Upside-Down Forks

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  • Upside-Down Forks
  • ndthornton
    Member

    fantastic idea – all bike forks should be upside down
    If only the new X fusion ones didn’t cost as much as a good car!

    clubber
    Member

    Wider tubes at the top/crown where there’s more stiffness benefit

    Trouble is many upside down forks have been noodly because of twisting at the hub end – thru axles certainly help here.

    ndthornton
    Member

    Has there ever been an upside down fork without a bolt through axle??

    Noodlyness is the only real problem that people seem to complain about – makes sense with the single crown ones. But surely not beyond the wit of man to sort out – Id be surprised if X-fusion haven’t managed it for a grand!

    Has there ever been an upside down fork without a bolt through axle??

    Halson Inversion

    Mountain Cycles Suspenders

    asterix
    Member

    didnt the motorcycle world go through the transition to upside down forks years ago?

    petrieboy
    Member

    Bolt on as opposed to bolt thru I suppose….

    You can’t have the arch across the lowers with an inverted fork. Other than that, there’s all sorts of small benefits like less unsprung weight, more oil around the seals, etc.

    hopefiendboy
    Member

    the other issue can be that the stantions are lower down closer to any obstacles / rocks and can be easily damaged unless they have guards.

    mindmap3
    Member

    The Shiver’s that I had on my Bog Hit were ace – they were so sensitive to bumps etc and felt great. I didn’t think that they were that flexy (certainly not as bad as people who had never ridden them made out). Only downside was that they weighed loads.

    Stanchion guards were great for putting stickers on too!

    The whole stiffness thing is interesting because we must be getting to a point where things are almost getting too stiff. Some flex is surely a good thing (i.e. it means that some bumps / vibrations are taken up by components rather than being transmitted to the rider).

    sharkattack
    Member

    This is how you build an upside down fork;

    Add a brace and protect the stanchions. Two inherent problems solved.

    julianwilson
    Member

    ^^ makes you wonder why no one tried it before! (looks?) iirc DVO claim that even though the ‘carbon torsion arch’ in the stanchion protectors is relatively insubstantial/light, it still makes a significant difference to stiffness/twistiness of the fork. They said this was the case for years on upside down forks on some high end motorcycles which have a mudguard that links the stanchion guards, and that was why they tried it for a bicycle (albeit without mudgard).

    £1800 quid for the fork, mind 😯 😯

    patriotpro
    Member

    What are the actual benefits of these? You know, like the Manitou Dorado and the new X-Fusion jobs…

    Personally I think they look brill but am interested in the actual benefits in use..

    What do you lot have to say on the matter?

    I keep looking at that bike and thinking “surely they could have found a black chain guide?”

    didnt the motorcycle world go through the transition to upside down forks years ago?

    Yes, but it was (and still is) the case that the USD forks weighed considerably more to keep them stiff (less of an issue on a 150bhp bike Vs a 1/8th of a horsepower one!) and didn’t work as well, something to do with damper arangements.

    Look at bikes like the R6 where weight/handling was more a priority and they hung onto conventional forks for a few years past USD forks becoming the norm.

    Orange Crush
    Member

    My first motorcycle (a 1950’s job) had upside down forks but “modern” motorcycles have seen upside down forks come and go, as fashion dictated, over the last thirty years. It’s doubtful if any difference can be felt by the majority of users in terms of it affecting how they use the bike, which I would guess will also apply to the pedal cycle version.

    USD forks were introduced into the motorbike world to make last years model look so out of date and so inefficient. Then a year later when the power rangers who had clocked up an all impressive 1500 dry miles in 12 months, the motor trade would offer them a pittance for their mint nick bike knowing they just had to have the next model because it had another gimmick, which after USD forks was radially mounted brake callipers.

    What we are seeing here is market(ing) forces.

    THe only benefit I see to USD MTB forks is the LBS’s will clean up selling new fork seals after the owners have learnt the lesson of neglect, corrosion and stone damage to the lower fork stanchions

    Premier Icon Northwind
    Subscriber

    Lubricating oil sits on the seals instead of relying on splashing around. Sort of like storing your forks upside down. Supposed to be less unsprung weight but it doesn’t automatically follow.

    And yep, agreed on motorbike stuff- not sure if big pistons etc would work with rwu forks but if you compared say a Showa USD and RWU from a SRAD 600 and 750 there was bugger all performance difference but everyone wanted the USDs. (er, including me, I had the choice and went with USDs because I’m a tart)

    butterbean
    Member

    Largely b*llocks, done for the sake of trying to be different.

    USD DH forks on a UK uplift = carnage.

    russjp
    Member

    My old shiver single crowns were so flexy that it was a nightmare balancing in 4X start gates.

