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Tech Week !!! Hot Rod Suspension Simplified!

Discussion in 'The Hokey Ass Message Board' started by SamIyam, Mar 5, 2012.

  1. This particular tech post is about a tried and true method of locating a hot rods’ front and rear suspension… with simplicity being the main focus!

    No torque arms, pan-hard bars, watts links, cross links or split ‘bones here.

    Henry Ford really did have it right.

    His front (and rear) suspensions on everything from the Model T through the 1948 Ford passenger car used the same basic design.

    The “wishbone” suspension was cheap to manufacture, and did a great job locating both front and rear suspensions. The term “wishbone” refers to the triangular shaped suspension component that is found on old Fords.

    You can see the wishbone on the rear of my original Model A chassis, here:


    Most guys that are in to hot rods have seen, built or at the least, know of the term “Split wishbones” or “split ‘bones”.

    This refers to the common practice of cutting the “yoke” out of the stock front wishbone, and then welding in some bungs to use heim joints, or rod ends, to connect the bones to the frame.

    You can see how we did it here on our B-Ville roadster:


    Starting in the late 40’s and early 50’s, the reason hot rodders split their wishbone, was due to the adaptation of the overhead valve engine, and later on… in the rear… due to the use of rear ends other than the Ford “banjo”.

    Originally, Model T and A fords had front wishbones that attached to the bellhousing.

    Like this:


    When you drop a big OHV engine in an old Ford Hot Rod, there is usually an oil pan, transmission pan, or bellhousing that interferes with the stock wish bone.

    Also, as hot rods got lower… and lower… ‘bones were split, even on the flathead equipped Fords, because of clearance problems associated with un-split wishbones hitting the frame.

    But there are a few inherent problems with splitting wishbones.

    Henry Ford’s original design “triangulated” the front and rear axles.

    This triangulation allows the front and rear axles to articulate, right tire up, left tire down etc.

    AND jounce, up and down, with no binding at all.

    The triangulation is also a perfect way to prevent side to side movement.

    When you split the ‘bones, and attach them to the side of the frame rails, the rear suspension is then allowed to parallelogram on the attachment points, and needs to be held in place by a track bar, or panhard bar.

    The extra bars that are required to locate a suspension that has split ‘bones leaves little room for exhaust pipes and sometimes requires floor pans to be modified.

    Henry Ford had it right… simple, with no extra fanfare.

    Sooooooooo… on to my “tech”!

    I am building a new chassis for my Model A coupe. It is a full fendered car, traditional in appearance, with old paint, Kelsey Hays wires, bias ply tires and a banjo rear end.

    But the engine is a more modern OHV motor with an automatic transmission.

    Now I don’t want anyone to get hung up on the old Ford hardware that I am using, the banjo rear, or even the front wishbone.

    This suspension system could be used on ANY hot rod… and my hopes are that someone will take and build a rear wishbone set up like this, with some round tubing, steel plate and use this system in a way that will free up some room on a really low hot rod.

    I have seen a lot of Model A sedans that sit 3” off of the ground and have no back seat.

    This rear suspension system could be used on such a car and free up two seats in an otherwise useless area of a super low hot rod.

    I also don’t want guys to get hung up on the work that was done on Solidworks, and with my friend’s Plasmacam… or even hung up on the TIG welding.

    When I first started fabricating… all I had was a jigsaw, a drill and a grinder.

    I started by drilling holes along a piece of steel that I wanted to cut out, use the jigsaw to cut from hole to hole, grind down the lumps, and then tack it all together with my dad’s torch set, using a coat hanger as filler wire.

    I would then bring it to my dad’s buddy who knew how to weld.

    So all you need is a welder, and some basic tools like a grinder, drill and tape measure...

    I started out by mocking the engine up in the chassis.

    You can see the wishbone in place here, and my original Hurst mount in place with some funky risers.

    I eventually made a new “Hurst” style front engine mount that uses Ford flathead engine biscuits.

    This mount does not drop the engine down as low as a stock Hurst mount does... so you can put the biscuits level with the top of the frame. The bottom pan rail is about 1" higher than the top of the frame.


    I then tacked a piece of 1” square tube to the bottom of the frame to hold the transmission at the height I wanted it. You will be able to see this piece of steel later on.

    Once the engine was mocked up, I removed the body, and flipped the frame, with engine in place, upside-down so I could get a better view of what I needed to build to hold the front and rear wishbones in place.

