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  1. #1
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    Rack on a Carbon bike

    Was hoping someone would take a look at my rigging job here and tell me this will do any damage. I'm wanting to put a trunk on my bike, but it's simply a road bike with no braze on's. It does have eyelets on the drop outs so I had to rig how it hooked up at the front. I used a piece of rubber hose that is about 1/8 inch think around the carbon seatpost and then a piece of preferated metal strapping to connect to the rack. I'm mainly concerned as I've heard from manufacturers that a clamp on rack is dangerous with a carbon seatpost, but I've heard that on this type of rack there isn't much weight on the front part that connects to the seat stays. Here's a picture.

    Thanks!
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    I am sure that will be stucturally satisfactory, but I think it would be neater if you attached the straps by the seatpost binder bolt. That may require a longer bolt, some washers and a nyloc stiffnut.

  3. #3
    Senior Member godspiral's Avatar
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    Does the rack seem sturdy when you shake it front to back? Doesn't really look like it would be.

  4. #4
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    Yeah, actually it's very sturdy. I tried it with a few book in it and it didn't move at all when I shook it. Road it a little and everything seemed fine.

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    Darn, you sent me 'treking' 3 stories down to my basement to check out my Trek Madone 5.2SL. No eyelets and the seat tube on my rather short frame is almost non-existent above the top tube junction.

    I am a "ten essentials" guy from hiking/backpacking and miss my rear rack/trunk even if other would make fun of it.

    I've wondered if I replaced the carbon seatpost with alloy/steel if I could use a cantilevered rack but suspect that the seat tube is not designed to take the cantilevered force hanging off the rear. Although, how bad could it be compared with my 165 lbs bouncing on the seat. Your setup distributes the weight/forces better, I'm sure.

  6. #6
    Banned. Bekologist's Avatar
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    the best rack for a full carbon bike is a TREK 520.

  7. #7
    bike rider jimmythefly's Avatar
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    Yeah, most recommend a non-carbon post if you're going to use a seatpost-clamp on rack. I can get the ten essentials in my jersey pockets and underseat bag. If that's not enough for you, Jandd also makes a massive underseat bag. (originally for full-susp. mtn bikers before hydration packs got successful). Of course, there are also tons of time-tested underseat-bags by brooks, berthound, etc.

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    why do people ever rock trunk bags? they are ugly, require a rack, which is heavy, and expensive. why not big english saddle bags? they hold more, potentially, dont require any frame to rack mounting, and arnt nylon so they dont degrade in the sun, nor when they rip do they continue ripping. just wondering.

  9. #9
    Senior Member Fredmertz51's Avatar
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    I use a seatpost reflector bracket. No chance of damaging the frame.

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    Quote Originally Posted by Fredmertz51
    I use a seatpost reflector bracket. No chance of damaging the frame.
    What in the world is this? Have a picture or link?

  11. #11
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    Quote Originally Posted by ridelugs
    why do people ever rock trunk bags? they are ugly, require a rack, which is heavy, and expensive. why not big english saddle bags? they hold more, potentially, dont require any frame to rack mounting, and arnt nylon so they dont degrade in the sun, nor when they rip do they continue ripping. just wondering.
    I didn't like the looks of them myself. I think the trunk looks more modern when on a modern bike. The saddle bags look really cool on bikes such as the Rivendales, but not on my new bike. Although, I do have a Brooks saddle on it....

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    Senior Member halfspeed's Avatar
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    Quote Originally Posted by knobster
    I didn't like the looks of them myself. I think the trunk looks more modern when on a modern bike. The saddle bags look really cool on bikes such as the Rivendales, but not on my new bike. Although, I do have a Brooks saddle on it....
    If you're worried about cosmetics, there is NOTHING dorkier looking than a rack on a carbon road bike. Get a Carradice in black and you'll be way ahead of the game.

