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  1. #1
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    C shaped tire cracks on low milage Maxxis CrossMark

    I have tubeless Maxxis Crossmarks on my bike that have been on it since I purchased it last year. I noticed this weekend that I have some cracks around the tire that are kind of C shaped. They wrap around the sidewall up into the tread about every foot or so. I have no idea how deep they are or what caused them.

    Is this a major concern for a tubless tire? What is the issue.

    Also, I have never put in any kind of sealant. The tires leak slowly but its not really a big deal to just check air pressure before a trip. Do I have to run a sealant in these tires? Should I be concerned about the cracks?

  2. #2
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    Could you post photos of the cracks?

    Also, what model tire is this? The UST CrossMark 29x2.1?
    Tire Design & Development Engineer. The opinions expressed in this forum are solely my own.

  3. #3
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    Quote Originally Posted by bholwell View Post
    Could you post photos of the cracks?

    Also, what model tire is this? The UST CrossMark 29x2.1?
    Yes, it is the UST 29x2.1. There are 2 places it is quite noticable. The other cracks are currently covered in dirt apparently as I can't see them clearly today.

    C shaped tire cracks on low milage Maxxis CrossMark-img_7058_1.jpg

    C shaped tire cracks on low milage Maxxis CrossMark-img_7059_1.jpg

    I will try to get the tires washed off tonight to see if I can get better pictures of the other cracks. As I recall they looked similar to image #1 but maybe not quite as deep.

  4. #4
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    Interesting. I haven't seen cracks like that before on a bicycle tire. It's almost as if the tire was subject to temperatures near the compound's glass transition temperature. I would recommend contacting the Maxxis Technology Center directly to get them warrantied.

    To answer your other questions, no, UST tires do not require sealant to retain air. And the cracks won't likely lead to catastrophic failure, but they will affect air retention, which could result in an unsafe riding condition.
    Tire Design & Development Engineer. The opinions expressed in this forum are solely my own.

  5. #5
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    Thanks for your reply. I will contact Maxxis to see what they say. Since I purchased the bike with the tire on it I don't have any reciepts for the tires. But who knows. They are obviously pretty new tires.

    I did ride the tires in the snow one day last winter. But it wasn't that cold out. The snow was melted by the end of the day. What kind of temps would be needed to reach the glass transition temp? Seems to me the tires would need to be heated up pretty high to harden. I've never ridden the bike in anything warmer than 85 degress +/- or colder than around 30+/-.

  6. #6
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    The Tg of natural rubber is around -100 deg. F, SSBR is around -65, and BR is around -90, and butyl is around -65. Tread compounds are usually a blend of two or more of these polymers (except for butyl).
    Tire Design & Development Engineer. The opinions expressed in this forum are solely my own.

  7. #7
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    Yeah, I think I'd remember if I had my bike in those temps!

    Thanks for the help. I sent Maxxis an email through there website, but I have not heard back from them.

  8. #8
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    Quote Originally Posted by Fargo1 View Post
    Yeah, I think I'd remember if I had my bike in those temps!

    Thanks for the help. I sent Maxxis an email through there website, but I have not heard back from them.
    I would call the Tech Center directly.

    Tel: (678) 376-4420
    Tel: (866) 509-7067
    Tire Design & Development Engineer. The opinions expressed in this forum are solely my own.

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