BMW G650XChallenge FRONT SUSPENSION

Discussion in 'Thumpers' started by lkongo, Oct 21, 2007.

  1. dirtsurfer

    dirtsurfer Challenged Adventurer

    Joined:
    May 10, 2006
    Oddometer:
    2,031
    Location:
    between the bings
    I am interested also
    #81
  2. "A"

    "A" numbum

    Joined:
    Aug 20, 2008
    Oddometer:
    380
    Location:
    Albany Western Australia
    When the alternative is a set of second hand White Power or Shiver forks from KTM or Husqvarna, then the mods to fit them such as I am currently doing, then $200-$300 makes good sense. I reckon there would be at least 5 potential clients in Australia, then youv'e got the rest of the world.
    #82
  3. Cruz

    Cruz Lost but laughing.

    Joined:
    Nov 3, 2008
    Oddometer:
    6,324
    Location:
    Northside Brisbane, Qld Australia
    As stated at the beginning, I am keen. :1drink
    #83
  4. The Jester

    The Jester Been here awhile

    Joined:
    Aug 26, 2005
    Oddometer:
    874
    Location:
    Cornwall, UK
    How about riders in other countries? Is there any way of getting the machining done locally rather than shipping my forks as this would mean having the bike out of action and hassles with customs? Could you work with a machine shop in each country and sell the bits through them?
    #84
  5. Deco

    Deco Been here awhile

    Joined:
    Sep 14, 2007
    Oddometer:
    246
    Location:
    Austin, TX
    +1

    Add a set progressive springs and leap tall buildings in a single bound.:evil
    #85
  6. evoluzione

    evoluzione Been here awhile

    Joined:
    Oct 5, 2005
    Oddometer:
    333
    Location:
    murrieta, california
    i understand your concerns (they're mine also). next week i'm going to try another idea i have and see if i can design something that would be easier for the d.i.y. type customer.
    #86
  7. gus007

    gus007 Been here awhile

    Joined:
    Jun 9, 2007
    Oddometer:
    111
    +1 in Australia.
    #87
  8. Gunslinger1

    Gunslinger1 GIVE'R

    Joined:
    Aug 22, 2006
    Oddometer:
    635
    Location:
    Rolla, MO
    This cured my front suspension.



    [​IMG]
    #88
  9. vince taylor

    vince taylor Adventurer

    Joined:
    Aug 18, 2004
    Oddometer:
    91
    I am definitely in, I am ready to ship the parts to you if you decide to build them . Thanks
    #89
  10. Redbull Addict

    Redbull Addict I need another one...

    Joined:
    Jun 24, 2006
    Oddometer:
    1,262
    Location:
    San Jose / Truckee
    So in order to do this, you had to buy the forks, new wheel and hub and disk brake? Did you have ABS before? Did you have to disable it?
    #90
  11. Gunslinger1

    Gunslinger1 GIVE'R

    Joined:
    Aug 22, 2006
    Oddometer:
    635
    Location:
    Rolla, MO

    :nod ........Emig Racing clamps, and the rest is KTM front end....forks, wheel, hub, brakes, fender...totally transformed the bike.....No ABS.
    #91
  12. vince taylor

    vince taylor Adventurer

    Joined:
    Aug 18, 2004
    Oddometer:
    91

    Any update ? Is there a chance this might happen before I need to start looking for another set of forks ? I know you have put a lot of time in this and just want to say thanks for all your time and effort.
    #92
  13. Cruz

    Cruz Lost but laughing.

    Joined:
    Nov 3, 2008
    Oddometer:
    6,324
    Location:
    Northside Brisbane, Qld Australia
    Just bringing this back up again to see if this is still progressing or anything else new out there?

    I have tried every suspension shop I can search on the web and no one makes a replacement cartridge for the X Challenge.

    There is a company in the USA who could make one up but the cost would be a minimum of $1700usd. Out of my price range.

    Just going to fit some Hyperpro springs and new oil to see how that goes and then maybe look at a steering damper to help with the deflection issues if they are still there.

    What weight oil have people used?