    The Model A uses a ball & socket arrangement to hold the front wishbone to the bellhousing. Here is a picture of a front yoke:


    Most old Ford parts suppliers sell a repair kit to repair old worn wishbone balls…

    The kit costs about $10, I bought mine from

    But you can also buy them on e-bay.

    They look like this, and you will need two… one for the front, and one for the rear.


    Because the rear suspension on an old Ford originally uses a torque tube… and I am using an open drive line (drive shaft)… I decided to use a front yoke mated to a rear ’36 Ford wishbone, in the rear.

    I ended up with the front wishbone mount needing to be 4 ¾” below the frame rails and the rear transmission mount/rear wishbone mount needing to be 2 ¾” below the frame rails.

    The nice thing about this set up is that you can use a stock length Model A wishbone in the front, and the mount will be at about the back of the bellhousing, where a manual transmission mounts.

    The wishbone clears the bellhousing perfectly.

    The other nice thing is that the crossmember that holds the rear wishbone also doubles as the transmission mount.

    As you will see, there are two little holes that are drilled in the rear crossmember that the transmission mount, mounts to.

    Once we had the dimensions of the crossmembers figured out, my good buddy Chopper Bob got to work on Solidworks, designing the mounts:



    And then he plugged in his Plasmacam… and cut them out!

    The material is ¼” steel plate.



    Now please understand folks… you don’t need the fancy machines to do all of this… just a welder, a drill, a jig saw, and a torch will suffice. :D

    Once we had the pieces cut out… we bent them up in his ironworker… I know, not everyone has an ironworker… you could very easily just cut the different pieces out , and weld them together, or use a torch to heat and bend the metal.

    We got them home, and set them in place. Everything looked good!


    You can see the 1” x 1” square tube that I used to hold the trans in place, here:


    Now that we had the basic parts made… they were trimmed up, and bolted to the bottom of the frame using weld in bungs.



    Here you can see the mock up of the rear suspension…


    And the rear end held in at ride height with some red straps.

    Measure twice, cut once!


    Here are the little brackets that I made and welded on to the axle housings to mount the rear to the '36 bones. They are made from 3/8" steel:


    Welded in place… I later welded gussets on the rear ’36 wishbones where I had welded the yoke on.


    Yes, they are strong enough. I have used this set up on a 12 second roadster that I beat-on for years…

    Just make sure you use the ’35-‘36 bones… or build some from scratch using 1 ½” .120 wall round tube.
    Last edited: Mar 5, 2012
    kidcampbell71 likes this.
  2. Once in place, I made some spars to reinforce the cross members.

    These were made by hand… so rest assured you don’t need the fancy shmancy machinery to do this.

    You can see the reinforcement on the rear ‘bones to Model A yoke, in this pic. Also, you can see where the crossmembers bolt to the inside of the frame rail with some tabs.

    Overkill, I know… but overkill is good.


    Top view of the front suspension.


    Top view of the rear suspension.


    Also, this is the rear mount that holds the rear ’40 spring to the frame.


    It is important to get the measurement, from shackle eye to shackle eye, on the original banjo rear end that your spring came off of. They made a few sizes, so be sure that you know what the spring came out of.

    If not, you can usually load the spring, and add the length of the two shackles to the eye to eye measurement on the spring, and that is where the eye should be on the rear ‘bones. Basically the shackles should sit about level when there is no weight on the car.

    Here you can see how I ran my exhaust… plenty of clearance, and the stock body fits this chassis with no modifications to the body. The frame is raised and narrowed.


    So there you have it!

    A suspension design that can be adapted to many different hot rods…


    I hope to see you guys use this in different applications… especially in the rear!

    Last edited: Mar 5, 2012
    kidcampbell71 likes this.
  3. rusty bill
    Joined: Oct 7, 2010
    Posts: 237

    rusty bill

  4. donut29
    Joined: Mar 6, 2006
    Posts: 1,518

    from canton MI

    Very nice work!!

    Thats the way I'm going to do my 34 frame

  5. voodoobuick
    Joined: Jul 11, 2009
    Posts: 64

    from geelong

    Very cool, I may use this on my next project.thanks again.
  6. striper
    Joined: Mar 22, 2005
    Posts: 4,498


    Cool. I just knocked this one up after seeing what you did....


