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  1. #51
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    Quote Originally Posted by coachboyd View Post
    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.
    Do you need to reach Al alloy melting temp to cause delamination of the C-fiber composite? At what temperatures do the resins used to build typical wheel composites begin to decompose?
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  2. #52
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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.
    I'm not seeing how this concept is any different from the Shimano C42, or HED Jet Express 5. Both of which have been around forever.
    Tis the season for all of us not hard enough to play to belittle those not hard enough to win. We are a funny lot. - dave @ November Bicycles

  3. #53
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    Carbon clincher being safe for descend on hills or mountains...

    Quote Originally Posted by skinewmexico View Post
    I'm not seeing how this concept is any different from the Shimano C42, or HED Jet Express 5. Both of which have been around forever.
    True, but the Mavic rim has a thin aluminum insert rather than a separate aluminum rim bonded to a carbon fiber cap. The braking surface is carbon fiber.

  4. #54
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    Quote Originally Posted by mfdemicco View Post
    True, but the Mavic rim has a thin aluminum insert rather than a separate aluminum rim bonded to a carbon fiber cap. The braking surface is carbon fiber.
    That's not a plus.....

  5. #55
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    Carbon clincher being safe for descend on hills or mountains...

    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 just picked up 2014 C24s...for Levi's . I didn't need to read that.
    PO is a liberal echo chamber.

  6. #56
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    Quote Originally Posted by spdntrxi View Post
    I just picked up 2014 C24s...for Levi's . I didn't need to read that.
    I wouldn't ride 16/20 spoked wheels on those roads. A friend of mine also had his C24s fail for Levi's but this was I think the 7800 version. The metal plate that's under each spoke just popped off or something, not quite sure.

  7. #57
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    Quote Originally Posted by spdntrxi View Post
    I just picked up 2014 C24s...for Levi's . I didn't need to read that.
    Then don't read this either.
    "When man invented the bicycle he reached the peak of his attainments."
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  8. #58
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    Quote Originally Posted by ibericb View Post
    C24s are an alloy braking surface.

  9. #59
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    Quote Originally Posted by deviousalex View Post
    C24s are an alloy braking surface.
    Yep. And where does the heat of braking go?
    "When man invented the bicycle he reached the peak of his attainments."
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  10. #60
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    "The sky is falling! The sky is falling!"

    Better to just be safe and take a cab on Levi's Grand Fondo.

  11. #61
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    Quote Originally Posted by ibericb View Post
    Yep. And where does the heat of braking go?

    How soon after the EPO dose?
    Quote Originally Posted by Robt57/Me!
    Everything you read that I post is just '1' guy's opinion, try to sort it all out best you can. ;) I will try to add value in my posts, if I miss the mark please let me know using a little decorum.

  12. #62
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    Quote Originally Posted by tvad View Post
    "The sky is falling! The sky is falling!"

    Better to just be safe and take a cab on Levi's Grand Fondo.
    I think the message should be if you ride steep descents with carbon rims, know what you're doing. I suspect many more have done it without problem than have experienced any kind of wheel damage. Those that had wheel damage in the past couple of years could probably be traced to rider braking technique. Al alloy is just more forgiving, or needs less attention than does carbon composite.
    "When man invented the bicycle he reached the peak of his attainments."
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  13. #63
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    Quote Originally Posted by tvad View Post
    "The sky is falling! The sky is falling!"

    Better to just be safe and take a cab on Levi's Grand Fondo.
    Two years ago I had Levi fly by getting motorpaced (literally by a motorcycle), does that count?

  14. #64
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    Carbon clincher being safe for descend on hills or mountains...

    I did it with enve 3.4 last year.. This year I can chose from C24s or Roval SLX
    PO is a liberal echo chamber.

