What happens when I feel this? [Δαφνη Ευτυχια Αρθουρος]

Something I've been wondering about that an article that vvalkyri linked to reminded me I wanted to ask ...

When I'm driving around a curve, and it feels as though the car (the whole car, or just the back end) slides about a centimeter, what am I really feeling? Has that actually happened, or am I misinterpreting the combination of tactile clues I'm getting, and really it's just the suspension doing something funny? Is it really sliding more than it feels like? Less? It's not enough to notice a visible difference in position (at least not while moving at speed). Are any of y'all both familiar with the sensation I'm talking about and sufficiently knowledgable to answer this question, or are any of you willing to either drive the chase car or operate the video camera for a couple of hours while I try to reproduce the effect intentionally so I can find the answer experimentally?

The sensation feels different from what I know as the "smooshing over on the suspension" feeling. It's not usually accompanied by audible tire squeal. It lasts a very short time and does not seem to affect overall handling except to serve as a bit of a warning that I entered the curve faster than I really meant to. I'm very sensitive to the feel of the wheel, pedals, and seat when I drive, and have used these clues at a gut level for years, so I'm not worried about changing how I react to them, but I've never been quite certain whether what I think is really happening underneath the car -- the 'head" reaction as opposed to the "gut" reaction -- is accurate.

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Call or e-mail me, please. I need to arrange to drop by your place tomorrow (Friday).

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It sounds like an effect caused by centripital force.

Either caused by centripital force (if I'm feeling the suspension reacting to that force) or a lack of sufficient centripetal force (if I really am feeling the tires slip by a centimeter). Care to narrow the guess a little?

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I suspect that it has to do with the suspension reacting to the curve. Is there a specific kind of curve that it reacts to like this? cornering? banked entrance ramp? A banked ramp will have more forces than just the one you're talking about. Or rather, becasue it is banked, the centripital force has more than one componant in your local coordinate system. There's the lateral force, which you think about all the time, and then the pseudo-gravitational force, which essentially means that yoru car is heavier than it woukld be otherwise. This combination means that the normal sqooshing of the suspension isn't going to act the way you're used to it doing the rest of the time.

so. More specific situations?

Oh, and no. The car isn't actually moving over. Or at least the tires aren't.

How can you be sure of this?

Glenn said specifically that there wasn't any tire squealing sound going on. Unless you get lifted up by wind at the same time that you're pushed sideways, any dynamic motion of the rubber is going to make the tires squeal. Just like if you corner too fast you can tell that you're doing to lose traction because the tires squeal before you even start to slide, the tires would make some noise if the car suddenly slid to one side.

So unless there is a slick surface that you can skid on silently, any lateral movement of the car that doesn't have to do with high wind conditions is going to be accompanied by some telltale sounds.

Another thought that comes to mind: Lots of cars have a thing that they do, where the tires lean inwards relative to the vertical under a heavy load. This is to add some stability to the car when turning (and because stopping it from happening is kind of like stopping the airplane's wings from shuddering in turbulance). In a tired car, going around a prolonged turn might puck on the "leaning" of the tires enough that the tires (*not* the suspension) tilt/lean to the left (assuming you're in a right-hand curving exit ramp).

This would also work with the fact that it only happens to the rear end of the car. Cargo weight gets carried on the rear axle, so those joints loosten up more readily, and will be more likely to flop like this.

Δαφνη Ευτυχια Αρθουρος

What happens when I feel this?

OT: Write to Me

Use the Force

Well, since the car isn't going in a straight line...

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