I need more rotation in my car for AX turns. I'm getting eatin'up in slow speed turns with too much push. I replaced the 180# with 200# springs in the rear. It helped, but not enough. Maybe too subtle a change?

Should I go to 225 or instead go on up to 250#? I don't want to go stiffer than necessary, but I don't want to keep buying springs! I have a 22mm Weltmiester adjustable swaybar up front set on full soft. For those of you with the experience, what should I do?

You could potentially put some toe-out in the front.

It has 1/16th" toe-out now (1/16th" toe-in rear), with 1.5 degrees neg camber front and 2 degrees neg in rear.

For a cheap (-ish) change, try a little more negative camber up front or a little less in the rear.

--DD

I dunno, but I'm workin' on it.
I'll know *something* Sunday evening

Hah! So come Sunday, you will be "experienced"?

What springs are you trying out? Which begs the question, what springs are you coming from?

From 200 to 225.
I was/am pushing in the tight stuff.
I've done several things that can effect Ov/Unsteer.

I'll prolly come back dumber

So you'll get several answers all at once?

Thas bout the size of it.

It's all part of the "while I'm there" syndrome. I do what sounds gud at the time (when I have the time), rather than one change at a time.....the logical way for evaulation.

Assuming I succeed in knocking out all or part of the push, I won't know which move had the most effect.

I softened the sway bar, put in stiffer rear springs, had the shocks revalved, went to needle brg rear bearings, changed the front & rear toe.

I am going to run the old tiars to see what, if any, performance increase all the stuff had. That idea goes out the window if there is an unfriendly course layout. This stuff ain't as cut & dried as some folks would have you expect.

JP that's exactly what I'm considering!

But since the change from 180# to 200# was so slight (subtle), I'm thinking instead of just going with another twenty pound increment, to go on to 250#. If it results in oversteer, I can dial it back out with the front swaybar adjustment. Theoretically.


What made you decide on 225 over 250#? Advice from others?

WAG? I wanna know.

This is kinda a long shot, but how much gas are you running? With the fuel tank toward the front, if you added more weight to the front wheels you will get better grip in the front = less understeer. I dont know if the tank is far enough forward, but its just a suggestion.

* edit- though it would add more weight to the car, you might also consider leaving the spare tyre under the bonnet? This is assuming, of course, your cooling system isnt already up there.

Hi Joseph,

I went from 200lbs to 250lbs for auto-x on my car and it made a pretty big difference. I have a 2.7L six in mine, so I was either pushing or also liftin an inside wheel during acceleration in a turn.

I have 23mm front T-bars, 22mm Welt adj front bar, rear 16mm bar connected (I have a GT limited slip) and the 250lbs springs in the back. Bilsteins all around.

With this combo I have the front bar set in the middle and have adjustability for the course.

On the tracks (Buttonwillow, Thunderhill, Laguna Seca, Sears Point) I run 400 or 450lbs rear springs and tighten up the front bar within a fraction of an inch of full tight. I do have a rear wing which provides downforce, but with this configuration at speed on the track I have very neutral handling and low speed oversteer, which is nice in the tight stuff.

I'm running cantilever slicks (23x9x15) all around and I think it feels great.

Just another input for you.

Have Fun!

Bill

Bill,
Thanks for ALL the good info. That tells me ALOT. Right now my adjustable 22mm bar is permanently set on full soft....so it's really not very "adjustable" for dialing in over/understeer preferences. Sounds like the 250s would put me in an adjustable mode.

Did you detect any ill effects or trade offs going from 200 to 250#? Is the "feel" about the same?

Are your bilsteins adjustable? Did you lean toward softer or firmer settings after going to 250s?

My car is only a 4 but it thinks it's a 6-

Our AX venues are rough as hell. I'm trying to keep the springs as soft as possible.
I even rasied the car up a touch.

