Dear Welder Series… four link setup

We get emails.  We reply to emails.  All of them.  Even those nice people who want to see me more satisfied.  (What’s a “male product”, anyways?  Am I a product of my own imagination?)  Anyways, I thought some of these tech type emails would be beneficial to more of you than solely the person who penned keyed the question.  Onward.

Dear Welder Series…

Hi there,
I recently purchased one of your triangulated 4-link from Horton’s (www.horton.on.ca).  I am currently building a 28 Model A Tudor and I am building my own frame.  I’m about ready to start fabricating the rear section of the frame and I was wondering if you can give any tips on how to rig up the rear suspension/frame so I can get the car as close to the ground as possible without loosing to much headroom since the car is going to be chopped.  I will be running 32″ tall rear tires and I would like the frame to be about 5 inches off the ground (at the floor before the rear Z).  Also, I will be channeling the body.

Thanks a lot for your help!
Paul

Dear Paul…

This will be a neat project, Paul, but will require some planning.

The rear suspension set-up depends on the tire size.  The frame mount for the lower bar should be about 5″ lower than the axle centerline (c/l), as shown in the installation drawing.  With your 32″ tall rear tire, axle c/l will be about 15-1/2″ from the ground.  We figure about 1/2″ for tire “squat” (the flat part of the tire on the ground).  Using this information and your 5″ frame-to-ground dimension, and assuming(?) a 4″ high frame rail, the lower bar frame mount will be about 1-1/2″ higher than the top of the frame rail (2-1/2″ if you use 3×2 rails).

The upper bar frame mount should be about 2-1/8″ higher than the axle c/l height, or about 17-5/8″ from the ground.  This would be about 8-5/8″ above the top of a 4″ frame rail or 9-5/8″ above a 3″ rail.

You might be able to incorporate both of these frame mounts into the kick.  Or the lower mount could be a “bump” on top of the rail and the upper mount could be on the kick-up.

I would do lots of mock-up work before cutting anything.  Then I’d tack everything in place and carry on with the build.  This makes it easier to deal with “ambushes” (things that crop up that you weren’t prepared for).  Specifically, check the angle and position of the upper bars.  This will have an effect on the frame width (or vice-versa).

I hope this helps.

Paul Horton

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