Cannondale 105 carbon aero seatpost

mikeq Posts: 141
edited April 2011 in Workshop
Has to be the worst design in the world. No matter how much I tighten the seat bolt, the inner clamps keep rotating

See seatpost here page 8 and 9

Post is a tear drop shape so cant just replace it I dont think.

Anyone any advise on what I can do?

Cycling from Glasgow to Paris to raise funds for Asthma UK


  • tri-sexual
    tri-sexual Posts: 672
    Hi mike, a little unsure of what you are trying to explain. Please explain again using cannondale's own terminology for the parts as listed in the manual you posted (which parts on page 8/9). Eg use the name cannondale themself use for the part you are trying to explain, so when you tighten which part, which part doesn't work etc.
  • tri-sexual
    tri-sexual Posts: 672
    hi mike, looking at the manual again, are you talking of the two bolts on pg8 concerning seat tube?
    if not then is it the seat clamp assembly on page 9? are you talking about the m6x50 clamp bolt?
    did you follow the instructions fully? did you apply loctite on the blue parts as instructed (the m6x50 clamp bolt and the outer threaded clamp?)
    it worries me when somesome say "it doesnt matter how much i tighten it", it generally mean that the part is over torqued and screw threads gets stripped or the thread is crossthreaded.
    check the threads to make sure that they are not damaged, if they are ok then apply loctite as instructed on the parts coloured blue then reassemble as in the diagrams, ensure that it is tightened to the correct torque, this will ensure that you do not damage the parts.
    if threads are damaged then replace bolt and /or outer clamp and reassemble.
    if threads on parts are damaged and you cant get hold of replacement, use a longer bolt, washer and bolt then reclamp the whole assembly (outer clamp may require thread drilling out), this method will work but its a bodge and therefore not really recommended.
    if parts are fine and you are using the a standard saddle with regular rails and the problem still exist, try a thin layer of tape around the rails of saddle and reclamp, the tape will pad out and hopefully hold everything tight.
    a new post may be required but i can assure you that cannondale replacement parts are often silly money
  • mikeq
    mikeq Posts: 141
    Sorry, should have clarified.

    Yes page 9, the outer clamp is not applying enough force onto the inner clamp to stop the inner clamp from rotating around the seat post head.

    Also clarify that this is after me changing to my Specialized saddle from the fizik saddle that came with it. I can reinstall the fizik saddle and do not have an issue.

    Both the fizik saddle and the Specialized saddle have round profile rails. I would have thought that rails were a standard diameter, but I could be wrong. I'm thinking now from your comments that rails can be different diameters and perhaps the specialized rails are thicker than the fizik ones and not allowing the outer clamp to apply even force on the inner clamp.

    Bad enough that it takes an age to find the right comfortable saddle, now I need to find one with the correct diameter rails that is also comfortable :(
    Cycling from Glasgow to Paris to raise funds for Asthma UK