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    correction, halfspeed, a seatpost rack is dorky on ANY kind of bike.....as well as a half baked solution.

    proper racks can be mounted on most any bike, using appropriate racks and fittings. But a seatpost rack is always going to be a poor performer, and dorky to boot.... In the OP's case, i'd reccommend a Tubus Fly or Luna, both of which can be attached to the rear brake thrubolt, and either the bolt thrus on the rear dropouts, or retrofitted for other types of bikes without rack fittings on the dropouts, using Tubus' nice, way nicer than P-clamps, seatstay clamps (non CF frame). I believe Tubus even offers a skewer option, similar to the Old Man Mountain racks, but not 100 percent positive on that...

    the blackburn expedition on a CF TREK is a bit, well, prot and a mixing of quality that echoes esthetic dissonance.
    Last edited by Bekologist; 08-20-06 at 05:28 PM.

  14. #14
    Senior Member Wogster's Avatar
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    Quote Originally Posted by ridelugs
    why do people ever rock trunk bags? they are ugly, require a rack, which is heavy, and expensive. why not big english saddle bags? they hold more, potentially, dont require any frame to rack mounting, and arnt nylon so they dont degrade in the sun, nor when they rip do they continue ripping. just wondering.
    Proper racks can add as little as 500g (just over 1lb) to the weight of the bike, and cost under $20, and loads do not have to fit the rack exactly, as long as you have straps or bungie cords that will allow you to lash the load down. Many potential items you might want to carry, do not fit into bags, for example a box of kitty litter or a bag of dog kibble neither of these will fit in any kind of saddle bag, but can be lashed directly to the rack, yes there will be some overhang, but as long as your mindful of it, it will not cause a problem. You can also lash down a knapsack or backpack, that can later be removed, and carried easily off bike.

  15. #15
    Senior Member halfspeed's Avatar
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    Quote Originally Posted by Wogsterca
    Proper racks can add as little as 500g (just over 1lb) to the weight of the bike, and cost under $20, and loads do not have to fit the rack exactly, as long as you have straps or bungie cords that will allow you to lash the load down. Many potential items you might want to carry, do not fit into bags, for example a box of kitty litter or a bag of dog kibble neither of these will fit in any kind of saddle bag, but can be lashed directly to the rack, yes there will be some overhang, but as long as your mindful of it, it will not cause a problem. You can also lash down a knapsack or backpack, that can later be removed, and carried easily off bike.
    Carrying doggy kibble on a rack on a bike not designed for it is, well, not something I'm willing to attempt. YMMV.

    If the point of mounting a rack on the OP's bike is to carry a trunk (and anything more would be inadvisable), I still think it would be wise to reconsider a large saddle bag instead.

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    I guess I will write Trek a message and see how they react (besides chagrin at someone messing up the visual lines of a Madone with a rack and trunk) to the idea of a rack if the seatpost were replaced by NON-carbon fiber.

  17. #17
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    Quote Originally Posted by halfspeed
    If you're worried about cosmetics, there is NOTHING dorkier looking than a rack on a carbon road bike. Get a Carradice in black and you'll be way ahead of the game.
    I like this idea. They have a few different options also. Looks pretty good. Looks like it would hook right up to a Brooks also.

  18. #18
    Cycling Above All njwbert's Avatar
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    That is an interesting solution. I learnt something new.

    I faced a similar problem with another bike that I had to install a rack on. Since there were no mounting ponts on the seat stays that I could use and the tubing was too large to use the supplied P clips, I bolted the metal plates to the seat post clamp as AndrewP as pointed out. Fortunately the clamp was not a quick release version. I used a longer bolt, washers to spread the clamping force over a wider area of the metal plate, and a size 10 nut.
    "Facta non Verba" - Unknown

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    A useful concept weith lugage systems is to consider the weight/volume (or weight/load) ratio. A rack+trunk bag is pretty poor compared to a saddlebag, even when using a heavy Brooks saddle with bag loops.

