Possible solution to death wobble with Dunlap 908 RR

Discussion in 'Crazy-Awesome almost Dakar racers (950/990cc)' started by armourbl, Jan 12, 2014.

  1. armourbl

    armourbl Adventure Life

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    Yeah or say it was your fault or some dumb crap like that.

    I think that settles it. I'll be ordering a new front tire. Forget trying to make this one work. Now I just need to figure out what tire to order...oh the madness, someone stop the madness...

    ben
    #21
  2. Bob59601

    Bob59601 Bob59601

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    On my bike it was the rear 908 causing the wobble, which leads me to suspect the suspension settings - at least in my case.:lurk
    #22
  3. Uneasy Rider

    Uneasy Rider The life of Riley

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    Thanks man. Thankfully I was almost fully geared up, minus the riding pants.

    Meh...I used to be somewhat anti-damper myself. Used to be...:wink:

    The SE is on the edge of being too twitchy, add high speed, worn tires or road debris & she will try to slap.
    I still love the bike & wouldn't trade it for anything else.:thumb

    BTW...I had a worn 908 on the rear & a fairly new 606 on the front.
    #23
  4. armourbl

    armourbl Adventure Life

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    How did you come to this conclusion? Only change the rear tire and problem went away?

    I know the rear is tall which probably contributes to the front, but really can't see how it can be the cause of the problem.

    ben
    #24
  5. Bob59601

    Bob59601 Bob59601

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    Almost. I changed the front 908 to a tkc 80 and still had the wobble although it was not quite so scary when it did happen. Then I changed the rear 908 to a karoo and it was gone. Admittedly the rear 908 was well worn when I replaced the front tire.

    I really like the 908 combo for the type of riding I do so especially in the early season. I keep the speed reasonable when I am on the slab.
    #25
  6. armourbl

    armourbl Adventure Life

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    Would be interesting if anyone ever tried changing the rear tire first and the wobble went away and they could keep the 908 front.

    ben
    #26
  7. Misery Goat

    Misery Goat Positating the negative Super Moderator

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    The solution is called preload.
    #27
  8. armourbl

    armourbl Adventure Life

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    Very insightful.

    ben
    #28
  9. Elusion

    Elusion Adventurer

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    I don't think there is any ONE thing that causes the wobble. I've done some internet searching and have found many Scientific papers on the subject. Here are a few:

    http://www3.imperial.ac.uk/pls/portallive/docs/1/35343696.PDF

    http://www3.ic.ac.uk/pls/portallive/docs/1/50172.PDF

    http://www.researchgate.net/publication/226465422_Advances_in_the_Modelling_of_Motorcycle_Dynamics

    I found that once I decreased the pre-load in the rear and increased the front that my "Wobble" decreased dramatically. But I also have 2000miles on my 908s, so that could be a factor.
    I want adjust the forks. Because one of the papers I read (I forgot which) said that an increase in fork length decreased wobble.
    #29
  10. slidewayes

    slidewayes slidewayes

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    Any of you that are tossing your 908s I would be glad to take them off your hands
    #30
  11. GJ990

    GJ990 Been here awhile

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    Not for me it wasn't. For me it was a different tire.
    #31
  12. armourbl

    armourbl Adventure Life

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    Second Update:

    Mounted up a new Michelin T63 to the front this morning and then rode for 60 miles. Just to recap, I'm still running with the Ride On product in the inner tube. With the new tire, I also removed the wheel balance weights. The road conditions were a mix of surface streets, freeway, hwy, asphalt and grooved concrete.

    It probably comes as no surprise to many of you, but changing the front tire was the cure for my wobble issues. Rode steady and stable on any and all road conditions at any speed. Make me a heck of a lot happier with the new bike.

    The T63 isn't an aggressive knobby tire, but still has enough there to make it good probably most conditions, but I'm guessing not great off road. For now, I'm happy with that. It will be a long while before I start single-tracking this beast, and most dirt it will see will probably be fire roads for the time being. And when it does see dirt I'm expecting to be loaded down and not trying to set any time/speed records off road. I have my CRF450R for that kind of riding.

    ben
    #32
  13. armourbl

    armourbl Adventure Life

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    Last update for this thread -- at least I think so...

