An Unholy Union III: WP 4860 USD Forks on an Airhead

Discussion in 'Airheads' started by Airhead Wrangler, Oct 21, 2011.

  1. jbcaddy

    jbcaddy Long timer

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    those new style rotors are lighter, run cooler and when you play in the dirt, can work longer before getting jambed up with mud. Motostrano has some kits with larger rotors for supermoto that will work for you

    http://www.motostrano.com/
    #41
  2. Airhead Wrangler

    Airhead Wrangler Long timer

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    They're lighter because they're half air. I'm thinking they'll probably last half as long.
    #42
  3. One Less Harley

    One Less Harley OH.THAT'S GONNA HURT

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    are all upside down forks from KTM 250 and up all 4860's?? What about spring rates, caliper mounts and axles? I assume they are different? Would it be better for the front end to come from a 250cc or larger and 2000 and newer? I haven't seen where this has been discussed w/ the 4860's. Just thinking of picking up a set for possible future use.
    #43
  4. Airhead Wrangler

    Airhead Wrangler Long timer

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    What's written below is MY UNDERSTANDING and should not be taken as fact. Do your own research. That said:

    They started using 4860s in 2001(?) I believe and not on all models, some got the 4357s. In 2003 they did away with the 4357s and changed the axle size on the 4860s from 20mm to 26mm. In 2007 they switched from what they call a single chamber design to a dual chamber (what the rest of the world calls cartridge forks). I can't remember which models from 2007 on got the closed damping cartridge (only SX models?). As far as I know all the 2003+ 4860s use the same 26mm axle except for the 950/990 adventures which use a 30mm axle. From everything I've read all the 4860s have the same caliper mounting arrangement. Steer clear of the supermoto models as they appear to be unique in a lot of ways and are incompatible with a lot of parts that all the other models share. Also, the 950/990 adventure models have longer uppers and shorter travel than the dirt bike models. The 640 adventure had forks that as far as I can tell are identical to the dirt models with the exception of optional dual discs.

    In short, the 125-525 SX, XC, EXC, models 2003-2011 are identical externally (length, travel, caliper mounts, axle). The SX models (I think) from 2007 on have closed cartridge internals.
    #44
  5. igormortis

    igormortis Cafe Reise

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    Have to agree with you there. Have you considered the HE discs?
    #45
  6. Airhead Wrangler

    Airhead Wrangler Long timer

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    Looks like brembo makes just what I'm looking for, but of course it costs $100 more than all the other oversize rotors on the market.

    [​IMG]
    #46
  7. One Less Harley

    One Less Harley OH.THAT'S GONNA HURT

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    Get them to knock off the $100 Brembo buttons.

    Thanks for the fork reply.
    #47
  8. Houseoffubar

    Houseoffubar HoFmetalworks.com

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    +1
    #48
  9. bgoodsoil

    bgoodsoil Dare to be Stupid

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    #49
  10. jimbee

    jimbee Airhead Intermediate

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    +3 thx

    this thread moves fast
    #50
  11. Airhead Wrangler

    Airhead Wrangler Long timer

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    Ha! I actually found exactly that. QTM uses the same exact brembo rotor on their own carrier - no blingy brembo buttons - and guess what - it's $100 cheaper. :rofl

    [​IMG]

    In defense of the brembo one, it DOES include a set of brake pads.

    QTM also sells this one which is a bit more... um... Judaic?

    [​IMG]
    #51
  12. Houseoffubar

    Houseoffubar HoFmetalworks.com

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    Ask, and ye shall receive!:lol3
    #52
  13. AntonLargiader

    AntonLargiader Long timer

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    I asked around on that issue about a year ago and didn't get much:

    http://www.advrider.com/forums/showthread.php?p=13103892#post13103892

    For me, the 225mm stroke is OK, 250 max. I just want better performance.
    #53
  14. Airhead Wrangler

    Airhead Wrangler Long timer

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    I think the biggest thing hurting the performance of the stock GS forks is the 20 pounds of wheel and front brake at the bottom of them. The wheel itself is 13 pounds, the rotor 4, and the caliper almost 3. I'd bet a lighter front wheel setup would improve things drastically, but as long as you're going that far it'd be easier to just do the whole front end.
    #54
  15. espressodrinker

    espressodrinker Cape Town Wanderer

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    I also like the idea of keeping the existing steering geometry - not that I really know if it's optimal. I can only assume that the infamous HPN cartridge inserts are actually standard parts from somewhere that they probably just tweaked a bit?
    #55
  16. AliBaba

    AliBaba Been here awhile

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    The HPN cartridge inserts have nothing to do with HPN.
    The inserts was available from BMW but different German tuners also had them in stock (I bought mine from Q-tech when they where NLA at BMW). HPN had a lot in stock, probably because they use them for their model HPN-Basis.
    ------

    The original front rim is heavy but it's also very solid. I used one for 180.000 kms without problems and no maintenance. On my KTM I change wheel-bearings at least every year and the rims get dented pretty easy. The wheel-axle is hollow and I wouldn't used it for a GS.

    Another issue is the KTM mastercylinder, the reservoir is small so guess what happens when the pads wear out... But all this can be fixed, and I'm not sure if the issues I mention is valid for all KTM-parts.

    4860 comes in a lot of variations (springs, shims, preload, number of bearings etc) and it would normally require a bit of fiddling to get them to work properly. But they are great shocks and parts and knowledge is widely available.
    The increased steering-radius is an issue but personally I think an upgrade to a WP4860 with 220-250mm stroke is an interesting upgrade for a bike with standard frame.
    #56
  17. Airhead Wrangler

    Airhead Wrangler Long timer

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    Care to tell us more about the 4860 setup you have on your HPN? You use the HPN setup with wider leg spacing and the R100GS front wheel, right? Do you happen to know what stem to leg offset the HPN triple clamps use and what exactly the leg spacing is? Any hints for spring weight and valving? How much travel on yours? Detailed pics wouldn't hurt.:evil
    #57
  18. Stagehand

    Stagehand Imperfectionist

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  19. AliBaba

    AliBaba Been here awhile

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    My HPN-setup is built to fit standard brake and wheel (they also have other options). I use a standard hub with a Behr-rim (not TL) and 4mm spokes.

    I don't have any proper tools handy so this is a bit rough:
    Leg spacing = 210mm (std =190mm)
    Stem to leg offset = 25mm (std = 38mm)

    The travel on mine is 300mm.
    My springs are a bit stiff. I use weight 5 oil with an airgap of 100mm, with a softer spring I think 105-110 mm airgap would be correct.
    Valving is difficult... Mine is pretty good but I know a suspension-tuner who has made a great setup for KTM950SE and I will talk to him next year when I change the springs.
    If you buy a used forks a lot of them have been revalved, and it's hard to know what you get. The WP4860 on my EXC is revalved and it's extremely nice, but it's far to soft for the BMW.

    A mix of old pictures:


    Building:
    [​IMG]

    Old and new:
    [​IMG]

    Lubed:
    [​IMG]

    Overview:
    [​IMG]

    Distance:
    [​IMG]
    #59
  20. Airhead Wrangler

    Airhead Wrangler Long timer

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    YES!! Thanks. That's some really good info. I was surprised that the offset was as small as 25mm. Everyone so far has told me that HPN used roughly the same offset as BMW, but looking at your photos it's obviously not even close. Any idea what your spring rate is??
    #60