Sway Bar Question

[HarryD]

Originally Posted by 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.

We certainly can (should?) arrange a "drive off" someday in the future.

Last winter I had my front pan replaced. I then took it over to Rothsport for corner balancing/alignment. If I needed new bushings, I'm certain they would have been replaced as part of their service.

[nickelplated5s]

Two things; I did put a lighter front bar on mine to avoid push. That said I can still get the inside front to lift on a curb cut.

Secondly which apparently no one notices. The AX was a relatively slow speed 'dive in' corner. High speed sweeper weight would go outside. That day that course weight went inside. I know what I saw and the times. Apex entry and exit speeds could change what I saw but I wasn't driving.

[PeteKz]

I'm in for doing a "drive off." That will be fun. I've already driven both of your cars, and Harry, you have driven mine. Harry's and mine are considerably softer sprung for use on the street, whereas Nickelplated5s' (B) has much stiffer shocks, and I've driven his.

B, I will bet you lunch that when you get out on the AX course next spring, we will see your inside front wheel lift too. Go back to Fred Pughs book "How to Make Your Car Handle," from 50 years ago, and you will see a picture of a 911 with its inside front wheel off the track.

Re springs and sway bars: There is a tradeoff between the spring rates of the torsion bars (or springs if you have those) and the sway bars. The lower the spring rates, the more the car will roll in sharp turns, and vice versa. BUT, the higher the spring rates, the harsher the suspension on rough surfaces. That's the tradeoff.

The sway bars partially reduce the roll of soft springs, thus allowing softer springs for street use and less roll for sharp turns. But again, it's a tradeoff, because when one wheel hits a bump or pothole, part of that deflection is transferred to the other side wheel through the sway bar, and also to the body through the bushings. So you can't just keep installing stiffer sway bars without compromising ride comfort on the street. And, as Bill V has pointed out many times, you need to strike a balance between rear and front sway bars to prevent the turning response from giving too much oversteer or understeer. More tradeoffs...

Unless you build a pure track car with a really stiff suspension, the inside front wheel will lift in sharp turns and especially when accelerating out of turns. It's just the nature of the beast with the weight of the engine in its ass.

[nickelplated5s]

Yup, front will lift but the rear won't, probably. Bring that Pughs book if you have it. I've got your other one for a return to keep things 'in balance.'
Page 19 here: https://www.early911sregistry.org/forums/showthread.php?54727-Show-your-engine/page19

Would be nice to get that local yellow car out too.

[Bill Verburg]

Both sways, shocks, geometry and springs contribute to roll stiffness, but springs are the only thing holding the car up

a spring operates on a single wheel

sways connect the wheels on opposite sides, they take load and hence grip from one side and add it to the other

as either increases in potency mechanical grip correspondingly decreases

of course, there are multiple other factors contributing not the least of which are wheels and tires

that's why wheels and tires and then springs are the first thing to spec and then sways are used to fine tune the package

you want to go as light as you can for both springs and sways while maintaining favorable geometry

[HarryD]

Pete. Are you referring to the Ray Scruggs book shown in post 37+ in this thread? https://forums.pelicanparts.com/porsche-911-technical-forum/97217-toe-adjust-techniquest.html

[PeteKz]

No. this one:

https://www.amazon.com/How-Make-Your-Car-Handle/dp/0912656468/ref=sr_1_1?crid=M0X8BSKXMQQD&dib=eyJ2IjoiMSJ9.vwsAyxv44jtLExoyGP0D-w.LQETL6aXk8TQYFs0bjyHXxMEiUrHTyDY3-FxCRtW258&dib_tag=se&keywords=how+to+make+your+car+handle+by+fred+p&qid=1731657485&sprefix=how+to+make+your+car+handle+by+fred+p%2Cap s%2C745&sr=8-1

[tobluforu]

I read the above book numerous times, great stuff even though some of it was way over my head. There is also the good ol, secrets of solo racing. I used to auto-x against that guy way back, never got close to his times, different classes though. He hot lapped my car a few times, first time he said to me... Needs work, lol, and of course he beat my best TOD by almost 2 frickn seconds, which is a lot. Next time he said, much better. Alrighty then.

