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Seatpost rack mounted to seat tube?

elcanielcani Posts: 280
edited August 2009 in Commuting chat
Hi

I've just purchased one of these:

http://www.wiggle.co.uk/p/cycle/7/LifeL ... 360033789/

and discovered it is more practical to clamp it to my bike's (Reynold 531c Ribble Road Bike) seatpost tube rather than the seatpost itself. I'm sure the answer to this question will be 'no', but is there any reason why this is a bad idea?

Cheers

Posts

  • AidyAidy Posts: 2,015
    I always wondered if there'd be clearance enough to do something like this.

    I'd've thought it would be fine, but you'd probably want to make sure that the seatpost still protruded far enough into the frame so that it would be under the clamped part.
  • elcanielcani Posts: 280
    Hi Aidy

    There is clearance through the rear stay, although - looking at it - there may be an issue with the backs of my legs fouling whatever is mounted on the rack, as the sloping angle of the seat tube means the rack is further forward than it would be if mounted on the seatpost.

    Re. your second comment, do you think seat tube alone could be too weak to support the rack without the seatpost inside it?

    Cheers
  • RoastieRoastie Posts: 1,968
    ElCani, I would think that the wall thickness of the seat tubes will be too thin to support the cantilevered load. It would be OK if the rack was clamped to a section of seat tube with post inside, but would still probably result in some damage to the tube..

    ps. I am a mechanical engineer.
  • AidyAidy Posts: 2,015
    ElCani wrote:
    Re. your second comment, do you think seat tube alone could be too weak to support the rack without the seatpost inside it?

    Depends on the strength of the seat tube, the weight of the load carried, the length of seat tube it's spread over and the how far away the load is from the seat tube!

    Seat tubes do often tend to be fairly thin though, and I'd be inclined to err on the safe side.
  • elcanielcani Posts: 280
    Right, thanks for the advice - I think I'll use the product as the designers intended and remount on the seatpost.

    It's just that because the frame is quite large, with 1980's geometry, I only have about 10cm of seatpost sticking out, meaning there isn't much clearance between the front of the rack and the bottom of the saddle. Oh well.
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