Carbon seat posts strong enough for racks?

Discussion in 'Cycling Equipment' started by Maury Robertson, Sep 12, 2007.

  1. Maury Robertson

    Maury Robertson New Member

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    I'm wondering if I can use one of those bike racks that clip onto the seat post with a carbon fiber post. Will it crush it? How tough are they?
     
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  2. gclark8

    gclark8 New Member

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    Check in your owner's manual, i'm sure it says NO! :eek:
     
  3. Maury Robertson

    Maury Robertson New Member

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    Thanks, George. I was afraid of that. Anyone have any brilliant ideas for how to get some bags attached to a carbon road bike? I use a backpack but I hate how it makes me so sweaty.
     
  4. mongooseboy

    mongooseboy New Member

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    carbon bikes are for racing....not pack mules.... probably the most you should think about putting on it would be an under seat bag/handlebar bag.

    maybe an aluminum or steel touring bike is more what you need? something designed to carry bags? :) just a thought (no hard feelings :))
     
  5. Maury Robertson

    Maury Robertson New Member

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    Thanks! I'm starting to get it. But it's so much fun to race to work! I appreciate your help.
     
  6. mongooseboy

    mongooseboy New Member

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    you can race to work on a nicely crafted Ti or cro-moly frame too...Ti doesnt rust, isnt as fragile as carbon, cost as much, supposed to have the ride of steel with stiffness of carbon (probably approximate) of course carbon can be made more aerodynamic and when your racing in the major tours, that matters. for the rest of us i think aerodynamics are the least of our worries (my bike glies through the wind, but i slow it down)

    Some day i might own a Ti or cro-moly custom frame. depending on where i live when i have that kind of money, it might be a mountain bike though :)
     
  7. JTE83

    JTE83 Member

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    You can always try it and see if it breaks your seatpost. But aren't seatpost designed to be crushed for clamping?
     
  8. Soderskungen

    Soderskungen New Member

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    Did a ride from Lyon to Cannes over 4 days a couple of years ago. My companion had a Campag Record carbon post with one of these attached to it..

    http://www.klickfix.com/matchpacke.htm

    No problems at all, and it was packed to capacity. He did remove it before we climbed Mont Ventoux though...

    They also do some nice rucksacks which fit to the same bracket..

    http://www.klickfix.com/rucksacke.htm

    I recommend filing the attachment bolt a little shorter as it can mark the seat post a little, which you probably wouldn't want on a carbon post. Either that a wrap a little cloth around the post under the clamp, which is what my mate did.
     
  9. unicos

    unicos New Member

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    It should be fine. I think you would break the rack before you break the seat post. The larger the contact patch on the seat post the better. If the seat post were to break it would be at the frame clamp point from the combined weight of the rider and the rack acting on it. Aluminum would break too.
     
  10. Maury Robertson

    Maury Robertson New Member

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    Thanks for all your input. I'm going to give it a try. If it cracks and I fall off onto my head I'll let you know. :D
     
  11. threaded

    threaded New Member

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    An awful lot of stuff out there sold as carbon, is really aluminium tube wrapped with a coating that looks like carbon weave. If its one of those then you'll be fine. Marketeers call it a carbon composite or some such. :rolleyes:

    If it really is carbon, then you risk crushing the tube and you'll most certainly find out before you get too far from home. The marketing will say it's pure carbon or some such.
     
  12. John M

    John M New Member

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    Take a look at these Tubus racks (scroll down the Peter white page to the Luna or Fly models and the skewer adapter). Expensive, but if you can afford full carbon, what is a little extra for a stylish rack that doesn't touch the frame/seatpost. The second link is to the Tubus manufacturer

    http://www.peterwhitecycles.com/tubus_racks.asp

    http://www.ortliebusa.com/cartgenie/prodList.asp?scat=16
     
  13. Z06C5R

    Z06C5R New Member

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    CF is supposed to be much stronger than steel, so unless it's only made of like 1 or 1 layers, it should be pretty strong. However, strengh has a lot to do with how it's laid up, and I can't speak definitivly here because I don't own a CF seat post, but I'd think it would be laid to take a mostly vertical load. Therefore, something pulling horizintally on it, like a rack, would probably put un-natural stress loads on it.
     
  14. Maury Robertson

    Maury Robertson New Member

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    What makes me want to try it is the fact that I can't find anything in my manual (I have a Specialized Roubaix) or on the Topeak site (the seat post rack I'm going to try) or any other rack site that warns me not to use it on a carbon fiber post. Obviously, I need to be careful about ratcheting down too tight but it seems like if it's that weak someone would say something.

    By the way, thanks for the Tubus link. Very interesting.
     
  15. dhk2

    dhk2 Active Member

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    Believe you'll be fine as long as the rack's clamp has no sharp edges which could notch into the CF post. (If you find any, just take them off with fine file.)
     
  16. artemidorus

    artemidorus New Member

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    I wouldn't do it. Every time I crash, the only thing that breaks rather than bends is CF.
    How would like to be sitting, suddenly, on the jagged shards of your seatpost on a bumpy descent?
    Simplest solution is to get an alloy post to use when you want to pack gear. Some alloy seatposts are dirt cheap. Get a long one so you'll spread the load over a large segment of the seattube. You could leave it permanently rigged with your rack and a second seat.
     
  17. Maury Robertson

    Maury Robertson New Member

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    All the different opinions are really interesting! So can anyone give me an example of someone who broke a carbon fiber seat post this way? Maybe I'll be the first. I've ordered the rack so when it gets here I'll be trying it. I road bike, so hopefully there won't be a lot of wild crashes. And I'll keep the load very light. Just a book or two and some clothes.
     
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