hey guys... my car tracks very nice. have 19mm torsion bars up front, 23mm tarett swaybar up front, 140 lbs springs, and konis up front/bilsteins in rear.

what does adding a STOCK rear swaybar do for me?
to compensate for the rear bar, would i dial in MORE front bar?

cant seem to get it right in my head

Adding a rear bar is the equivalent of adding more rear spring rate. I'm REALLY surprised that your combo works without understeer. The Tarret bar with stock torsion bars and 140's is what appears to work best for sticky tire'd 914's (with those parts) I run rear bars because I *may* need more rear spring rate and I dont want to have to change the rear springs for every event. It is VERY easy to pop a link off the rear bar if need be.

I'm betting you have the Tarret set on full soft.


B

right again.....
and koni reds set at half to full stiff

so if i add a rear bar, put front bar on full stiff?

Right now you have NO adjustment. Adding a rear bar will allow you to dial in more front bar if need be.


B

hmmmm

rear bar makes it oversteer right?

General easy rule of thumb:

If the front is loose.. tighten the rear (tighten rear bar or add more spring rate)

If the rear is loose tighten the front (add more front bar or increase torsion bar size.

I could run 19mm bars on all my cars if I wanted to run 26mm torsion bars. I prefer not to "spring" the car so heavy and let larger sway bars handle the roll control. The adjustable bars allow me to dial the car in for each event without changing torsion bars or rear springs rates.


B

thanks for the insight B,

looks like i'll install a stock rear bar..and play with the front bar

Dont get messed up. Stick with: loose in front tighten rear... loose in rear tighten front.

There is a cross over point... but it is not important. It will just screw yor head up thinking about it.


B

last question..i PROMISE

adding a rear bar makes the rear looser right?

thats all my cognative ability

I want you to think the other way: It will tighten the front. Effectively it *will* loosen the rear but ONLY because the front now has more grip.


B

ok.. makes sense.

im just a grasshoppa in the world of performance driving and suspension tuning.

thanks brad.

Now you understand how I can 31mm sway bars in cars with stock torsion bars. The cars actually still ride nice going down the road.


B

got it

cool..more food for thought

You want to adjust. 99% of the "old guy's" out there just drive and compensate with the gas pedal. This works great for them, but it may have taken them 15-20 years to get to that point. Once a driver understands what his/her car is doing they will become better drivers faster. Understanding what needs to be adjusted is even better.


B

I agree with everything Brad says & will continue to do so till the evening of 22 March.......after that, we'll see

Weeeee!

Love 31mm

I have driven 914's with and without sway bars, I have watched cars with only front bars and heavy springs, I personally, will never own a 914 without front and rear bars. I installed them on the Chalon as it came with nothing, I went with a 23mm front adjustable and a stock rear bar. I am not sure how it is going to handle yet but give me another week or so and I will let you know. I know my little S-10 truck handles awesome and it has front and rear bars and Bilsteins all around.

scott..our 'chat' prompted this thread. i need a new trunk floor pan anyway.. ill just get ones with the mounts

thanks scott/brad

With that large a bar in the front and 140# springs in the rear, I'm surprised the handling is "balanced".

I'm not a guru, but when my car had a similar combination, it suffered from extreme understeer (especially for AX).

I progressed to 180#, 200#, and finally 250# to achieve the rotation I was looking for.

I am running 8X15 wheels in the rear with 225/50s, so that may explain why I had to go to 250# springs to get the rear loose. When these tires wear out, I'll be looking to swap out for some 7X15s if anyone's interested.

Oops... got off topic.

I suggest you install that rear swaybar for sure. If after awhile, you sense it's an "improvement", you might consider going to a stiffer rear spring. While the rear bar will add some increase in spring rate, it may add wheel spin in turns that you won't find satisfactory.

IF.. you have a good front bar... the car will stay FLAT in the corners and not lift the inside rear wheel causing wheel spin.


B

I can say from my experience over this a/x season with all my suspension changes, that the rear bar, big 31mm bar and 150# rear springs is pure magic. As a bonus, the car is a joy to drive on the street.

Just set the shocks on soft and go!

Wow, what a ride. Brad, you know things...

KT

not a guru, but pro-rear bar.

the suspension seems to "load up" in ways i don't like when it's disconnected.

stock tbars, 21 welt, 140s

What about the issue where the droplinks contact the trunk floor (on lowered cars that still have a trunk)?

I have a Welt rear bar that I have been thinking of reinstalling now that I have an LSD and bunch of other mods that should make it effective again...when I bought the car it was clearly detrimental and I yanked it out.

Well, I might add that I am running 180 poound rear springs for the extra support of the small block chevy engine. The front torsion bars are from a 72 911, whatever they are. I never measured them.

Chris,

We flip the stock rear bars upside down. This moves the links way down and keeps them from hitting the trunk floor.


B

This is ssssssssssso cool. I was goig to post my own thead about this.
Slightly different tho. Somewhere I read an article about tuning suspenion at the track. Tire pressures, shock settings, front bar.
The article went about telling the same easy logic that Brad used. "if it's doing this, Do this".

