Paging the trailer towers (behind cars with bikes on them, not behind bikes)

Discussion in 'UK Motorcycles' started by Pete Fisher, Apr 2, 2009.

  1. Pete Fisher

    Pete Fisher Guest

    I think my trusty Tarn 3 bike trailer needs some TLC. It is a testament
    to the longevity of hot dip galvanised chassis and alloy 'runners', that
    if it was a bike it would have made it eligible for the VMCC for the
    last 5 years. Champ seemed unimpressed by this at Prescott a couple of
    years ago, but it justifies what I paid for it back in Manx Millennium

    After 30 years of use, though it has begun to 'thrumble' in a
    disconcerting way at motorway speeds (not saying exactly what, but on
    autoroutes you can 'drive through it').

    At first I thought it was wear on the tow hitch (because it was worn),
    and a new tight fitting one (too tight in some ways) has helped. The
    taper roller wheel bearings seem OK. I repack them with grease and
    adjust them (just perceptible rim rock) each spring, and they spin
    smoothly, though TBF one is a tiny tad rumbly I suppose. Possibly a
    really badly out of balance wheel, and I must do some primitive checks
    to eliminate that.

    But I am also wondering if it could be knackered 'indespension' units
    giving some fore and aft play IYSWIM.

    As a 30th birthday pressie I could treat it to new ones (complete with
    new bearings) as it doesn't owe me much otherwise, except for tyres (and
    lighting boards).

    BTW, for those of you with canbus electrics cars and towing attachments
    two tips:

    1) If you manage to plug in a manky old lighting board socket upside
    down (don't ask), pay attention to the strange combination of lights and
    accompanying strangled noise from the flasher relay beeper. Unplug
    rapidly before it blows the fuse (eventually traced to the one supplying
    the rear 12v auxiliary socket.

    2) If you don't heed tip 1 and despite plugging in a known good lighting
    board the right way up, after replacing the blown fuse, find you gave no
    brake lights on the trailer - all is not necessarily lost. Take it back
    to the place that fitted the kit (not the supplying main dealer in my
    case). If they are a salt of the black country earth, man and lad in a
    shack setup, they may suck their teeth, and then swap the connections to
    use the 'spare' relay on the control box. This is used for reversing
    lights on twin socket or 13 pin socket set ups. As mine is only a pikey
    single 7 pin job I have no need of it. So that's 2 quid for a pint of
    Bathams instead of 25 quid for a new unit plus labour to remake all the

    | Pete Fisher at Home: |
    | Voxan Roadster Gilera Nordwest * 2 Yamaha WR250Z |
    | Gilera GFR * 2 Moto Morini 2C/375 Morini 350 "Forgotten Error" |
    Pete Fisher, Apr 2, 2009
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  2. Pete Fisher

    Pip Guest

    Mine "thrums" at ~70mph, just to remind me I should really be doing
    60. It's wheel balance, since the tyres have worn a bit. The
    bearings are the same as yours, but their thrum is at lower speeds and
    you can tell as it comes and goes with cornering, especially when
    loaded. The higher-speed thrum lessens considerably when loaded,
    otoh, when there's more load on the wheels.
    I'm not convinced that they do that, you know. I think they just jack
    it in, catastrophically.
    Pip, Apr 2, 2009
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  3. Pete Fisher

    antonye Guest

    You've not seen mine. It's shit. Really shit. But it works.

    Best place for *everything* trailer related is here:

    You could build your own from the parts book!
    antonye, Apr 2, 2009
  4. Pete Fisher

    Pete Fisher Guest

    In communiqué
    Indeed. There is a branch not far away. I think Pip may have confirmed
    what the problem is likely to be though. I'll get it up on axle stands
    and see if one of the wheels keeps stopping in the same place after a
    gentle spin.

    | Pete Fisher at Home: |
    | Voxan Roadster Gilera Nordwest * 2 Yamaha WR250Z |
    | Gilera GFR * 2 Moto Morini 2C/375 Morini 350 "Forgotten Error" |
    Pete Fisher, Apr 2, 2009
  5. Pete Fisher

    Pete Fisher Guest

    Very logical. I'll do some rough and ready balance checks.
    Well TBH I only have a vague idea how they work. The blanking off ends
    of the square box section bit that presumably holds the rubber torsion
    thingy has rusted away (the only bits that have) and I wondered if the
    rubber may have perished. But as you say, they probably twang like
    knicker elastic and go completely FUBAR.

    | Pete Fisher at Home: |
    | Voxan Roadster Gilera Nordwest * 2 Yamaha WR250Z |
    | Gilera GFR * 2 Moto Morini 2C/375 Morini 350 "Forgotten Error" |
    Pete Fisher, Apr 2, 2009
  6. Pete Fisher

    gazz Guest

    indispension units are simple, 2 bits of square section steel (outer housing
    which welds/bolts to the trailer, inner bit with the swing arm on it,
    inserted 45 degrees offset), 4 rubber inserts, and not a lot else.

    i guess over time they are bound to wear the rubber inserts away, and when
    that happens i would guess the swing arm bit can move a bit too much on the
    housing, wouldent take much to allow the suspension arm to oscilate as you
    go down the road.

    personaly, i'd just spunk down the dosh for a pair of new suspension units,
    think i paid around 60 quid for a pair of 450 kilo rated ones when i built
    my motorcycle trailer a few years ago, you get the hubs and thus new
    bearings as well, and in one go you've replaced 80% of the moving parts on
    the trailer.

    just depends if they are bolted on or welded on to how much of a bitch they
    are to change out.
    gazz, Apr 3, 2009
  7. Pete Fisher

    Pete Fisher Guest

    In communiqué <>, gazz
    That was my theory. No obvious sign of free play though,
    Six bolts on each. I might soak them in plusgas in anticipation of
    dismantling, but a very crude test suggests that one wheel is
    significantly out of balance. I think I'll get both re-balanced at a
    tyre bay first and take it from there.

    | Pete Fisher at Home: |
    | Voxan Roadster Gilera Nordwest * 2 Yamaha WR250Z |
    | Gilera GFR * 2 Moto Morini 2C/375 Morini 350 "Forgotten Error" |
    Pete Fisher, Apr 3, 2009
  8. Like all Metalastic type things, they fail eventually by separation of
    the rubber from the steel. Indespension *may* have incorporated a
    retention flange or something similar to prevent the moving element or
    complete bush parting company from the mounting tube, but I don't recall
    Grimly Curmudgeon, Apr 3, 2009
  9. Pete Fisher

    Pip Luscher Guest

    Without nipping outside to look, ISTR that the inner box section & the
    outer one are simply held together by flanges that are pressed onto
    one of the box sections. IIRC the rubber isn't bonded to the metal at
    all: it consists of four rubber cylinders that are shrunk by freezing
    using something like liquid nitrogen, then simply inserted from one
    end. As they warm up, they expand and that provides the suspension
    pre-load and retention grip. It was on the telly so it must be true.
    Pip Luscher, Apr 3, 2009
  10. Perhaps it was an earlier design or some other make, then. I distinctly
    recall the design I mention, and thought it a bit iffy.
    Grimly Curmudgeon, Apr 3, 2009
  11. Pete Fisher

    Pip Luscher Guest

    Well the TV prog in question was a long time ago, so wibble.
    Pip Luscher, Apr 4, 2009
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