Sway bar at front or rear?

[CS14]

Have some problem to keeping track at the end of the curve then I accelerate. I have 3-link Mooser 3:55 and 15", the big tyres have some problems to get grip but thats quite normal compared to 17".

I think the best way to make it easyer for the front tyres is to put the sway bar at the rear, other ideas?

[CraigS]

I don't understand what you mean by this
"Have some problem to keeping track at the end of the curve then I accelerate"
What is happening here? When you accelerate does the rear end want to swing wide? Or does the car try to go straight even though you still need to be turning to finish the corner? Also,just so we can try to be more helpful, can you tell us what shocks and springs you have on the car.

[Bob Cowan]

It sounds like you're talking about oversteer. Sometimes a sway bar is helpful, and sometimes it's not. There are lot of factors that contribute to that, so you need to figure out what the real problem is. Here's a good article about that: http://www.drivingfast.net/car-control/oversteer.htm#.UDwfZ8GPVc0

[CS14]

Now afterwards, I see that my discription is little complicated, I have problem with understeer! The car want to go straight in the end of the corner then I push the gas pedal.

I have the set up with Koni included from ffr and have the right wheel alignment done.

The idea is to find a setting their the inner front tyre get more grip and can help more to fulfill the curve. The springs is quite hard for a road set up but thats ok. If I compare front and rear, with the 3-lnk the rear are much softer, one sidebisulated. Ex, if I just take a jack on one side and lift, it goes up on that side quite easy and at the same time the other side decompress. With simultanisly compression, both sides are fine.

Therefore I think the best effect is to put a sway bar at the rear. Any other opinion?

[FritoBandito]

Lots of influencing factors. Springs, shocks, and antisway bars all work in concert to achieve various but related objectives. In oversimplified understeer vs oversteer terms it looks like this.





Stiffer
Softer


Front Anti-sway Bar
More Understeer
Less Understeer



Rear Anti-sway Bar
More Oversteer
Less Oversteer



Front Spring
More Understeer
Less Understeer



Rear Spring
More Oversteer
Less Oversteer



Front Tire Pressure*
Less Understeer
More Understeer



Rear Tire Pressure*
Less Oversteer
More Oversteer



Front Shock
More Understeer, later in turn
Less Understeer, later in turn



Rear Shock
More Oversteer, later in turn
Less Oversteer, later in turn




Think I'd start out by balancing the front and rear roll by changing springs. Personally I think FFR tends to spring these cars a little soft at the rear so I vote stiffer rear springs. Once you've got that better balanced, use anti-sway bars to further fine tune minor over/understeer and reduce body roll.

Mario

[skullandbones]

CS14,

I know you are trying to solve a problem. Don't want to say I'm happy you had the problem but am enjoying the thread and the great information. Let us know how you alleviated it and if it gets rid of your understeering problem. Personally, I think under steer is a more dangerous situation not that oversteer can't hurt you. I guess there it's a matter of opinion. I tend to agree with you that the rear bar may help but I haven't seen the rear sway bar setup. Could you give some detailed numbers on the spring stiffness and other parameters like how you have your camber and castor setup? Thanks, WEK.

[dallas_]

Personally I'm more concerned about oversteer, especially anything that can throw you into a spin.
Seen too many videos of roadsters experiencing snap spin and some rolling from a spin.

Not to say that too much understeer isn't a problem. Like the others have stated, balance is important.

[skullandbones]

I agree Dallas that balance is important. The reason I feel more comfortable with oversteer is that I think I have more experience recovering from that problem (accelerate or counter steer). However, I don't know much about getting out of an understeer issue except braking which would leave me with a pretty bad feeling of "out of control". Should have qualified that. WEK.

[Mike N]

So to determine a little more about what's going on try driving in a big circle in a open lot. Does the car push, is it loose, or is it neutral? You need to figure out if it's a static or transient issue. If the car is well balanced in a constant circle then you need to work more with shock settings and alignment rather than adding roll stiffness with bars or springs.

[Jeff Kleiner]

If the car is well balanced in a constant circle then you need to work more with shock settings and alignment rather than adding roll stiffness with bars or springs.

Or work on driving style.

Jeff

[CraigS]

Usually you want to add a rear bar to counteract understeer. VPM has a great one for the 3 link.
http://www.vpmcobras.com/
I am a little reluctant to recommend a rear bar without a front bar however as that would be very unusual. Two other changes that would help get rid of understeer would be larger front tires or more front negative camber.
Tires- If you are running 17 inch tires go to 275s for the front. I am not sure what is available in 15 inch.
Camber- Most of us autocrossers are running between 2 and 2.5 degrees negative camber.

[CS14]

Thanks guys

I will try with some more negative camber together with laboration of the tire pressure during the fall. Next step is to mount sway bars during the winter. The one from VPM looks interesting for the rear and I think one in the front also will contribute.

[Mike N]

Or work on driving style.

Jeff

More right foot ;)

[CS14]

Jeff, driving style are fine, thanks, but i guess it's more like Mikes idea about the right foot.... Unfortnately thats when I press the gas pedal hard in the end of the corner it wants to go straight.... :-)

[Mike N]

Peter. Here's a good short article from a well know professional driver. http://www.randypobst.com/index.cfm?template=magazine&mag_id=15939

[CS14]

Actually, I brake before the corner, maintaine the speed after braking through the curve and then in the end I accelerate.

Just to give the right propotion of the problem, I'm picky, have a race licence and spend some times at track days. One of the minus factors is that I like the vintage style with 15" wheels, the old look of the car in a racing enviroment together with old outfit so with that kind of setup I will never have the perfect handling on the track. Based on my opinion, the set up with the springs in the kit from ffr is quite soft in the rear so my question about "in front or rear" is like a sounding board to hear yours ideas. I really appreciate your input guys!

The fall is coming and we must have something fun to do in the garage during winter.... :-)