Hi Joseph,

The biggest difference I felt going to the stiffer springs other than the firmer ride was that the car wouldn't squat as much under hard acceleration. The nose of the car stays down pretty well and all 4 tires are on the ground, especially with hard acceleration into and out of a turn. I was worried that the stiffness would be too much but I'm happy with the car and those settings.

If you don't have a limited slip you may want to run without the rear bar hooked up, but to tell you the truth, I liked the way the car turned with it is hooked up, even when I had the 4 cylinder in it and no limited slip. Driver preference I guess

I'm going to a Zone 7 auto-x in 2 weeks that is a 2 day event. I plan on running my tried and true 250lbers the first day, and trying 350lbs the next, just to play.

I'll post how it feels.

Bill P.

JP,

Now that you've joined the el cheapo cookie crowd, what size tires did you mount on those things?

I'm getting really bad at the track....I'm now keeping a sticky set for my timed runs that I only run during those few laps...I don't even let the wife run em....

Bill P.

I'm thinking 250lb springs for the rough course auto-x's and 300 or 350's for the nice "airport" venues....

Bill P.

If this is a dedicated autocross car you could run some toe out on the rear. What are you running for t-bars?
What are you running for tires and pressure? If you drop the front tire pressure you will be able to rotate the car better.

You need more toe out up front try 1/8. Make sure your sway bar is not binding up, it must not be preloaded. on most lowerd cars it is so you will have to fix that.

What are you running for bushings? What about shocks? remember shocks only help in turn in and corner entry. In a steady state turn they have no effect. If you are running Konis up front go full soft.

If this is indeed a dedicated autocrosser you could up your spring rates dramatically biggest bars in the front and something on the order of 300+ on the rear.

If you are running a LSD it should tend to push more on corner entry, I don't know as I am running open diff.

Get a rear bar.

It's a dedicated AX car.....although I always take it to the streets a few times a week...it's my idea of a mid-afternoon martini.

Here is my current setup: koni sport adjustables all around, a 911S front end (to include the big aluminum S calipers), which frontend I think incorporate 19mm torsion bars - not sure on this spec....turbo tie-rods, bump steer kit, new steering box, 22mm weltmeister swaybar, weltmeister stiffening kit, 200# rear springs, fuch 15X7 F, 15X8 R....hoosier 205 F, 225 R.

It has 1.5 neg camber F, 2. neg R. 1/16" toe-out F, 1/16" toe-in R. Car is 4.25" to ground from doughnut.

I've gone from 40# cold to 30#cold (against hoosier's advice, but with advice from other autocrossers). At the last AX, I ran 8 lbs more in the rear to get it looser to rotate better. I know this is not the ultimate way to balance the car...hence my rear spring questions.

Right now, the car is very neutral. Throttle lift on 60mph off ramps and the rearend kicks out just a little bit - not even enough to need any steering correction. However, the car is STILL not rotating enough in slower AX turns. I know slow speed push is difficult to eliminate, especially in porsches, but it's just not doing it's job. I'm not over-driving it, I'm not "pushing" it thru turns, in fact, I've adjusted my driving style to work with it. This is why I'm asking you guys for some help in getting it to a more optimized balance.

I sure appreciate all your insight.

Go to 15x8's up front and put 225's all around.
You will be able to run the front bar tighter too.
In fact, get a soft rear bar and stiffen up the front bar a lot.

Bill:

Ayup,cheep cookies are good.
225 X 45 A3S04 Hoosiers.

I couldn't get silcks under my rear fenders. I need another .5-.75 in width there...rats.
the S04s are quite a bit different than the S03s.....stickier also,I'm told. The tiar guy said that they are getting closer to their slick compound.

The toe-in in the rear is part of your problem. you should run at least 0 toe in the rear in your case you might run 1/16 toe out.

Throw a rear bar on the car, run the konis at full soft. For this weekend I would change the alignment and shock settings and see what happens.

Racer Chris,
I wish I could, but I'm running a stock body. I do have 911 rear fender wells grafted on that allows me to run bigger tires in the rear, but 205 (hoosiers) is as far as I can go for stock fender wells up front. I run 225 hoosiers in the back.

