Fork Springs Comparison (Picture)

Discussion in 'Parallel Universe' started by ride2little, Jan 27, 2013.

  1. Loutre

    Loutre Cosmopolitan Adv

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    now I'm hesitating between both fork springs :cry
    #21
  2. deguoren

    deguoren 该出手时就出手

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    I will go the Wilbers way.

    next month.....
    #22
  3. Gumbeaux

    Gumbeaux The Chameleon

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    All this talk of springs has me wondering.

    I had the Ohlins NIX kit put on the front by the guys at Ohlins USA, and they told me they would just use the stock springs cause they were good enough when combined with this new kit.

    I am really happy with this Ohlins transformation, just a little secret that the stock springs are still in there...not sure if they still do it that way.

    Anyway...I guess if you are doing springs only, it makes sense you would see a huge benefit.
    #23
  4. DoWorkSon

    DoWorkSon Been here awhile

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    I would think with the upgrade of the cartridges to adjustable, you would eliminate the need for new springs since you can adjust everything to your weight/riding style. So stock springs might be ok with new cartridges.
    #24
  5. Schai

    Schai Adventurer

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    Ride2Little,

    With oil height set at 120mm (below the top of the tube, fully compressed fork legs, and no springs), you might experience very harsh bottoming. At 75mm it will never bottom.

    I put a set of Hyperpro progressive lowering springs on my F800GS. I removed enough oil to hit their spec., for my springs, of 110mm. The first time into the woods, it started bottoming really harshly, even on bumps that my KTM would totally ignore. Back home, I spent a Sunday inspecting and measuring forks.

    The problem is that the frugal (a polite word for cheapa**) German engineers didn't include any parts for a bottoming cushion on the F800GS forks. Personally, I've never seen this in a fork before. Instead, they specified an oil height of 60mm. Adding the volume of the spring and fork cap, that would leave about 3mm of space for air when fully compressed. If you could bottom, that would compress the air space from about 250mm when extended to 3mm compressed, raising the pressure to about 83 atmospheres (bar) and over 1,200 psi. Given maybe 4 square inches of cross sectional area, you are looking at around 5,000 lbs. or 2,200 kg. to bottom the forks. Can't happen. The forks never bottom. Don't need cushions. Saves a few euros. Maybe someone got a bonus. The forks also get a lot stiffer just part way into the stroke. However, if you follow the Hyperpro spec, developed for best overall handling, and add another 50mm of air space, then you only have 5 atmospheres (bar) and 75 psi. You are only getting a few hundred pounds of resistance instead of a few thousand, so the forks now can bottom, flat metal to metal, and they do.

    With a 110mm oil height, the bike handles smoother but sounds like a car crash when the forks bottom. Also rims bend easier (had to straighten one of those too). Riding just on highways and regular gravel roads, my guess is that it should rarely, if ever, bottom. However, go off on some trails with any speed and you'll hear the forks say "OUCH!" every few minutes.

    Note:
    How I got the 75mm: On my particular springs, I measured the volume of the stock spring and my Hyperpro spring. The Hyperpro springs have more coils and are larger, so they fill up about the same volume as 12mm of oil height. Stock spec is 60mm. Adding 12 mm for the larger springs gets to 72mm, which I rounded up to 75mm. With your 120mm height, If it doesn't bottom on you the way you use the bike, don't worry. However, if it does, start adding oil up from 120mm to 75mm. This is just my untrained amateur opinion. :eek1



    #25
  6. machinebuilder

    machinebuilder Long timer

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    As I understand supension

    Adjusting to the load weight (you+gear+cargo) is done with spring rates (Preload just Precompresses the spring to increase ride height)

    the Damping (shock absorbing) is where things are adjusted to your riding style (compression and rebound)

    going off poor memory the Theoretical Ideal is 15% compression with just the weight of the bike and 30% with rider, commonly refered to as sag. Most of this applies to both ends of the bike.

    On the F8 the forks have 230mm? travel so with the riders weight they should compress about 60mm

    With the Stock springs (.55kg/mm) mine sagged about 80-90mm (almost 50%). With the springs Traxxion put in (.65kg/mm) the sag was textbook on the money.

    IMHO fixing the damping without fixing the spring rate will just slow down the bottoming out.

    It could be Gumbeaux happens to be the weight that the stock springs work for, when I got a quote for the Ohlins they wanted to know a lot of info so the suspension would be built to my specs (weight, cargo, riding style etc).

    I realize most of us aren't looking for the "ideal" setup, but just one that works well for us, and that depends on many things.
    #26
  7. DoWorkSon

    DoWorkSon Been here awhile

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    Wilbers suggested 70mm air gap. I believe stock is 60mm?

    I was surprised that hyperpro was almost double.
    #27
  8. itsatdm

    itsatdm Long timer

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    The stock spring is .46kg, Ohlins .55kg, Bitubo .60kg, Hyperpro .52-.74kg, Wilburs ?
    #28
  9. DoWorkSon

    DoWorkSon Been here awhile

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    When I compared them, looked same as stock, but not certain
    #29
  10. Casejeep

    Casejeep Been here awhile

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    I have RaceTech springs .95 on order. Im hoping that the new springs and the adjustable cartridge and top cap of the xChallenge will give me a totally new feel for $300. im going to use 7.5 oil too.
    #30
  11. Bayner

    Bayner Long timer

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    That's a pretty stiff spring... :eek1
    #31
  12. machinebuilder

    machinebuilder Long timer

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    That's what Traxxion uses for their on road setup, I wouldn't want it for anything rough.
    #32
  13. Casejeep

    Casejeep Been here awhile

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    Sorry forgot to add that i have a TT Tank. so it needs to suport my fat ass and 40lbs of fuel.
    #33