Geometry

Discussion in 'Triumph General Discussion' started by Red Thunder, Jun 30, 2016.

  1. Red Thunder

    Red Thunder Crème de la Crème

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    #1 Red Thunder, Jun 30, 2016
    At 'certain' speeds, my handlebars start to swagger in a way that could potentially build up to a tank slapper if I go any faster.
    My reasoning for this would be because there isn't enough weight on the front wheel, maybe caused by the geometry of the bike being to high at the front
    I am tempted to lower the front by 5-10mm to make it more agressive, but what other effects would this have and how do you calculate what is the correct level?
     
  2. 711jrp

    711jrp Active Member

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    #2 711jrp, Jun 30, 2016
    Dropping the front end normally improves turn in but at the COST of high speed stability so I'm not sure this is the way to go.
     
  3. steve lovatt

    steve lovatt Something else

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    #3 steve lovatt, Jun 30, 2016
    Need to be careful here mate - you don't want to find out the hard way!
     
  4. Red Thunder

    Red Thunder Crème de la Crème

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    #4 Red Thunder, Jun 30, 2016
    When I had my front suspension done, they put the forks back in at their highest position (so the top is flush with the pinch grip)
    So I was hoping for a way to 'measure' what the angle/geometry should be
     
  5. Red Thunder

    Red Thunder Crème de la Crème

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    #5 Red Thunder, Jun 30, 2016
    Cheers for the response guys
    I am confident the rear shock is set up correct, it has the correct Sag for my 16st saddle weight
    I will try the 5mm at a time and see how it goes
     
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  6. sprintdave

    sprintdave Nurse, think it's time for his medications.
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    #6 sprintdave, Jun 30, 2016
    Last edited: Jun 30, 2016
    If you lower the front it will get worse. Is it set up standard or has someone already lowered it. Try standard setting.
    I would also check tyre pressures and experiment with them, also condition of tyres can be critical.
     
  7. Sprinter

    Sprinter Kinigit

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    #7 Sprinter, Jun 30, 2016
    I am with half ton, steering head bearings.
     
  8. tcbandituk

    tcbandituk TC
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    #8 tcbandituk, Jun 30, 2016
    Could be the profile of the tyres. Different tyres have different profiles in the same size and may not suit the bike.
    I had a GSXR1100L which was great on the Michelins with a rounded profile, but when I put Pirellis on with a more triangular profile, it was a twitchy buggar.
    But I used the same Pirellis on a ZXR750J and it was as stable as anything on them.
     
  9. Red Thunder

    Red Thunder Crème de la Crème

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    #9 Red Thunder, Jul 1, 2016
    I have Metzeller Z8 fitted front & rear, standard profile with 34psi front and 42psi rear
    Could be head bearings...I will see if they can be tweaked
     
  10. tcbandituk

    tcbandituk TC
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    #10 tcbandituk, Jul 1, 2016
    Just to clarify, you can have two tyres the same size and profile measurement but the actual profile shape of the tyre is different.
    The weight of the tyre can also vary a lot, although that's not relevant here.
     
  11. old git

    old git Well-Known Member

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    #11 old git, Jul 13, 2016
    I've had this with various bikes over the years and every time when tyres have been changed the symptoms disappear.
     
  12. darkman

    darkman Crème de la Crème

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    #12 darkman, Jul 14, 2016
    You could be sitting wrong, ride your bike and as the bars start to move lean forwards by bending your elbows :)
     
  13. Red Thunder

    Red Thunder Crème de la Crème

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    #13 Red Thunder, Jul 14, 2016
    Cheers Darkman, I did retrospectivly look back at what I was doing at the time and the symptoms would be consistent with not enough weight on the front making it light and skittish.
    So when the road was open, I reached the speed again but this time with my head tucked in near the clocks and it was a lot more stable
    My usual position is quite upright and I think with the wind resistance I must have been pulling on the bars to keep myself on.
    I don't usually get to the speed this happens at, so it doesnt happen often.
    The tyres were also 2psi down in each, so this has helped a bit too.

    Cheers for the help guys
     
  14. steve lovatt

    steve lovatt Something else

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    #14 steve lovatt, Jul 14, 2016
    Tyre pressures are always worth checking - 2psi can make a difference
     
  15. darkman

    darkman Crème de la Crème

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    #15 darkman, Jul 14, 2016
    Excellent, Now you can try rotating the bars forwards a little :)
     
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