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Discussion Starter #1
I have quite a few corners on my favorite local roads that apex at a small "hill". Meaning the the corner starts low, climbs up and then goes down, all as part of the curve of the turn. Total elevation change might be a few feet to a dozen or so.
If I take these corners fast, the car noticeably lifts on the suspension (a "negative G" situation), causing a significant and abrupt loss of traction that pulls the car a few feet outwards. This is not severe enough to lift the tires from the road, though.
A similar situation might happen on highway ramps when there is a lip of a few inches dropping the car - the car would pull outwards on the curve at that place.
Other than just driving slower, is there any way to mitigate this?
 

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When the car goes light, if you're going fast enough for aerodynamics to take effect, then aerodynamics can help. The effect of the lip can be mitigated with shock tuning, but that can quickly get expensive. Final thought is that driving technique might help, by anticipating the lightness with straight steering and/or throttle lift.
 

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Gemery gave good advice. Without some kind of active suspension or aero that adjusts downforce with change in vehicle angle of attack, this is a driving question (even with that kind of tech, I'd argue that it still would be, just to a lesser degree). I am not a trained instructor and I'm a lousy teacher, but I do have a lot of driving experience on gravel and snow at speeds I probably shouldn't have been doing, so I'll try to give general advice. Less weight means less traction. Turning, braking, and accelerating all ask for their share from the tires' maximum available traction. Every one of those tasks, therefore, reduce the available traction for any of the others. As you go over the crest, you have reduced traction front, then rear, followed by an increase in traction over what you had before the crest when the front comes down the incline, followed by the same with the rear as it settles back, so there's a rapid change in traction front to rear. With the crest being on a turn, you are also getting an imbalance in available traction from one side to the other. Really, all four tires are experiencing a change in weight/traction at slightly different times. As a driver, it's your job to get the most of the available traction from the tires as it changes dynamically, making the best compromise for your situation. From here, I don't want to get specific and be responsible for anything you might do, but at your disposal is the ability to manipulate the available traction (or even work outside the tire's envelope, but we'll ignore that for this) by shifting weight around. To shift weight forward, you have brakes or lifting off the accelerator (braking also reduces the total traction available for turning). To shift weight backwards, you have the accelerator. To shift it side to side, you have the steering. You need to work a combination of these things at the right times to get the best out of the car's handling capabilities. I don't know if that helps.
 

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Discussion Starter #4
That makes a lot of sense, and is inline with what I was expecting. In general I try to keep the car neutral during turns, but I'll consider what weight/steering shifts will do to some of these corners (I have a couple right next to my house in a fairly low use stretch of road).
Originally when I asked the question I was envisioning a suspension setup that would compensate (to a degree) for the body of the car lifting and force the wheels downwards. The highway ramp example might be better to illustrate this - when going through the turn on the ramp and hitting the drop in the pavement, the front wheels are momentarily off the ground, so the front end of the car continues straight. A moment later the fronts hit the pavement, then the rear do the same. If the suspension could have kept the wheels in firm contact with the pavement, perhaps the sideways move of the car wouldn't happen.
Imagine something like Bose's electromagnetic suspension that would react to the road dropping (in the highway ramp example) or to the car lifting (in the crest mid turn).
Granted, in the crest mid turn case there is a negative vertical acceleration component, so the overall theoretical force available to press down on the tires is lower than in level driving.

For regular passive suspension, I can imagine that "pushing down" harder and faster would give this effect in these two examples. I'm not versed in car suspension terminology, but would that be the spring rate? So a higher spring rate would "keep the wheel on the road" better? I understand that suspension tuning is complex and has many side effects, I'm just asking specifically for this case.
 

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Spring rate, in this case, is more about keeping the car from leaning over too far and destroying the tire's contact patch. Controlling the downward push of the suspension are the shocks, specifically in rebound. Having them on stiff means they extend more slowly. The stock Ford units are too stiff in rebound for the stock springs. Since this is an abrupt drop, it is more likely the province of the high speed rebound rather than the usual low speed rebound. Low speed rebound is what you can adjust with adjustable Konis, though it will also somewhat change the high speed rebound.

High speed rebound, unfortunately, is where things start getting expensive as you'll be talking to a shock rebuilder to make a difference and that's going to be $250/shock for the adjustment if you've got shocks that can be rebuilt... some of the coilovers available will have that adjustment available without a rebuilder getting involved.
 

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Discussion Starter #6
I tried lifting the accelerator right before the crest (shifting weight forward, counteracting the unloading of the front wheels as they pass over the crest), and going back on the accelerator right after the crest (shifting weight backwards to do the same for the rear wheels as they pass the crest), and that seemed to help. I'm not sure if the outward slide was really reduced, but the car felt more composed (vs. the abruptness of the shift outwards when keeping the car neutral during the turn through the crest).
I'll probably won't do any suspension mods in the near term, but I'll try to learn more about this. Thanks for the insights!
 
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