Bad vibe

Discussion in 'Norton Commando Classic Motorcycles' started by Danno, Apr 15, 2018.

  1. Danno

    Danno

    Joined:
    Feb 7, 2010
    While testing the Titanic, I noticed a judder in the front end at around 70-75mph. Looked down at the front wheel and noticed the tire buzzing in a tight wobble.

    Back at the garage, I spun the wheel and held a piece of chalk with the fender brace and got this:

    [​IMG]

    This is one of four new Avon Roadrunner tires I bought for both bikes, although I don't remember the particular source. anyone else ever see one of these apparently warped at the sidewall?
     
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  2. 850cmndo

    850cmndo

    Joined:
    Dec 9, 2009
    How confident are you of the rim?
     
  3. Fast Eddie

    Fast Eddie VIP MEMBER

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    Oct 4, 2013
    Personally, I’ve never had a bad Avon, and I’ve had a few over the years.

    Did you check the rim?
     
  4. Danno

    Danno

    Joined:
    Feb 7, 2010
    I am going to double check it. I know it wasn't perfect after I changed half the spoke nipples on one side.
     
  5. Danno

    Danno

    Joined:
    Feb 7, 2010
    The rim has a tiny bit of axial and radial runout (as I said it's not perfect), but not near as much as the tire and there doesn't seem to be a corresponding flat or warp on the rim at the point the tire hangs out.
     
  6. Danno

    Danno

    Joined:
    Feb 7, 2010
    The tire is static-balanced like all the tires I mount and the vibe isn't apparent until you get it going pretty good.
     
  7. L.A.B.

    L.A.B. Moderator VIP MEMBER

    Joined:
    Nov 20, 2004
    Are you sure the tyre bead is fully 'up' on the rim as it looks as if it might not be?
     
    chaztuna likes this.
  8. JimC

    JimC

    Joined:
    Oct 12, 2007
    I did have an experience of high speed weave/wobble with the old Avon Venom. I replaced the tire with the exact same size and model Avon. Weave/wobble was gone. Like L.A.B., I too suspected faulty mounting.
     
  9. rvich

    rvich VIP MEMBER

    Joined:
    Jul 25, 2009
    Is that a stock rim? I had some real trouble the last time I mounted tires getting the bead to pop out properly. The tire looked correct until you checked the bead carefully around the edge of the rim. I could see some spots where the tire was essentially trapped in the rim. I believe it is probably due to the narrow rim. I had to get it good and slicked up and get air into it from a compressor and not a hand pump.


    Russ
     
  10. cliffa

    cliffa

    Joined:
    May 26, 2013
    Danno, Is the tyre evenly seated on the rim?
     
  11. JimC

    JimC

    Joined:
    Oct 12, 2007
    Wouldn’t hurt to deflate, break bead (both sides), snot up beads and re-inflate.
     
  12. Danno

    Danno

    Joined:
    Feb 7, 2010
    It looks ok and I always overinflate when mounting tires, especially tubeless, so they seat on the rim. I guess I could deflate it, smear some NoMar lube around and then reinflate.
     
  13. Danno

    Danno

    Joined:
    Feb 7, 2010
    Stock original rim. I have a 90/90 on the front of the SS clone. I might just swap the two.
     
  14. Madnorton

    Madnorton

    Joined:
    Jun 9, 2008
    They can be a pig to fit and get on the rim square, looks like it is mounted across the rim, inflate it and bouncing it tends to get the bead settled concentric, check both sides are the same when done. I prefer to use chalk dust when fitting tyres to avoid any moisture getting behind the rim and under the bead.
     
  15. L.A.B.

    L.A.B. Moderator VIP MEMBER

    Joined:
    Nov 20, 2004
  16. Danno

    Danno

    Joined:
    Feb 7, 2010
    The tiny inner line (looks different than that one) takes a small dive just in front of the asymetrical sidewall spot. I will try to take a pic. I shined a bright LED light on it and used my best cheaters to see it. Camera has a better eye.
     
  17. Danno

    Danno

    Joined:
    Feb 7, 2010
    I took several pics and blew them up and examined them and there appears to be a spot slightly clockwise from the 'bulge' where the tiny edge marks (I think there are 3 ridges) are not quite where they should be, sort of folded in a bit?

    At the center of the 'bulge'
    [​IMG]

    A bit clockwise
    [​IMG]

    A few more degrees clockwise and this appears to be the center of the spot that doesn't look right (to me)
    [​IMG]

    The last pic is the area I'm going to concentrate on.
     
  18. XTINCT

    XTINCT VIP MEMBER

    Joined:
    Jan 10, 2012
    Agree 100%
     
    JimC likes this.
  19. Danno

    Danno

    Joined:
    Feb 7, 2010
    Thanks to all for the suggestions. With most tires, it's readily apparent if they aren't seated correctly. After close examination, I still can't really see if it is or isn't, so I will proceed as if it isn't and see if it makes a difference.
     

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