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headset tightening - what am I doing wrong?

LowlanderLowlander Posts: 14
edited March 2010 in Workshop
Hi

I have a new supersix with integrated headset.

She's a beauty - but having adjusted the handlebar height downwards and taken out some spacers, I can't work out how crank down the headset and take play out of the system. The steerer tube is too long for now, so I've put a spacer on top of the stem to meet the top cap.

As the steerer tube is carbon there's an expanding wedge arrangement - but this only seems to expand inside the tube and not actually create compression. So if I tighten the top nut as much as possible it has no impact on levels of play - I'm dependent on my weight alone to tighten up the system (clearly nowhere like enough!).

Please, can someone explain what I'm doing wrong as however I do it I end up with massive amounts of play in the system.

Thanks!

Posts

  • amaferangaamaferanga Posts: 6,789
    Are you loosening the stem bolts before tightening the bolt in the bung?

    If you are then is the top of the spacer you put above the stem a few mm higher than the steerer tube?
    More problems but still living....
  • deswellerdesweller Posts: 5,271
    It sounds like you are screwing the top cap down onto the steerer tube rather than the spacer. The top of the uppermost spacer should be higher than the top tube by a couple of mm.
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  • You say you took out some spacers have you put all of them back on top of the stem now you've lowered it.
    The spacer thats now on top of the stem should be about 5mm higher than the fork steerer tube to give the expanding bolt room to compress the head set down.
    Also make sure that the expanding bolt drops far enough into the steerer tube you don't wont the expanding part up against the top cap when you insert it..
    just another thoughtn are the stem bolts are loose as you tighten the headset .
  • on-yer-bikeon-yer-bike Posts: 2,974
    You are in very dangerous territory. I agree with the other posters that the spacer probably isn't higher than the steerer. The steerer needs to 3 mm lower than the top of the spacer.
    Its best to leave at least 1 spacer above the stem with a carbon steerer so that you are not tightening the stem on the top edge of the steerer. Carbon steerers are very fragile so don't over tighten the compression plug inside the steerer and do not over tighten the stem bolts. Use carbon assembly paste and don't tighten to what it says on the stem. I have learnt the hard way.
    Pegoretti
    Colnago
    Cervelo
    Campagnolo
  • Hi guys

    thanks a million for your tips. I've had a further fiddle and worked it out - indeed I didn't have enough space between the top spacer/cap and top of the steerer to get the compression I was looking for.

    A further question though - you voice a lot of concern about over-tightening stem bolts and expanding plug as the steerer tube is fragile. Realistically - is failure a real possibility? And if so, would that be when it was being adjusted or could it be triggered by i.e. tough cornering or road bumps with too much tension in the system?

    Thanks for sharing experiences and I'm about to order a torque-wrench!
  • I think on-yer-bike is a little over the top with his comments.
    you could over tighten the top cap if you go mad but just slowly tighten it untill there is no movement in the headset.
    As for the stem bolts just go easy nip up the bolts a little at a time until the stem can't move.carbon paste might be a could idea as you dont need to tighten things up as much for everything to grip.
  • on-yer-bikeon-yer-bike Posts: 2,974
    I think on-yer-bike is a little over the top with his comments.
    you could over tighten the top cap if you go mad but just slowly tighten it untill there is no movement in the headset.
    As for the stem bolts just go easy nip up the bolts a little at a time until the stem can't move.carbon paste might be a could idea as you dont need to tighten things up as much for everything to grip.

    Maybe. But I wouldn't like to be riding down a hill and have the the steerer break. I have cracked a steerer tightening the stem bolts to 4 NM without a spacer on top. I have also heard of steerers being cracked by over tightened compression plugs. I'm very wary about specified torque settings actually being too tight. Alu steerers would probably be better and no heavier.
    Pegoretti
    Colnago
    Cervelo
    Campagnolo
  • ajb72ajb72 Posts: 1,178
    The top cap should only be nipped up enough to take the play out of the headset - it isn't supposed to be load baring and should never be so tight as to risk damaging the steerer tube.

    Nip up the top cap, then tighten stem bolts second, job done
  • topdudetopdude Posts: 1,557
    You are not going to damage the carbon steerer tube by tightening the top cap or stem bolts, thick carbon tube is a lot tougher than people would have you think :?
    I did an experiment with the bit of steerer i cut off and tried to squash it in a vice, it survived a lot of pressure and sprung back to it's original shape. If it had been alloy it would be a flat bit of metal now :D
    He is not the messiah, he is a very naughty boy !!
  • da gooseda goose Posts: 284
    Best advice is be careful....I have experienced a strange creaking from a carbon fork (high quality high price) thankfully I stripped it down...to my horror the carbon tube had split and was slowly fragmenting....would have snappd nasty? :evil:
    Forget the quoted amounts just cinch up each bolt in equal turns very slowly holding a normal allen key on the `T` end...thereby using minimal strength.
  • da gooseda goose Posts: 284
    Best advice is be careful....I have experienced a strange creaking from a carbon fork (high quality high price) thankfully I stripped it down...to my horror the carbon tube had split and was slowly fragmenting....would have snappd nasty? :evil:
    Forget the quoted amounts just cinch up each bolt in equal turns very slowly holding a normal allen key on the `T` end...thereby using minimal strength.
  • sandbagsandbag Posts: 429
    Certain carbon models, all the spacers have to be below the stem, and not allowed above it. Check your manual.
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