Headset adjustment - spacers and stack height

jordan_217
jordan_217 Posts: 2,580
edited May 2013 in Workshop
According to Cannondale's tech manuals, adding any spacers above the stem is a big NO NO! - However, some manufacturers actually recommend a spacer is placed between the stem and top cap. Anyway....

I'm in the process of sorting the position on my CAAD10 - I've stacked two spacers on top of the stem (that were previously underneath) and don't want to cut the steerer until I'm satisfied the position is ok.

Are Cannondale just being over cautious here or, is there a good reason why I shouldn't do this, albeit temporarily?
“Training is like fighting with a gorilla. You don’t stop when you’re tired. You stop when the gorilla is tired.”

Comments

  • smidsy
    smidsy Posts: 5,273
    This very issue was raised previously. The general consensus was that Dale are probably being over cautious but if the steerer fails and they can prove it was run with spacers above they will try to void the warranty.

    As you correctly state it is actually common practice to run a small (3mm ish) spacer on top of the stem of a carbon steerer as this reduces the wear on the top of the steerer tube. Here's mine.
    8468553536_678382ca0c_z_d.jpg

    The issue that Dale are highlighting is that if you run large spacers on top you are clamping the stem below where the bung is, which may put undue pressure on the steerer tube.

    In the short term it will be unlikely to cause an issue IMO.
    Yellow is the new Black.
  • jordan_217
    jordan_217 Posts: 2,580
    smidsy wrote:
    This very issue was raised previously. The general consensus was that Dale are probably being over cautious but if the steerer fails and they can prove it was run with spacers above they will try to void the warranty.

    As you correctly state it is actually common practice to run a small (3mm ish) spacer on top of the stem of a carbon steerer as this reduces the wear on the top of the steerer tube. Here's mine.
    8468553536_678382ca0c_z_d.jpg

    The issue that Dale are highlighting is that if you run large spacers on top you are clamping the stem below where the bung is, which may put undue pressure on the steerer tube.

    In the short term it will be unlikely to cause an issue IMO.

    Cheers, this is what I was thinking. I actually have a 3mm spacer on top of the stem on my Enigma and haven't had any issues. I'll probs cut the steerer down after one or two rides but just wanted to check there's no Cannondale specific problems with running this set up.
    “Training is like fighting with a gorilla. You don’t stop when you’re tired. You stop when the gorilla is tired.”
  • bernithebiker
    bernithebiker Posts: 4,148
    smidsy wrote:
    to run a small (3mm ish) spacer on top of the stem of a carbon steerer as this reduces the wear on the top of the steerer tube.

    Don't get it. How does this reduce wear on the top of the steerer tube? (Compared to no spacer).
  • keef66
    keef66 Posts: 13,123
    bernithebiker wrote:
    smidsy wrote:
    to run a small (3mm ish) spacer on top of the stem of a carbon steerer as this reduces the wear on the top of the steerer tube.

    Don't get it. How does this reduce wear on the top of the steerer tube? (Compared to no spacer).

    Me neither. The steerer tube isn't moving against anything in either scenario; everything is securely clamped together.

    And if it's the clamping argument, why don't Cannondale just say install the bung so it's in the clamping zone?
  • Monty Dog
    Monty Dog Posts: 20,614
    The reason for having a spacer above the stem is to allow the steerer to protrude slightly above the stem and therefore the clamp force is more even. If the steerer is below the top, then the force from the top bolt is disproportionate and could lead to cracking of the steerer, particularly if the bung isn't fitted correctly. Some top caps are quite deep too - so it's hard to get them to sit flush on top without hitting the fork bung, so you need a spacer anyway. Can't see the logic in Cannondale's argument to say not to use a spacer above either.
    Make mine an Italian, with Campagnolo on the side..
  • tonye_n
    tonye_n Posts: 832
    keef66 wrote:
    bernithebiker wrote:
    smidsy wrote:
    to run a small (3mm ish) spacer on top of the stem of a carbon steerer as this reduces the wear on the top of the steerer tube.

    Don't get it. How does this reduce wear on the top of the steerer tube? (Compared to no spacer).

    Me neither. The steerer tube isn't moving against anything in either scenario; everything is securely clamped together.

    And if it's the clamping argument, why don't Cannondale just say install the bung so it's in the clamping zone?

