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Saddle clamp on carbon frame/post: do I need torque wrench?

notnotnotnot Posts: 284
edited October 2012 in Workshop
I had my saddle height set when I got my new/secondhand bike serviced. I'm more used to clipless pedals now, so want to try a bit higher.

The max recommended torque for the saddle clamp is 6.5Nm. Do I need to get a torque wrench to adjust this (or something like this http://www.totalcycling.com/a-z/torque_ ... ORQUE.html ) or should I just man up and open/tighten the clamp the old-fashioned way :)

Probably a stupid question, but it's my first carbon frame and I am cack-handed... Tempting to just go for it, but I've got a vision of expensive mistakes.

Posts

  • ba68ba68 Posts: 156
    Assuming the clamp was originally tightened to the correct torque all you need to do is put your Allen key in at a certain position (e.g. vertical) under the bolt by a number of exact turns to the same position, adjust the seat height and then tighten by the same number of turns you used to loosen it. This does however assume the clamp was tightened to the correct torque to start with. In the long run if you have a carbon frame you are probably better off getting a torque wrench.
  • notnotnotnot Posts: 284
    ba68 wrote:
    Assuming the clamp was originally tightened to the correct torque

    Good point - thanks! LBS tightened it without using a torque wrench, but clearly haven't cracked the frame... So would it be safe to loosen then retighten to the same torque?
  • Get a Ritchey torque key if the bolt is 4mm. That tightens to 5Nm. 6.5Nm is too much torque, max torques written on parts are often too much. On my carbon frame its 4.5NM max. Seat posts crack as well as frames.
    Pegoretti
    Colnago
    Cervelo
    Campagnolo
  • notnotnotnot Posts: 284
    Thanks - 4mm is standard allen key size?

    Would it be OK to loosen then retighten to the current torque in the meantime, or best getting something to measure torque?
  • Something like the Torque Key is a great idea. Gives you the peace of mind and works for a lot of parts.

    I suspect you've got to really gorilla a seat post to crush it but given the possible eye watering consequences I'd spend the £12 (and save your warrenty in the process).
  • notnotnotnot Posts: 284
    Right, just getting this sorted out for next week. Looks like a Torque Key will be useful - think I might play with adjusting handlebars etc. too... - is the Ritchley rather than the Bontrager the one to go for?

    In the meantime, am I best waiting for the key to arrive or could I safely loosen and then retighten the saddle to its current torque? Hoping the weather clears up enough for a ride later today :)
  • dodgydodgy Posts: 2,890
    If you use carbon assembly paste you can use even less torque on seatposts.
  • andy46andy46 Posts: 1,666
    +1 for the Ritchey Torque Key, I use this on my carbon seatpost/frame with no problems.

    You'll be surprised how tight 5Nm actually is.
    2019 Ribble CGR SL

    2015 Specialized Roubaix Sport sl4

    2014 Specialized Allez Sport
  • g00seg00se Posts: 2,221
    dodgy wrote:
    If you use carbon assembly paste you can use even less torque on seatposts.

    +1 - and for stems too...
  • Also using Ritchey Torque key and Taxc carbon paste (satchet from PBK) . Just after I bought this I spotted a Bontrager torque key with both size 4 and 5 allen keys - swappable - very handy! It was from China, whereas they seem to be rare as hens teeth here - or maybe it's my google search skills?
  • fortyonefortyone Posts: 165
    SIMPLE! Tighten it just enough that it doesn't move.
  • on-yer-bikeon-yer-bike Posts: 2,974
    I have found that carbon seatposts crack easier than you think.
    Pegoretti
    Colnago
    Cervelo
    Campagnolo
  • notnotnotnot Posts: 284
    Just to update - got a torque key and been playing about with saddle height. I've noticed that the seat post is pretty stiff to adjust - much more so than on my steel mountainbike. Is this meant to be the case - so it will stay put at low torque - or do I want to use some grease?
  • g00seg00se Posts: 2,221
    Don't use grease - the stiffness may be down to some carbon assembly paste on there already. If it's stiff due to a close fit, then all well and good (as long as it's not an imperfection that's scoring the carbon post).
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