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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    Checked my sag numbers today.

    Rear was very close. Only had to adjust it one turn on the dial to get 63mm of race sag.

    Front, as I'm sure you can guess, preload maxed out and still have 83mm of race sag. Can't get it to 63mm with these stock springs.

    ben
    #61
  2. wsmc99

    wsmc99 Been here awhile

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    What is the stock suspension travel on your bike? 230mm or 210mm?
    Your sag (Dynamic) should be roughly 25-33% of the travel.
    The 25% of the equation best fits street/sport and 33% dirt. I was about smack in the middle.
    So 57-76mm and 52-69mm respectively. (230mm vs. 210mm)
    I had .52 springs in my forks and stock rear spring which wa too soft for me at 210 lbs.
    With a MT21 front and a 908 rear I had 67mm of sag at the front and the rear preload was turned in 12 turns.
    #62
  3. armourbl

    armourbl Adventure Life

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    Mine is the 210mm of travel bike. Someday I hope to make it like an S version, 265mm. Might settle on 245mm though.

    63mm is 30 percent of 210mm.

    ben
    #63
  4. Bad_Weather

    Bad_Weather Adventurer

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    Armourbl,

    You're getting much better advice in this thread than in the "lower tire pressure for fire / gravel roads thread !

    Guys there wanted to run 40 psi offroad......:huh......sheesh.
    #64
  5. wsmc99

    wsmc99 Been here awhile

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    So what is the bike doing?
    If you don't have the spring, then you will have to compensate at the other end. Lower the rear preload and push the forks down in the triples until you get the correct springs.
    #65
  6. armourbl

    armourbl Adventure Life

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    Since changing the front tire the bike isn't doing anything so wrong that it bothers me. I was just posting my sag info because so many said get the sag right to correct the issues with the Dunlap.

    Can't say for sure if I'll give the 908RR front another try or not. If I rode a higher percentage of off road and more aggressively then it might be worth the trade off of some instability on the pavement. Maybe someday. I've got a lot more acclimating to do on this big bike first.

    ben
    #66
  7. Apple Jam

    Apple Jam Forest Flyer

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    That is exactly what I did for several years. It was not until year 4-5 somewhere when I was ready for what the 908 front had to offer. I woulda hated it too for those first few years.
    #67
  8. armourbl

    armourbl Adventure Life

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    I'll probably end up throwing the 908 front on my CRF, hopefully before the rubber starts to harden from sitting in the garage. At least that way the tire doesn't go to waste.

    ben
    #68
  9. Mr Head

    Mr Head PowerPoint ADV

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    I felt the wobble. It got better as the sharp edges of the front I get a little wiggle now at about 70, that goes away and comes back a little north of 90.
    I figure to run a TKC80 front with the 908 rear once I burn the last of the knobs off this front.
    #69
  10. Nowwhat

    Nowwhat I'll Go Second...

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    Just an opinion....but....

    If you guys look back through the least few years of input on this forum you will see some well accepted precepts.


    1) The TKC in the 21" flavor is not really a knobbie and is one of the most dangerous tires on the highway if you get a flat. The sidewall is sooo soft on the TKC that it pinch flats or tacos rims more than any tire ever made...In a blowout situation at speed the lack of sidewall rigidity makes it a pucker ride...ask me How I know....

    2) If you are riding enough dirt to justify a 908 rear....then the 606 front makes the most sense...The 606 is pretty damn good on pavement and will out perform anything short of the 908 in dirt....Also the stiffer sidewall protects the rim and can handle pressure loss at speed..

    3) Mitas, MT21, Kenda, Karoo, Heidis, Mefos etc etc are street tires that do not need to me mated to a 908 rear....
    #70
  11. Johnf3

    Johnf3 Long timer

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    I agree with most everything you say, but you are wrong about the Pirelli MT 21. It is every bit as much a true knobby tire as a Dunlop 606. It also works great with a rear 908. I have several thousand off road miles with this set up and many others do as well.
    #71
  12. Apple Jam

    Apple Jam Forest Flyer

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    I agree completely. I would use another 606 front (have used 3? previously) if I was concerned about higher pavement speeds. I am not, so my current 908 front setup is perfect for me. I have not tried the MT21 front.
    #72
  13. bluedog52

    bluedog52 Been here awhile

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    Probably not practical for freeway commuters, but what I do as the wobble starts I let go of the left side handle bar put my left hand on thigh or inside between thigh and seat. This is not under hard acceleration of course just cruising at 75-80 vary rare for me to go any distance on tarmac . Just seems sacrilegious with 908 knobbies. Save your knobs, change tires or just stay in the slow lane -75mph.
    #73
  14. Mr Head

    Mr Head PowerPoint ADV

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    Since I ride to dirt when I can and am willing to only manage on one set of wheels on one motorcycle, I'm going to find a combination I like. The wobble from the pair of 908's is probably the worst with the light front springs up front and a bit too much of a load too high up in back. Coupled with too much speed on maybe rain grooves? I do notice the bike is twitchy with any cross-cuts/cracks seams in the pavement angled with travel. Rocks on dirt don't seem to bother it much. Though on dirt my speeds are much, much lower.
    Commuting I end up riding pretty fast. I'm working on training myself to ride slower. I've moved over a couple of lanes to accomplish just that. More for economy than wobbles. In my case the sharp new edges on that front was the culprit initially. The rear doesn't move around like the offset knobbies I've ridden before. I don't have that much experience with them, but some.
    I like the 908 in the dirt enough to put up with it on the street. I like the Scorpion best for street and I've ridden the 19/17 set up on my old BMW Adventure on sand and such with Scorpions, though not the aggressive tread available for the KTM. The old non-A/T version. The tread on that was similar to the Tourance. I'm way too cheap to buy two sets of wheels, or put up with keeping a second set someplace in the garage.
    For the BMW I ended up just buying TKC80's all the time and ignoring the wet weather issues since we don't get much of that here.
    I'm hoping a front TKC80 on the KTM will last a bit longer and take less balance weight than the 908.
    Time will tell.

    Over the weekend I flipped the front 908 around to wear off the other side of the blocks. IT feels fine. The morning after a rain commute was fine.
    #74
  15. Bad_Weather

    Bad_Weather Adventurer

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    If you're ever around HB, I pulled a decent tkc80 off the front of mine prob 70% tread left if you want to try a freebie before you spend $, I went to a 606 up front and ain't going back.
    #75
  16. Katoom119

    Katoom119 Mmmm....Orange Kool-aid

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    +1

    The 908 front is terrifying on pavement until the knobs start to round of a bit.

    TKC's are so soft you can break the bead with your boot, I've done it. I hit a parking lot curb at 25 mph with my 908 front HARD and I didn't even get a pinch flat, much less damage to the tire or rim.

    I'm debating on trying a 606 front or staying with the 908 for my off road wheels, but the Karoo's are essentially street tires with a funny tread pattern.
    #76
  17. wsmc99

    wsmc99 Been here awhile

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    Kenda Trackmaster 760 - seriously folks, try it. DOT approved, good sidewall, good on the road, does the biz in the dirt.
    #77
  18. crofrog

    crofrog Long timer

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    Going to be pretty hard to get a good front ride height with to soft springs.

    The lower the front is, the more wobble, until you get way to much trail and then it comes back again.
    #78
  19. armourbl

    armourbl Adventure Life

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    I have the right springs now, but haven't tried the 908 yet with them. Might try that after this T63 wears out.

    ben
    #79