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  • 30.9 Thomson Covert post rattling in 30.9 seat tube.. what's the norm?
  • slimjim78
    Free Member

    New build again – this time when inserting the Thomson Covert post there is a noticeable side to side movement on the post before tightening the seat clamp. It’s very slight, but more than i’m used to feeling.

    My immediate fist impression was of an incorrect sized seat post – although i’ve triple checked on multiple sources and the seat tube on my 2015 Cromo NS Eccentric is 30.9mm

    Also, when I tighten the clamp to a force I feel necessary (proper tight!), the split section of the seat tube seems to bulge outwards slightly at the point where its drilled. I’ll try and upload a photo of this later but my eye was immediately drawn to it.
    Again, it seems like the post diameter is too small – causing the seat tube to pucker just under the clamp.

    I dont have another 30.9 post to test in its place, nor calipers to measure seat tube. Do Thomson droppers come up on the small side of accurate??

    Should I be concerned or do I just clamp it tight and forget about it?

    I’m reluctant to complete the build and test ride because both frame and post are brand new and should be good for return/refund if required (CRC).

    Posted 8 years ago
    wwaswas
    Full Member

    Thomson have traditionally had a reputation for being ‘a bit under’, not sure if their droppers have followed suit, though.

    Posted 8 years ago
    slimjim78
    Free Member

    anyone else find their Thomson dropper a bit on the loose side?

    Posted 8 years ago
    letmetalktomark
    Full Member

    Can’t help with the Thomson dropper bit …. but their non dropper posts can be a bit undersized.

    I have a steel frame, 30.9mm ST 34.9mm clamp that my Reverb is loose in – much like what you describe.

    I spoke to the manufacturer and they advised removing the post and with nothing inserted (ooh er) tighten the seat clamp until the metal really touches and leave for a while. Repeat a couple of times.

    Helped me out a little and with a fair bit of carbon paste the post is fairly still.

    If this is a new frame maybe speak to the shop?

    Posted 8 years ago
    rocketman
    Free Member

    Just for balance I’ve got a couple of 31.9 Thomson fixed posts and they barely need a clamp to keep them in place

    Have also got one of their 31.9 droppers and it’s a pretty good fit in three frames

    Thomson make accurate stuff ime

    Posted 8 years ago
    slimjim78
    Free Member

    yes it’s quite possible that the frame is the culprit – perhaps being a smidge oversize. No more in stock anymore so if I send it back im unlikely to have a new build at all.

    Im much more comfortable with an inteference fit, and would be ok if the seat tube fitted more snuggly the further down inside the frame – but even at its lowest possible setting there is a small amount of play – you can hear/feel the seat post knocking still.

    I’m not a whippet either so need a bloody tight fit to prevent the post turning.

    Posted 8 years ago
    hypnotoad
    Free Member

    Best thing to do is measure with some digital calipers.

    If there is a little play a cut up drinks can may make a good shim if you fancy a good bodge!

    Posted 8 years ago
    slimjim78
    Free Member

    so LBS confirmed that they were completely happy with tolerance when I demonstrated it. Commencing with carbon paste for a bit of added friction, and a deep fitting Straitline seatclamp winging its way to me.

    Posted 8 years ago
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