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  • Torsion Bars

    found this as well

    Torsion Bars Explained




    There still is a lot of misconception about the nature of torsion bars. Hopefully this will help clarify the nature and design of the torsion bar independent suspension setup.



    To begin with, the torsion bar, like the leaf and coil, is simply a spring. A piece of material which when distorted tries to return to its original position. Like the leaf and coil, the torsion bar can loose its memory [sag], or break. The torsion bar, like the conventional leaf or coil spring is at one end fastened to the frame so as not to move during operation. The other end of the torsion bar is fastened to a pivot [the control arm]. Now as force [weight] is applied to the pivot end [control arm] it tries to move and take the torsion bar with it, the opposite end being fastened to the frame, can not move so the bar twists and then tries to return to its memory position. This being the point at which the pivot end [control arm] originated. With no applied force [weight], the torsion bar will keep its pivot end [control arm] at the position or angle in which it was originally set. As a constant applied force [set weight] acts upon the torsion bar the torsion bar is resisted from returning all the way back to it's memory or set position. the amount by which the torsion bar can not return to its memory [set] position becomes pre load. Pre load is solely controlled by the amount of force [weight] applied to the torsion bar.



    To adjust the ride height of the vehicle by winding the adjuster bolt at the fixed [frame] end of the torsion bar does not add any more force [weight] to the pivot [control arm] end of the torsion bar, therefore the pre load is unaffected, hence ride quality and torsion bar life theoretically remain unchanged. Winding the torsion bar adjuster bolt is the same as installing blocks between the axle and lief springs or a set of coil spacers, it simply moves the spring to a different position.



    The reason the truck may ride a little stiffer is because of the new angle of the pivot [control arm]. As this angle [control arm to ground] becomes grater, the pivot [control arm] exerts less force on the torsion bar effectively reducing the pre load.



    Other reasons for a harsh ride after winding the adjuster bolts is, YOU WENT TOO FAR. This is when there is not enough room or no room between the control arm and upper bump stops, leaving no room for downwards travel of the control arm. When to replace your torsion bars with larger ones is if you have added substantial weight [winch, large bush bar, heavy bumper, heavier engine, etc.] or if you are looking for a firmer ride. The affected longevity of related components such as c.v. joints, ball joints, spindles, etc. will be the same weather the heavier torsion bars are used or the originals are adjusted, since these components are affected by the selected angle of the control arm. After a height adjustment is made either way, it is a good idea to have an alignment, but you will most times find that everything is still in spec.
    (\__/)
    (='.'=) SQUIRREL MUNCHER GRRRRRRR
    (")_(")

  • #2
    Hi

    Good explination, Ive read alot of messages on here saying that you should not adjust your torsion bars more then 1.5 inches or you may run into problems.

    The trouble is I dont know if my torsion bars have already been adjusted to the max or if they are still at factory settings.

    Is there any way of finding out if they have already been adjusted?

    Is there a maxium distance from top of wheel arch to top of rim. Ive got 15 inch rims with 31/10.50R15.

    cheer's
    Jameson
    *************
    1990 SURF 2.4TD

    Comment


    • #3
      Originally posted by Jameson
      Hi

      Good explination, Ive read alot of messages on here saying that you should not adjust your torsion bars more then 1.5 inches or you may run into problems.

      The trouble is I dont know if my torsion bars have already been adjusted to the max or if they are still at factory settings.

      Is there any way of finding out if they have already been adjusted?

      Is there a maxium distance from top of wheel arch to top of rim. Ive got 15 inch rims with 31/10.50R15.

      cheer's
      The reason for not adjusting the torsion bars more than 1 1/2" has nothing to do with the torsion bar and not overstressing it, it's all to do with not exceeding the most extreme angle for the CV joints to work at. Any more and you will kill the CV joints.

      I'm pretty sure thats the case unless anyone knows different.

      Cheers

      Comment


      • #4
        Originally posted by lucky
        The reason for not adjusting the torsion bars more than 1 1/2" has nothing to do with the torsion bar and not overstressing it, it's all to do with not exceeding the most extreme angle for the CV joints to work at. Any more and you will kill the CV joints.

        I'm pretty sure thats the case unless anyone knows different.

        Cheers
        Bingo, Toy CV's won't run at much more angle than standard, so increasing the angle they work at by altering the ride height with the torsion bars will lead to premeture wear. This can be over come by fitting manual hubs and leaving them off, or lowering the diff.

        Any amount of tweeking the torsions brings the upper bumpstop closer together, leading to a bumpy ride, they need cutting in half to get some movement back into the front suspension (not that you get alot with Toy IFS anyway).

        You'd better check, but I think 14" is the normal measurement from top of wheel rim (15" rims) to wheel arch lip on the wing for standard 2nd gen Surfs.

        4x4toys.co.uk - Keeping you on and off the road...

        Comment


        • #5
          I'm pretty certain that when I fitted the uprated bars I set the rim to arch distance to 14-3/4". However as Tony says to make use of this you need to change or cut down the bump stops as it pretty much sits on the standard units at this height.
          Roger

          My Pointer ate the dog trainer

          Comment


          • #6
            Cheer's guys,

            Thanks for the info!

            So if 14'' is the default setting you could go as far as 15 1/2" as long as you trim the bump stops? (with more wear on cv's)

            I think I measured mine as being 16" on one side and 15 1/4" on other. Ive never adjusted them but that does seem to much, although Ive never had any prob's with bump stops or with bumpy ride.

            Got her on axel stands at mo, waitng for brake pads. So when she's back down on the ground I will confirm measurments.
            Jameson
            *************
            1990 SURF 2.4TD

            Comment


            • #7
              offical word on the front, manual is offically for the LN 80 to 111 chassis, but cant see newer ones being that different, lets have a communial measure, and see what we end up with...
              Attached Files
              4x4toys.co.uk - Keeping you on and off the road...

              Comment


              • #8
                Got mine back down on the deck and she's measuring 14 1/4 inches from top of wheel arch to top of 15" rim.

                gonna crank her up to 15" and leave it at that.
                Jameson
                *************
                1990 SURF 2.4TD

                Comment

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