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Posted by: Cracker May 1 2012, 07:03 AM

Rear Sway Bar
Need the pros & cons, options and what YOU have actually used. Basically, I have found that there is only the small factory assembly and the Weltmiester system available. I spoke with Ira at Tarret Eng. yesterday but the few prototypes he built years ago are all gone.

Goal
I'm running 315/35/17 rears, a LSD and 300 lbs rear springs. I still have way too much rear body roll than I want. I've tightened up the front sway bar and removed rear camber and that has helped but feel I need a rear bar help beyond that with the body roll out back.

Your thoughts & options?

Posted by: RobW May 1 2012, 07:18 AM

Rear body roll doesn't come from a rear sway bar.

What is your full suspension set up and are you braced with a roll cage or roll bar?

Posted by: brant May 1 2012, 08:32 AM

I run a rear bar...

but your talking about needing a bigger front bar
I put a smart front big bar on mine

Posted by: DanT May 1 2012, 08:47 AM

Have never run a rear bar on any of my personal 914s, but have driven several with rear bar...
Properly setup, I have never felt the need for a rear bar.

Posted by: stewteral May 3 2012, 12:41 AM

Hey Cracker,

I'm in the middle of resolving this same issue currently with my car! I'm running a Chevy V8 with a 930 trans & quaide TORSEN Diff, 400 lb springs with 11" rims and the same size rear tires. I just bought a new set of Goodyear slicks.

My question is what is your car doing currently?

I fought HUGE understeer for a long time until I stiffened the rear springs enough the get the rear-end to "move" so I could tell what it was doing. Then came the issue of trying to balance out the understeer/oversteer to a mild understeer.

In working at balance the understeer, I built a rear bar that was contributing 98 lbs per inch of WHEEL RATE (not the swaybar rate, but what the wheel sees). I can tell you that the car was VERY unstable applying power while coming off corners.

With the help of AndyS, I have come to understand that high roll-stiffness from a swaybar is a very sensitive issue with 914s due to the inherent LOW POLAR MOMENT OF INERTIA (i.e. all the weight in in the middle of the car and it rotates easily)

I have since completely rebuilt a new rear bar and am starting out at 60 lbs/in WHEEL RATE. I won't know for sure what the final setting will be until this Saturday when I'll be out at Willow Springs Raceway. As a preview this week, I drove the car on the street in wet conditions and found it CONTROLLABLE! Instead of the vicious snap-spin behavior, I was actually able to get the rear lose and catch it with simple steering corrections. I'm pretty sure I'm going the right direction.

I hope this helps you! My only caveat is that all my springs rates will me higher than a 911 or 411 engined 914.

Best of luck,

Terry

Posted by: Racer Chris May 15 2012, 07:03 AM

Between those two, the Weltmeister bar is probably a better choice since its slightly stiffer than the factory bar and is adjustable.
I used to run mine with the drop links reversed so the arms of the bar were below the shock mount. This made more sense with the car lowered as much as mine.
One shortcoming of the Weltmeister setup vs the stock one is the method of attachment at the shock bolt. The Weltmeister shock bolt is drilled to accept an 8mm bolt which supports the rod end in single shear. I've bent those 8mm bolts before.
I do have another (used) non-adjustable rear bar which I've never installed. I think the brand may have been H&H. It uses a third attachment method.

Posted by: Cracker May 15 2012, 03:59 PM

Thanks to Bob/Naroescape - I now have his old Welt. rear bar set-up. I'm having my machine shop fabricate the shock bolts with provisions out of tool steel for the drop links. I'll post pics when I get them in my hands.

I've since moved up to 400 lb rear springs over the last week...its better but still more Texas-two-step than I like. The rear is still very delayed in it's reaction to the front input. I'm hoping the bar set to full soft will help the chassis balance. Time will tell...

Posted by: stewteral May 15 2012, 08:58 PM

Hey Cracker:

UPDATE INFO: On 05 May, I ran a track day at Willow Springs (the Big track)
and found I kept adjusting the rear swaybar SOFTER & SOFTER until it was the Best at only 28 lb/in Wheel Rate. This is a BIG reduction from the previous 96 lbs/in.

Last Thursday & Friday I was at Infineon Raceway and found that the Willow setup with 1 step SOFTER front bar gave me my best results ever.

The lesson here is to get most of your wheel-rate from the rear springs and just use a SMALL amount of rear bar for fine tuning. With all the weight in the center of the car (Low Polar Moment of Enertia) the car needs only a small amount of Roll-Stiftness to work. As I learned, a big rear bar means nothing but rear instability!!

With the softer rear bar, I picked up more understeer, but softening the front bar made it BETTER! Roll is NOT a bad thing as the goal is BALANCE!

I'm running a Chevy V8 so my rear springs are at 400#, if you have a 911 motor, of course your springs will be softer. Regardless, dialing in mostly with spring rate and then fine tuning with a "light" rear swaybar is the path to success.

Best of luck

Terry

Posted by: Trekkor May 16 2012, 12:19 AM

31mm front bar, stock torsion bars.
Stock rear bar, 200# rear springs.
Koni yellow adjustables all around.

