back 5 minutes...already have another question, rear springs....a question of balance Options

[Joseph Mills]

My car has 180# springs in the back with 19 or 21mm torsion bars front. Koni adjustables all around.

This summer I installed a 22mm Weltmiester swaybar to cure some EXCESSIVE oversteer (to put it mildly).

Now it's about as neutral handling as you could hope for on the street. At 60mph on off-ramps taking it up to the final point of adhesion, you can abruptly apply throttle lift and the back-end just jumps out a little....real nice. If you floor the throttle, it will slowly start to push. ALL VERY controllable.

But at slower 30-40mph speeds typical of some tight autocross turns, it has a slight tendancy to push. I've always heard that slow speed pushing is very difficult to overcome. But I hope that I can still get the car to rotate a little better yet.

I'm considering going to 200# springs. I've even considered 220 or 240# springs, but I don't want to end up with TOO much oversteer again.

I know many of you have been here before. What shall I do? (IMG:style_emoticons/default/confused24.gif)

[redshift]

hmmm....

understeer... oversteer.... you need to make the front stiffer, and lose the rear bar.

(IMG:style_emoticons/default/smile.gif)


M

[ChrisReale]

914's have a tendency to push in tight slow spots. Are your 180's progressive? I bet they are. That would explain slower speed pushing and higher speed (more load) stability. Try 175 or 200# coils that are not progressive

[Joseph Mills]

Are your 180's progressive?

Nope. They are non-progressive.

I guess my real question is:

Will I feel a noticeable change from 180 to 200#, or should I go to 220# springs? I just don't want to over compensate for what I want to be a somewhat subtle adjustment.

Incidently, the Weltmeister bar is ALREADY set on full soft.

I was thinking that JP was going to put heavier springs on his car for much the same reason. Wonder if he did? (IMG:style_emoticons/default/ph34r.gif)

[ChrisReale]

Who made your rear springs? I have never seen any 180# springs that were not progressive..

[Joseph Mills]

180# 2.5" ID springs that came with the Adjustable Ride height kit from Paragon products (about 10 years ago?).

All 8 turns of the coils are equally spaced (there are two more turns that touch at either end.

You are right. These are VERY rare and valuable. Wanna buy'em? (IMG:style_emoticons/default/laugh.gif)

When I remove them I can take a photo of them if you like.

[ChrisReale]

They still are progressive, they just dont look like it (IMG:style_emoticons/default/laugh.gif)

Dont know what to tell you....

[Joseph Mills]

They still are progressive, they just dont look like it (IMG:style_emoticons/default/laugh.gif)

Damn! That's VERY progressive (IMG:style_emoticons/default/smoke.gif)

[SirAndy]

Incidently, the Weltmeister bar is ALREADY set on full soft.

yupp, if you have a back sway-bar, try disconnecting it.
if that doesn't help, get heavier springs in the back ...

obviously, you can't loosen the front any further (IMG:style_emoticons/default/wink.gif)
soooo, tigthen the back.

go with the 220!!!!
you should have plenty of adjustement in the front if the 220 are a bit to heavy for the front being on full soft ...

Andy

[SirAndy]

btw. i have the 911 carrera front end with a tarett 22mm sway bar and 180 progressive springs in the back (no sway bar in the back).
225 all around on 7" and spaced out to the flares.

the front bar is almost full soft, about 1" in ...

the car handles like "on rails" (IMG:style_emoticons/default/wink.gif)
Andy

[ArtechnikA]

...if you have a back sway-bar, try disconnecting it.

obviously, you can't loosen the front any further (IMG:style_emoticons/default/wink.gif)
soooo, tigthen the back.

these two statements are self-contradictory...

more rear bar will add (not reduce) oversteer. just like more rear spring.

i couldn't get my car around an AX course for anything (plow), finally added a rear bar that made it manageable. that was a long time ago. i have since been pursuaded/convinced that times have changed, tires have changed, and technique must change. hearing Ben Messenger's stories of having a 23mm front bar and wanting more led to a long exchange on technique. i'll be working on that when we AX the 911, but i don't think i'll have the suspension stable before the start of the season so it will be something of a moving target...

anyway - the [oversimplified] upshot was - abandon the tight line, DRIVE the car to the turn-in point, brake HARD to plant the front, transfer load to the front tires, and unload the back, then power through the turn.

i see this happen all the time on the NASCAR short tracks - the outside line -is- longer, but you are travelling -so- much faster that it more than makes up the difference. and AX is not won or lost by inches, but by hundredths of a second.

as an engineer it's seductive to think that the car can be infinitely modified to compensate for driver technique, but sometimes, we must learn new trhings. that's hard, but it is rewarding, and it keeps the game interesting...

anyway - for less understeer, yes - tighten the back - more spring or more antiroll bar.

