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Hot Rods Setting up 4 link front and rear

Discussion in 'The Hokey Ass Message Board' started by dubie, Feb 10, 2016.

  1. dubie
    Joined: Aug 17, 2004
    Posts: 698

    dubie
    Member

    Hey guys, I'm going to start mocking up the front and rear 4 link on this 1930 Model A chassis this weekend and could use a few pointers. I've read that you should set the bars parallel at ride height, does that apply to the front as well as the rear? And is it parallel to the frame or to the ground?
    I'm going to run coil overs on all 3 corners with panhard bars to keep the side to side action at bay.

    Any tips and tricks you could lend a guy?
     
  2. jetnow1
    Joined: Jan 30, 2008
    Posts: 1,638

    jetnow1
    ALLIANCE MEMBER
    from CT
    1. A-D Truckers

    I am no expert but I would think that parallel to each other, if it is parallel to either the frame or the ground would be a function of how the bracket on the frame is mounted vs the batwing on the axle. Simple geometry would seem to
    indicate that as long as they are the same length and parallel they should function as designed. Of course it was 45
    years since I took geometry.
     
  3. Jalopy Joker
    Joined: Sep 3, 2006
    Posts: 25,517

    Jalopy Joker
    Member

    post pics of your car, and parts that you are going to install - what brand kit(s) are you using? have you contacted manufacturer, or distributor for installation instructions? what front axle & rearend? etc
     
  4. DSCN0763.JPG
    Parallel
     
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  5. I like the wish bone over the pannard bar. Also if you are putting in the effort for a four link do your self a favor and add a anti rollbar.
     
  6. LOL
    Only about 10 years since my last geometry class and I believe you are correct sir.

    As long as the links are parallel to each other they will function properly. Parallel to the ground or the chassis would make for a different aesthetic and maybe someone would take that into account but for pure function @jetnow1 has a fair handle on it.

    There is an exception to the rule. When setting up a competition rear 4link the links are close to equal length to start with but not necessarily parallel to each other, you change the angle of the links to set your instant center, the lower link locates the rear front to rear on the car and the upper link sets your pinion angle, they sometimes end up at slightly different lengths, but there is seldom any major difference on length. The length is controlled by the arcs cut into the 4 link brackets, so if all is correct the difference is usually only thousandths.[​IMG]



    That said you want a front 4 link to ne neutral so parallel and equal length is what you are striving for.
     
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  7. dubie
    Joined: Aug 17, 2004
    Posts: 698

    dubie
    Member

    axle1.jpg bracket.jpg roady.jpg
    I have the install instructions for the rear 4 link, it was purchased from Paul Hortons Welder Series. The rear axle is out of a Chevy S 10 pickup
    The front axle is a chrome tubular axle and 4 link that I bought of another car guy that ended up selling his project before installing it. He unfortunately didn't know the brand name. It came with all the bars and fasteners but no frame bracket so we made up bracket that will fit. It's always nice to know a boilermaker.
    We are building this car out of parts we are accumulating or had laying around from previous builds. It a 27 T roadster on a 30 Model A chassis axle1.jpg bracket.jpg axle1.jpg bracket.jpg
     
  8. dubie
    Joined: Aug 17, 2004
    Posts: 698

    dubie
    Member

    Thank you for the replies gents!
     
  9. stubbsrodandcustom
    Joined: Dec 28, 2010
    Posts: 1,314

    stubbsrodandcustom
    Member
    from Spring tx

    for helping the chassis, on the rear upper link bar, dont mount them parallel... Put some down angle in it, this will help your instant center and roll center drastically. So It attaches to axle, then from there the bars basically pinch closer together at frame attachment point, 2 degrees with your setup should be perfect.
     
  10. Parallel to each other and as close to parallel to the ground worked very well for me. Try to get it parallel to the ground at ride height with the engine and trans in , it will look better , as you can see there is quite a difference loaded and not. The rear came down to very close to parallel with the body and gas tank on. I would also look into tri-angulated in the rear , it eliminated the need for a panhard in the rear , cleans it up a little back there. 000820.JPG 000530.JPG 001480.jpg 001500.jpg 001460.jpg 000820.JPG
     
    Last edited: Feb 11, 2016
  11. dubie
    Joined: Aug 17, 2004
    Posts: 698

    dubie
    Member

    thanks for the pics man,that helps out a lot. How much clearance do you have out back from the rear axle to the frame rail? and what weight ratio did you use for coil overs? This is a really nice clean set up.
     
  12. The amount of room you actually need for clearance depends a lot on what type of springs you are using. Unless you are jumping one for example the average cross leaf setup travels 2" max. I have seen coil overs that would travel 3" but that is usually an indication that you are getting close to being too light with your springs. Desert racers want a lot of travel street vehicles not to much.

    Anyway I personally shoot fro 3-4" clearance and have set them as tight as 2" without problems except in extreme situations.
     
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