    Premier Icon rOcKeTdOg
    Subscriber


    benefits: huge mud clearance, no crown so 29er/27.5/26 wheels will fit, fork is lubed by gravity at the seal instead of just compression
    non benefits, they flex more than right side up forks

    asterix
    Member

    didnt the motorcycle world go through the transition to upside down forks years ago?

    Yes, but it was (and still is) the case that the USD forks weighed considerably more to keep them stiff

    Yes I agree that’s what I understood too.

    What we are seeing here is market(ing) forces. THe only benefit I see to USD MTB forks is the LBS’s will clean up

    this made me smile – shock horror stuff changing to keep the market alive – bit like wheel sizes 😆

    Premier Icon ir_bandito
    Subscriber

    I’ve got SC32s
    They’re mega-plush, light weight, have oodles of clearance and look frikkin’ ace, (which matters to me on this bike):


    DSC_0282 by ir_bandito, on Flickr

    If you hold the wheel ‘tween your legs, you can twist them. But I’ve never, ever been riding along and thought “ooh, they’ve twisted”

    clubber
    Member

    Yeah but you ride a bike powered by a rubber band, so what would you know? 🙂

    Premier Icon rOcKeTdOg
    Subscriber

    my SC32 flex to the left when you brake hard, only noticable when static though, not riding along

    Why would you brake hard when static? 🙂

    Premier Icon rOcKeTdOg
    Subscriber

    to make it flex! 😛

    Premier Icon ir_bandito
    Subscriber

    you ride a bike powered by a rubber band, so what would you know?

    🙂
    indeed.

    Dibbs
    Member

    I’ve got four MTB’s with SC32’s and another set in a box for spares.

    I’m still rocking 8-year old shivers on the DH bike. Gonna treat myself to some Dorado’s for next season purely for teh bantorz and lightness.

    For me it’s all about having the oil sat on the seals.

    Cant imagine the unsprung weight thing matters.
    Normal fork unsprung weight = front wheel+brake caliper+lowers+axle+half a damper cart+half a coil spring+some oil
    USD unsprung weight = front wheel+brake caliper+stanchions+axle+half a damper cart+half a coil spring+some oil

    I’d guess you would see as big a change in unsprung weight by putting a lighter front wheel on – and noone says ‘yea my suspension feels ace with this lighter wheel on…’

    patriotpro
    Member

    So more inherent negatives with usd then. Doesn’t stop me wanting a set.w 8)

    wobbliscott
    Member

    Yes but each half of a damper cartridge do not weight the same. One half is a can of oil. The other half is a thin lightweight stanchion. With a USD fork the heavier half that contains the oil is sprung as opposed to unsprung so IN THEORY a USD has less unsprung weight. However as with most of these things is it really noticeable in the real world? I suspect not.

    Motorbikes have had USD forks since the late ’80’s/early ’90’s and stuck with them – certainly high performance bikes, so there must be other benefits. I also thought it was stiffness and less stiction as the stiffer and larger diameter part of the suspension legs are the top half of the fork so the torsional stiffness is greater (when you turn the handlebars) and the bending forces while under braking are being resisted by the larger and stiffer part of the fork higher up their length due to leverage.

    Yes but each half of a damper cartridge do not weight the same. One half is a can of oil. The other half is a thin lightweight stanchion.

    The stanchion isn’t part of the damper, there is a separate rod which enters the ‘can of oil’. The damper is a separate unit, so the chassis type shouldn’t affect the weight of it. IIRC there was very little difference between the carts in my shiver and the cart in the early 888’s I once attempted to replace the shiver with.

    wobbliscott
    Member

    I meant the thinner rods rather than the larger visible stanchions – I just couldn’t think of a name for them. Its clearly less of a difference between an MTB fork and a motorbike fork which is probably why USD forks haven’t really made an impact in MTB. But I think it is the extra stiffness of the thicker uppers with USD forks that is the key on motorbikes.

    Premier Icon GavinB
    Subscriber

    Owned a pair of SC32, and would never, ever own another. Noticeably flexy in really rough bits of trail, kinda like an old pair of QR SIDs, although they were lovely and light.

    Interested that companies are still pushing this.

    compositepro
    Member

    dunno why single legged forks never took off

    chives
    Member

    Given how much of the time is spent riding across loose surfaces, just how ‘stiff’ do you need a fork (or wheel set / back end for that matter) to be? If everything was (from an engineering point of view) absolutely unyielding surely the ride quality would be awful, unless the tyre pressure adjusted itself for different surfaces, and suspension tune was absolutely dreamy (impossible on a hardtail).

    If it goes where you’ve pointed it most of the time, and the rest of the time’s a controlled drift, what’s not to like?

    walleater
    Member

    My old Shiver DC was stiff enough when it was deep in it’s travel battering through chunder (i.e. doing what it was designed to do). It was a bit of a noodle when cruising along gravel trails though. So I can understand why people who didn’t ride decent trails, or were slow would think that the Shiver DC was very flexy 😉

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