    I rode the bike about 250 miles on Monday. Rode from Phoenix area to Sedona (Arizona). The T63 did very well. Was two up with the wife on back. Even rode on a rock-infested jeep road for about 5-6 miles.

    The more miles I put on the new tire the better it gets. On the way home there was some wind and buffeting from big trucks, rough pavement, etc., it just took it all in stride. My butt was a little sore near the end though, damn hard seat for an overland bike...

    ben
    #33
  14. GJ990

    GJ990 Been here awhile

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    It seems to he related, at least somewhat, to the size of the knobs 😳. The KBB on my bike also has a larger, less aggressive knob design. So, I guess it's a compromise between all out dirt vs dual sport.

    Yea, yea, let the large knob jokes commence.
    #34
  15. KEELAYMONSTER

    KEELAYMONSTER BRRAAAAPPP!!!

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    The biggest reason 908's are "loose" is besause they are in fact...a KNOBBY!

    Yes propperly setup suspension, steering dampners and the like help it considerably. The real deal is whether you feel comfortable enough as a rider to deal with a wiggly, loose riding bike.

    I had a set of 908's that were mostly worn and not so great for the dirt anylonger. I kept them on and commuted on them for the rest of their life. I like to get my money's worht out of my tires :D. My commute is CA HWY680 cruising anywhere between 80-85. Yes, they were loose. Keep a loose grip on the bars and let it wander a bit. Just Imagine you are riding through a really loose trail. Its not for everyone but some dont mind.

    I say do whats comfortable for you. The best thing you can have on your motorcycle is confidence.
    #35
  16. wsmc99

    wsmc99 Been here awhile

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    I ran a 908 rear with a MT21 front and it would wag at a given speed.
    By playing with the geometry I was able to eliminate that.
    There was never any issues with TKC80's or the stock Scorpion A/T's.

    I would say they both contributed to the imbalance and I had the same wag issue with an MT21 front on my DRZ400.

    I put a Kenda Trackmaster 761 on the DRZ, stable as could be, so the MT21 is a bit particular to set up.

    I liked the 908 in the dirt in Baja and it was fun to light it up sideways up my drive on the way home too! ;-)
    #36
  17. armourbl

    armourbl Adventure Life

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    Glad I didn't try the MT21, it was that or the T63 for choices in stock at the dealer.

    ben
    #37
  18. Beer

    Beer 950 SE

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    i think by far the best solution is called a steering damper

    Ive been running a Mt21 front and D908 Rear combo on my SE for the last 17000 miles - the first 5000 or so were without a steering damper and the bike would slightly weave at speed when i accerated hard - never unduly woried me but i always had a slight concern in the back of my mind it might go into a tank slapper....


    ...anyways a couple of years ago i fitted a ralle moto steering damper it and transformed the feel of the bike - made it far more stable and gave the mighty SE much more of a 'road bike feel'.

    http://www.rallemoto.com/contents/en-us/d7.html

    Its up to you you can try adjusting suspension settings etc till the cows come home, but if you want to get rid of the risk of a major tank slapper once and for all in my book the only answer is a steering damper.

    Safe riding lads!!
    #38
  19. youngblood

    youngblood Been here awhile

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    Make sure the sequence of properly installing a front wheel is followed. So many folks just torque their stuff up without properly preventing fork binding. These principles are demonstrated here: http://www.youtube.com/watch?v=siSIue3IWeI

    Love the D606 knobby especially when pushing the big 990S offroad. Like a rudder compared to other tires! For me, the high speed wobble was something that was so rare (I hate slab!) that it was worth the tradeoff.

    My setup is not stock as have a steering damper with an Emig front triple and damper so it is more pronounced with the steeper angle. At 90+mph dropping the left hand off the bar allows things to settle down although the wobble did not ever try to approach a slapper.

    If you do that much slab, you should find another tire for sure. The TKCs are a good compromise from all accounts.
    #39
  20. Misery Goat

    Misery Goat Positating the negative Super Moderator

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    If your sag is correct you wouldn't need a different tire.
    #40