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  • ladder bar length--vs--wheelbase

    so im burning the candle at both ends trying to work on the 2 vettes,
    the 55, the chopper, and now the k5 blazer too. typical carcrackhead,
    right? anyway i have both a 48" and a 67" set of ladders, given the
    relatively stubby 106.5" wheelbase of the blazer but also taking into
    account the monster 10" suspension lift (with 6"rear spring/4" rear blocks
    and full 10" spring no blocks up front), the giant 36"x13" tires & 5k+ weight etc.

    which set is more suited for me to use? i know at least one of the regulars
    out there must have a better idea than i do about which length i should run.

    ( NO, superbuick-- we are NOT 4 linking it.... )

    thanks in advance.....
    Last edited by fatguyzinc; April 25, 2019, 12:07 AM.

  • #2
    I see ladder bars on trucks w/ leaf springs sometimes but, being as the paths the axle takes during suspension movement while mounted on leafs or at the end of a ladder bar are in conflict I don't know how it would work too well without also installing something like these to take up the difference:
    Click image for larger version

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    This device is not made to get a bunch of dirt in it and you'd still have the problem of body roll (necessary) being prevented unless the front mounts were very close together, as seen from above.

    Otherwise if the "ladder bar" is just a link such as this...

    Click image for larger version

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    ...then it wouldn't matter so much, just the the line between bar front and rear mounts has to be parallel with the line between the leaf spring front mount and where it goes across the axle, as shown in the pic.

    As far as length goes, seems like for an off-roader longer would be better but used as a conventional ladder bar the longer part stresses the housing more in roll, due to the added leverage. Just a guess; I'd think that more than half the wheelbase would be excessive.

    Sometimes in older trucks people have the springs so stiff that there isn't enough movement for geometry issues to show anyhow.

    I bet SBG would be happy to send you over to Pirate 4x4 with your question.

    ...Maybe better to just search and find what's already been written...
    ...

    Comment


    • #3
      Is it just simply a length that never touches the spring at the angle they are on?

      Now we are getting ready to cut the new driveshaft for the camaro, I look at the "correct" points on the dowel of the spring and the brackets that all we did was weld two metal bars in to make up the difference in the multi leaf springs. The tire (too big 275-60-15) has about 2" of space to the front of the quarter and more room in back. I drilled new holes for the dowel in the bracket and slid the axle back the inch and a half it needs, but the bracket then sits on more of the up swing of the spring. I am pretty sure the big u bolts will keep a rear axle in place, but maybe adding this would be an answer. I have just never seen them attached to the frame, I thought they just pivoted under the spring.


      I did want to do the four link back there, but could never figure out the coils and shocks.
      Last edited by anotheridiot; April 25, 2019, 05:36 AM.

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      • #4
        Originally posted by Loren View Post

        ...Maybe better to just search and find what's already been written...



        yup, thats always the first thing i do.
        50,000 threads and not a dang thing
        about wheelbase vs ladder length
        or how to size em up, other than
        the generic "long car long ladder/
        short car short ladder".

        even google wasnt my friend on
        this one...........

        Comment


        • #5
          There is some discussion about how the set up of four link bars affect the "instant center", and where the instant center should be, relative to the CG, and a line drawn through the intersection of various points on the car. One of these points is the front wheels.

          The ladder bar has a fixed "instant center", so you can't adjust where it is, without changing the length of the ladder bar.

          Reading up on this subject might give you some insight...but probably you'll decide it's not something you should fight?

          My fabulous web page

          "If it don't go, chrome it!" --Stroker McGurk

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          • #6
            Way I understand it is the "way to do it" keeping springs and adding ladder bars is they need to be the same length up front from rear center line.
            A system I saw work good on a Jeep pickup with 46's or 48's was the bar was level, with the front spring eye, set on the rear with a pedsel.
            Longer (or shorter) makes different actuating points, causing bind.

            This might be too simple..

            Comment


            • #7
              Originally posted by Loren View Post
              I see ladder bars on trucks w/ leaf springs sometimes but, being as the paths the axle takes during suspension movement while mounted on leafs or at the end of a ladder bar are in conflict I don't know how it would work too well without also installing something like these to take up the difference:
              Click image for larger version

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Views:	2548
Size:	11.3 KB
ID:	1241220

              This device is not made to get a bunch of dirt in it and you'd still have the problem of body roll (necessary) being prevented unless the front mounts were very close together, as seen from above.
              I suspect that putting a shackle at both ends of the link would accomplish the same thing in a more dirt-resistant manner.

              The ladder bar length and mounting points determine anti-squat and anti-dive effects of the suspension. There's a decent write-up of that here:
              Good evening friends and welcome back to my website. In the last post, I have started weight transfer theory in vehicles. So, continuing the topic today I would be writing about how to design...

