A matter of sway bars

[Whiskey11]

Among the many things I learned yesterday at the autocross (including the fact that Chris Conant's 1988 M3 is 4.5 seconds faster than me =\...) is that with my set up, I'm still getting a fair amount of push. To the point of having probably a little too much grip in the back that throttle on oversteer is basically non-existent in second gear without upsetting the car violently somehow (parking brake).

Here is what is done to the car and what settings various bits of suspension are adjusted to)
Steeda Sports (200 lbs/in front rates and 175 lb/in rear rates, 1" front drop and 1.25" rear drop)
Tokico D-Specs (3.5 out from full hard on the front, 5 out from full hard in the rear)
Strano 35mm front bar (set in the stiffest position)
Strano 25mm rear bar (set in the middle position)
Fays2 Watts Link (prop bolt in bottom hole)
Steeda HD Mount (Alignment at -1.7º camber, neutral toe, +7.5º Caster)
Dunlop Star Specs in 245/45/18 (31 PSI front, 32 PSI rear)

So, the question comes up, which bar would be the best to change to dial out the understeer? I could take the front bar down to the middle setting and give up some steering responsiveness and go further into positive camber in hard cornering (sadly already doing that) or take the rear bar up and risk an easier to upset rear end. I am looking for some thoughts from people who know more about which would be the preferred bar to change for autocross. I'm thinking the obvious choice is the rear bar to leave the front bar to add some needed spring rate.

And about that 4.5 seconds! Talk about embarrassing (not really as I was expecting a severe schooling)! I'm not sure this car will ever make that up with the wider tires and wheels, CAI, exhaust and tune, and a driver worth a hoot but that is what it would take.

 

[Department Of Boost]

Taking into account your spring rates aren't very aggressive for what your doing (AutoX) it makes sense to add more rear bar (more rate) opposed to taking out some front bar (less rate).

But if you are not too far off from the balance you are looking for you could also play with tire pressure. Taking a PSI out of the front and add a PSI to the rear could change the cars balance quite a bit. I'm surprised your not playing with tire pressure every run.

Not subscribed

 

[Whiskey11]

Taking into account your spring rates aren't very aggressive for what your doing (AutoX) it makes sense to add more rear bar (more rate) opposed to taking out some front bar (less rate).

But if you are not too far off from the balance you are looking for you could also play with tire pressure. Taking a PSI out of the front and add a PSI to the rear could change the cars balance quite a bit. I'm surprised your not playing with tire pressure every run.

Not subscribed

That was my thoughts as well. I suppose at worst I would have too much rear bar and it gets oversteery and I take the bar back to the middle position.

I have been playing with pressures but it seems like every time I add or remove pressure the car becomes hyper twitchy or completely numb. The wear mark on the tires also supports the pressures I am at (which where found by tweaking tire pressures! )

The spring rate issue IS unfortunate but this car is a daily driver with an occasional autocross event and I didn't want to add too much spring rate and make the ride suck. That said, it is one of THOSE regrets I have in my car set up, like the tire size... I should have just bought those 265/40/18 RS3's and mounted them on stock rims and maybe some stiffer springs. Hindsight is 20/20 right?

Thanks for the response!

 

[Vapour Trails]

I highly doubt your understeer is an equipment issue. Most of the time it is simply the driver asking too much of the front tires under the circumstances (or in other words your going too fast or your line is wrong).

 

[Whiskey11]

I highly doubt your understeer is an equipment issue. Most of the time it is simply the driver asking too much of the front tires under the circumstances (or in other words your going too fast or your line is wrong).

That thought has always crossed my mind. It just seems odd that a RWD relatively high HP car can't throttle oversteer without a serious upset to the chassis.

I have uploaded a video that shows my line, which is probably really bad to begin with... that said, I would have thought in the last corner to get at least SOME throttle oversteer but the only place it could be found was via first gear at the start...

http://www.youtube.com/watch?v=fBN64bhAcdk

 

[Conekiller]

What about moving the watts link prop bolt up one spot? I think I read on here that will raise the rear roll center which would possibly loosen up the car.

 

[Whiskey11]

What about moving the watts link prop bolt up one spot? I think I read on here that will raise the rear roll center which would possibly loosen up the car.

