2012 Bonneville Handling Issues

Discussion in 'Technical Help' started by AGP556, Feb 12, 2021.

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  1. AGP556

    AGP556 New Member

    Feb 12, 2021
    3
    3
    Malta
    Hi All,

    I just bought a 2012 Bonneville which has been messed about with. It now sits on a spoked 17" rear and an 18" also spoked front wheel, instead of the standard spec 17". I seem to be fighting the bike to make it go round the bends and I put this down to the trail and rake being messed up because of the change in front wheel size. Is it possible to correct this without changing the front rim?

    Albert
     
  2. Samsgrandad

    Samsgrandad Senior Member

    Dec 15, 2019
    496
    213
    Somerset
    Is it just the wheel sizes that have been changed or have the forks been changed as well?
    If original forks then may be a new 17" rim laced onto your existing hubs.

    Can you post a few photos of the bike, it might help other members offer advice
     
  3. dav.a

    dav.a Well-Known Member

    Jul 29, 2018
    158
    93
    Argyll
    When using a lowering kit it is advisable to lower the forks in the yolks by a small amount to maintain the trail and rake and hence maintaining the bikes handling. Fitting an 18" wheel will have raised the front and unless the forks have been adjusted to compensate the trail and rake will now be different. I read somewhere that lowering the front makes it easier for a bike to turn in so if I were you I would lower the front forks in the yolks probably by about 10 to 13mm and see if there is an improvement. I think there will be.
     
    • Agree Agree x 1
  4. tcbandituk

    Subscriber

    Apr 8, 2016
    2,763
    1,000
    Reading
    There could be a lot of other things causing the issue (tyres, poor suspension set up etc) but assuming they're ok, the Bonnie is a sweet handling bike on the 17" wheels (better than with the bigger diameter wheels).
    So I'd say either switch to cast wheels and get the advantage of having tubeless tyres as well or, if you want to keep the tubed wire wheels, get a 17" rim put on as Samsgrandad suggests.
     
  5. AGP556

    AGP556 New Member

    Feb 12, 2021
    3
    3
    Malta
    BONNEVILLE 2012.jpg

    This is my Bonneville. I am not sure whether the forks have been changed or not but certainly the paint has been removed off the sliders and these have been polished up instead. I have taken some measurements of the new trail which amounts to 148mm. This seems too much to me when compared to the original factory figure of 117mm.
    A
     
    • Like Like x 1
  6. AGP556

    AGP556 New Member

    Feb 12, 2021
    3
    3
    Malta
    I believe this is the way to go dav.a. I have measured the new trail and found it to be 148mm. The original factory dimensions is 117mm so there is quite a bit to go. But I will try lowering the front as you suggest and see how close I can get to the 117mm figure. IThe bike is stable as is but I have to fight it to make it turn, hopefully lowering the forks will have the desired result.

    Thanks,
    Albert
     
  7. Alatamoc

    Alatamoc Senior Member

    Mar 29, 2019
    493
    113
    Uk
    And of course check your tyres aren't underinflated.
     
  8. andyc1

    andyc1 Lunarville 7, Airlock 3

    Feb 4, 2017
    2,858
    1,000
    N. Ireland
    If the larger front wheel is causing the issues you could try to find a smaller tyre? Assuming the profile is a 100/90 then a 100/80 would get you within 2 or 3mm of where it should be. I don't know how common a profile like that is though and could be a problem trying to find an odd size.
     
  9. Smilinjack

    Smilinjack Guest

    Didn't that model originally have a 19" front? I'm sure the T100 did, for example. The alloy wheel 865 Bonnies like mine (SE) were 17" front and rear. Is it the 865 engine? What model is it, exactly? :)
     
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