I do have a bone stock rear sway bar which I early on disconnected. When I installed the 22mm swaybar and introduced mild understeer into the car, I connected the rear sway bar in hopes that it might help the newly aquired push problem...didn't seem to help.

Thanks to those that knows...it's starting to apear that 250# springs is okay for me....to try...THANKS!

You guys are pretty great!

I've got this channel click click clicken' thru my head....

any elvis costello fans out there besides seanry?

I thought this was a no-no

Not for auto-X.

Chris for a road car and a road race car toe out can create very unstable handling at the limit. The factory designed the rear suspension to toe in during roll for safety reasons. For competetive driving this can cause problematic handling. With a little work you could calculate and increase the amount of Ackerman in the front end. THis would help load your tires better in slow speed corners.

I've been running 21mm front bars with small weltmeister sway (set almost full soft)
and 180 rear springs no bar, with probably . It doesn't usually work,
I end up locking up the inside front.

I tried rear steer.....didn't much like it. Prolly wouldn't be much of a problem under 40 mph ...in a parking lot.

Brett,

I'm unfamiliar with this term - what is "Ackerman"?

In hard cornering it is better to have the inside wheel turn more then the outside wheel due to distributed forces (there is more force going to the outside wheel because of the inertia a car produces). To combat uneven handling and to get sharper cornering, designers include ackerman to assist the inside wheel for even steering.

Does that make sense? Essentially the inside wheel turns more then the outside wheel on the front. More ackerman increases that difference.

Thanks Matt. I can use that term at my next AX. Maybe throw off my competitors. "Dude, you Ackerman is way off."

Hey Cork, I'd like to buy your 250's if they're for sale.

I guess I have some 180s & 200's for sale.

Thanks everyone for all the great insight, including the camber adjustment idea and the full tank of gas suggestion. Will let you know how it works out.

Right now it is 80 degrees with a blue sky. I think I need to go test my teener's Ackerman!

Mskala, 21 bars up front are too big to balane with 180s you will need something like 220-300 in my opinion.

For purpose built autocross cars you are better off with really high spring rates and minimal swaybars to allow the car to transition faster from side to side. For a road car and road race car running softer springs and stiffer swaybars will allow the suspension to react better to differences unconformaties in the track. Thus not upsetting the car mid corner.

Ackerman is very useful in creating higher clip andgles on the tires at slower speeds. On this years FSAE car we are running something in the neighborhood of 110% ackerman. Our speeds are so slow that the tires can't generate any grip with a vehicle wieght of 400-500 lbs. For High speed turns Ackerman is not as important because the slip angles are much higher.

I would hang to the springs until your have tried the other free options. Maybe I am just a cheap bastard.

first, don't add weight to the front of the car!
run with 1/4 tank or less and have a 5 gallon container to fill her up when needed.

quick fix, without spending any money, either drop the front another 10mm or so or RAISE the back, if you can.

both will transfer weight to the front.

then, once you got some $$$ in your account, go for the 250lbs springs so you can actually put yer nice swaybar to good use

Andy

Brett: Are you competing in formula SAE? What school do you go to?

Sir Andy: Why do you say no to adding weight? Wont you get more grip in the front if there is more weight over the wheels? The drag coef. is altered by weight. uk=mg, so if mass goes up then uk is greater=more grip (u is mu, i just dont have greek symbols here). The only disadvantage I see is more inertia in the turn, but I highly doubt the weight of fuel or a spare tyre will affect inertia too much. In front engined RWD cars, they try to take weight out of the front and move it to the back, like moving the battery to the back, so they can get more rear traction. Since they have enough front traction with the engine over the wheels, they can sacrifice the weight of the battery in the front traction.

The front wheels will have more traction, but not enough to hold the extra weight that you added. The coefficient of friction is less than one and it is non-linear.

If you think about it, if adding weight increased cornering power, everybody would be running the heaviest car possible for the best roadholding.

