Okay, I know this has been discussed ad infinitum, and I tried reading the old threads, including the one where I mention it, but today, I did the same section of a road, and was toggling PASM setting, and it's very clear, that on my car, what I would call the part 2 of a speed bump encounter is better with PASM stiff setting engaged, and I can't get my head around why?
The posted speed limit is 15 MPH in the bumps, but I took them at about 25MPH (basic speed law, still safe).
With PASM SOFT the initial contact with the bump is a bit less jarring, but the part 2 after the bump seems to be more angled and likely to leave the car feeling awkward, and out of balance.
With PASM STIFF and the second part of the bump seems to have more continuous contact with the ground and tires, and the car leaves the bump more poised.
This seems very counter intuitive to me, as wouldn't the softer suspension setting and supposed adaptation of the PASM be in theory, better for speed bumps? Well, it doesn't seem to feel that way?
Anyone want to try and explain if this is an illusion (better control on the stiff setting), or what is going on. It's kind of perplexing me... At the moment, I am sorting out some ideas for tuning suspension on another car, and this is an issue for me.
So I will bump my own "speedbump thread".
My guess is that: the first contact with the bump, front wheels passing over, happens in a state of deceleration, and the mass of the car acts to load the front end with a net downward force, and as the body of the car progresses, before the front end rises to neutral, the rear wheels encounter the speed bump, the rear of the car rises, and that adds more net force downward on the front end.
The stiffer setting of the PASM keeps the car in a more neutral position.
I don't know much about suspension, so if there is someone who does, especially someone who can try it in their own car with the PASM option, that would be of interest.
On soft the suspension travels a lot more on "Part 2" of the bump and depending on how straight you hit the speed bump, the car can be leaning more towards one side or the other leaving it out of balance.
On suspension stiff, the car is well, stiffer, and holds itself up better which is as you said, more poised. Making the car and the driver feel more solid on part 2 of the bump
