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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.

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.

(As a side note, if I were to pursue this 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. Other drivers will likely find it quite odd seeing a car with no hood and having sand bags in the engine compartment.)

Moreover, I think that hitting a deep pothole will result in a lot 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. If this does occur, then when the bags come back down and reestablish contact with the top of the strut housing, 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.

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 over the top of a car's strut housing reduce the jarring impact felt when the car hits a pothole?

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I expect the sandbags will not have any positive effect; and quite likely they will make things worse.

There is in the history of car manufacturing a car that was designed specifically for use in rural areas: roads with many potholes.

That car, the Citroën 2CV is an extreme instance, which makes it suitable as an example.

The suspension of the 2CV has a lot of travel, and it moves very readily up and down. So when the farmer bringing his eggs to market drives over a pothole the wheel just plunges into the pothole while the body of the car remains pretty much at the same height.

The trade-off is: when you go through a sharp corner the car leans over a lot.

It is always that trade-off. A car with a stiff suspension will have very little tendency to lean, and very little tendency to rock from side to side, so on smooth roads the car goes through corners very steadily.

But yeah, that stiff suspension is ill suited to dealing with potholes.

If you are serious about changing the physical characteristics of the car then pretty big changes are necessary. Things like raising the car and replacing the springs to give the suspension more travel, and anything you can do to reduce the stiffness of the suspension.

It could be, I don't know, that the 2CV didn't have shock absorbers at all. Without shock absorbers: then when the car is rocking from side to side that rocking motion takes some time to subside.

Manufactures of shock absorbers make them in a range of stiffnesses. So it seems to me you have the options of replacing the existing shock absorbers with the softest shock absorbers that are available, or you go without shock absorbers at all.

(In countries with mandatory car safety inspection: I guess missing shocks is a fail.)


Incidentally: the name 'shock absorber' is not a good description of what its purpose is. The purpose of the absorber is to add friction to the suspension travel. When a car without absorbers drives over something like a speed bump the car will bob up and down several cycles. The purpose of the absorbers is to drain the velocity of that up-and-down bobbing. The stiffer the suspension, the faster that energy is drained.

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For a given spring stiffness, adding mass to the body of the car (this is called sprung mass) will inertially clamp the car body, reducing its tendency to bounce up sharply when you run over a pothole. And reducing the mass of the wheel, tire and suspension components (the unsprung mass) will also reduce the transmission of bumps to the car body.

The disadvantage is that the added mass tends to make the car body wallow and roll slowly up and down as you drive over uneven pavement. To counter this you must add extra damping to the suspension system when carrying a heavy load. The last pickup truck I owned had a mechanism which sensed the amount of squish in the springs (corresponding to how heavy a load the truck was carrying) and stiffened up the shock absorbers in response. It worked but I haven't seen it used in modern trucks.

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