[Bill Verburg]

Millikens library is the Gold standard

[nickelplated5s]

Started going through the Puhn book I was loaned yesterday. Copyright 1976 for a whopping $3.25. There's an inside joke about the price sticker I can needle the owner about. I know where and about when it was bought. Not anywhere near a bookstore around here.

[PeteKz]

Well, guess what?

In the newest issue of Panorama, I counted at least three pictures of Porsches coming out of turns with their inside front wheels off the track. See pages 154 and 155. I didn't bother to look for the page numbers for the other pic(s).

Point made and beat in with a sledgehammer.

[tdw28210]

This thread is timely as I am about to embark on a sway bar project, but honestly I am a bit confused as to what to expect as a result. My track day focused 3.8 only has a front sway bar. My plan is to upgrade the factory mounts to solid ones and install a Tarret style adjustable rear bar. The car currently rides on HD Bilsteins (that I am planning to change to B6's) and 17" staggered wheels with wide tires, especially in the rear. The car got a little loose in the rear a couple times on exiting a couple turns during my last track day but I attributed that to the tires not being up to temp. What should I expect by reintroducing a rear sway and upgrading to B6's?

[nickelplated5s]

As BV says it's all about how you want to drive it. PK can chime in on what he has as it's a closer car to yours than mine. Start with full soft or stiff on the adjustable links and then dial it in for what you want. I can actually tell the difference based on fuel load... should have bought a fuel cell when I replaced the tank.

[PeteKz]

Lots of discussion in parallel threads about how changing sway bar stiffness changes the oversteer/understeer characteristics. Search for recent responses by Bill V.

My first question to you is, what do you want to achieve? Will you keep it as a track-focused car, or do you want to make it more civilized on the street? If strongly biased to the track, go with solid bushings/mounts. If you want a bit more comfort on the street, stay with rubber ones. Either way, I would go with an adjustable rear sway bar so that you can see how the adjustments change the handling, and dial it in to your preferences, or adjust for different tracks.

[stownsen914]

If a car is balanced without a rear swaybar, and you add a rear swaybar, you can expect it to oversteer if no other changes are made.

[Bill Verburg]

Originally Posted by tdw28210

This thread is timely as I am about to embark on a sway bar project, but honestly I am a bit confused as to what to expect as a result. My track day focused 3.8 only has a front sway bar. My plan is to upgrade the factory mounts to solid ones and install a Tarret style adjustable rear bar. The car currently rides on HD Bilsteins (that I am planning to change to B6's) and 17" staggered wheels with wide tires, especially in the rear. The car got a little loose in the rear a couple times on exiting a couple turns during my last track day but I attributed that to the tires not being up to temp. What should I expect by reintroducing a rear sway and upgrading to B6's?

wide or SC/Carrera, it does make a difference

w/ a 3.8 you can light up even sticky tires fairly easily coming out of a corner, w/ my 993 3.8 W/ Cup/RSR trans w/ Motorsport lsd. I had to be careful coming out of medium speed corners it's fun driving a bit sideways but not particularly fast.

here's a comparison of 4 different t-bar sets on a 2800# w/b w/ 22mm through body front and 18mm rear sways, and Bilstein(b6 and hd are the same shocks)

you want to set the basic nature of the beast w/ wheels/tires, T-bars and shocks then fine tune for local variations in conditions conditions

I have adj front and rears but only change front, w/ the exception of 1 day where I tried both at LRP which only has has 1 lefty, it exacerbated the traction issue coming out of that left so end of experiment.




when adding a sway where none lived before expect a decrease in understeer/ increase in oversteer, 2 sides of the same coin or looser if you are NASCAR orineted.

[shoooo32]

The first time I visited Ecurie Motorsports I was surprised to see that none of their C Production (LWB 2.2l) race cars had rear sway bars. I just assumed that a race car would definitely run a rear bar, but they told me after the 2nd car was totaled in the kink at Road America they took them off. Apparently its too much oversteer to safely correct at 110mph...