Why run a front sway bar?

[ITLBTU]

I know what the bar does... but why do we need it? If the car is set up correctly and the geometry is good, I would think that a moderate spring and no sway bar would be ideal for handling. That way the inside tire could better plant to the pavement, instead of being pulled away by the sway bar. Am I missing something?:hmm:

[Samckitt]

I think the spring that would be required to handle the weight on the inside wheel during a turn would have to be so stiff that it would cause the suspension to not work properly. The end result would be wheel bounce & cause the tire to not grip properly. Resulting in you being off the road. Plus strait line travel would be extremely rough due to the stiff spring.

Just my $.02

[Dipstick]

F1 cars have gone practically 'solid' meaning they have very very little suspension travel so they use stiff springs and minimal sway bars and rely more on the spring rate of the tires. This of course only works on real nice surfaces.
Here's a quote from Allan Staniforth's book 'Competition Car Suspension'
"What is often not realised is that the anti-roll bar is a very powerful instrument and correctly dimensioned and fitted it can provide effects five or ten times greater than simply fitting stiffer springs."
It goes into a lot more detail, and is really a good read. Covers all the basics.

Grant Rogers
www.ludicrouslouis.com (http://www.ludicrouslouis.com)

[Norm Peterson]

The roll stiffness of a typical US domestic car that comes OE with some performance intent is typically 65% - 85% bar, with conventional springs in the 400-ish lb/in range. I prefer a firm ride, and can tolerate a good bit more than the 640 that's on the front of the Malibu (which is still 78% bar at that end!). But I'm pretty sure that I'd be drawing the line before the 1600+ lb/in that having no bar suggests, at least for anything that's being considered for daily driving.

Eliminating the front bar entirely might start to make more sense when you get your sprung mass CG height down much closer to the suspension roll center heights. Having relatively less roll under any given maneuver means that you don't need as much roll resistance to keep wheel camber within a reasonable (and realistic) range. And since you still need at least a certain wheel rate from the springs it makes more sense to trade off sta-bar stiffness. After a couple of iterations of dropping the CG height and going thinner on the bar, it may not be that big a step to start going heavier on the spring until the bar is gone. But a sufficiently low CG and stiff springs is starting to define such a beast as being a dedicated track car rather than a daily or even an occasional street driver (for example, how low can you drop an engine without dry-sumping it?)

I do understand that there are gains to be had from letting the inside wheel have an easier time following the back sides of bumps. But to realize the gain there, you're giving up somewhere else (aka, no free lunch).


Norm

[David Pozzi]

No matter what you do with the suspension, at 1 G lateral for instance, a car is going to have X number of pounds of weight transfer from inside wheels to outside. Tuning springs, bars, or shocks will however influence how the car handles bumps and transitions.
David

[ITLBTU]

I'm not planning on removing my sway bar. I just brought up the question because I'm redoing my front suspension, with GW uca, lca, ats tall spindles... and since my camber gain should be corrected body roll shouldn't be a problem because the tire patch should be maintained. The swaybar will take weight off the inside tire, and I'm guessing that it will help create an understeer condition. So it seems...:drive1:

[Norm Peterson]

A front sta-bar provides both understeer and oversteer effects. Understeer is due to the additional lateral load transfer that you attract to the front (assuming the same springs), and the oversteer effect is from the smaller roll and, normally, better camber on the outside front. It's possible for either effect to dominate, but which effect actually does depends on a number of things that are separate from the bar itself.


Norm

[David Pozzi]

I'm moving this thread to the regular suspension section. It's not an advanced discussion topic.
David

[ITLBTU]

I'm moving this thread to the regular suspension section. It's not an advanced discussion topic.
David

I'm trying to be more advanced! :bicycle:

[Slow Ride]

Well my drag car has no front sway bar and it is a beast to get around corners. I'm hoping that the new bar in my pseudo-pro-touring pontiac will make it handle much better even with the added spring rate I added while droping it 2".

I studied this with a friend back in college. He was on the SAE formula team. They ended up with an adjustable bar, because even a 5% change in weight caused significant changes in the way the car handled. That was much easier to change than minute spring rate or ride height adjustments.