If the vehicle weight remains the same, transferring weight to the driven wheels gives more traction for accelerating, but the cornering power will actually go down on that end of the car.

Did I make any sense? I'm in a hurry.

Andrew

Oh crap, you're right. I used the wrong equation too... I have a physics final next week and my brain is fried.

My thinking was throwing off the front/rear balance. Its a ratio independent of values. What I was thinking is; when a car goes into a turn, its inertia is independent of front/rear, it s a total mass and is rotational instead of linear. And with more weight on the front wheels its like you're adding traction to the front without adding a significant amount to the total inertia. Lets say a spare tyre is 30 lbs. If the front end of the 914 weighs approx 800 lbs without the tyre and the rear weighs the remaining 1600 lbs, if you were to ad 30 lbs to the 800 in front you would increase it by a percentage of ~4%. But adding 30 lbs to the total weight of 2200 lbs is only an increase of ~1%. Now this model is assuming the weights are equal distance apart from the center of mass, which I know they arent, and there are moment arms and stuff, but I dont have the figures to calculate the answer.

So having a mid engined car is better then a rear engined car, theoretically. Is that right? Due to moment arms and the such, the 914 should be a better car then the 911... I always tease my "914's are VW" friends about that.

50/50 is best in turns, rear weight bias is best under acceleration (assuming rear drive) and braking.

Andrew

Also look at aerodynamics. Some cars produce large amounts of drag at high speeds. While the 914 probably has lift, the concept remains. Putting a force toward the center of the earth on the suspension will give the tyres better grip. It isnt quite ideal beacuse with aerodynamics those values are greatly decreased at low speeds through tight sections making the car "lighter", but the concept that weight will add stability through turns I still think is valid.

it is, but you can archieve the same without adding weight which is more beneficial cauze you have more "thumb" per lbs of car

lowering the front of the car will transfer weight to the front.
you don't change the overall weight of the car (moah HP per lbs),
but you change the current weight distribution.
let's say he has 50/50 right now and the front is pushing in hard corners.
drop the front 10mm (or raise the back!) and you might have 55/45.
that will give you more grip in the front, you get what you wanted,
and most of all, you don't have to schlepp any additional lbs around with you.

Andy

I don't think so.

Adding weight and weight transfer are two entirely different things. When you add weight you increase inertia. More force will be required to counteract that inertia in a corner. If the tires are already at the limit there is no more force available. Transfering weight by decelerating increases the available force on the front wheels without increasing the inertia, thereby improving cornering grip.

Thats important. I am assuming the front tyres arent skidding at all. And addressing the inertia, there are two types of inertia focused on in a corner; rotational and linear. The rotational inertia is hardley affected by a gain of ~30 lbs on the total weight of the car because it is distributed left - right, and since the tyre is in the middle it almost cancels out. And there is an advantage to be gained by adding weight for the linear inertia (maybe its momentum not inertia). Since the weight transfers to the rear under acceleration I am proposing keeping some weight up front to help with front tyre grip.

I understand what you are saying andy about the weight transfer and suspensions. I posted my ideas because I read he had already done lots with the suspension. But I agree, stiffening up the rear, or changing ride height, or possibly even shock position (if possible) would change the handling characteristics most drastically.

Thank God the Gurus showed up & I no longer have to add to the blat.....er ......valuable data.

The car's bout ready to go out & test *my* ideas.

They do not include:

A full gas tank.
Rear toe out
Changed (to whut?) ackerman
Wider front track using spacers
shocks that don't dampen in a corner
front/rear weight jacking

Sure hope this doesn't offend ....everyone....youz guys are welcome to test this stuff out on your own cars.

The only thing I can add is when (if?) I find a good set-up (for me), the less I'll have to say about it

Happy motoring

This forum really has me wondering. After I get the feel for my car Im going to try taking a few laps with a spare tyre in the front (and mybe in the back for comparison's sake). Good luck though!

Just remember to change one variable at a time so you can isolate improvements.