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  1. #26
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    Quote Originally Posted by spdntrxi View Post
    I was on my Enve's during the Levi's Gran Fondo.. the issue was not me so much but all the traffic. I actually stopped for a few minutes and let it clear out and passed them all again on the incline...obviously safer. I got caught behind a wreck that closed down the road for like nearly an hour.. so that pretty much guaranteed a larger then normal group on one of the nastier descents. = no fun.
    Did your wheels melt or tubes pop? I ran Reynolds DV3Ks on Levi's a couple years ago without issue. That being said I don't drag my brakes constantly.

  2. #27
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    Quote Originally Posted by redondoaveb View Post
    If the outside of the aluminum brake track (which is only a couple of mm's thick) is too hot to touch then I've got to believe the inside of this this piece of aluminum is just as hot on a descent. How can the inside be getting cooled and the outside is too hot to touch. I believe the outside would get cooled first since it's exposed to the air.
    Yes, they alloy would be hot. That's the advantage. The alloy absorbs the heat instead of sending it directly to the tube.

    Trying to dispute the science of this is just a red herring anyway. No rational person would argue that alloy and carbon rims react the same to heavy braking or that the potential for blowing a tire due to heat is the same.

  3. #28
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    Quote Originally Posted by deviousalex View Post
    Did your wheels melt or tubes pop? I ran Reynolds DV3Ks on Levi's a couple years ago without issue. That being said I don't drag my brakes constantly.
    neither.. they just got pretty hot. I did see a lot of people tending to flats in that area with what looked like older Enve's ( I'm on the 3.4s) and other mfg. It was also very hot last year..nearly 100 in places.

  4. #29
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    A lot of times if you reach down and touch your brake track after a long descent it will feel pretty hot. But think about temperatures for a bit.

    Most of the higher temperature rated resins in wheels nowadays is rated to hit between 170 and 200 degrees Celsius. 200 degrees Celsius is twice the temperature to boil water. Next time you are boiling water think about how long you can put your finger inside that water. A second or two at the very most. Hell, I know when I am cooking chicken and get the inside to 165 F (just under 74 degrees C), I can only keep my finger there for a few seconds. So when you can hold your fingers on your brake track for a couple seconds and realize it's hot, it's probably nowhere near the temperature required to melt the resins.

    Granted, the rim does start to cool fairly quickly when you come to a stop. So, say it was at 74 degrees Celsius by the time you grabbed the rim. It could have been hotter than that during the braking. I actually just bought an IR thermometer that I am figuring out how to attach to my fork and point it at the rim. I want to see what kind of temperatures we are hitting in real world conditions while riding the brakes.
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  5. #30
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    Quote Originally Posted by coachboyd View Post
    A lot of times if you reach down and touch your brake track after a long descent it will feel pretty hot. But think about temperatures for a bit.

    Most of the higher temperature rated resins in wheels nowadays is rated to hit between 170 and 200 degrees Celsius. 200 degrees Celsius is twice the temperature to boil water. Next time you are boiling water think about how long you can put your finger inside that water. A second or two at the very most. Hell, I know when I am cooking chicken and get the inside to 165 F (just under 74 degrees C), I can only keep my finger there for a few seconds. So when you can hold your fingers on your brake track for a couple seconds and realize it's hot, it's probably nowhere near the temperature required to melt the resins.Granted, the rim does start to cool fairly quickly when you come to a stop. So, say it was at 74 degrees Celsius by the time you grabbed the rim. It could have been hotter than that during the braking. I actually just bought an IR thermometer that I am figuring out how to attach to my fork and point it at the rim. I want to see what kind of temperatures we are hitting in real world conditions while riding the brakes.
    Does 'melting the resin' really have anything to do with this? I was under the impression that delamination and/or blowing the tire of the rim is the concern here.
    So while resins may be rated to xxxx degrees before they actually melt does that matter if the tire's going to be blown off well before they get to that temp?

  6. #31
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    On some rims resin can melt. Most older gen resins worked until somewhat over 200f. There are many rims out there for which this is still the case. When we did our testing last summer, where we went down a bunch of hills and measured heat (similar to Boyd's plan) we regularly saw temps over 200* f. So a lot of older rims and many current rims that haven't yet gone to new gen resins would have failed in that testing. And that testing was hard, but not beyond what people do.

