DRZ Forks and HPN Tank on a R100 GS PD

Discussion in 'Airheads' started by Daithi, Jan 2, 2012.

  1. Daithi

    Daithi Destination Unknown.

    Joined:
    Dec 18, 2007
    Oddometer:
    180
    Location:
    Cork, Ireland
    Thanks for posting those pics Prutser, the gap between the spring and tyre is very reassuring. PhreakyPhil's figure of a 25mm offset for the 2.50"x17" makes the likelihood of the 2.50"x18" working out based on the space I have between the swingarm and my 18"x4.00" rear with a tourance fitted.

    Thanks for all the help !
    #61
  2. Box'a'bits

    Box'a'bits In need of repair

    Joined:
    Sep 26, 2008
    Oddometer:
    3,169
    Location:
    Wellington, New Zealand
    Also has the Boxer Supplies (Matt Beckers) shortened torque arm to change the angle of the FD & raise the back end. :clap
    #62
  3. Daithi

    Daithi Destination Unknown.

    Joined:
    Dec 18, 2007
    Oddometer:
    180
    Location:
    Cork, Ireland
    How much shorter is the torque arm than standard ?
    #63
  4. Prutser

    Prutser Long timer

    Joined:
    Aug 5, 2012
    Oddometer:
    1,338
    Location:
    The Dutch swamp
    This one I made my self years ago.:D
    I don't know at what length the new owner is using it now.Its adjustable.

    I did take of some of the exhaust to keep the tire from touching it with the 17" rim using the torque arm.
    #64
  5. Daithi

    Daithi Destination Unknown.

    Joined:
    Dec 18, 2007
    Oddometer:
    180
    Location:
    Cork, Ireland
    Will shortening the torque arm lessen the likelihood of failure at that joint ?

    BTW, 18" rim and 1100 hub are gone to Hagon for lacing with the 25mm offset.
    #65
  6. Box'a'bits

    Box'a'bits In need of repair

    Joined:
    Sep 26, 2008
    Oddometer:
    3,169
    Location:
    Wellington, New Zealand
    AFAIK the shortened torgue arm is to gain height from rotating the FD around the pivot. Don't know what impact it has in the Universal Joint nr the FD. Prutser might be able to answer that.If/when I do this I'll be looking to put in the aftermarket driveshaft so that I can service the U-joints.
    #66
  7. Prutser

    Prutser Long timer

    Joined:
    Aug 5, 2012
    Oddometer:
    1,338
    Location:
    The Dutch swamp
    When I used the shorter torque arm I could use a bit longer shock before the drive shaft was rubbing inside the swing arm.( when you do this check iff the bottom spring cup doesn't hit the swing arm when the shock is fully compressed)
    #67
  8. _cy_

    _cy_ Long timer

    Joined:
    Sep 25, 2011
    Oddometer:
    6,505
    Location:
    Tulsa, Oklahoma
    what a project!
    #68
  9. Daithi

    Daithi Destination Unknown.

    Joined:
    Dec 18, 2007
    Oddometer:
    180
    Location:
    Cork, Ireland
    I have an adjustable torque arm (BELOW) awaiting collection, and the wheel should be with me middle of next week. [​IMG]
    [​IMG]
    I've two questions,
    ......the final drive kicks upwards relative to the drive shaft, shortening the torque arm will raise the rear end which is the main reason I'm fitting it, but it should straighten the final drive joint which should make it less prone to failure, d'ye think this would is this the case ??

    .....Box'a'Bits, I saw a photo on here (BELOW) where the torque arm was bolted to a mount welded to the swingarm, it was correctly suggested the weld could tear out of the swingarm if the load was to great which would be bad, but what was the benefit supposed to be ?
    [​IMG]
    #69
  10. Prutser

    Prutser Long timer

    Joined:
    Aug 5, 2012
    Oddometer:
    1,338
    Location:
    The Dutch swamp
    Hi Daithi,

    What tire size are you planning to use ?
    #70
  11. Airhead Wrangler

    Airhead Wrangler Long timer

    Joined:
    Mar 4, 2008
    Oddometer:
    6,839
    Location:
    Back in Seattle, FINALLY
    As a paralever newb still learning the perils and pitfalls of paralever use, I'd be concerned by the fact that these shortened torque arms severely change the angles of the U-joints in relation to one another. These u joints are phased so that they cancel each others' vibrations when they are both operating at similar angles. If one joint is nearly straight and the other is at an angle, then that will result in vibration and axial loading that was not intended by whoever designed this abomination of a driveline. I've been reading up way too much on drivelines trying to eliminate a nasty vibration on my pickup with a 2 piece shaft w/ carrier bearing getting pinion angle and midshaft angle out of the trans within a degree of right. It's been interesting.
    #71
  12. Daithi

    Daithi Destination Unknown.