    In order to add/have spacers above the stem, you have to raise the top cap no?
    Well... raising the top cap means raising the position of the bung.
    Cannondale are worried that the mores spacers you have above the stem, the higher the position of the bung within the steerer tube.
    At some point you will be using the stem to clamp/squeeze on the steerer tube at a position that is bellow the position of the bung. Thus increasing the likelyhood of crushing the steerer tube under load..
  • keef66
    keef66 Posts: 13,123
    tonye_n wrote:
    keef66 wrote:
    bernithebiker wrote:
    smidsy wrote:
    to run a small (3mm ish) spacer on top of the stem of a carbon steerer as this reduces the wear on the top of the steerer tube.

    Don't get it. How does this reduce wear on the top of the steerer tube? (Compared to no spacer).

    Me neither. The steerer tube isn't moving against anything in either scenario; everything is securely clamped together.

    And if it's the clamping argument, why don't Cannondale just say install the bung so it's in the clamping zone?

    In order to add/have spacers above the stem, you have to raise the top cap no?
    Well... raising the top cap means raising the position of the bung. *
    Cannondale are worried that the mores spacers you have above the stem, the higher the position of the bung within the steerer tube.
    At some point you will be using the stem to clamp/squeeze on the steerer tube at a position that is bellow the position of the bung. Thus increasing the likelyhood of crushing the steerer tube under load..

    *moving spacers from beneath the stem to above the stem isn't raising the top cap; the stack height remains the same. It does move the clamping zone down though, possibly below the location of the bung. In which case why don't Cannondale allow you to move the bung down and use a longer bolt to secure the top cap? Still cannot see why they think spacers above the stem to be a bad idea...
  • smidsy
    smidsy Posts: 5,273
    bernithebiker wrote:
    smidsy wrote:
    to run a small (3mm ish) spacer on top of the stem of a carbon steerer as this reduces the wear on the top of the steerer tube.

    Don't get it. How does this reduce wear on the top of the steerer tube? (Compared to no spacer).

    This has pretty much been aswered but just so I can say I have responded:

    The spacer gives a few mm of steerer above the stem so when you tighten it the steerer tube is not having undue pressure applied right at the open end (where fibres are exposed, particularly if you have cut the steerer down). This provides a firm grip on the tube without compromising it.
    Yellow is the new Black.
  • keef66
    keef66 Posts: 13,123
    smidsy wrote:
    bernithebiker wrote:
    smidsy wrote:
    to run a small (3mm ish) spacer on top of the stem of a carbon steerer as this reduces the wear on the top of the steerer tube.

    Don't get it. How does this reduce wear on the top of the steerer tube? (Compared to no spacer).

    This has pretty much been aswered but just so I can say I have responded:

    The spacer gives a few mm of steerer above the stem so when you tighten it the steerer tube is not having undue pressure applied right at the open end (where fibres are exposed, particularly if you have cut the steerer down). This provides a firm grip on the tube without compromising it.

    So nothing to do with "reducing wear on the top of the steerer tube" then? :wink:
  • smidsy
    smidsy Posts: 5,273
    keef66 wrote:
    So nothing to do with "reducing wear on the top of the steerer tube" then? :wink:

    If you are being perdantic I suppose.

    The wear is from the clamp of the stem acting against the steerer end. If it is very close to the exposed end there is an increased chance the steerer will crack due to the constant vibration/jarring through nornal use.

    Whether you class that as wear or fatigue or failure, the outcome is the same.
    Yellow is the new Black.
  • keef66
    keef66 Posts: 13,123
    Pedantry indeed. :D

    No, I'm with you on the spacer above the stem. It's Cannondale et al's blanket ban on them I find puzzling. They clearly don't trust people to put the expander bung in the right place. Or more likely their lawyers don't...
  • bernithebiker
    bernithebiker Posts: 4,148
    Well you learn something new every day!

    My steerer tube is already cut to just below the top of the stem, so I can't do the 'add a spacer on top' thing anyway.

    (And I have no spacers below either).

    But I doubt I'd do it given the choice as it looks a bit fugly, and I've never had an issue in 20 years doing it the old fashioned way!
  • smidsy
    smidsy Posts: 5,273
    This thread is for carbon steerer tubes.

    Metal steerer tubes are still required to be cut below the top cap.
    Yellow is the new Black.
  • bernithebiker
    bernithebiker Posts: 4,148
    smidsy wrote:
    This thread is for carbon steerer tubes.

    Metal steerer tubes are still required to be cut below the top cap.

    Yep, mine's carbon.
  • smidsy
    smidsy Posts: 5,273
    bernithebiker wrote:
    smidsy wrote:
    This thread is for carbon steerer tubes.

    Metal steerer tubes are still required to be cut below the top cap.

    Yep, mine's carbon.

    A 20 year old carbon steerer tube - impossible :mrgreen:
    Yellow is the new Black.

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