    My full dressed weight (bumbag & toold etc) is 110kgs. 10 weight?
    #93
  14. tbarstow

    tbarstow Two-wheelin' Fool

    Joined:
    Jul 9, 2007
    Oddometer:
    3,534
    Location:
    Viva Lost Wages!
    TrailTricks.com fixed my front suspension. It was spendy but completely worth it.
    #94
  15. Cruz

    Cruz Lost but laughing.

    Joined:
    Nov 3, 2008
    Oddometer:
    6,324
    Location:
    Northside Brisbane, Qld Australia
    But what did they do to it TB?
    #95
  16. tbarstow

    tbarstow Two-wheelin' Fool

    Joined:
    Jul 9, 2007
    Oddometer:
    3,534
    Location:
    Viva Lost Wages!

    They respring and revalve the forks. The OEM valves are crimped on (or so I'm told). TrailTricks has the set up to crimp the new valves in. I don't know which valves got put in, but its an incredible difference afterwards.
    #96
  17. davesmyth

    davesmyth Connoisseur

    Joined:
    Oct 21, 2009
    Oddometer:
    124
    Location:
    Coastal Georgia
    Gentlemen,

    I've been reading a lot of threads that advocate softening up the suspension to improve the ride of the G650X Challenge. To a certain extent, I agree; especially if you're going long distances on hardball or improved dirt roads. Soft suspension, however, doesn't solve the constant problem of fork dive, and is particularly bad for riding in sand and loose dirt. Here's what I've come up with, so please take it or leave it as you see fit:

    BMW sets the Compression and Rebound at approximately +11 clicks from "0" (all the way counterclockwise to full stop). I don't know if this is true across the board, but that seems to be the general consensus. If these settings are made for a 75kg man, then it stands to reason that you can do a little Algebra and arrive at the perfect setting for your weight. I fiddled with the suspension to get the best road setting for me using Pirelli Scorpion Rally tires, front and rear (very aggressive knobby tires, but DOT approved). I arrived at +11 for Compression, and +9 for Rebound. Rear suspension was set to 114psi and "Soft" setting using the following equation: 85kg/ 97.2psi = 100kg/ x. x = 114psi. I used 85kg because 97.2psi is what BMW recommends for a 85kg man in the G650X Challenge Owner's Manual.

    +11/ +9 (from "0") is fine for a 75kg man off-road, I suppose, but I weigh 100kg with riding gear. For whatever reason, my Compression adjustment has 23 clicks, while my Rebound adjustment has 25 clicks. Doing some quick math, I realized that my optimal road settings put my Compression at 48% of max, and my Rebound at 36% of max. That is a perfect 4:3 ratio, which made it very easy for me to adjust my off-road oriented setting for my weight. I set my Compression to +15 from "0" (75/11 = 100/ x; x = 15), and my Rebound to +12 from "0" (75/9 = 100/x; x = 12). I set my Rear Suspension to "Hard", and left the same air pressure at 114psi.

    I took my trusty bike off-road and rode in the training area near my house. The sand out there is terrible, and with soft suspension, your nose dives and it is miserable going. With my harder settings, I was able to glide effortlessly through the sand. I accidentally hit a 3ft deep, 10ft long, and 4ft wide hole coming over a blind hill that I couldn't avoid. My suspension soaked it up like it was nothing! I also drove through a creek that had water crashing completely over the bike. The bike was totally submerged and made it through like it was the most normal thing in the world. I would estimate that the water was 3.5-4ft deep. My balls and ass definitely got wet!

    On improved and gravel roads, the front wheel felt like it floated a bit, but I never felt like I was not in control. I was also moving down the road at 55-60mph (90-100kph). On the road, these suspension settings allowed for a smooth, firm ride with no headshakes until around 70mph (110kph). For the type of riding that I do 90% of the time, that is about ideal. If I want to ride longer distances and spend more time on hardball and improved dirt roads, I can adjust my settings easily back to my +11 C/ +9 D, change the Rear to the "Soft" setting and be good-to-go.

