Automotive suspension systems: Curves

[Ivan Seeking]

If you wish to negotiate a curve while traveling at high speed, the largest radius should be followed through the curve in order to minimize the lateral forces acting on the car. However, in practice it doesn't really work this way. I have long noted that the car can actually be more stable while following a tighter line [smaller radius] than when following the maximum radius as mentioned above.

My thinking is that since the suspension is stiffer when under greater load, the car is, or at least can more stable even though greater lateral forces are experienced. At slower speeds it can feel like the car is floating- I assume that this is a comfort feature. Depending on the speed of the car and the radius of the curve, a sudden weight shift can occur can when the suspension compresses that could cause the car to lose traction, or even to roll. But if the curve is taken at a higher speed, or, if the radius of the curve is reduced, the suspension "sets" almost immediately and remains stable throughout the curve.

This would also explain in part why I was taught by an ex-pro to "set" for a turn in one move. Ideally, you only move the steering wheel twice for any turn - once on the approach, and once to exit. At high speeds, you never want to steer through the curve.

 

[edward]

Everything you mention is basically correct. But I wouldn't advise a person to go out and try a high speed turn just to find out. Knowing your own capabilities, and having a good feel for the vehicle you are driving are probably as important as vehicle suspension.

Most of the curves on the interstate highways have a fairly even radius. State and local roads vary a lot. When the radius of the turn changes half way through, corrections must be made and that is when all hell breaks loose.
Even a midway change in the bank of the turn can throw drivers for a loop.
I guess that is why every community has a "dead man's" curve.

It looks to me like a lot of the car manufacturers are trying to compensate for tacky suspension systems by putting bigger wider tires on their vehicles.

Many of the more expensive newer cars are coming out with various forms of stability control. Most of them involve an automatic (computer controlled) application of the rear brake on the side that the car is turning towards. This helps get the vehicle through a turn by giving it a gentle pull in the correct direction.

 

[Lapin Dormant]

**AHEM** the reason why going faster holds seemingly better is because you have these things called Sway Bars, or torsion Bars, they help to hold the car body Flat to the ground, and act best under loading, ie when turning HARD.

Experiance it.

After that, the newer things like computer aided traction controls.

 

[greasemonkey]

i wouldn't think cornering abilty would be better at higher speeds due to body roll, tyre wall flex, tyre tread flex, etc. i could be wrong as I am just thinkin aloud...

 

[Danger]

Everything that I've driven was less stable at higher speeds, including a Porsche. There might be more aerodynamic downforce in a vehicle that's designed for it, but I wouldn't expect that in a normal one. Maybe it's just an illusionary phenomenon because you don't pay attention to the stability factor in a slow curve. Having the stabilizer bars or whatever maxed out isn't a good sign; when they can't 'give' any more, something else will. Definitely don't experiment with it using a '65 Mustang!

 

[Lapin Dormant]

Did they have stabalizers on-in 65's?

They generally don't 'max out' but the G force can exceed the cars abilities as per it's weight, etc.

 

[Danger]

'Stangs were notorious for rolling on corners, especially if they were jacked up as was more popular then than now.

 

[Lapin Dormant]

Nowadays it is Airflow design for body styling, best efficiency.

 

[Ivan Seeking]

It may be that the point of interest is when the response of the torsion bars becomes significant. And I don't mean to say that faster is better than slower, I am saying that this is true at certain speeds depending on the car; and in fact I was really talking about following a tighter line [smaller radius of curvature] through a curve at a particular speed. Obviously at maximum speeds one chooses the largest radius of curvature.

 

[Danger]

Hmmm... that might be an effect of particular front-end alignment settings.

 

[Lapin Dormant]

If your doing a 'known' Curve, or you know which side your turning, left or right, you can 'set up' the Car quite well, tensioning the 'Bars' to express themselves faster and Tighter, Not any harder though, they are only counterbalancing, not forceful, then wheel sizing can also be played with, suspension and alignment settings, makes it corner one way-way better then the other way.

LD
Hey it corners Way-way