    Joined:
    Dec 18, 2007
    Oddometer:
    180
    Location:
    Cork, Ireland
    Hi Prutser, based on what you suggested I'll go with 120/90-18 Michelin Comp 3 and a 90/90-21 Comp 4 in the front. Can't wait.[​IMG]

    I won't be going extreme with shortening this, just a small bit to raise the arse end of the bike and maybe straighten the FD out a bit, thanks for the heads-up though.
    #72
  13. Prutser

    Prutser Long timer

    Joined:
    Aug 5, 2012
    Oddometer:
    1,338
    Location:
    The Dutch swamp
    For the rear i use AC10. 120/90. And a comp 4 at the front.
    #73
  14. Box'a'bits

    Box'a'bits In need of repair

    Joined:
    Sep 26, 2008
    Oddometer:
    3,169
    Location:
    Wellington, New Zealand
    Unfortunately I don't have an answer to that. The photo was one I collected sometime ago, & I do not now have details on where it came from. My guess is that the person was seeking to have a straight drive shaft (single u-joint) without needing to go down the monolever conversion route. But there is no sign that the shaft then became 'an oil in shaft' swingarm, so whether he/she achieved what they were seeking from this... don't know.
    #74
  15. Phreaky Phil

    Phreaky Phil Long timer

    Joined:
    Mar 18, 2006
    Oddometer:
    2,173
    Location:
    NEW ZEALAND
    Been thinking about this, i'm sure the BMW triple clamps are closer together than the DRZ ones, therefore with the axle point raised, you could slide the forks down in the clamps and maybe run a flat bottom clamp, not needing a gull wing type ? These are more redily available. I'm thinking about this for a long travel rear end.
    I will have to wait until I get our DR home so I can measure. ( picking it up tomorrow:clap )
    #75
  16. Dmaster

    Dmaster Been here awhile

    Joined:
    Apr 3, 2012
    Oddometer:
    265
    Location:
    Netherlands.
    This mod brought it to this:
    [​IMG]
    Fully compressed the tire (90/90-21) hits the fender and there is just enough space for the dust seal.
    Running a "flat" bottom triple tree is still not a option unless you want much clearance between tire and fender fully compressed. If you want to use full stroke (285mm i guess i measured) your front will be high (something i do not want) I shortened it anyway I'm using my stock swing arm at the back and i still use my stock center stand :D.
    #76
  17. Phreaky Phil

    Phreaky Phil Long timer

    Joined:
    Mar 18, 2006
    Oddometer:
    2,173
    Location:
    NEW ZEALAND
    I was thinking of this setup with a long travel rear and sliding the forks down in the clamps by approx 20mm to use a flat bottom clamp. On page 1 a pic shows a spacer under the top clamp to pack it up as the BMW steering tube is shorter than the DRZ one. Without this spacer, the forks tubes could be slid down. I hope that makes sense !
    #77
  18. Prutser

    Prutser Long timer

    Joined:
    Aug 5, 2012
    Oddometer:
    1,338
    Location:
    The Dutch swamp
    Using the flat tripple would make the bike higher.
    Dmaster made a new stem. And isn't using a spacer under the top triple.(correct me if i'm wrong mate)
    If you would use a flat bottom triple clamp and would fully compress the fork untill the sliders touch the clamp.
    Than there is about 1" of space between the tire and the clamp. This 1" is extra height at the front that can not be used for wheel travel. For the handling of the bike you need to lift the rear end. You could give the rear less sag but that way you will loose traction and comfort.
    Keeping the bike high for ground clearance is nice but the lower bikes handle much better than the high ones with technical riding. ( not talking about fast or straight tracks)

    With this mod the bike can still be low at the front with a lot more travel than original. And some real damping !!!!!
    The damping of the drz fork can be tuned to the needs of the airheads and still use soft springs without the bike bottoming out all the time or dive to the max with hard braking.

    The long travel rear does cost a lot for a few cm's extra wheel travel.
    With the drz fork mod u can gain a lot of travel and controle but still use the stock swing arm.
    #78
  19. Phreaky Phil

    Phreaky Phil Long timer

    Joined:
    Mar 18, 2006
    Oddometer:
    2,173
    Location:
    NEW ZEALAND
    I have thoughts of building up an Expedition bike using my paralever GS and converting it into a longer travel monolever.For 2up riding long travel is needed as you cant stand in the rough stuff so the suspension must soak up everything. Another reason for a long swingarm is with 2uo it moves the weight behind the rear wheel forward. ( I would like to try a longer swingarm in my DR to see if would help stability and steep climbs) The Paralever is maxed out at 190mm of travel. The 1100/1150 Paralevers can be grafted in but the monolever i think is simpler and tougher, and probably lighter ? I think 250mm of Travel would be good. More may be better but the seat height may become a problem. I'm only 5'10" My DR650 with DRZ front and rear running minimal sag before luggage has me on tip toes. You mentioned wanting a clamp with more offset for the DRZ front. I have not ridden an Airhead with small offset clamps and am interested in your thoughts on the handling between the two ?
    Cheers Phil
    #79
  20. Dmaster

    Dmaster Been here awhile

    Joined:
    Apr 3, 2012
    Oddometer:
    265
    Location:
    Netherlands.
    I do use a spacer but it's thin only 10mm i guess (can't remember the exact size)
    I made the new stem as long as the stock DRZ stem but with the bearing sizes and spacing of the BMW bearings.

    what triple tree are you planning to use?

    Suspension wise this is the best i've had.
    Handling wise it's not.
    If i'm riding it with my "super motard" setup (110/70-17 and 130/80-17) at the time it steers well (lowering the front) it will get unstable. I've had a Showa UDS fork with KTM triple tree, this setup was way better (at handeling, but the fork was :puke1.)
    With my offroad setup (90/90-21 and 110/100-18) its steers ok, but is unstable. I've compared it with a stock R65GS and its way better, but the suspension sucks :cry

    Much ground clearance isn't a holy grail IMO.
    At times i got stuck i saw lightweight enduro's all around me get stuck......
    Using your brains before riding into a puddle of mud will help more :evil
    And if I topple over because I can't get my feet to the ground what did I actually win?

    And i always wondered, why a huge HPN tank? The stock PD is big enough right?
    Where are you going if you really need all that gas?
    #80