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              • #8
                Originally posted by squirrel View Post
                There is some discussion about how the set up of four link bars affect the "instant center", and where the instant center should be, relative to the CG, and a line drawn through the intersection of various points on the car. One of these points is the front wheels.

                The ladder bar has a fixed "instant center", so you can't adjust where it is, without changing the length of the ladder bar.

                Reading up on this subject might give you some insight...but probably you'll decide it's not something you should fight?
                yes this. for the life of me I can't imagine why you wouldn't 4-link then use the leaf springs with floating pads...Squirrel hit it, you need to find your instant center and the ladder bar needs to lift at that point. At 106" wheelbase, the 67" bar would be wayyyyy too long since your instant center tends to be the middle of the rear main seal... that said, it's easy to shorten them, not so easy to lengthen

                The concept is your using the axle twist to lift at the heaviest point of the vehicle to gain better traction. That said, what motor and gears? I've seen a lot of trucks with tricks but not hp treat.....
                Doing it all wrong since 1966

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                • #9
                  and what you do with the instant center calculation is different on a 4x4 then a street car... where you want a neutral launch (no separation or squat) in a car, a 4x4 benefits from a touch of separation when you nail it.... but you need to find the center of mass, then design a bar that lifts at that point.... which isn't easy to do with traction bars.
                  Doing it all wrong since 1966

                  Comment


                  • #10
                    basically im trying to stop the 'porpoising' these trucks are famous for in sand...
                    with a 4" rear block im sure i need some kinda 'stop hop' assist, even though its
                    just a little ol 350 for now it will eventually get a 454--and the 350 is a bit raunchy
                    anyway. the 36" tires and 5k+ weight dont help either im sure...........

                    the 'traction lifts' i posted in another thread worked great on the last k5, and that
                    one was REALLY gnarly with 2.5 rockwells and a tunnelrammed 496. (.060 over 454+1/4 crank)
                    but seems MOST things i ran before are no longer available for these trucks.
                    who woulda thought an 82 would be too old.............

                    Comment


                    • #11
                      I'm thinking on running some kind of bar from the frame to the axle just to stop the radical pinion movement it feels like I'm getting from take off ( gently as I can without getting everyone cranky ) and the reverse of it while braking.
                      Previously HoosierL98GTA

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                      • #12
                        if you have a short wheelbase, you're always going to have trouble with the nose lifting.... in that case, you want separation between the rear tire and the wheelwell, so put the instant center behind the center of mass.... so while I have mine at the center of the crank and at the bellhousing, you'd put it somewhere in the middle of the transmission.

                        or think of it this way - to stop porpoising, you'd put the weight.... where? traction lift bars would help because the suspension simply doesn't compress. You don't have to be so draconian with traction bars..... still, I'd 4 link it but use the leaf springs to suspend it. Save money by using poly bushings rather then heim joints.
                        Doing it all wrong since 1966

                        Comment


                        • #13
                          Originally posted by SuperBuickGuy View Post
                          if you have a short wheelbase, you're always going to have trouble with the nose lifting.... .

                          not so much the nose lifting like pulling wheelies ( not yet at least, hah hah...)
                          but these trucks as well as the short K10's tend to start wheelhopping the front,
                          then the rear, then the front again, rear again, etc...and it starts to cycle viciously
                          between the front/rear and the trucks 'porpoise'-- like a dolphin jumping out of
                          the water then back in, then out, in, out, in.....

                          always seems like bigger tires/stronger motors make it even worse. i knew a guy
                          with a GMC jimmy (k5 clone) that saved all his old shocks and mounted them with
                          a longer through bolt at the shackle/spring connection to try and stop it, that actually
                          sorta helped but not 100%, even with 2 shocks per spring/shackle.

                          the old traction lifts i had killed the porpoising 99% on my last k5, but they
                          aint made no mo apparently.

                          Comment


                          • #14
                            the traction lift severely limits travel.... in short, we're beyond that in suspension tech. Ladder bars and floating leaf springs would achieve the same goal while still maintaining reasonable cost and streetability.
                            Doing it all wrong since 1966

                            Comment


                            • #15
                              Originally posted by SuperBuickGuy View Post
                              the traction lift severely limits travel.... in short, we're beyond that in suspension tech. Ladder bars and floating leaf springs would achieve the same goal while still maintaining reasonable cost and streetability.
                              even if i had unlimited funds i still wouldnt 4link it-- its an old truck, needs old tech.
                              no LS motor, no electronic o/d, no fuel injection.....see where im going with this?
                              i mean, its got solid axles front and rear and 4 corner leafsprings--thats about as
                              old tech as you get.

                              PLUS--i already have a set of ladders AND can either float the leafpack
                              or use a shackle at end of ladder so it doesnt bind with its differing instant center...
                              so.....................67"seems too long............... use the 48" i guess?
                              Last edited by fatguyzinc; May 3, 2019, 08:41 PM.

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