurt. Even though the rear doesn't brake nearly as much as the front, it still helps.

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    Judging from the way I often fall behind on descents, I am more of a brake-rider than most people. I have never had a problem caused by hot rims even while descending on a bike with gear weighing 90 lbs. I will disengage the brakes from time to time to allow for cooling.

  5. #5
    Senior Member snowman40's Avatar
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    Quote Originally Posted by Mithrandir View Post
    I imagine my rims heat up significantly sometimes, but I've never had a blowout, and I try to avoid descents that are either too curvy or end in stop signs/lights. Added to the fact that I haven't really done any descents that most cyclists would consider "large".

    Regardless, I attempt to alternate brake levers at regular intervals when I'm descending. No clue if I really need to do that but I figure it can't hurt. Even though the rear doesn't brake nearly as much as the front, it still helps.
    Yes, that is what I do. No idea if I need to or not (probably not).
    Quote Originally Posted by snowman40
    If you must speed up to pass me, you don't deserve to pass me
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    farts are greatly appreciated as long as the other riders are talented and experienced. at the precise moment of release, a vacuum is formed. this is the optimal time for the rider behind you to get as aero as possible and "ride the brown rhino". his face should be within 2-3mm of the anus to receive maximum benefit (reduced drag...duh, its in a vacuum). i have hit speeds of over 53mph in such conditions.

  6. #6
    Senior Member Homeyba's Avatar
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    I had a tire blow off the rim many years ago coming down a 7 mile/6-11% winding descent. Luckily it happened at the very bottom of the grade and I felt the tire going bump, bump, bump so I stopped. As soon as I got off the bike and looked at it the tub blew up. I haven't had a problem since even on my tandem.
    It doesn't get harder, you just go slower.

  7. #7
    Senior Member Seattle Forrest's Avatar
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    Quote Originally Posted by Mithrandir View Post
    ... I try to avoid descents that are either too curvy ...
    Really? I go out of my way for them, seek curvy descents out. They're the main reason I climb hills!

    Quote Originally Posted by Mithrandir View Post
    Regardless, I attempt to alternate brake levers at regular intervals when I'm descending.
    I'll do this too, sometimes. The rear brake doesn't have that much power in a panic stop, but it's a good speed regulator, and can help slow you down.

    Quote Originally Posted by CliftonGK1 View Post
    I haven't encountered any long descents around here where I felt it necessary to ride the brakes. At the 7% grade for most of the pass roads I've been pretty comfortable with a 45 - 48mph downhill coast for 12 miles. (Think: SR-2 coming off Stevens Pass headed west.)

    Hard braking on shorter, steeper descents heats up the rims, I'm sure; but not to the extent that I've suffered problems. My daily commute has me hard braking on a 10% downhill grade from keeping up with 40mph traffic to making a 90-degree right at a light. No rim failures so far.
    When I did the ride to Steven's Pass, I came back down heading west, but it was on a pair of carbon Zipp wheels, which, apparently, have a lot of proprietary R&D for not overheating. I didn't have any trouble here, but it sounds like that isn't indicative of other wheels. ( Or that's probably just marketing? ) But I did Snoqualmie Pass and the North Cascades Highway on alloy clinchers, with no problems. I ride the brakes when I come down Dravus, which is at least half a mile at 19 %, because you never know when a car will cut you off from a side street. I ride West Seattle, Queen Anne, Cap, and Beacon Hills, and so on, on my metal wheels.

    I haven't had any issues with the rims getting too hot, although I've stopped and noticed they're warm. On the other hand, it didn't take that many miles to wear the braking surface down, partly because of road grime, but probably also in part because of the inertia thing. Is it fair to assume heat isn't something I need to do much worrying about, as I figure the wheel question out?
    Don't believe everything you think.

  8. #8
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    Quote Originally Posted by Seattle Forrest View Post
    ... but it was on a pair of carbon Zipp wheels, which, apparently, have a lot of proprietary R&D for not overheating. I didn't have any trouble here, but it sounds like that isn't indicative of other wheels. ( Or that's probably just marketing? )
    Zipp Carbon Clinchers(at least the older ones, not sure about the brand new ones) have a metal brake track and thus don't suffer the heat buildup to the same extent that full carbon clinchers do.

    The heat build up shouldn't be a problem on short descents, it only becomes an issue on longer descents if you're dragging/riding your brakes for an extended period of time.

  9. #9
    Fat Guy Rolling dcrowell's Avatar
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    I've never had a problem, but on a long descent in the mountains of NC I had to scrub some speed quickly due to an upcoming turn and something was a bit burnt-smelling for a few seconds.

    It was probably due to ten seconds of intense braking, not the occasional squeeze I was giving down the descent.
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  10. #10
    Banned. Mr. Beanz's Avatar
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    Never had a "problem" on the road bike. On long descents in 100 degree temps, I will stop half way down to feel the rims. Only one time the rims were real hot. I stopped took some pics letting them cool off. I was braking more than usual waiting for another rider.

    But the only time I thnk I ever had a heat induced blow out was on the mtb. Another 100+ day, descending on 10%+ dirt grades in the heat I flatted while seriously riding the brakes. Never did find out what flatted the wheels so I assume the heat and the rims were steaming hot.

  11. #11
    Senior Member Seattle Forrest's Avatar
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    Thanks, folks!

    It sounds like this shouldn't be a factor in my deciding which wheels are right for me...
    Don't believe everything you think.

  12. #12
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    Back when I rode sewups I had the rim heat-up. I worked at the top of a small mountain, cat 3 climb. The beginning of the ride home was all down hill with a 4 way stop at the bottom. Enough traffic that you did have to stop. I was riding on the flat after the descent. Looked down and my tire looked like the tread was white. I figured that I ran over some paint. Stopped. The tire had rolled around so that the tape was showing and the tread was on the rim. Probably more a bad glue job than heat softening the glue but the rim was pretty hot. Went to clinchers.

    Bill

  13. #13
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    My/our problems have been minor. We're a (combined) 470-pound tandem team, and on a few descents I've pushed the rear disc brake rather hard (Krueger Canyon, for anyone familiar with the northeast outskirts of San Antonio). Afterward, I get chatter (both in feel and in sound) from the brake. Looking at the rotor closely, I can see some discoloration on the metal leading out to the rotor. I've heard some worse stories about the Avid calipers, so one of these days I'll stock up on the recommended spare parts so I'm covered.

  14. #14
    Nigel nfmisso's Avatar
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    Standard practice for tandems doing serious downhills is to have a drum drag brake in addition to the front and rear rim brakes. The drag brake is set to a constant friction, and the rim brakes are used to modulate the speed.

    With regards best way to minimize heat build in your rims - which can result in a blow out - brake hard for very short periods and drop your speed by a large amount, then coast for a long period, letting your speed build up and your rims and tires cool off. Riding the brakes with moderate force is the worst thing for heating rims up.
    Nigel
    Mechanical Design Engineer

  15. #15
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    Quote Originally Posted by nfmisso View Post
    Standard practice for tandems doing serious downhills is
    Standard practice for tandems doing serious downhills was what you wrote, but disc brakes have matured fairly well, and get the job done.

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