    In rims using new gen resins, the fuse has moved - the rims can take nearly 2x that heat but maybe tires can't, both from heat and pressure. Maybe the tire lasts but the resin loses integrity. But this all happens at WAY HOTTER temps than what th old resins could take. 180*f is generally the point of 'too hot to hold.' Now double that and you're what good new rims can take. 220 pounds of bike and rider with good pads and good rims, braking as badly as possible down a steep slope still leaves a huge margin of safety to that point.

    The other thing about well-designed newer rims is that they put a bit more mass on the brake tracks. This works on the same principle as a big pot of water taking a longer time to boil than a smaller volume of water. I always cringe when people are excited about improbably light carbon clinchers.

    No rim, no brake system, no nothing is failure proof. Good practices are still valid. Use good technique and make good purchase and use decisions. If that minivan won't let you pass no matter what down Switchback Mountain Road, let it get a minute or two head start. Stuff like that.

    And yes, pads make a huge difference. Yellows are awful

  7. #32
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    Carbon clincher being safe for descend on hills or mountains...

    I haven't ridden Levi's, but have ridden all the roads out there. I blew a tube once when my plastic rim strips melted and blew through a spoke hole in the aluminum rim. Don't use plastic rim strips.

  8. #33
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    Reading this thread about carbon rims, braking characteristics, resins, temps, etc.,makes me want to ask two questions (and if I am hijacking this thread, plz forgive me, as it's just I'm not sure whether to start another thread given that these questions might be sort of related to what's being discussed here);

    1) question 1: What is the way forward for carbon rim manufacturers with regards to braking performance? I'm no materials scientist and/or metallurgist, but I do read quite a bit of technical journals. From those, I am always wondering why carbon wheel makers are not experimenting with carbon composiites in the rim area. Is it out of their reach at the moment? Too technical?? I ask this because it appears this tinkering/experimenting in this area is quite common for more than a decade now for places like NASA and the ESA. Doesn't stuff usually trickly down by now, especially in out hyper-adoptive "always new" culture? NASA ansd ESA (among others) have been experimenting successfully with carbon composite materials, in what appears, from reseach articles, experimenting with aluminum and/or various borides mixed with carbon. they seem to do this without any compromises to structure integrity and/or strength, and you read about how the material withstands a factor or two more high temps before things start happening to the carbon structure/integrity. Wouldn't carbon wheel manufacturers be huge benficiaries of this sort of thing?? (ok, I am nearly over my knackered brain right now trying to write this... ;-o )

    2) 2nd question: do any of you believe that carbon rims, for the cycling industry, are NOT the long term way forward in terms of materials for wheels? I would imagine that the vast majority of cyclists in the world are still mainly on alu rims, a decades-old proven technology. But, that said, even at local rides, or races, or just small group get togethers, you see quite a surprising range of individuals who have carbon rim wheels. And, interestingly, if you ask them about, for example, the braking performance of their wheelsets, and which pads are being used, some of them actually stare at you sort of blank-faced. I think they honestly don't know, mumble something that makes no sense, and then turn away-----which is sort of disconcerting to me (disclaimer: I own no carbon wheels as of yet, as I am happy with and enjoy the personal success I have with alu wheels, and this is no matter when I am climbing something like the Altamont on Paris Mtn (in S.C.) during the summers when I am back in the States, or if I am here at home in Europe for the rest of the year riding either Flanders/N. France roads and/or heading down for weekend jaunts to ride the alps). I'm just trying to say that carbon does not present to me an actual advantage, at the moment, over anything aluminum currently offers, no matter the terrain. Still, one day, I imagine as carbon prices drop, I'll have to consider them, even if it is just for the strength they provide in rim depth vs comparable alu deep rims. I just hope stuff like this worrying about braking heat generated, blowing tubes/tires, melting rim strips (I'd neve heard that one before), or what and which pads (black vs yellow vs whatever) are being used, etc., etc, are all solved by then ;-)


    Again, excuse if I am off-base with this post in this thread.