  20. #20
    Rat Bastard mcoomer's Avatar
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    Quote Originally Posted by halfspeed
    If you're worried about cosmetics, there is NOTHING dorkier looking than a rack on a carbon road bike.
    I think that this dude is going to hell for putting a rack on a carbon frame...but maybe that's just me
    It's better to burn out than fade away...or slip out of your pedal and face plant on the side of the road!!!

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  21. #21
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    Here's the message I wrote to Trek and then their response:

    ..... begin quote ..........

    "Comments: I am \"old school\" and like to know I have enough stuff with
    my whether I am hiking or road biking and occasionally even have a
    digital camera to capture some photos. So while this question is odd,
    odd in the sense of the kind of chagrin that would be caused by
    \"ruining\" the lines of a Trek Madone 5.2SL, I would like to know if I
    can put a
    cantilever rack and small trunk on it using the seatpost.

    I know that the stock Bontrager Carbon fiber post would not support such
    a setup but I was wondering if using an alloy seatpost would work? The
    question really is whether the seat tube can support cantilevered weight
    hanging off the rear? I don\'t intend to turn this into a touring bike
    with panniers just a light rack and trunk holding about 10 pounds or so.
    I, myself, weigh about 165 pounds.

    I would appreciate any information that you or others can provide.

    Thanks in advance."

    ........ end quote ...........

    The RESPONSE:

    ......... begin quote .............

    "Thanks for writing. The frame would be able to handle the weight that
    you have supplied. I would not recommend going adding much more than the
    10 lbs on the post.

    Matthew Gutowski
    Tech Support
    Trek Bicycle Corporation"

    ....... end quote .............

    So Hell is a potential stop on the Madone rider's route

  22. #22
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    Quote Originally Posted by Wogsterca
    Proper racks can add as little as 500g (just over 1lb) to the weight of the bike, and cost under $20, and loads do not have to fit the rack exactly, as long as you have straps or bungie cords that will allow you to lash the load down. Many potential items you might want to carry, do not fit into bags, for example a box of kitty litter or a bag of dog kibble neither of these will fit in any kind of saddle bag, but can be lashed directly to the rack, yes there will be some overhang, but as long as your mindful of it, it will not cause a problem. You can also lash down a knapsack or backpack, that can later be removed, and carried easily off bike.
    proper racks? a proper rack is steel, and costs about 100 dollars. loads that dont fit exactly? i have carried a case of beer (bottles, 24) and grocerys home in mine and could have lashed a sleeping bag and mat on top, no problem.

  23. #23
    Senior Member grolby's Avatar
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    Quote Originally Posted by ridelugs
    proper racks? a proper rack is steel, and costs about 100 dollars. loads that dont fit exactly? i have carried a case of beer (bottles, 24) and grocerys home in mine and could have lashed a sleeping bag and mat on top, no problem.
    Nonsense! A "proper rack" can be made from aluminum, and can be purchased for $20. A good example is the Axiom Journey on my bike. It's a $20 aluminum rack that weighs perhaps 2 pounds, and depending upon who you ask, is rated to either 70kg or 75 lbs. It certainly looks and feels as if it could support that kind of weight. It has heavy tubular construction and feels stiff and sturdy.

    There is no question that Carradice bags are both practical and visually attractive, but a rack is a very practical accessory that increases the versatility of any bike you mount it on, for a minimum penalty in price and weight. I personally think bikes look a bit strange without a rear rack! But there certainly isn't any reasonable argument you can make that racks are too pricey and heavy to be practical. Even the boutique steel racks that you refer to are eminently useful, though it is paying a high price for their utilitarian value. For the many high-quality, inexpensive aluminum racks, there's really no competition at all.

  24. #24
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    seems like time for a nice shiney touring bike

  25. #25
    Senior Member Fredmertz51's Avatar
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    Quote Originally Posted by knobster
    What in the world is this? Have a picture or link?
    One of these, only remove the l-shaped reflector mount and bolt the rack braces on. This is what it is in the world.
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