I haven't made any changes since this set-up.
No need to. The balance is perfect for me.


KT

Posted by: campbellcj May 18 2012, 12:08 AM

I have used a rear bar almost continuously for many years as well. I recently switched from a Weltmeister to a factory setup due to the crappy geometry and hardware issues (bent and sheared bits) noted above. I've saved the Weltmeister and someday may try to re-work it...

Posted by: yeahmag May 23 2012, 11:39 PM

Big Track, Short Track, or Autocross?

Posted by: Cracker May 24 2012, 04:11 AM

No autocross...largely "large" track @ 2.4+ miles. I installed the sway bar yesterday and immediately was HAPPY with how the chassis responded.

Now, the rear quickly reacts to steering input and rotates much, much quicker - more like the front/rear are ONE rather than the aforementioned lethargic response (rear). My next "tweak" is to fine tune the front bar - all small stuff moving forward.

Thanks fellas for you thoughts - literally, between alignment, spring rates and rear sway bar my car has been transformed BACK INTO a car that can be driven hard with confidence!

FWIW: The front toe was the culprit to the horrible handling was the front toe (more than anything else). I ended up at +.10 - the difference is night and day. I indexted the rod ends between O to +.10 (@ O the steering was still WAY, WAY darty).

Posted by: grantsfo May 24 2012, 12:41 PM

If I were to build another 914 I'd seriously consider Treks setup. Very balanced with excellent turn in.

Posted by: RobW May 24 2012, 10:28 PM

I had really good results with 21MM front torsion bars and a 19MM front sway bar, Bilsteins, and a stock rear sway bar... camber at 1.5-2.5 deg and some toe in...

Posted by: OU8AVW May 25 2012, 06:41 AM

Are you guys corner balancing?

Posted by: Randal May 25 2012, 10:46 AM

+1

Posted by: SirAndy May 25 2012, 02:55 PM

-1

WARNING: Personal opinion alert!

I added a rear (stock) bar and it made quite a difference. Not so much in handling, as you can dial in pretty much any type of handling to your personal preference anyways.

What it did do however is that it really helps keeping the rear of the car level and planted during hard cornering.
Many track cars get the same effect by going with very heavy springs and stiff shocks in the rear.

But in my personal opinion, it is beneficial to use a rear bar and be able to run a softer setup on the springs and shocks.
This has allowed me to step down on my rear spring rates from 250lbs to 200lbs yet the car is flatter through the turns and the rear seems to have more "bite" than before.

Posted by: Cracker May 26 2012, 07:12 AM

-2 (on Andy's lead/logic)

I'm still amazed at how much improved the rear bar tightened up the chassis...I have not corner balanced yet - planning to next week though prior to RA weekend. I recogonize that not everyone likes the same feel/chassis response characteristics. Good input here...thanks again guys!

Cambellcj - Which bolts sheared on your Welt kit???

Posted by: John Jentz May 26 2012, 07:29 AM

I think the biggest negative to running a rear bar is the problem of the bar hitting the trunk floor and going to max stiffness. Since you're not likely to be carrying luggage in your car, have Lewis cut some slots in the trunk floor so the bar cannot bottom. Variations on this theme were used by most teams back in the day.

Posted by: Cracker May 26 2012, 07:49 AM

John - We're neighbors. I installed the system myself at Lewis' last week. My system
is set up to prevent bottoming out already. Thanks.

Come out to RA next weekend (6/2) - I've got an air conditioned trailer for comfort and it's always good to have another 914 around too (99% of the time that is)!

Posted by: Randal May 26 2012, 09:03 AM

If I had a car I was driving on the street I might also use a bar and softer springs and shocks. That would help to keep teeth in your mouth. Guessing that your car, which weighs more than mine, would require some real heavy springs to keep the rear end flat if you didn't have the help of a bar thrown in.

Bill Pickering always runs rear bars and is quite good at getting the whole "system" to work correctly. It does take lots of adjustment to dial in the setting and you'll find yourself changing settings between morning and afternoon sessions to alter behavior.

You can get good balance either way, but my personal preference is to concentrate on the course instead of trying to dial in behavior.

Posted by: campbellcj May 26 2012, 09:38 AM

Last failure I had on the Welt setup. This is due to the hitting the trunk floor / lame geometry issue.

http://www.flickr.com/photos/cjcam/4025122446/
http://www.flickr.com/photos/cjcam/4025122446/ by http://www.flickr.com/people/cjcam/, on Flickr

Posted by: Racer Chris May 26 2012, 10:50 AM

Thats exactly why I modified mine like this:

Posted by: Randal May 26 2012, 11:16 AM

Hey there is a bunch of rust on that caliper and it needs to be cleaned off; at the track of course.

Posted by: Trekkor May 26 2012, 10:50 PM

Using the stock bar, mounted upside down, I have never compressed the suspension 3 inches to bottom out.

I was thinking of making the stock bar adjustable at one point.
Never did. The car is fantastic right now.


KT

Posted by: Trekkor May 26 2012, 10:56 PM

KT