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swapping cal tracks for a 4-link

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  • swapping cal tracks for a 4-link

    I had already put in minitubs and narrowed my 12-bolt to get 10.5 drag radials under my 65 chevy II but Im going to go ahead and back-half it in this off-season. Mine is not an all-out racer. Im foot-braking and only making about 700 HP max. Anybody running the pro-street (bushing-type) 4-link? Im thinking they will be more street friendly than a solid 4-link set up.
    ed

  • #2
    i just rewelded the front attaching crossmember for the
    ladders on my younger brothers back-halfed 56 belair
    for the 3rd time in a year...

    i think it keeps cracking because the solid/rod ends he
    runs wont let it 'see-saw' in and out of driveways very well.

    i would DEFINITELY run bushings if the car sees any street use,
    i will be using some sort of poly bushings in my own ladder setup
    when i finally get around to working on my car instead of "EBESBM"...

    like all of you, im mr fixit-- so im always dealing with
    "everybody elses sh*t but mine"....

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    • #3
      big difference between 4 link, and ladder bars! the 4 link lets it twist, even if it has metal rod ends.

      Interesting about going to a 4 link at that power level. That's where my Chevy II is, it's running around 10.0 in the quarter. I have the original monoleafs, and home made cal tracs. They work great, I would never change this car to a 4 link.

      But...I'm working on a new car, which will have around 1000 hp and hopefully get into the high 8s. I intend to use a 4 link in it. With metal ends, not bushed. And I intend to drive it on the street quite a bit.

      My fabulous web page

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

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      • #4
        At any setting other than dead-parallel (making "instant center", as they call it, be at infinite) a four-link acts like a ladder bar, just the effective pivot point is where lines drawn along the links would intersect (in space) instead of at a set mechanical point. All advantages of a ladder-bar apply (and then-some because of the adjustability), and also the disadvantages such as not allowing body roll at any normal setting (such as having I.C. near the center-of-gravity) unless component flex or bushing compliance are letting it happen which does become the case as the I.C. is set forward very much. 100% rear roll stiffness is not a good idea on the street but happily, big mushy tires and an educated driver can mute the oversteer tendency somewhat.

        ...

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        • #5
          Uh...yeah...you're right!
          My fabulous web page

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

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          • #6
            Well anything I know is probably because I tried it the wrong way first...
            ...

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            • #7
              Originally posted by Loren View Post
              100% rear roll stiffness is not a good idea on the street but happily, big mushy tires and an educated driver can mute the oversteer tendency somewhat.
              as I'm always the contrarian - the FJ40 I drive everywhere is fully linked and that includes 4 linked in the back (triangulated), and doesn't have a soft-connection anywhere. I use johnny joints which allows far more twist but there is no vibration dampening anywhere in the suspension. The only reason to use bushings is to damp vibration, so consider what is vibrating and where it's vibrating before you put poly or rubber in the system. Rubber (and to a lesser extent poly) deflects under twisting force. Vibration usually comes from the motor and transmission - the point is I suspect that no where in your rear suspension is anything which could be vibration or does not have twisting forces that need to be controlled. For street duty, about the only thing I'd 'modify' is lubable heims or johnny joints.

              Doing it all wrong since 1966

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              • #8
                I don't understand any of the technical stuff above BUT I do have some experience.
                I have been running an equal length 4-link set up (with some bite - upper bar two holes down in the front) on my wagon for over 70k miles. I have had chromoly rod ends in the links for over 67K without any issues. I am running a full length panhard bar (with chromoly rod ends). The car has a tubular rear torsion bar and a solid from sway bar. I run a decent size front tire (245/50 - 17) with a 29 x 18 - 15 tire in the rear. Power levels over the years has ranged from high 600 to low 800 (currently 840).

                It handles very well - I don't usually have any problems keeping pace in the twisties.

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                • #9
                  Hey, we're the internet, you can trust us...

                  Originally posted by SuperBuickGuy View Post

                  as I'm always the contrarian - the FJ40 I drive everywhere is fully linked and that includes 4 linked in the back (triangulated), and doesn't have a soft-connection anywhere. I use johnny joints which allows far more twist but there is no vibration dampening anywhere in the suspension. The only reason to use bushings is to damp vibration, so consider what is vibrating and where it's vibrating before you put poly or rubber in the system. Rubber (and to a lesser extent poly) deflects under twisting force. Vibration usually comes from the motor and transmission - the point is I suspect that no where in your rear suspension is anything which could be vibration or does not have twisting forces that need to be controlled. For street duty, about the only thing I'd 'modify' is lubable heims or johnny joints.
                  My particular comments were more about general geometry, does it allow side-to-side body roll (or pothole absorption) or not, but...

                  Yep NVH (noise/vibration/harshness), and wear when there's metal-to-metal movement, are the only reasons to use elastomeric bushings...in your case, from the back end of your FJ you'd probably be hearing road-tire noise and gear mesh at speed through your body panels if there weren't a half-dozen other things already making more noise. OEM guys have to be chasing down NVH all the time, we down here in it for fun usually don't care as much.

                  I have one metal bushing in the Chero, where my front suspension "torque arm" pivots at the trans crossmember, and you can hear it on the freeway all the time but that's just because the rest of the car is factory-cushy-quiet. Opening a window is enough to drown it out.

                  In the case of the original poster doing a back-half, solid bushings combined with a few flat interior panels picking up resonance are going to be very noticeable at the driver's ear on long trips. Soft bushings will help a little (plus not wear). Or, just open a window or turn up the radio... If the suspension is going to be of the type that allows body roll and soft bushings are used they are going to have to be soft enough to handle the twist produced, why Delrin is not a choice unless there are some other means such as an internal spherical feature. For a heim joint, yeah that's what they're made for, a Johnny joint even more so.