  15. #65
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    Quote Originally Posted by ibericb View Post
    I think the message should be if you ride steep descents with carbon rims, know what you're doing. I suspect many more have done it without problem than have experienced any kind of wheel damage. Those that had wheel damage in the past couple of years could probably be traced to rider braking technique. Al alloy is just more forgiving, or needs less attention than does carbon composite.
    How about: Inexperienced Rider + Mountains = Alloy Rims.

    Definition of Inexperienced Rider: one who rides the brakes on descents.

    In defense of the riders, both inexperienced and experienced, these large organized rides are sometimes overbooked or clumped with riders, which makes descending at normal speeds nearly impossible...thus the necessity to ride the brakes.
    Last edited by tvad; 02-12-2015 at 03:00 PM.

  16. #66
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    Quote Originally Posted by tvad View Post
    How about: Inexperienced Rider + Mountains = Alloy Rims.

    Definition of Inexperienced Rider: one who rides the brakes on descents.

    In defense of the riders, both inexperienced and experienced, these large organized rides are sometimes overbooked or clumped with riders, which makes descending at normal speeds nearly impossible...thus the necessity to ride the brakes.
    Sounds about right.

    It's a recurring theme with carbon composites in general - they are wonderful materials, but they aren't very forgiving for the negligent or inattentive, or in this case the inexperienced.
    "When man invented the bicycle he reached the peak of his attainments."
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  17. #67
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    Quote Originally Posted by spdntrxi View Post
    I did it with enve 3.4 last year.. This year I can chose from C24s or Roval SLX
    Enve has done a lot of testing, including specifically brake track testing. They even released a video showing how they do the brake track testing. Pretty impressive machine.
    "When man invented the bicycle he reached the peak of his attainments."
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  18. #68
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    Quote Originally Posted by tvad View Post
    How about: Inexperienced Rider + Mountains = Alloy Rims.

    Definition of Inexperienced Rider: one who rides the brakes on descents.

    In defense of the riders, both inexperienced and experienced, these large organized rides are sometimes overbooked or clumped with riders, which makes descending at normal speeds nearly impossible...thus the necessity to ride the brakes.
    The latter was my case.. I'm nothing like I was when I was young but I can still go down those mountains... Levi's for me really sucked in that their was a rather bad accident before the famous bridge that required a lengthy road closure (for helicopters).. this caused a huge amount of traffic for the descent, which left me riding my brakes trying to avoid people... not to mention lots of volunteers trying to slow people down. In the end I wish I was on Al clinchers.

  19. #69
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    Quote Originally Posted by spdntrxi View Post
    The latter was my case.. I'm nothing like I was when I was young but I can still go down those mountains... Levi's for me really sucked in that their was a rather bad accident before the famous bridge that required a lengthy road closure (for helicopters).. this caused a huge amount of traffic for the descent, which left me riding my brakes trying to avoid people... not to mention lots of volunteers trying to slow people down.
    Good example of the point I was making, which is that on many of these big organized rides, it doesn't matter how experienced one might be riding down mountains at 40-50mph in 90 degree heat. When we're in groups of hundreds of riders and we're forced to ride the brakes constantly on our way down 9 mile descents, we're going to be heating up our rims and brake pads beyond our normal routines. In that scenario, "laying off the brakes" isn't possible, and it's probably wise to use alloy rims despite our belief that vast experience will allow us to minimize heat build-up on our bling-y carbon rims.

  20. #70
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    I found this video on you tube. Notice the temp gauge reaching 192 degrees at the rim. https://www.youtube.com/watch?v=ETQpEXfJy-4.......and this article gives real concern over tyre pressures at that temp. Carbon Wheel Technology and Testing. On this you tube video https://www.youtube.com/watch?v=M2aliE626vc one comment by a blooger Calvin writes that I will never pump my tyres to 160psi so no problems but tell the law of physics that then it comes to the conservation of energy. With physics in mind are these testers testing a 60 kg rider or and 85KG one when they are applying loads to the rim. It would also be an idea to categorise descents as they do ascents. Food for thought.

  21. #71
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    Quote Originally Posted by voss View Post
    ...one comment by a blooger Calvin writes...
    That's funny.

