Wheel wobble on acceleration

Discussion in 'Sportster Models' started by Crambo, Oct 30, 2008.

  1. Crambo

    Crambo Active Member

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    Just had a stage 1 installed on my Nightster and I'm experiencing wheel wobble on acceleration between 140kph 180kph 4th gear, just enough for me to have to back off.
    To be honest I am wringing the snot out of the throttle, I want to see what she does in each gear with the stage 1 installed to see if the fuel manager can handle it (the bike certainly can) it's not running as smoothly as I expected it to but I only had it set up yesterday so I'm trying to nail down any gremlins that may be in there, so far popping and wheel wobble , the last thing I want is to push on ahead and end up with a tank slapper...these underpants have to last me till the weekend:D
     
  2. hjacobson1

    hjacobson1 Active Member

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    Crambo;

    It is very difficult to point you in the right direction with so little data to go on. Most assuredly there cannot be a link between the installation of a stage 1 kit and the handling characteristics of the bike.

    I too have a Nightster and have experienced that the faster it is ridden, the smoother the ride and the better the handling. That said, you should know that I discarded the components that H-D mistakenly calls fork springs and shock absorbers in favor of the real items available from Progressive Suspension.

    Your weight, the position of the foot pegs, tire wear, tire inflation, suspension components, suspension component settings, the wind, road surface can all effect the handling of the bike. In fact, the CG of the bike, and the dynamic loading of the tires can contribute to wobble or in extreme cases a "tank slapper"

    Steering head bearings, adjustment of steering head bearings and things mounted to the handlebars (windshields) can also produce the same effects.

    Also try looking at

    Chassis, Suspension and Front End - Harley Davidson Community

    to see if you can glean any help with this issue.

    Hope you get it solved.
     
  3. glider

    glider Veteran Member

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    Hope you have checked the obvious things like tire pressure and spokes if you have them, also wheel itself for wobble or bearing problems.

    Great post hjacobson1:s
     
  4. Crambo

    Crambo Active Member

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    Thanks for the input guys, I mentioned the stage 1 which consists of Vance and Hines sides shots/Screamin eagle pro heavy breather and V&H fuelpak, because acceleration (I'll do it in mph :p) between 80+mph - 110+mph is much quicker than before apart from the above the Nightster is stock, tyre pressure 30psi front 36psi rear, quite a bit of wind but I've been up this stretch of road before (pre-stage 1) under the same conditions and never had this happen before, it happened twice and exactly between the same speeds and in fourth gear.
    Just a thought, I was talking to a friend of mine about how much the engine vibrates now with the stage 1 setup compared to before, and I'm still waiting for V&H to get back to me because I still haven't got my Fuelpak dialed in correctly, it should be running a little better than it is in my opinion, so could it be possible that between those speeds in that gear my bike is now producing a vibration that matches the resonant frequency of the front wheel setting off a wobble?
    I pretty much matched the resonant frequency of my head whilst driving through a tunnel on the way back home these pipes are way too loud...:small3d012:
     
  5. Crambo

    Crambo Active Member

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    Just a quick update, I recieved an e-mail from Fuelpak support and dialed in the new values, the result was alot less engine vibration, and the pipes sounded a bit quieter...:20:
    I went back onto the same stretch of highway as last week, and climbed up through 80 - 100mph in fourth gear and...nothing!...no wheel wobble, did the same thing three times and not a quiver...:D

    I also came across this on the net which I thought was very interesting...:p

    Speed wobbles are a complex phenomenon and any vehicle with a single steering pivot is capable of exhibiting one. All things have a resonant frequency and when the resonance frequency of the front wheel interacts with that of the frame you get a speed wobble.

    By Jez Loftus

    Q&A: Speed Wobble - BikeRadar
     
  6. NEWHD74FAN

    NEWHD74FAN Experienced Member Retired Moderators

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    Are you using stock tires, worn tread (definitely will cause a wobble), lost wheel weight or bent rim, also sounds like 30 PSI in the front is a little low, I believe manual says it should be 34 or so. May not seem much, but bikes are in a high state of tune, changing tires, adding accessories like sissybar or luggage including low inflation pressure may alter the steering geometry. When was the last time you changed/checked shock fluid and level. I know these should not be a problem with a new bike, but fluid and air can leak out through a bad seal or the like. :bigsmiley32:

    Also, like Glider said, check the axles, tires & wheels along with front end for looseness, run-out, balance and alignment. :newsmile079:

    Hold the front brake hard and push forward and back hard, there should be no unusual clicks or pops when diving the front end, may have loose or worn steering head or bearings. Lotsa luck, with intermittant wobble there are a lot of things to check! :s