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I live in an urban area where many of the streets have pot holes and some of these streets have some very large and deep potholes. I have been wondering lately if it would be worth the effort to try to reduce the jarring impacts of hitting deep potholes by placing two 40lb sand bags directly on top of each strut housing located inside the car's engine compartment.

I am not sure how much weight should be placed over the strut housing. I just think that using a total of 80lb on top of each strut housing seems like it would be a good amount of weight to use for this proposed road test experiment.

(As a side note, if I were to pursue this road test experiment, I would first need to remove my car's hood so that the sand bags can be placed directly on top of the two strut housings and then these bags could be held down in place with bungie cords. I would then put a thick tarp over the engine compartment to keep rain and dirt off of the engine.)

The way I see it is that a certain amount of the kinetic energy traveling upwards through the spring and strut as the car's tire is impacting with the pothole should be transferred into the two 40lb sand bags lying on top of the strut housing which the strut is fastened to.

Moreover, I think that hitting a deep pothole will result in a large amount of kinetic energy transferring up into the sand bags and this will likely result in these two sand bags momentarily lifting up off of the strut housing. They will be able to lift off of the strut housing due to elasticity of the bungie cords.

If this does occur, then when the bags come back down and reestablish contact with the top of the strut housing, I think that a certain amount of the kinetic energy within the sand bags should then be transferred downwards into the spring and strut, then into the car's tire, and then into the ground.

So, this partial absorption of, and redirection of, the pothole-inducing kinetic energy back down into the ground should result in a less jarring impact felt by the driver when hitting a deep pothole.

Also, I understand that adding on 160lbs of weight to my car will reduce my car's fuel economy, but experiencing less jarring impacts from hitting deep potholes may be worth it.

Would placing sand bags on top of a car's strut housing reduce the jarring impact felt when the car hits a pothole?

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    $\begingroup$ The unibody/structure at the top of the strut housing carries the weight of the car. So it should be quite stiff. I can't imagine that adding anything on the top side would make a difference. Passenger car suspensions just aren't made for big potholes. The impact will put a lot of wear on ball joints and strut bearings too. IMO. Check with the automotive stack perhaps for more in depth knowledge ... mechanics.stackexchange.com $\endgroup$
    – Pete W
    Commented Apr 30 at 14:03
  • $\begingroup$ It's possible there may be a substitute strut coil with a different profile, which would trade off "typical" ride quality vs more suitable action in potholes. Don't know. There's probably only so much you can do without increasing the suspension travel $\endgroup$
    – Pete W
    Commented Apr 30 at 14:10
  • $\begingroup$ it should make a difference, but the difference would not be noticeable ... you can test by adding a 160 lb passenger $\endgroup$
    – jsotola
    Commented Apr 30 at 15:12
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    $\begingroup$ It's a good diagnostic test (the spring towers do flex) but it is not a practical solution, and the force you are objecting is more likely to be longitudinal than vertical, in which case the spring towers don't come into it. So depending on your architecture you need to allow the wheel to move backwards and forwards in a suitable manner. You may also need to change the valving in your shock absorber, but I never found that helped much (yes car companies do look at this sort of thing - the Square Edge Pot Hole test for example) $\endgroup$
    – Greg Locock
    Commented Apr 30 at 23:58
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    $\begingroup$ Nah, get a Bose electromagnetic car suspension: youtube.com/watch?v=3KPYIaks1UY&ab_channel=CNET $\endgroup$
    – Transistor
    Commented May 1 at 10:16

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The work done by a spring displaced by X units is equal to the potential energy in it:

$$ W = \frac{1}{2}kx^2$$

  • W = work
  • x = displacement
  • k = spring stiffness constant

If we reduce $x \ $by $\Delta x$ by adding sandbags, we increase $k$ to $k*\Delta x$, but decrease work by $(x-\Delta x)^2 $ Say if we reduce x to 0.9x we get$\ W_2= 1.1k(0.9 x)^2 \approx0.9 W_1$ So we have less energy absorbed and more punishment for the car.

This gets even worst by the fact that the car suspension is not designed to react linearly, the more the suspension is displace the less flexible it becomes.

There are expensive alternatives that include changing the the strut and lower suspension control arms.

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