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Torsion bars causing harshness?

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  • Torsion bars causing harshness?

    Can anyone explain how the torsion bars aging (200,000km) on a series 2 Pajero can lead to a harsh ride? It's been mentioned on the forum a few times, but I can't see how it would affect the ride. Oh, and it's standard height.
    1999 3.5 NL Exceed Auto, Adelaide, South Australia

  • #2
    the torsion bars are just another kind of spring. they get metal fatigue and go 'soft' with age/use just like any other spring.

    with soft springs, you tend to bounce around more
    '93 NH GLX LWB - Snorkel - Cargo Barrier - 305/70/16's - Long Range Tank - 2" Body Lift - 2" Suspension Lift - Winch - Overhead console/UHF/Lots of Switches - Dual batts - Factory Rear Locker - Front Lokka - Rear drawers - Compressor & Air Tank - Engine Swap 3.8 VP Commodore v6

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    • #3
      I thought they would age strain and go harder/stiffer, causing harshness?
      Current ride. EP91 Starlet Auto
      Missus car: 2005 Platinum DiD Auto, H/R Towbar, Rhino Sportz Aero Bars, Redarc Isolator, Elec Brake Controller. 2" Lift and LT Tyres.

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      • #4
        Yeah, you could be right about that too, depending on how hard/easy a life the vehicle has had, most of it could just be creep since the torsion bars are under a constant load just from the weight of the vehicle, even if you never moved it. This causes creep failure and is where you get yield/strain hardening/strain recovery repeating over a long time and is basically causing the torsion bar to ?unwind? at a microscopic level so the torsion bar has to twist more before it starts to 'take the strain'.

        Fatigue causes microscopic cracking at the points where stresses concentrate. This reduces the effective cross sectional area of the torsion bar, reducing the spring rate. A low spring rate is softer. The torsion bars of that age will likely be suffering the effects of both failure modes combined but possibly more creep than fatigue.

        But enough of that rubbish. If you think you have a problem don?t rush out and buy new torsion bars, wind up the old ones (or reindex them) to counteract the creep losses and see how they go. You might get a few more years out of them - you might get a lot - depending on how much/hard you drive.
        '93 NH GLX LWB - Snorkel - Cargo Barrier - 305/70/16's - Long Range Tank - 2" Body Lift - 2" Suspension Lift - Winch - Overhead console/UHF/Lots of Switches - Dual batts - Factory Rear Locker - Front Lokka - Rear drawers - Compressor & Air Tank - Engine Swap 3.8 VP Commodore v6

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        • #5
          Thanks guys. Both points of view sound valid. It sounds complex.
          1999 3.5 NL Exceed Auto, Adelaide, South Australia

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