Suspension theory

[The Atomic Ass]

I've read here that while perfectly aligned wheels front and back might be good for FE, they generally make for a squirrelly-handling car.

Am I remembering correctly, that a car will generally track straight, but will squirrel in turns, or is it that the car won't track straight with perfect alignment?

What I'm brain-storming here, is for my future not-even-on-the-drawing-board electric car, a suspension system wherein all adjustable elements, (toe/camber/caster), are controlled with stepper motors by a computer, to maximize efficiency in straight line AND maximize stability when making the tires screech.

Compromise is such a filthy concept.

[tjts1]

You need to do a lot more reading on suspension geometry.

[Frank Lee]

I have read about proposed "active alignment" for heavy semi-trucks. I generally don't think the complexity is necessary on a light vehicle.

[gone-ot]

there's: toe, caster and camber...which do you plan on "adjusting" while driving?

...some roads have crowns, others don't and some have banks while others are flat.

[Peter7307]

You can get the alignment you want with out stepper motors which add costs , weight and complexity not to mention trying to sell a car fitted with them.

Complianced bushings do all that you need and keep the geometry where it should be.
Have a look at the "Weissach axle" from Porsche for an example.

I agree with TJTS1...do more reading about suspension geometry first and especially the forces involved.

Pete.

[drew1d]

I once saw a setup for an Ep3 (honda civic Si 2002-2005) when the top hats (the part that the strut and chassis touch at the top) were on this weird bar setup with the steering rack.

It gave the wheels more camber in a turn. (sort of like camber steering on motorcycles.) But I haven't heard anything for years.

Never heard of any suspension changing thing with motorized parts.

[some_other_dave]

Zero toe angle will give you the least amount of rolling resistance. Something near zero camber as well, and I don't think caster angle makes any real difference.

Zero static toe will tend to make your car wander a little bit, as the compliance in the bushings of the non-driven wheels will tend to lead to toe-out, which is dynamically unstable. If you've driven a car with toe-out, you probably know the feeling--the ability to change lanes without realizing it when you look down to change the radio station.

Static toe-out is even more squirrelly, as you get even more toe-out at speed.

Even with zero toe-out when the car is at speed makes for a car that tends to wander and hunt. It will like to follow any grooves or ruts in the road as well.

I don't think that having dynamic toe-change with speed will be worth the complexity. Having toe angles that change as the suspension compresses (presumably from the car going around a corner) can be; that's more or less what the aforementioned Weissach axle does. There are some other designs that have similar features, like the "passive rear steering" in the 1988 CRX Si models. Though it seems like that was done for less stability and more agility, unlike the Weissach axle which was designed for more stability.

-soD

[gone-ot]

...caster is "how far" the tire patch contacts the road AHEAD/BEHIND the projected pivot/axle.

...if the contact point is right under the pivot or behind it, you end up with the "grocery-cart" vibrations.

...if the contact point is too far forward, the tire edges will be scrubbed with every light turn, which definitely will kill FE (and the tires!).

[jamesqf]

The original Insight has zero toe. I don't find its handling squirrely at all, but quite light & responsive. But I admit I do prefer & am used to sports car handling. The only problem is that it does tend to wander on grooved pavement, though I don't know whether that's due to the toe-in, the tires, or the light weight.

[Peter7307]

Originally Posted by Old Tele man

...caster is "how far" the tire patch contacts the road AHEAD/BEHIND the projected pivot/axle.

...if the contact point is right under the pivot or behind it, you end up with the "grocery-cart" vibrations.

...if the contact point is too far forward, the tire edges will be scrubbed with every light turn, which definitely will kill FE (and the tires!).

I hate to indulge in pedantic semantics here...
Caster is the ANGLE formed by a line passing through the upper and lower suspension pivot points at the wheel hub when viewed from the side.

The distance between the point where this line meets the road surface and a vertical line drawn from the wheel centre to the centre of the contact patch (also when viewed from the side) is the "trail" distance.

The resultant side effects , resulting some times in "interesting" handling , mentioned above are both correct.

Pete.