Stem swapping...please remind me...

Discussion in 'Beginners' started by punkypossum, 10 Mar 2008.

  1. punkypossum

    punkypossum Donut Devil

    I've done it once, absolutely ages ago, and someone gave me instructions then, but they died together with my old computer... Would like to move my stem down a bit, i.e. swap one of the spacers up and all I can remember that there was something important about the order of losening the steering tube bolts and the headset topcat and retightening them. And then there was something about one of them not being too tight as that could damage something else... And that's all I can rembember - I don't really want to have a go, but don't really want to get the lbs to do it either, because it's not exactly a difficult job and I've done it once before (then again, I was selling that bike, maybe that made me more confident and relaxed about messing it up :evil:)
  2. bonj2

    bonj2 Guest

    Loosen the stem bolts, they are the ones that there are probably 2 of and they go through the back of the stem horizontally and clamp it to the steerer tube.
    Then undo and completely remove the top bolt, this is the one that goes vertically down from the top cap down the middle of the steerer tube. The top cap should then just come off.
    It doesn't really matter too much which order you do the preceeding two steps in.
    Once you have done those things, you should then be able to take the stem off (leave the handlebars attached). You can then take a spacer off and put the stem on underneath it, you will obviously then have to put the spacer back on over the stem in order to achieve compression*. The steerer tube should come up to past the bottom of the spacer but not as high as the top of it.
    Then you can put the top cap back on, and put the bolt that you took off back down through the middle of it, and screw it back into the star fangled nut. This is where you don't want to tighten it too tight, otherwise you will ruin the star fangled nut! (yes I have learnt this the hard way). It's not the end of the world but you will need a new SFN banging in if you do. Once it is reasonably tight**, then tighten the stem bolts most of the way, then get your handlebars aligned with your wheel, and then tighten them the whole way.
    Like I say it doesn't matter which order you UNtighten them, but it DOES matter however which order you do the tightenings in - you must do the top cap bolt before the stem bolts. The top cap bolt is largely to compress the headset initially, and the tightening of the stem bolts is to keep it like that, so if you do the stem bolts first, it will never be compressed enough and will always wobble horribly.

    *However, if you decide you like the stem in its new position, then at some point you MUST take your forks off and cut your steerer tube down by the amount of the spacer you have removed. Failure t do this will result in you being identified as someone-who-hasn't-cut-their-steerer-tube-down-enough.:evil:

    ** I find a good approximate measure is as tight as you can but with the multi-tool straight rather than in the L-shaped position, this is akin to limiting the amount of torque you can give to that of a screwdriver.
  3. bonj2

    bonj2 Guest

    btw you can't really 'mess it up' if you do it wrong, so just do it!
    - The worst that can happen is (a) that you won't compress it properly and it will be wobbly, but you'll know soon enough and just do it again, or (:evil: that you will ruin the star-fangled nut. They probably cost next to nothing, it not actually nothing, from the LBS, but you do need a special tool to whack it into the steerer tube with, which i'm guessing you haven't got (but the LBS will have).
  4. bianco

    bianco New Member

    Bonj - one of the best ever answers - top job!
  5. OP

    punkypossum Donut Devil

    Cheers, I'll have a go!!! I blame you if it goes pearshaped :evil:
  6. Undo top cap bolt and remove top cap.
    Loosen stem bolts.
    Remove stem and spacers from steerer and reassemble as required.
    Reinstall top cap / bolt but don't tighten fully
    Tighten both stem bolts just enough that the stem grips the steerer slightly but can still be turned on the steerer.
    Hold the bars, apply the front brake and rock the bike backwards and forwards. You'll be able to feel any play in the headset bearings as a clunk.
    Tighten the top cap bolt in small increments just enough that the bearing play disappears.
    Check bar/front wheel alignment then tighten both stem bolts (alternate between the bolts- half a turn each until they are tight).
    Rock the bike on the brake to check for play, also lift the front wheel off the ground and turn the bars back and forth to check for overtightness.

    Its a really quick job but one of those things which gets easier the more often you do it.
  7. fossyant

    fossyant Ride It Like You Stole It!

    South Manchester
    Ahhh...can follow these instructions - as a user of quill stems - that's a whole lot easier to adjust a headset and change things..progress I'm sure !
  8. 02GF74

    02GF74 Über Member

    yep - this is how I set up the headset bearing; also good to turn the bars with front wheel off the ground to feel for any tight spots.
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