    Suspension is a very personal thing, so you have to find what works best for your style of riding. I hope that these numbers provide you with a good start point for your own suspension adjustments. If you have any questions about how I arrived at my numbers, feel free to send me a PM.

    Regards,
    Dave
    #97
  18. sideway5

    sideway5 Mudmuppet

    Joined:
    Mar 13, 2007
    Oddometer:
    36
    Location:
    Stockholm Sweden
    The reasoning behind the setting for the rear shock I can totally dig, but you misinterpret the front settings imho. The compression and rebound settings has nothing to do with rider weight per se. What these settings do is simply limit the speed of which the fork is allowed to compress or retract and their setting is ultimately determined by your riding style and to the terrain you ride. They provide a dampening effect to the spring which is the actual component that according to BMW is chosen to suit a 75kg rider. So in essence, if you weigh significantly more or less than 75kg you really should consider replacing the spring with a proper one for your weight. That being said, your setting for the fork may be excellent, but your "math" to get there was somewhat strange.

    Happy riding!
    #98
  19. davesmyth

    davesmyth Connoisseur

    Joined:
    Oct 21, 2009
    Oddometer:
    124
    Location:
    Coastal Georgia
    Sideway5,

    I'm going to disagree with you on the statement that the springs themselves are designed for a 75kg rider. If the springs were designed for a 75kg rider, then there would be no reason to adjust for Compression and Rebound. As justification, I would ask you to refer to the manual where it provides rear suspensioin ratings for both 75kg and 85kg riders. Additionally, BMW states that your Front Suspension Settings (Hard or Soft) need to marry up with the Rear Suspension Settings (Hard or Soft). If you are over 50% on the "+" side of the Compression or Rebound, I'd advise to set your Rear Suspension to "Hard"; if you are over 50% on the "-" side, I'd advise you to set your suspension to "Soft".

    Mass has everything to do with suspension settings and how those settings respond to the Force applied to the suspension. Force = Mass (measured in Kg) x Acceleration (Meters/ Seconds Squared).

    Once again, suspension settings depend on your size, fitness and style of riding. Why don't you try my formula and see how it rides? If it doesn't work for you, throw it out. If you don't try the formula and test-ride it yourself, you can't speak with authority as to whether or not it works.

    How do you adjust your suspension?

    Regards,

    Dave
    #99
  20. sideway5

    sideway5 Mudmuppet

    Joined:
    Mar 13, 2007
    Oddometer:
    36
    Location:
    Stockholm Sweden
    With all respect, that statement is just...completely wrong. A spring with no damping would wobble like crazy. You would have absolutely no traction at all.


    I'm guessing now as I don't have the manual in front of me, but those figures refer to air pressure in the bladder right? The pressure in the bladder is also known as PRELOAD. A higher preload (higher pressure) ,somewhat simplified, does the same as a spring with higher spring rate would do to the forks. It has absolutely nothing to do with comp or rebound dampening.

    No argument there.

    Also correct but if you have the wrong spring rate for your weight your fork will not perform in optimal conditions. If you weigh significantly more than the spring is rated for your forks will operate in a constant too compressed state. The spring compresses in a linear fashion so to compress the first say 5cm is going to require half the energy compared to the following 5 cm. This means if you are riding around with your fork constantly 5cm compressed your fork isn't going to be as supple as if you fork was extended to where the optimal ride height is. You need to understand that NO amount of compression or rebound dampening can correct this. The second and equally important thing to understand is that if your fork sags too much it will affect the geometry of the bike making it either nervous or too stable(hard to turn).

    Here is a good guide on setting up your suspension the correct way. Please note the last section on setting up the fork where it says "-Your static sag should be within the limits given in your owners manual. If it is not, you need to change the
    spring, set the race sag, and measure again."

    http://www.harrymoto.com/MX/RaceSag/set_your_race_sag.htm

    I can speak with authority on that formula as it is in part based on bad assumptions.

    I am fortunate to weigh approx 75 kg so my setup is very close to neutral. I have a few clicks negative on rebound and compression as I like it on the soft side.

    No hard feelings, just trying to help out.
    brgds / sideway5