                  But note (and here's an example of doing something wrong first), I was convinced on the Challenger that because of it being primarily a street car I needed soft bushings at the ladder bar fronts and welded in receiver sleeves for that instead of having Heim joints. Terrible mistake, did you know ladder bars can wheel-hop? At a particular tire pressure it was amazing-bad, surprised the heck out of me. I had to just not try to do a burnout until I got back under there and made aluminum bushings to go in the holes instead and that cured it. (How things become common sense.) In fitting urethane bushings to a drag car rear suspension you'd have to really trust that whoever worked out the hardness of the things plus how pivots and stuff are spread out in an architectural sense has it all tuned so you don't just wind up getting something like what I did. My El Camino w/ factory link-style suspension was another one, to -improve handling- I took out the rear rubber bushings and put harder urethane ones in instead, ***blammo*** horrific wheel hop, whatever hardness those things were worked perfectly with the resonance of the stock frame etc. to make it undrivable at the strip. For whatever thought and effort I put into that all I did was take something that sorta worked and turn it into something that definitely did not.

                  So like everything else, answer to the question "solid bushings or soft?" is, "It depends".

                  Back to the roll-stiffness thing again, with a rear suspension that doesn't permit roll you're never going to notice it just cruising around on the street mellow within what tires and such can handle. You'd have to be either cornering at the limit or, say, out in the rain going around some curve in which case you might find yourself with swapped ends before you knew what happened. The other downside is, stress on components. Find a pothole with just one rear tire and without the ability to absorb the one-side hit, everything that bump had to give you went into suspension links, brackets, the frame and rearend housing. I once saw a four-link-setup housing with a lot of street miles literally peeled apart from that...the welds were good but axle tube metal finally failed.


                  ...

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                  • #10
                    Originally posted by Loren View Post

                    Yep NVH (noise/vibration/harshness), and wear when there's metal-to-metal movement, are the only reasons to use elastomeric bushings...in your case, from the back end of your FJ you'd probably be hearing road-tire noise and gear mesh at speed through your body panels if there weren't a half-dozen other things already making more noise. OEM guys have to be chasing down NVH all the time, we down here in it for fun usually don't care as much.

                    The johnny joints I'm using have teflon lining that inner the ball rides on. They also are greased and greasable - net result is very little NVH. With that said, I spent a great deal of time making sure I wouldn't - including spray on sound deadener, bed liner, poly bushings on all the motor mounts, quality drive shafts, etc. The elephant in the room, though, is those big, squishy tires. If I had forklift tires on it, then no amount of rubber in the suspension, body mounts, etc would quiet it down.

                    Wheel hop - I had the same thing happen with my 70 Buick and Plastic one (75 Corvette). The poly kept it from launching violently sideways (because failed rubber bushings), but they both wheel hopped after the install of poly or solid (respectively). My working theory is the solid uncovered other suspension issues that were masked by the poor state of the original.
                    Doing it all wrong since 1966

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                    • #11
                      Originally posted by SuperBuickGuy View Post
                      Plastic one (75 Corvette). The poly kept it from launching violently sideways (because failed rubber bushings), but they both wheel hopped after the install of poly or solid (respectively). My working theory is the solid uncovered other suspension issues that were masked by the poor state of the original.
                      In the case of the El Camino I'd have to wonder what the other suspension issues would be... As a big-block car, upper and lower links are factory boxed with welded-in stampings and there is a strut between upper and lower frame mounts, plus being an El Camino the frame is heavily boxed and 'way back when I added a crossmember behind the axle plus other reinforcement. I think the bushings just "bounce" at the same rate the chassis and tires do, softer bushings didn't hit that resonance and worked better. When I get around to going over that car again I may just switch to a "torque arm", 3rd-gen Camaro style. One thing that car used to do well (before the bushing change) was long smokey burnouts. Kinda missed that.

                      ...

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                      • #12
                        Thanks all. I actually had wheel hop with the cal tracs (initially) but cured it when I softened the adjustable shocks and backed off on the cal trac preload. The leafs and cal tracs worked fine. The real reason for the switch is that Im having the trunk retubbed, a brand new stainless fuel cell installed, and new sheet metal. To do it right, it needed to be back-halfed. Plus the stance of the car will look better (its too high. see the current set up on ). Anyway, I have a professional doing the install and he had a spare Chris Alston prostreet 4-link available that will save me some money. I'll send the group the after pics in a few weeks.
                        ed

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                        • #13
                          They can never be too high!

                          My fabulous web page

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

                          Comment


                          • #14
                            "The other downside is, stress on components. Find a pothole with just one rear tire and without the ability to absorb the one-side hit, everything that bump had to give you went into suspension links, brackets, the frame and rearend housing. I once saw a four-link-setup housing with a lot of street miles literally peeled apart from that...the welds were good but axle tube metal finally failed."....

                            pretty sure thats whats going on with lil bro's ladder setup--
                            my welds arent cracking, its cracking the metal next to the weld...

                            that tells me he needs more side-to-side 'play', either with hi misalignment
                            spacers on his existing rod ends, or bushings of some sort.

                            race cars are easy, street driving is brutal compared to idling in/out
                            of a trailer, doing a burnout, and running 1/4 mile straight and flat at
                            a time.

                            the driveways, see-saw action, speedbumps, potholes, etc...all wreak
                            havoc on 'normal' drag stuff.

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                            • #15
                              Originally posted by squirrel View Post
                              They can never be too high!

                              Squirrel. In your case, I stand corrected!

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