Seat always moving to the back

Ferrals
Ferrals Posts: 785
edited May 2015 in MTB workshop & tech
My seat seems to always end up sliding on it's rails until it's as far back as possible. Happened with my old post all the time, no matter how much I cleaned it etc. I recently bought a new one (Thomson so should be good quality), fitted it yesterday, put some carbon grip paste on the rails to be sure it didn't slip, tightened it up (meant to be 5nm so finger tight) and yet it still slipped backwards.

Clearly the obvious answer is tighten it up more, anything else? I started to wonder if maybe I just needed my seat that far back, but I find it hard to believe as I am at the lower end of the height range for the bike and I don't think I have abnormally long thighs!

Comments

  • The Rookie
    The Rookie Posts: 27,812
    5Nm is is a lot more than finger tight! Sounds like you are under tightening to me, although the rails are probably now damaged from the sliding anyway, so you probably need a new saddle.
    Currently riding a Whyte T130C, X0 drivetrain, Magura Trail brakes converted to mixed wheel size (homebuilt wheels) with 140mm Fox 34 Rhythm and RP23 suspension. 12.2Kg.
  • Ferrals
    Ferrals Posts: 785
    Why would the rails be damaged? Some superficial damage to the paint but otherwise seem fine. Bike spend budget exhausted for the time being!
  • PXR5
    PXR5 Posts: 203
    If you're someone who enjoys faffing with the bike get yourself a torque wrench which works from about 2 -15Nm
    You can get them from about 30 quid upwards. I reckon as a rule of thumb (pun intended) finger tight is about 1.5 - 2N and even then you need bloody good purchase on what you're trying to turn, add an allen key as a lever and you have not really much idea of how much torque you are applying. I learnt my lesson many moons ago on Jap motor bikes about torque settings.
    I've also had problems of a seat moving about, normally associated with an accompanying creaking noise etc, the only way to sort it was to strip it all down, clean thouroughly and remount it, i'm not actually convinced copperslip or equivalent helps much, you will need to torque to the right setting, but don't go mad and tighten too much or the dreaded "crack" noise will be heard followed by much swearing...
    Every time I go out, I think I'm being checked out, faceless people watching on a TV screen.....
  • cooldad
    cooldad Posts: 32,599
    Forget torque wrench and tighten it so it doesn't slide. Simple.
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  • The Rookie
    The Rookie Posts: 27,812
    Ferrals wrote:
    Why would the rails be damaged?
    Every time they slide through the mounts the rails are being worn, not just paint.
    Currently riding a Whyte T130C, X0 drivetrain, Magura Trail brakes converted to mixed wheel size (homebuilt wheels) with 140mm Fox 34 Rhythm and RP23 suspension. 12.2Kg.