Suspension Gone Awry? SOLVED!! See #6

Pilotdave

Pilotdave

Well-known member
After adjusting the shocks in our Roadster to allow the springs to depress moderately with significant effort (me pushing down hard on the bumpers), I headed out for a test drive. Every time I hit a pothole deeper than an inch +/-, I'm hearing and feeling a loud bang, seemingly from under the car. This is a heavy metal-to-metal "bang" - not a light/tinny one. I'm trying to figure out what's causing this....no luck yet.

Here's what I've done in search of the cause:

1. I have checked to make sure that the shock arms aren't hitting the inner fender wells.

2. I've gone around the car looking for a loose body part(s) such as a bumper, running board or fender. None are guilty.

3. Removed the trunk and secured the trunk rack so it can't move.

4. Checked that the body bolts are tight.

5. Checked the U-bolts securing the rear spring to the cross member. The bottom plates are squeezed tight against the bottom of the spring stack.

6. Removed the rumble seat cushion and lashed the rumble seat cover open.

7. Driven the car with the passenger door lashed open while holding the driver's door open.

8. Looked for indications that the drivetrain is hitting the bottom of the car.

9. Checked that the muffler is securely in place - no loose tail pipe clamp.

10. Checked under the seat cushion to make sure that there's nothing stored under there. [I did find a few washers, two short bolts and a nut....so not entirely a wasted effort!]

I am seeing nothing that would account for the bang, but I'm definitely not a pro at this!

I have also inspected the springs - they are showing rust where the leaves meet. The shock arms all move and were adjusted as described above.

I am missing something - I'd surely appreciate suggestions on what might be causing the "bang" and other things to check.

But first a question: when the tire exits the pothole and the spring compresses, what stops the tire's upward motion? And could whatever that is be the source of the "bang" I'm hearing?

Thanks very much!!
 
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Re: Suspension Gone Awry?

Consider unhooking the shocks. That would eliminate them. Look for shines spots under the spring shackles and the front axle. Probably why the shocks were closed down, or worn shackles/bushings.
 
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Re: Suspension Gone Awry?

Or first, put a floor Jack under the front axle, and look for movement at the spring eyes that would indicate bad bushings/shackles. If the front spring is tired it will be resting on the front axle.
 
Re: Suspension Gone Awry?

Thanks, Bob. I take it that there should be no "play" at the spring shackle eyes? I jacked both ends of the front axle, one at a time. There's about 1/2" between the shackle and the axle, both sides, and the separation on both sides did not change to my eye as I jacked the axle ends.
 
Re: Suspension Gone Awry?

A good Model A friend asked me if the floorboard was screwed down. It was not - did so and did NOT hear the bang on my test drive! I think we may have gotten it - finally!

Thank you to all who read/responded/thought about responding to my original post.
 
This is a very good thread. It offers myriad areas to explore re: suspension. When it gets below 97 degrees in my garage I’m gonna do some work on the suspension on my coupe. Portland streets are almost impossible to drive a Model A on. >:(
 
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Dave,

Just to help narrow it down ...

Was noise made by the angled part of floorboard or the flat part?
 
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