destructdiscGood. Fuck them.
I think one of the reasons that SUV’s and ‘crossover’ type cars have become so much more popular is that they make speed bumps less of a nuisance and allow the driver to cross them without slowing down as much
I’ve had suv drivers brag to me about that as a feature they like
it’s a mix of factors as for why heavier vehicles go over bumps better
1 - bigger/taller vehicles generally have more suspension travel which is also softer
2 - heavier vehicles have more inertia (which results in less body movement when going over bumps)
3 - bigger wheels mean a larger radius which means bumps feel softer when hitting them - think pushing a shopping cart versus riding a bike over a crack
4 - the bigger and heavier wheels actually act against the smoothness of the ride here, but the suspension is designed for that and the overall inertia of the sprung mass seems to mostly cancel it out
I will say that I generally hate speed bumps as a concept. I think that they are ineffective and annoying to everybody.
cons of speed bumps:
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annoying to the driver
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annoying to everybody else who has to hear cars and trailers squeak and smash over them
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annoying to drivers behind drivers who crawl over them at a snail’s pace
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annoying to cyclists (if they don’t have cutouts for bikes)
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they interfere with snow plowing operations
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they distract drivers from paying attention to their surroundings, and have them focused on speeding up and slowing down for each bump because they must get there faster faster faster always
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drivers accelerate and brake between each bump, causing engine tire and brake noise for everybody nearby
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the constant accelerating and decelerating of 4,000 lb vehicles is incredibly wasteful
it annoys me so much because like you can get the same result by just narrowing the lanes and designing your streets better instead of having a literal highway-speed-designed road with two lanes each direction and raised median and 6 ft painted paved shoulder until a curb with no sidewalk immediately adjacent to the pavement with a 50 km an hour speed limit slapped on it
TehdastehdasNitpicks:
2 - You’re wrong about inertia being helpful. 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?
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. A featherweight Citroën 2CV gives a very soft ride.