    An alternative to '36 rear bones is to use front bones off a '48 (for example). They are pretty beefy.

    Nice write up and good pics.
  7. 1950ChevySuburban
    Joined: Dec 20, 2006
    Posts: 6,188

    Member Emeritus
    from Tucson AZ

    Nice! Where were you when I did mine a couple months ago! Great pics and write-up too, thanks
  8. Dirty2
    Joined: Jun 13, 2004
    Posts: 8,903


  9. Mart
    Joined: Mar 3, 2001
    Posts: 4,375


    Nice work, Sam.

  10. need louvers ?
    Joined: Nov 20, 2008
    Posts: 12,906

    need louvers ?

    Nice! I always liked unsplit wishbones. So much less in the way of forces being translated into the frame itself... Let the suspension do the work.
  11. I have not read all the tech threads, but of the ones I have read...this gets my vote.
  12. gnichols
    Joined: Mar 6, 2008
    Posts: 10,950

    from Tampa, FL

    Nice tech piece and photos. Gary
  13. Love it! Great tech.
  14. harmless
    Joined: Oct 20, 2009
    Posts: 39


    nice work, thanks
  15. Sam...up to your usual good works I see. That's a great thread for the new guys and a timely refresher for us old guys.

    Thank you Sam and Chopper Bob.
  16. Ian Berky
    Joined: Nov 28, 2007
    Posts: 3,644

    Ian Berky

  17. mashed
    Joined: Oct 15, 2011
    Posts: 1,474

    from 4077th

    I dig the coaxing through the Solidworks and Plasmacam programs. My eyes did start to glaze over as I fought through the urge to jump to the next thread. Also thank you for assuming everyone on this site hasn't had the oppurtunity to hot rod an old Ford. I have taken up barn peeking and hunting prairie dogs though.
  18. flatheadpete
    Joined: Oct 29, 2003
    Posts: 10,122

    from Burton, MI

    So basic yet it works everytime! Thanks.
  19. Rich Wright
    Joined: Jan 9, 2008
    Posts: 3,922

    Rich Wright

    Beautiful, Sam...
  20. pasadenahotrod
    Joined: Feb 13, 2007
    Posts: 11,776

    from Texas

    Great post, well illustrated and explained BUT I believe you left out one important measurement.
    At least 1" should be added to the dimension for eye to eye measurement for the rear spring mounts, or front spring mount as well, to spread the spring and put the spring under tension as Ford designed it to avoid having to install a Panhard bar to limit sway. You probably did this but just left it out in error.
    Using your dimensions would mount the spring like the stock 42-48 Ford design to make a softer ride which do NOT have the spring installed under tension when mounted so Panhard bars are required front and rear.
  21. Crankhole
    Joined: Apr 7, 2005
    Posts: 2,624


    Exactly what I had planned on for my A build. Now I could use this for reference. Great tech! Thanks.
  22. 3wLarry
    Joined: Mar 11, 2005
    Posts: 12,804

    Member Emeritus
    from Owasso, Ok

    cool thread...
    kidcampbell71 likes this.
  23. Southfork
    Joined: Dec 15, 2001
    Posts: 1,464


    Yes, Henry did have it right. He used those wishbones for about 40 years!
    Thanks for the reminder as to why he did that.
    kidcampbell71 likes this.

  24. I probably need to clarify what I was saying... because when it's all said and done, I think we'll be on the same page.

    I used a '40 Ford spring... and used the '40 Ford rear end that the spring came off of to get my measurements from "eye to eye" on the rear end.

    When the body is off of the chassis, and all of the springs are in the spring pack, the spring is definately under tension, in fact... it's under the same tension as it was stock, because the mounting points on the rear end for the shackles, are the same.

    If you use the stock measurements, especially on a light car, there is no need for a panhard bar.

    I removed a couple of springs to make it right... as the stock '40 spring pack is a bit stiff for a Model A.

    The real test will come when I get my first drive.


  25. Beau
    Joined: Jul 2, 2009
    Posts: 1,883


    EXACTLY what I'm working on building now. The other threads on here have sparse info. This is a WINNER IMO.

    Great job!
  26. 39cent
    Joined: Apr 4, 2006
    Posts: 1,569

    from socal

    I did this baknthday but welded some metal along the top and bottom of the rear wishbones, to add strength for open drive. Fords wishbone setups were used on many 200 mph lakes cars.
  27. Excellent thread!:cool:

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