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Excessive Understeer

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  • #16
    Hi Gordon,

    By measurement and calculation the original caster angle was 3.5 deg. (As per the technical manual). The shims that I installed gave an angle of 2 deg. rotating the axle forward so the current caster angle is around 1.5 deg.

    Regards,
    Dick


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    • #17
      Hi Dick,

      Many thanks for your reply. It is great to see such good technical information published along with an evaluation of its effect.

      Regards,
      Gordon.

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      • #18
        Hello, Alistair,

        Nice to hear from you.....you have been very quiet recently.

        I have a theory about Talbot steering but I will wait until I can carry out more road testing then I may do a write up on it.

        sorry to hear about your gearbox......had a lot of issues with mine but now, fingers crossed, it is ok and even silent on tickover.

        take care snd stay safe,

        Dick.

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        • #19
          Today I went shopping in the 14/45 so It was the first time I had tried the car with wedges fitted between springs and axle. This reduced the caster angle from 4.9 to 1.9 degrees. Steering transformed - much lighter and runs true on a flat road without steering input. Thanks to Dick Campbell for allertng me to Talbots tendency for their chassis to take a set that increases caster angle. Also as Dick suggested with Perrot shaft brakes reducing the caster angle would require the front brake rod lengths to need resetting and I found the amount was significant. Also thanks to David Adams in New Zealand for suggesting that 'tuning' the caster angle could be quite productive.

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          • #20
            I finally went tested my reduced caster wedges yesterday.

            These were Land Rover caster correction wedges which are used on leaf sprung Series Land Rovers when the ride height is increased by 2" to restore the prop shaft geometry.

            The wedges have a 3° taper so left around 0.5° of caster.

            This modification gave the same result as Gordon's post above. It really transformed the steering and handling with no apparent negatives. I now have lighter steering, only sleight understeer, not a bad idea, and wander on undulating roads is much reduced......so it appears to be win, win.

            The question now though is why.

            My front springs are flat when loaded, the starting handle lines up perfectly with the dynamotor dog, so no distorted chassis.

            I am pleased with the outcome but would be happier if I could understand what the original fault was.
            Click image for larger version

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            Here are some photos of the general idea, showing the wedge as bought and then modified to go around the spring clamps and provide fore and aft axle location.

            Regards,

            Dick



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            • #21
              Dick,
              Excellent news on the results. I am surprised that starting with just +.5 degrees on spec caster angle should have given so much effect on your steering and handling. Do you think that the extra weight of your engine could be the critical factor here? Certainly a reduction of 3 degrees in caster on both our cars has had a significant beneficial result although the underlying cause for both of us is different.
              Regards,
              Gordon.

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              • #22
                Hi Gordon,

                I started with 3.5°. I have not measured it as now that the axle is tilted the slope of the spring will not be the actual caster angle, so the 0.5° is just an arithmetic deduction.....3.5° original minus 3° wedge angle.

                Dick.

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                • #23
                  Hi Dick,

                  And a very reasonable one too.

                  Gordon.

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