[DNHunt]

Are you sure of your alignment. I just got a corner balance and agressive street alignment and it helped every aspect of the cars handling. I still don't know what the car is capable of since the old limits don't apply anymore. Might be a thought.

Dave

[SirAndy]

these two statements are self-contradictory...

ooops, you got me there ...

you're right!
Andy

[J P Stein]

the car handles like "on rails"  ;)
Andy

Ah, but what happens when it jumps the rails?
At some point, one looses tire adhesion.

My experience with 914s tells me that the "ideal" AX situation would be for the back end to step out first.....that helps the car rotate. Unfortunately, it seems that mine (presently) will do so nicely on meduim to long radius turns (in AX terms), but plows on the tight stuff. If I could get it to be neutral in the tight stuff, I can rotate the car with the loud pedal....but I don't need it to then be loose as a goose in the sweepers. That may be entertaining for the spectators, but it isn't the fast way around. It also makes the car a handful (or just flat dangerous)
on the big track.

[Dave_Darling]

Also, remember the general tendency of all cars to understeer more at low speeds and oversteer more at high speeds. That's just the way they work.

--DD

[ArtechnikA]

Also, remember the general tendency of all cars to understeer more at low speeds and oversteer more at high speeds. That's just the way they work.

well - RWD cars, anyway...

drive traction shifts you on the friction circle, which is why RWD cars tend to have bigger rear tires.

FWD cars just tend to understeer.

if you've watched the British Touring Car Series, you've seen the FWD cars with big rear wings, and it wasn't until recently that i figured out what that was about... they're obviously set up with so much suspension oversteer to make them turn in for the slow corners that they'd be evil-tailhappy in the fast stuff (aero lift...) that they hafta plant 'em...

[Eric_Shea]

the car handles like "on rails"

It's on a trailer... (IMG:style_emoticons/default/lol3.gif)

[redshift]

ROFLMAO!

M

[Joseph Mills]

My experience with 914s tells me that the "ideal" AX situation would be for the back end to step out first.....that helps the car rotate....

but I don't need it to then be loose as a goose in the sweepers.

I have found this to be true and agree whole-heartedly. That's why I'm so hesitant to increase the rear stiffness in anything more than pretty small incremental amounts.

I'm not sure at this point if I can squeeze out any less slow speed plowing without creating oversteer elsewhere.

The car has been very accurately aligned (caster/camber/toe-out/toe-in) and lowered. I'm holding out on corner balancing UNTIL all other aspects of suspension tuning are finished (or until I THINK they're finished (IMG:style_emoticons/default/blink.gif) ).

What about any of these options:

I've got about 1.25 neg camber F, and 2 neg R. I could loose some of that rear camber to create a touch more rotation. Bad idea?

I could hook up the stock rear sway bar. It's so wimpy compared to current springs/shocks/front swaybar, I'm not sure it would do much. I've always "heard" that it just creates more wheel spin (if so, why is it recommended to use it for -6?).

I could run the F shocks on full soft, run the R on full hard. Sounds whacky.

Run 30# in F tires and 40# in R.???

Is there any merit in any of these ideas? Pros/cons?

Rich touched on a good point which I have been trying to incorporate. And that is change my driving style. I sure like the no $ cost aspect! (IMG:style_emoticons/default/laugh.gif)

I try to enter turns utilizing throttle lift to help bring the rearend out, and try to avoid accelerating thru any tight stuff. Makes a big difference.
It would seem in theory that once you learn what your car does badly, you can start driving it in a fashion that suits what it does well.

Any further feedback is appreciated. I'm obviously (IMG:style_emoticons/default/confused24.gif)


Eric, that was pretty funny.....

[drew365]

Experimenting with different driving styles is always a good idea. It'll teach you car control, get you tuned in to what output follows your input. (IMG:style_emoticons/default/ohmy.gif)
I wouldn't play with different tire pressures front and rear. It's hard enough finding the right pressure for your car and tires without trying to balance the car with changing pressures.
I wouldn't get rid of any negative camber. The negative camber will give you the grip you need. Balance that grip with spring rates and swaybar adjustments. I think going up to 225# springs will bring your front swaybar to near mid point which is a good place to be. I think there is more stress and preload on the drop links when they are at the extremes.