Sway Bar Question

[HarryD]

I feel like this is a dumb question but here goes.

My car has front and rear sway bars. If I disconnect the front sway bar entirely, what does that do my handling? More oversteer? More understeer?

Thanks.

[brianlay]

Will increase oversteer

[stownsen914]

Yup. Having a rear bar and no front will make the car unstable in terms of oversteer, not recommended.

[nickelplated5s]

Watched your car at the last PDX AX. Yours' and the white 73 were unweighted on the outside rear in corners. In other words start with that. Your front looked fine. As an alternative just disconnect one side of the front sway for a test drive. That is is whenever it gets dry here.

[Bill Verburg]

Originally Posted by nickelplated5s

Watched your car at the last PDX AX. Yours' and the white 73 were unweighted on the outside rear in corners. In other words start with that. Your front looked fine. As an alternative just disconnect one side of the front sway for a test drive. That is is whenever it gets dry here.

Don't see how any outside tire can be unloaded w/o spinning

[Bill Verburg]

Even the small 15/15 sways used on the '72/72 add significantly to the wheel rates, w/o a frt bar the front roll rate is cut almost in half, massive oversteer is the result.

[brianlay]

I don't see how any outside wheel can ever be unloaded.

[Bill Verburg]

Originally Posted by brianlay

I don't see how any outside wheel can ever be unloaded.

Hit a patch of coolant puked up by a GT3 and they unload pretty da** quickly

[HarryD]

Originally Posted by nickelplated5s

Watched your car at the last PDX AX. Yours' and the white 73 were unweighted on the outside rear in corners. In other words start with that. Your front looked fine. As an alternative just disconnect one side of the front sway for a test drive. That is is whenever it gets dry here.

The reason for the question is that I have a front end squeak. I am thinking it may be the front sway bar bushings and want to disconnect it to see if it goes away.

As far as lifting my INSIDE wheel, this is a common 911 trait. Per Steve Weiner (RIP) i can make it better by raising my roll center but I do not want to bear the cost and pain to get there.

[brianlay]

I disconnect mine all the time for diagnostic/troubleshooting purposes. Be careful when approaching the limits when disconnecting the rear.
That's a lot of inside front lift...maybe stiffen the rear ARB a bit.

[HarryD]

Originally Posted by brianlay

I disconnect mine all the time for diagnostic/troubleshooting purposes. Be careful when approaching the limits when disconnecting the rear.
That's a lot of inside front lift...maybe stiffen the rear ARB a bit.

Not really. Victim of an Autocross course design. I am coming off a long sweeper where there is a bump in the middle. I try to time the bump to rotate the car for a tighter turn. This was one of my more successful attempts.

[Bill Verburg]

Originally Posted by HarryD

The reason for the question is that I have a front end squeak. I am thinking it may be the front sway bar bushings and want to disconnect it to see if it goes away.

As far as lifting my INSIDE wheel, this is a common 911 trait. Per Steve Weiner (RIP) i can make it better by lowering my roll center but I do not want to bear the cost and pain to get there.

You need to raise the roll center to reduce roll, or use bigger t's and/or sways

[HarryD]

Originally Posted by Bill Verburg

You need to raise the roll center to reduce roll, or use bigger t's and/or sways

I stand corrected. My conversations with Mr Weiner were a long time ago.

[stownsen914]

For troubleshooting only, no big deal. Just drive with oversteer tendency in mind

[nickelplated5s]

Car(s) were going left. Right rears were lifting, unweighted. I was standing at the club house and from my POV that's the outside. The white car has 26 rear TB's, in his sig line. Owner has a set of 27's at home, really nice shop BTW, that he may put in this winter. Personally if you have adjustable sways I'd start with stiffening them, pretty easy.

Re your 'squeak.' I had that and my front end was gone through this spring. Was the sway bushings but I put a bunch of ER stuff in too. The rear will be this spring along with the Dyno for my MFI but that will be a different story.

Harry, you still have an invite here to drive mine if we get a dry day or two. White car already agreed. I'm sort of in the middle of us three.

[Mark Salvetti]

To diagnose the squeak, can't you just disconnect the bolted end of the sway bar, and then bounce each corner by hand?

If the A-arm bushings are old and deformed, it could easily be a torsion bar rubbing.

Mark

[nickelplated5s]

Yes, you could and drive it too. Best guess though is if those are bad the others are also. I still work so bit the bullet and took mine to a shop. FWIW Al said it was the sway bushings in mine. With a 67 I just called it preventive maintenance...hmm? Maybe I should turn that into a work car so I can write it off.

[Jeff Higgins]

Originally Posted by Bill Verburg

Don't see how any outside tire can be unloaded w/o spinning

Originally Posted by brianlay

I don't see how any outside wheel can ever be unloaded.

Originally Posted by Bill Verburg

Hit a patch of coolant puked up by a GT3 and they unload pretty da** quickly

I think we are mixing terminologies. "Unloaded" means "unweighted", i.e. there is no longer any weight being transferred to the ground through that particular tire. In other words, if we were somehow able to measure the load that tire is transferring to the ground at the moment (like through a load cell, etc.), it would read "zero".

Sliding in a coolant puddle left by another car (I did that once at Pacific Raceways, following an Alfa Giulia through turn two when it lost a coolant hose) is a different matter. That's a loss of grip, not an "unloaded" tire. The sliding tire can still have plenty of weight, or load on it, it's just lost traction.

And I agree - there is no way for the outside tires on any car to "unload" - to actually lift off the ground - when cornering. Physically impossible, unless the car hits a bump or something. Cornering forces simply cannot do that.

The rule of thumb regarding sway bars is that the front sway bar affects rear traction and vis versa. If you want more rear grip, increase the stiffness of the front sway bar. More front grip is achieved through stiffening the rear sway bar.

[tobluforu]

I did this years back, disconnected the front 22mm bar and went for a spirited drive-up Mt Tam. Needless to say, when you are used to driving the piss out of your car with that bar connected, and then disconnect it, it's a hair-raising experience. That run lasted all of 10 minutes.

[Bill Verburg]

Originally Posted by Jeff Higgins

...

Sliding in a coolant puddle left by another car (I did that once at Pacific Raceways, following an Alfa Giulia through turn two when it lost a coolant hose) is a different matter. That's a loss of grip, not an "unloaded" tire. The sliding tire can still have plenty of weight, or load on it, it's just lost traction.

.....

The rule of thumb regarding sway bars is that the front sway bar affects rear traction and vis versa. If you want more rear grip, increase the stiffness of the front sway bar. More front grip is achieved through stiffening the rear sway bar.

they unload pretty da** quickly

yes they slide but w/o grip the suspension is no longer loaded after the initial very fast transition from full to zero grp. It doesn't slide loaded.

when you increase a wheel rate whether by spring, sway, shock or geometry you decrease mechanical grip

adding more sway in front decreases grip in the front which causes more under/less over which ever way you want to look at it, it also speeds up front steering response and decreases power off steering at corner entry

reducing front sway does the opposite

the sole reason to use higher spring or sway rates is to eliminate or at least reduce the negative geometric effects from roll