Conflicting Information about Swaybar Tuning

[EchoOfSilence]

Alright, so here's the deal. Upon reading information from a lot of people, I seem to be getting conflicting information regarding swaybar tuning.

Understeering.
Case #1. Get a bigger front sway, a smaller rear sway (or stiffer front, softer rear) or both.

Case #2. Adjust your front to be softer or remove the stocker, or get stiffer rear.

I always thought that the stiffest end will lose traction first, which follows case #2. But some Solo2 and autoX/road racing drivers say that case#1 is actually correct.

How would getting a stiffer/bigger front correct understeer, if it adds stiffness to the front? wouldn't that make it lose traction easier?

[Chernobyl]

#2 is right.

The autox guys are talking about FWD cars.

[EchoOfSilence]

for example...

Don from PDM Racing
"I asked him how to set up sways to fix understeer, he said put the fronts stiffer, or only install the front sway."
and

HaLo
"It works.
I did get a big ass front sway bar and it understeers much less than before."

[jmauld]

The goal is to maintain the most contact area with the pavement. If a bigger front swaybar is going to help that, then you will increase grip.

[TheWolf]

this all depends on springs rates and types of dampers.. . understeer can be caused by several things and sway bars are offten improperly used to bandaid fix these things. in an street situation such as taking an exit ramp at say 70mph when it's posted 30mph.. notice the roll of the vehicle. If it's flat and the car is skating understeer then soften the bar up and try again. If it's plowing understeer then stiffen it up and repeat. different situations. progressive springs often cause funny things to happen with swaybars

[SpeedMonkeyInc]

Check out Whiteline's FAQ about swaybars:

http://www.whiteline.com.au/faqswaybars.htm

[Nan Desu Ka?!]

as far as i know, #2 is GENERALLY correct for RWD aplications. personally, i have never heard #1 in reference to our (FR) cars.

[s13coupedrfter]

It's really easy...

UNDERSTEER=bigger diameter front bar, smaller diameter rear bar

OVERSTEER=bigger diameter rear bar, smaller diameter front bar

I've been toying around with sway bars for a long time with FR and FF cars and it's the same rule for both platforms. Sure, spring rates have an efffect on over/understeer but this info is purely for swaybar sake. If you get an aftermarket swaybar set and let's say you think it still has too much understeer, increase rear spring rate. The swaybar rule works with spring rate rule the same way. Hope is helps

[Rennen]

Originally Posted by jmauld

The goal is to maintain the most contact area with the pavement. If a bigger front swaybar is going to help that, then you will increase grip.

Bingo!

Often if the springrate is too soft up front, and your alignment isn't setup to compensate, you will put more load out the outer edge of the tires, and loose front grip. Adding a larger front bar will, in this case, increase grip up front, and decrease understeer. However, if the front of the car is already stiff with springrates or bar, and you aren't maximizing your front grip (i.e. too much negative camber) then a softer front bar will lead to more grip and less understeer.

Everyone's setup is different, so the only true way to know for sure is a tire pyrometer. If you are serious about any form of motorsport, this is one of the most valuable tools to have. Each suspension/alignment/tire pressure change you make should be followed by taking inner, center, and outer tire temp measurements at track temps. If you keep track of these values it will be easy to see if your changes fixed the problem.

In my opinion, it is more important to maximize the front's grip to reduce understeer before you go throwing a huge bar out back as a crutch to create oversteer.

-Matt

[EchoOfSilence]

That makes sense, Rennen, but 'stiff spring rates' from what frame of reference?

obviously the stock springs would be pretty soft, but would 8kg/6kg be stiff? There are stiffer setups out there, and make 8/6 look like they're in the middle of the stiffness curve

[jmauld]

That's going to also depend on the tire you're running. You really can't look at one component by itself. You need to look at what you want out of the car, and then build the overall system around it.

If you are building this for street use, then I would suggest sticking with softer springs and stiffer swaybars. If you're autocrossing it, then start taking tire temps and measuring your spring travel after each run. Those two things will tell you more than anyone else can.

For a reference, I have no rear swaybar, yet no one who drives it complains that my car understeers too much. The thing is that, you just can't use that information and blindly apply it to your car. You would also need to know my camber settings, springrates and tire choice for that to be at all useful.

[altitude]

A swaybar (anti-roll bar) will always transfer some of the load to the outside tire.
The more roll you remove using it the more load you transfer from the inside to the outside tire.

Simply put, that reduces the cornering capability at that end of the car unless the resulting contact patch area is significantly enlarged by doing so BUT this should more effectively be cured by adding negative camber, increasing spring rate, etc. This is because the cornering force a tire can generate is not linear to it's load; i.e. you're better off having the load on your 2 tires on one end as close as 50-50 as possible.

However, swaybars provide for an easy way to adjust the balance of the car. A bit like playing with tire pressure. Some race cars can even have the swaybar stiffness adjusted by the driver as they race.