gap between steerer tube and stem top cap...critical?

markyhud
markyhud Posts: 98
edited October 2012 in MTB workshop & tech
I've just bought a shorter Raceface stem. The instructions state that the compression gap between the top of the steerer tube and the top of the stem should be 2mm min and 3mm max (Talk about fine tolerences :shock: ). When I took the stock Giant stem off the gap is about 5mm. Is it totally critical to get this spot on in which case I will have to buy some teeny spacers or should it just be a few mm in general? These instructions seem a little extreme!!!

Comments

  • nicklouse
    nicklouse Posts: 50,675
    well it the gap is not enough you will not be able to preload the bearings. if the gap is too much the top stem bolt maybe above the top of the steerer.

    it needs to be correct but not precise.

    see Parktools for more info.
    "Do not follow where the path may lead, Go instead where there is no path, and Leave a Trail."
    Parktools :?:SheldonBrown
  • The Rookie
    The Rookie Posts: 27,812
    A 1mm tolerance is laughable... As Nick says, must be some gap but as a rule of thumb as long as the top of the steerer is obove the centreline of the top pinch bolt you'll be OK.
    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.
  • markyhud
    markyhud Posts: 98
    I did a double take when I first looked at the destructions to be honest. I laughed and then thought........hope it doesn't snap!! Thanks for putting my mind at rest. I've just measured it with a combo of spacers and it's 4mm...........oooooh what a rebel eh?
  • leaflite
    leaflite Posts: 1,651
    I dont know if I have misunderstood here, but your op implies that the steerer tube is coming up past the top of the stem by the amount you state? If this is the case, you just need to put in some spacers above the stem that come up at least 2mm above the top of the steerer to allow you to preload the bearings. In this case as long as the gap is enough to preload the assembly the size of the gap is irrelevant.
    If the steerer tube is below the top of the stem, as long as it isnt too far below it should be ok, but if it is below the top bolt of the stem the fork steerer is too short/you have too many spacers below the stem.
    GT Hardtail
    The Apollo Project
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  • markyhud
    markyhud Posts: 98
    The steerer tube is below the top of the stem and the top pinch bolt on the stem is well below the top of the steerer so it's all good thanks :)

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