2 - Inertia doesn’t help. It cancels out because the suspension must be equally stiffer to carry the added weight. There’s a correlation, which is more because bigger cars are more expensive, which have better suspensions and stiffer bodies.
4 - Unsprung mass helps and hurts comfort. It filters out high frequency vibration, forcing the tyre to flex more, but the mass bounces higher up from bigger bumps, hitting the suspension harder.
accelerating and braking between each bump causes engine and tyre noise, and tyre and brake dust, which are toxic.
could you elaborate on the cancelling out more? I’m not a suspension guy, but I am mech eng, and I am interested in knowing more about where specifically to look into that topic.
I didn’t think that simply having stiffer suspension would result in that being cancelled out. mitigated, sure, but not cancelled
Thought experiment: weld two cars together side by side - double weight, double suspension stiffness carrying the weight. Why would there be any difference in vibration when they drive together over a double-wide speed bump?
It’s the same as with dropping objects of different weights (in vacuum) - the feather falls as fast the hammer, because weight and inertia cancel each other out.
hmm, I guess if you assume each side of the axle is acting together as one paired unit, that works.
I’m just trying to reconcile this with my experience of “heavier vehicle feels better over bumps” regardless of age of vehicle, or even across multiple conditions for the same vehicle. for example, old van vs newer sedan. or if I’m loaded up with a bunch of bags of soil over my rear axle (stuff that stays in place and doesn’t bounce around), as long as I’m not bottoming out the travel, it just feels smoother going over the bump, like the reaction of the wheels going up is dampened by the additional sprung mass.
I will admit that suspension design, like electrical stuff, is basically sorcery to me. not my kind of thing at all. also I could absolutely be misremembering scenarios.
Loading up weight does make the ride smoother because suspension stiffness stays the same, unlike when a heavier car is designed.
The newer sedan was likely designed to tolerate spirited driving. When designing a car, they’re aiming for an appropriate resonant frequency for body up-down bounce, under 1 Hz for good comfort, more for sportier ride. Featherweight Citroën 2CV gives a very soft ride.
Nitpicks:
2 - Inertia doesn’t help. It cancels out because the suspension must be equally stiffer to carry the added weight. There’s a correlation, which is more because bigger cars are more expensive, which have better suspensions and stiffer bodies.
4 - Unsprung mass helps and hurts comfort. It filters out high frequency vibration, forcing the tyre to flex more, but the mass bounces higher up from bigger bumps, hitting the suspension harder.
could you elaborate on the cancelling out more? I’m not a suspension guy, but I am mech eng, and I am interested in knowing more about where specifically to look into that topic.
I didn’t think that simply having stiffer suspension would result in that being cancelled out. mitigated, sure, but not cancelled
Thought experiment: weld two cars together side by side - double weight, double suspension stiffness carrying the weight. Why would there be any difference in vibration when they drive together over a double-wide speed bump?
It’s the same as with dropping objects of different weights (in vacuum) - the feather falls as fast the hammer, because weight and inertia cancel each other out.
hmm, I guess if you assume each side of the axle is acting together as one paired unit, that works.
I’m just trying to reconcile this with my experience of “heavier vehicle feels better over bumps” regardless of age of vehicle, or even across multiple conditions for the same vehicle. for example, old van vs newer sedan. or if I’m loaded up with a bunch of bags of soil over my rear axle (stuff that stays in place and doesn’t bounce around), as long as I’m not bottoming out the travel, it just feels smoother going over the bump, like the reaction of the wheels going up is dampened by the additional sprung mass.
I will admit that suspension design, like electrical stuff, is basically sorcery to me. not my kind of thing at all. also I could absolutely be misremembering scenarios.
Loading up weight does make the ride smoother because suspension stiffness stays the same, unlike when a heavier car is designed.
The newer sedan was likely designed to tolerate spirited driving. When designing a car, they’re aiming for an appropriate resonant frequency for body up-down bounce, under 1 Hz for good comfort, more for sportier ride. Featherweight Citroën 2CV gives a very soft ride.