  9. #34
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    Quote Originally Posted by looigi View Post
    Only if it defies the laws of physics. Heat is equal to the kinetic and potential energy being dissipated, nothing else. Resultant temperature is almost entirely dependent on the thermal properties of the rim material and its shape. For example, aluminum has a higher specific heat and is much more thermally conductive than CF so peak temperatures will be lower.
    The black pads have to generate the same amount of heat according to the laws of physics, but they don't have to hold it for any particular length of time. They can be much better at dissipating the heat generated, thus they don't heat the rims at much. Right? This is why different manufacturers use different pad formulations and why most have gone away from the yellow pads. And why SS has come out w/ the black prince pads...right?
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  10. #35
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    This thread just screams for carbon discs.
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  11. #36
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    Quote Originally Posted by Jay Strongbow View Post
    Yes, they alloy would be hot. That's the advantage. The alloy absorbs the heat instead of sending it directly to the tube.

    Trying to dispute the science of this is just a red herring anyway. No rational person would argue that alloy and carbon rims react the same to heavy braking or that the potential for blowing a tire due to heat is the same.
    So the aluminum gets too hot to the touch on the outside and obviously is just as hot on the inside but it doesn't transfer any of that heat to the tube. Is there some kind of magical barrier between the tube and rim to keep the heat off the tube?

    I'm just giving my results of what I found when I did the test. I've put over 15,000 miles on my carbon clinchers (almost 10,000 last year alone) and probably a third of that was climbing some of the toughest climbs in So. Cal. (yes, we have some HC and Cat 1 climbs here) and have never had any issues.

    Not disputing the science because I don't know the science. Just giving real world results. Can you do the same?
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  12. #37
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    Quote Originally Posted by skinewmexico View Post
    This thread just screams for carbon discs.

    Funny you should say that. My full intention upon getting the Sora Disc SL4 Roubaix was [after pulling the Sora in favor of a 7800 Group [second day] which came off my Strong to make it a SS] was use my 29er wheels until I shopped all the nice carbon rims and hubs, thinking no brake interface to the rim, perfect.

    Except it became clear it was already stiffer and rode stouter than expected by a margin and going further in that direction with 38-50mm rim was out. Wound up using Pacenti SL25s.
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  13. #38
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    Quote Originally Posted by redondoaveb View Post
    So the aluminum gets too hot to the touch on the outside and obviously is just as hot on the inside but it doesn't transfer any of that heat to the tube.
    No one has said none of the heat gets transferred to the tube with alloy. Just that more gets absorbed on the way there.


    Not sure why you'd say "obviously is just as hot on the inside". Heat changes as it leaves it's source and passes though something. Nothing obvious about that at all.
    Last edited by Jay Strongbow; 02-10-2015 at 09:51 AM.

  14. #39
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    Quote Originally Posted by Jay Strongbow View Post
    No one has said none of the heat gets transferred to the tube with alloy. Just that more gets absorbed on the way there.


    Not sure why you'd say "obviously is just as hot on the inside". Heat changes as it leaves it's source and passes though something. Nothing obvious about that at all.
    I could give an example. I have an aluminum pan that I use when bbq'ing. When I take something off the bbq and put it in the pan, the bottom of the pan immediately becomes too hot to touch. The pan isn't much thinner than an aluminum brake track. I (assume) the inside of a brake track is getting hot in the same way. That's my science

    That reminds me, I think I'll bbq tonight. Steak, yum!
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  15. #40
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    Carbon clincher being safe for descend on hills or mountains...

    Quote Originally Posted by skinewmexico View Post
    This thread just screams for carbon discs.
    Someone already tried carbon rotors. They didn't work too well. That's probably not what you meant though. Brifters don't work with hydraulic brakes and mechanical disc brakes are heavier and don't stop as well as hydraulics. Plus disc brakes are heavier than caliper brakes. They are also a maintenance headache.
    Last edited by mfdemicco; 02-10-2015 at 11:16 AM.