  22. #72
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    One thing that I think people may be neglecting is the phase-change enthalpy (the heat required to break down the inter-molecular bonds that hold a material in solid form) of the brake pad material. I believe that brake pads for carbon wheels are designed to melt/ablate to help dissipate the heat buildup. Different materials can have radically different phase-change enthalpies and therefore "absorb" or dissipate more heat than others in an application like this. This is one reason (the melting/ablation) that carbon brake pads don't last nearly as long as pads designed for aluminum rims. I assume this is at least partly what's behind the different rim temperature results since, when melting, a material doesn't start to heat up further until all of the material is melted; any additional heat input just goes to melting more material. Same reason why a pot of boiling water stays at 100C until all the water is boiled off, no matter how high you turn up the heat.

    As far as carbon rims and hills goes, as I've said elsewhere and as others have said here, carbons rims are used with success on descents of some of the steepest grades in the world. All it takes is experience/knowledge in proper braking (yes, grab-and-release does work, even on steep grades, you just grab/release faster/more often) and descending at speed.
    Well, you know, that's just, like, your opinion man. - The Dude

  23. #73
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    [QUOTE=OldChipper;4803982]One thing that I think people may be neglecting is the phase-change enthalpy (the heat required to break down the inter-molecular bonds that hold a material in solid form) of the brake pad material.]

    They are starting to make improvements. SwissStop Introduces Black Prince Carbon Rim Brake Pads, Yellow No Longer the Leader And at least now you do not have the issue of cleaning the yellow pad dust off the rims due to ablation. It would be interesting if they could make the pads slightly larger to incorporate some form of like copper conductive strands and intergrate/connect it with the aluminium rims brakes as some form of heat sink.If Nissan GTR are using nitrogen in their inner tubes for a more stable heat expansion when compared to air, it would not be a big stretch for us to do the same given we use co2 cannisters. In boiler plumbing systems they use mini expansion relief valve, Maybe a presta relief valve that release air when the pressure hits 160. Basalt braking surface have been a leap forward in reducing rim temps but given the heat dissipation properties of ceramic why not use more ceramic dust in the resin mix or a combination of both. The newer wider rims promote lower tyre pressure. But I fail to see any empirical data which justifies claims by manufacturers that they have the latest and greatest braking solution, campy 3 diamont braking surface for example.

    [/As far as carbon rims and hills goes, as I've said elsewhere and as others have said here, carbons rims are used with success on descents of some of the steepest grades in the world. All it takes is experience/knowledge in proper braking (yes, grab-and-release does work, even on steep grades, you just grab/release faster/more often) and descending at speed.]

    I have seen this argued on a number of cases, cadence braking makes sense to me but as for alternate braking, not sure how that helps one given that your reducing the effective braking surface by area 50% when scrubbing of a given amount of thermal energy, all things being equal. If you look at this video 12.5 mins in https://www.youtube.com/watch?v=HjWOl2aCWOk....not as if they don't brake at all!!
    Last edited by voss; 02-15-2015 at 10:44 PM.

  24. #74
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    The future of the smart wheel EB14: Lightweight Makes SmartWheels to Sense Pressure, Brake Track Temperature & More but once again crazy prices!

  25. #75
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    I do some alpine climbing and descending each summer. Wheels of choice are Campag Shamal Ultra 2-way fit, with tubeless tires. The only carbon clincer I'd consider would be the Enve 3.4, but they're twice the price and still need a tube. Interesting to learn about delamination issues with the Shimano C24 types.
    I like safety margins. I don't ride my brakes a lot. That said, So. Cal. canyons are steeper than French alps.
    They do anything just to win a salami in ridiculous races. I take my gear out of the car and put my bike together. Tourists and locals are watching from sidewalk cafes. Non-racers. The emptiness of those lives shocks me. It was the illest of times, it was the dopest of times. And we looked damn good. Actually the autobus broke down somewhere on the Mortirolo.

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