Seems different AX courses need different things. tight parking lots the car pushes all over. I connected the rear bar and made it better. Then dropped some air in the fronts got little better still. Then the day was over.

I need a car handling for dummies. and a check list of things to do. I think a "dope book" (ala sniper data log) to keep track of what I did for which tracks

My car is a stock 70 with 75 2.0L & side shift trans. I ran with stock sway bars front & rear and with adjustable koni all around. I found for me, that I do better AXing with the rear bar disconnected, koni's set to full firm all around and the running 40psi in the falkens. YMMV

Listen to Brad he knows a hell alot more than I do.

Car set up for dummies.

Try: "How to make your car handle" author? available at most Barnes and Noble. Is a great Suspension set up for dummies!

Followed by "Racecar Technology" and then "Racecar vehicle Dynamics" by Miliken and Miliken (bring your brain) I am sure others exist, but these are the ones I have found to be concise and factual.

Brad is absolutely on the track of current fast trends.

Everyone used to spring the cars VERY stiff, and smaller sway bars were used, this is mainly due to small shock shaft velocity (m/sec) being less important (and less understood) to shock manufacturers than they are now. Back in the days we controlled attitude of the chassis with spring (very stiff) for transients, now we use shocks that are very sensitive at low shaft speeds with digressive rate pistons/valving for good bump compliance. Springs still control load but less now that shock manufacturers have developed new valves and valving.

So. we can use softer springs to reduce initial tire loading while we use the shock to spread the load over time. This is really the key, spreading load over time, that is why it is fast to be smooth, LOAD OVER TIME. Coupling this with sway bars that control body roll, we get the best of all worlds. ie... more grip.

Roll rates reduced (sway bars) less static geometry must be set (camber), Spring rates reduced (more mechanical grip), Better shocks have allowed this advancement. Remember when the tire hits a bump the tire will deflect first, the trailing arm/strut motion will start, so if the springs that we used to use are very very stiff, then the tire becomes much more of the suspension than the suspension does, plus the tire has no (other than hysteresis) rebound limiting mechanism, whereas the shock certainly does. So with very stiff springs the mechanical grip can not be maintained. The limits for a 914 would be dictated by how stiff the chassis is, how sticky the suspension bushings are ETC... (Thanks Chris, love my rear bushings, they work great) and what tires you are running, oh and how hot you can get them prior to your run.

Since suspension engineers now understand a bump and it components. We now better understand how to dampen the bump, I would go into critical damping but don't think it would be much help. The way Brad has asked you to think about tuning the car is the easiest. Lastly, don't listen to what everyone else is running, tune your car, keep good notes, write everything down. While an idea of what everyone else is running is good to make sure you are in the ballpark, there are so many variables in the equation, that it can be difficult to use the same set up exactly on two different cars and get the same result. Even chassis cycles can affect how the car performs. 10K car VS 200K car. Run the rear bar, BUT, and this goes for everyone, Sway bars must be free to rotate in their blocks/bushings/bearings even loaded this must happen, if not it just does'nt work.


Erik Madsen

Post Script: I use a rear bar, it allows me to fine tune the chassis. Without it, a variable is removed from the equation. And the changes become limited to adjusting one thing to compensate for something else which I don't care for.

Brad, my car is lifting the inside rear wheel (JP told me so it must be true). I have stock front and rear sway bars, stock torsion bars and 180lb springs, Koni yellows. What is the solution? Bigger adjustable front bar?

So, ideally one could run stock front torsions and stock rear springs and have an adjustable front bar and adjustable rear?

Ayup....and 175 X 78 tiars....it would be a cool AX weapon:D

Jim,

Lose the 180 rears or get a 23 Tarret front bar. You have WAY too much spring in the rear of that car for what you have in the front. Right now you have the equivalent of 200 rate rear springs with the bar attached. I bet the car spins like a top... it probably turns in great and slings the ass end all over the place.


B

I surprised no one has fabbed up a sliding drop link mount that let's you adjust the stock bar.

You could move it to any of the yellow spots or in between.

KT

They have a rear sliding bar... it is called "Weltmeister"

Thanks for backing me up Eric. I know WAY to many chassis engineers that over complicate setups on real race cars. I have attended some pretty kickass setup classes over the years (most of them geared towards open wheeled cars) and they can BLOW you away with the sheer number of adjustments. Our cars are VERY easy with the limited amount of "stock" pieces we can adjust.

Dont even get me started on "Ackerman"


B

Does, anyone know where the term Rule of Thumb came from?

Back when we had the Thirteen Colonies, you could legally beat your wife with a stick no thicker than your thumb.

Do not try this at home, this is only for trained professionals.

Seems in this thread opinions were split a little more on rear bar or no rear bar: http://www.914world.com/bbs2/index.php?act...uch%20bar&st=40

Well I had a few minutes of garage time today, so I reinstalled my Welt rear swaybar to see how it feels. It's set on full loose for now.

In the meantime my muffler heat shield "fell off" (OK I helped it a bit ) Actually a few of the spot-welded bracket points were broken, probably due to minor rear trunk rust, and so the sucker was probably rattling/resonating like crazy and I had never noticed it was loose until today. The muffler/swaybar area is SO much more accessible with it gone.