  16. #41
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    Quote Originally Posted by mfdemicco View Post
    Someone already tried carbon rotors. They didn't work too well. That's probably not what you meant though. Brifters don't work with hydraulic brakes and mechanical disc brakes are heavier and don't stop as well as hydraulics. Plus disc brakes are heavier than caliper brakes. They are also a maintenance headache.
    What do you mean by this? And they're called 'shifters'. Both SRAM & Shimano make shifters that work hydro brakes.
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  17. #42
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    Carbon clincher being safe for descend on hills or mountains...

    Quote Originally Posted by cxwrench View Post
    What do you mean by this? And they're called 'shifters'. Both SRAM & Shimano make shifters that work hydro brakes.
    The late Sheldon Brown used to call these integrated brake and shift levers "brifters."

    Didn't know this. I stand corrected. How much weight do you think disk brakes would add, assuming the frame and fork weight would increase too?

    Mavic seems to have solved the heat and braking problems.
    Last edited by mfdemicco; 02-11-2015 at 04:58 PM.

  18. #43
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    Quote Originally Posted by mfdemicco View Post
    Didn't know this. I stand corrected. How much weight do you think disk brakes would add, assuming the frame and fork weight would increase too?

    Mavic seems to have solved the heat and braking problems.
    Mavic hasn't solved anything...

    Heat? Really? Free hub engineering? No. Spoke material? Don't make me laugh. Aerodynamics? They completely ignore this w/ the except of the track wheels.
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  19. #44
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    Carbon clincher being safe for descend on hills or mountains...

    Quote Originally Posted by cxwrench View Post
    Mavic hasn't solved anything...

    Heat? Really? Free hub engineering? No. Spoke material? Don't make me laugh. Aerodynamics? They completely ignore this w/ the except of the track wheels.
    How does using an aluminum liner and high temperature epoxy not solve the heat problem, plus special surface treatment to improve braking not address this issue?

    http://www.bikemag.com/pavedmag/mavi...cher-wheelset/
    Last edited by mfdemicco; 02-11-2015 at 11:57 AM.

  20. #45
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    Quote Originally Posted by mfdemicco View Post
    How does using an aluminum liner and high temperature epoxy not solve the heat problem, plus special surface treatment to improve braking not address this issue?

    Mavic Rolls Out Its First Carbon Clincher Wheelset - BIKE Magazine
    Have you actually ridden these or are you basing your post solely off the information in bike magazine?
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  21. #46
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    Carbon clincher being safe for descend on hills or mountains...

    Quote Originally Posted by cxwrench View Post
    Have you actually ridden these or are you basing your post solely off the information in bike magazine?
    Basing it on the Mavic video contained in the article that shows reasonable engineering data. My point is not to endorse Mavic (or Shimano), but to point out that a hybrid rim design (alloy rim bed, carbon fiber cap) seems to address the heat and braking issues that full carbon fiber rims have; that's all. I have no data or experience on the reliability of these wheels.
    Last edited by mfdemicco; 02-11-2015 at 04:54 PM.

  22. #47
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    Quote Originally Posted by mfdemicco View Post
    Basing it on the Mavic video contained in the article that shows reasonable engineering data.
    Your mistake here is that assuming that any truthful engineering "data" comes out of a marketing video.

  23. #48
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    Quote Originally Posted by mfdemicco View Post
    Basing it on the Mavic video contained in the article that shows reasonable engineering data. My point is not to endorse Mavic (or Shimano), but to point out that a hybrid rim design (alloy rim bed, carbon fiber cap) seems to address the heat and braking issues that full carbon fiber rims have; that's all. I have no data or experience on the reliability of these wheels.
    A buddy of mine was riding Levi's Fondo and delaminated his ca. 2012 C24 carbon clinchers with the aluminum brake track. Clearly a lot of rider error involved but....

  24. #49
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    Quote Originally Posted by mimason View Post
    A buddy of mine was riding Levi's Fondo and delaminated his ca. 2012 C24 carbon clinchers with the aluminum brake track. Clearly a lot of rider error involved but....
    I would love to see a picture.
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  25. #50
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    The melting temperature of 6061 aluminum is 1090 degrees Fahrenheit. It would be pretty hard to reach those kinds of temperatures by braking alone, unless you are descending inside a volcano.
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