Why are headset cups not threaded?

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  • Why are headset cups not threaded?
  • Threaded like HTII bottom bracket cups I mean? and the frame threaded to suit?

    Or put another way why are bottom bracket cups not press fit?

    I know the answer to the second one is because that’s how frames were made for square taper and it would mean a whole new design of frame but with HTII so prevalent now surely this could save a few grammes?

    nickegg
    Member

    Some BB’s are press fit!

    cynic-al
    Member

    No need for threads on headsets.

    Good point re: bb’s – no reason why cups could not have been press fit.

    _tom_
    Member

    Old bmx’s used to have press-fit “american” cups. Pain in the arse to fit/remove in comparison to threaded BB.

    Premier Icon whippersnapper
    Subscriber

    would there more chance of knackering the bearings in a press fit BB with the continuous spinning?

    nickegg
    Member

    Would the fit of a press fit BB cup become very loose over time? I mean, a headsets bearings can be replaced without removing the actual cups. If a BB cup was as they currently are then the relatively frequent replacement might become an issue.

    Pain in the arse to fit/remove in comparison to threaded BB.

    That was my thought as to why headset cups are not threaded, would make it a much simpler process to fit and remove

    Junkyard
    Member

    large rotational forces on a BB so they screw the other way to the rotation. BB are pressed and the movement on them pushes them in to the frame so wont ever undo. i suspect a BB could unsrew or rotate itself loose [or more likly to withiut expensive engineering /small tolernaces] if not threaded

    Premier Icon mintimperial
    Subscriber

    Threaded headset cups would tend to unscrew.

    BBs and pedals rotate mostly in one direction, and are (usually) reverse threaded where necessary to avoid unscrewing in that direction. Threaded axle hubs are held down with both locknuts and QRs, so they can’t easily unscrew. But a headset will rotate 50/50 in both directions, and if threaded would therefore be quite likely to unscrew over time. Even with locknuts & whatnot it can be a problem: I remember threaded-steerer headsets from the bad old pre-Aheadset days, and they could be a right royal pain in the hoop to keep done up.

    Skyline-GTR
    Member

    Headsets are subjected to heavy compressive loading in the bottom cup that BB’s don’t have to handle that could damage the threads and make it more difficult to replace one, if not, ruin the frame in some cases.
    Plus Zero Stack and Integrated headsets that allow for longer forks these days wouldn’t have been developed as the threads wouldn’t need to be removed.
    (just 2 very basic reasons off the top of my head with no real engineering data to back it up)
    But U.S. BB’s were used on BMX back in the day with OS shell and cups. The bearings are so big, they don’t need changng that often, but they weigh a hell of a lot more than current designs. BMX frames have now gone back to Euro (threaded) BB shells to save weight.

    IanB
    Member

    Along similar lines, why do fork steerers not have a grove in them to correspond with an extra bit on the inside of a stem so that the stem is always on straight. I mean, how often do you want to ride with your stem crooked?

    steve_b77
    Member

    Thats actually a damn fine question, it wouldn’t take much to key headset bearings to adapt to this too.

    Premier Icon cookeaa
    Subscriber

    manufacturing costs? shoving a thread on the head tube would mean yet another process and tooling when making the frame with no real benefits, I’ve never had a press fit headset cup come loose yet have any of you?

    As for press fit/push fit BBs there are plenty of them to choose from…
    “standards” include:
    Mid (now quite common on BMX)
    spanish
    US
    BB30
    BB92
    ISIS Overdrive (I think it was called that – don’t think anyone made a frame for if though)

    Press fit BBs make sense all round but as ever there’s too many competing so called standards to stop most MTB frame and component manufatcturers sticking to the established and just about still adequate Euro….

    I think Mid would have been great for MTBs but then HT2 MTB chainsets came along with such a stupidly OTT axle diameter and pretty much scuppered that idea..
    ce la vie.

    Skyline-GTR
    Member

    Overdrive was a very big, very coarse thread.
    But you’re right, nobody adopted it.

    The oversize axles mean that U.S 3 piece cranks made from lighter materials open up a whole new standard to be expl;oited as the “next best thing” though.
    You have to embrace the future technologies, even though they’re just reworked versions of past examples made with different materials.

    Premier Icon cookeaa
    Subscriber

    Right you are… memory getting fuzzy with age.

    Premier Icon Northwind
    Subscriber

    Old headsets used to be threaded of course, back in ye day. Can’t say as I ever saw a drawback, but it went out the window when a-headsets arrived.

    Old headsets used to be threaded of course, back in ye day. Can’t say as I ever saw a drawback, but it went out the window when a-headsets arrived.

    I think the OP is referring to headset with threaded cups and a frame suited to the thread. The old threaded headset you refer to only had a thread on the fork steerer. Problem with them used to be mainly that if they loosened on a ride it was nearly impossible to correct. Aheadsets much easier to adjust with allen keys.

    RealMan
    Member

    Old bmx’s used to have press-fit “american” cups. Pain in the arse to fit/remove in comparison to threaded BB.

    +1, I’ve got 2 or 3 bmx frames with press fit BBs. Bloody awful to fit and remove.

    martinxyz
    Member

    As far as stems that have a notch on them/steerer with a groove are concerned,on cheaper stems it would be a nightmare.You could be selling lower end bikes with stems that line up with the tyre and have customers questioning why the bars feel so squint! “erm,unfortunately my allen keys CANT sort that problem out”

    There are a lot of cheap stems out there that are so poorly made that you can either align the stem with the wheel or choose to do the right thing by aligning the bars so that they run parallel with the axle in the hub.
    The drawback is, when doing it the right way the stem itself can often look out of alignment when sighting it with the tyre. This can all be “humoured” by finding a nice medium but i would have to say that bars should run parallel with the axle of the front wheel.. even if the stem does start to piss you off when you glance down!

    High end stems like Thomsons never have this issue.Luckily its less noticeable on shorter stems.Its a shame they cant make a stem that retails for around 20 quid these days without getting it slightly wrong but ..oh well.

    Skyline-GTR
    Member

    Threaded steerers did have a notch in them to accomodate a spacer that sat above the headset lockring.
    The quill stem fitted inside the steerer and could still be set off centre a Halfrauds gibbon and corrected by the owner or a decent mechanic.

    You don’t need precise steering because the majority of shops don’t know how to set uo suspension. The front wheel is barely in contact with the ground, so it has no effect.lol

    julianwilson
    Member

    Problem with them used to be mainly that if they loosened on a ride it was nearly impossible to correct.

    One of the ‘extras’ you could buy for the original cool tool was a headset spanner.

    I also remember threaded headsets that used the notch in the steerer and a couple of toothed spacers that bit together to stop your headset undoing itself mid ride. Never understood why all threaded headsets didn’t have the same arrangment. Stack height maybe? (added up to 8mm to it iirc)

    PeterPoddy
    Member

    Kona Impact threaded headsets NEVER came loose and were designed to be tightened by hand and then locked with an Allen key…….. 🙂

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