sway bars

[10speed]

are double bars an option?

[jhoefer]

are double bars an option?

I'm not sure what you're asking. Using two anti-roll bars on the same end of the car? For what purpose? If it's just to increase the spring rate of the anti-roll bar, the rate is proportional to Diameter^4. That is, just a 19% increase in diameter will double the spring rate. A 7/8" diameter anti-roll bar is 85% stiffer than a 3/4" bar. A single thicker bar is cheaper and simpler than two. Or were you thinking of something else?

[helowrench]

I'm not sure what you're asking. Using two anti-roll bars on the same end of the car? For what purpose? If it's just to increase the spring rate of the anti-roll bar, the rate is proportional to Diameter^4. That is, just a 19% increase in diameter will double the spring rate. A 7/8" diameter anti-roll bar is 85% stiffer than a 3/4" bar. A single thicker bar is cheaper and simpler than two. Or were you thinking of something else?

So, what does the difference calculate out to between the 3/4" empi, and the 20mm 944 bars with all else equal?
(admission: I am lazy and do not want to do math right now.)

[FJCamper]

Hi Whiteboyspooky,

I don't know your car and havn't seen you drive, but having 3/4" front and rear bars on a '69 bug provides a great deal of roll resistance.

That's eough roll resistance to put your car up on two wheels in a sharp quick corner.

Now in general, the slower you go (autocross, for instance) the more roll resistance you can have. At very high speeds, you need weight transfer and predictability.

Too stiff, and your car just skips and slides. Is this what's happening and you're thinking you need more roll stiffness to stop the breakaway and sliding?

We're all friends here. It might be your driving. Tell us what kind of events you've run.

FJC

[whiteboyspooky]

Hi FjCamper
So far ive done mainly canyon runs and lower speed driving. I haven't felt comfortable taking the car to a big track (Streets of willow later this year) yet because of various reasons. From the driving i have done, which i admit is different than driving on a track, i have experienced understeer when pushed hard and some but not too much body roll. Maybe iam expecting too much of my car without much practice behind the wheel. I think i need to start working on my "driver mod" haha i think i keep trying to modify the car to be faster without making myself a better driver

[whiteboyspooky]

helowrench
if my math is correct a 20mm bar is around 50% more stiff than a 3/4(19mm) bar. roughly.

[Bruce.m]

Assuming no material / other differences, 19mm to 20mm is just under +23% increase.

[buildabiggerboxer]

What's the rear setup? I'm guessing swing, but there's no mention what it is. It is understeer that's the hardest to overcome with swing, that's even with having all the front torsion arm bearings and wheel bearings all at zero play and the alignment set correctly, you need extra camber nuts too, set for maximum negative camber, Swing axle rear can be made as stiff as you like by bigger torsions, but generally 26mm short bars, ie, 12/1300, are as stiff as you need for the street, up to 30mm for race track use, but don't go that stiff with IRS, As mentioned earlier, 924/944 24mm torsions work well for IRS, but need appropriate spring plates to suit, and you may NOT need a fear ARB with them.

[FJCamper]

Hi Spooky,

Take a look at this handling post

http://www.shoptalkforums.com/viewtopic ... 1&t=127619

Your '69 (IRS rear suspension) Bug will understeer, even stock. Both the front and rear suspensions are designed for understeer.

Driver preference or perception is important. What makes a driver comfortable is not always the fastest setup to get around the track. Since you are both driver and crew chief, it's hard to argue with yourself, but try this. Go to an old airfield, parking lot, wherever you can drive like a maniac safely, and set up a slalom or mini-road course and have someone time you.

Time yourself with different tire pressures, then with the rear sway bar disconnected. Run enough laps to get averages. Now you have data.

A tire pressure tip. Check the front and rear TP's as soon as you come in, to see which tire(s) are getting the hottest. The hotter the tire, the harder it's working. For instance, if my rear tires both went up six psi after three to four laps, I'd know my rear suspension is really being worked and that's where I need to find the answer. If my front tires stayed at the original pressure or went up just 2 psi (normal) I'd know the suspension there is sorted out.

You have a ball joint front end. Get an alignment with at least one half to one degree negative camber. If your camber adjusters won't adjust out that far, get a set of the aftermarket adjusters that will.

FJC

[VW&MGman]

I have a set of Toyo R888s, and my car has a similar set up as yours. I have very little under steering tendencies in full race conditions.

[whiteboyspooky]

FjCamper

Ive actually read your article several times start to finish. Ive somehow neglected to use anything ive learned from your article...chock that mistake up to being young and dumb. My first step im going to take is go through all the suspension components front and back. All bushings and bearings that havent been replaced will get replaced or fixed. Ive been thinking of changing big things when i should have started with getting the car solid with all the small stuff.
I know this is somewhat unrelated from the original topic but what are the pro and cons or using urethane or delrin bushings instead of needle bearings in the front beam? I can start a new thread if need be.
Thanks

[FJCamper]

Hi Spooky,

Needle bearings are smoother in operation, excellent for a street car. Polyurethane bushings (the long ones) for your trailing arms can bind or squeak like a bitch if not well lubed.

I favor the urethane bushings because they give more support than needle bearings in a race car.

It is a good guess that your spring plate-to-torsion bar bushings are flat, hard, and split. This allows the car to steer itself as you brake and accellerate. Replace them with urethane. But don't use urethane for your transmission mounts. For the street, good new stock mounts work just fine.

And last on mounts, if you replace your front transaxle nose cone rubber mount with a solid steel mount, it will transmit more road noise into the cabin, but you will have a far more positive gear shifting experience, especially if you have a new shift rod bushing.

FJC

[whiteboyspooky]

all the bushings in the rear were replaced with Bugpack urethane ones. Only ones left to replace are the pivot arm bushings. I replaced all the trans mounts, front is a Rhino mount rear are stock replacements. I also have a empi mid mount which seems to help alot (i ripped the old mounts...)
Im considering getting a Kafer cup brace in the future but after I setup the rest of the suspension properly.
Is there any benefit of Delrin over urethane? Is it worth the extra cost?