Indeed it would loosen the car up some. The whole point of the 25mm rear bar was that Sam mentioned when I talked to him no one was using the bottom hole in the Watts link because of too much push. I really just got all the squeaks out of the Watts link center pivot bolt, the prospect of bringing them back makes me nervous! It kind of defeats the purpose of having the rear roll center adjustment for a hole lower if you never use it right?

 

[Norm Peterson]

How does it behave while slaloming? The answer should give better direction, because for a SS push and good slalom behavior I'd stiffen the rear bar first. For an unwillingness to slalom I'd be looking more at roll steer (and raising the WL main pivot).

Lowering the car combined with a lower rear RCH has increased your roll steer in the vehicle understeer direction.


Norm

 

[DILYSI Dave]

I wouldn't add more bar. At least not yet. Get the front tires working better. More camber would be my first thought. More spring maybe. But definitely more camber. 1.7 isn't much at all, especially as wallowy as that thing is. IIRC, Vorshlag was running as much as 4* of camber, and they have stiffer springs in addition.

There's also what Vapour mentioned. It doesn't matter what the car is, what the setup is, etc. Overdrive it and it will push. Even high HP RWD.

 

[Whiskey11]

How does it behave while slaloming? The answer should give better direction, because for a SS push and good slalom behavior I'd stiffen the rear bar first. For an unwillingness to slalom I'd be looking more at roll steer (and raising the WL main pivot).

Lowering the car combined with a lower rear RCH has increased your roll steer in the vehicle understeer direction.


Norm

It's fine in the slalom but I feel like once I get going too fast I just get push when trying to maintain the rhythm in the slalom which I expected. In any other corner any increase in throttle position just results in push, even when mashed. Turn in off the gas is fine, turn in with any throttle is a little bit of push as would be expected.

EDIT:

I wouldn't add more bar. At least not yet. Get the front tires working better. More camber would be my first thought. More spring maybe. But definitely more camber. 1.7 isn't much at all, especially as wallowy as that thing is. IIRC, Vorshlag was running as much as 4* of camber, and they have stiffer springs in addition.

There's also what Vapour mentioned. It doesn't matter what the car is, what the setup is, etc. Overdrive it and it will push. Even high HP RWD.

Sadly proper camber plates are not in the budget this year. =\ I'm hoping the next time the front struts come off is to install coilovers to take care of many of those problems!

 

[Norm Peterson]

It's fine in the slalom but I feel like once I get going too fast I just get push when trying to maintain the rhythm in the slalom which I expected. In any other corner any increase in throttle position just results in push, even when mashed. Turn in off the gas is fine, turn in with any throttle is a little bit of push as would be expected.

Then I agree with Dave, that the problem is front grip.

Can you use the Ford camber bolts, being that they're an available method of adjusting camber in normal non-competition applications.


Norm

 

[Whiskey11]

Then I agree with Dave, that the problem is front grip.

Can you use the Ford camber bolts, being that they're an available method of adjusting camber in normal non-competition applications.


Norm

I can use any camber bolt in STX that I want but I am not really keen on using them, let alone a set of them costing $110 to get them to my door! Omaha is a city of major pot hole problems and the last thing I want is a bolt moving or compromising the front end's strength. In general I simply don't trust them.

I guess I should have added that I did feel in the final sweeper in the video above (which for some reason wont embed?) the driver's side front tire getting extremely light and the picture in my signature shows that happening as well which suggests a rear spring rate issue. I'm not sure tweaking the bar will solve that issue in the correct manner. Of course in that final sweeper it didn't really matter since it was opening up and the understeer didn't really matter as much as other parts in the video.

One thing is for certain, I'm hoping to be able to focus some energy on getting some proper coilovers with plates sometime next year to deal with the spring rate issue.

I fully realize that you guys are correct on the need for more front end grip and I really wish I had the budget to throw down for some proper camber plates to get more adjustment but I'm kind of waiting on spending that money until I get coilovers due to the spring perch change so I don't have to buy extra parts or a whole new set of plates. I was kind of hoping that it may be much more effective to use the adjustments I already have on the car to tweak the balance without spending more money. In that regard I think I'll move the rear bar to full stiff and see how it is. I realize it isn't the ideal or correct direction but in autocross we often do things that don't make any sense (like using shocks to control over/understeer in stock) to work around problems with the set up. Hopefully next year I can afford to do things the correct way and put the rear bar back down to a softer setting.

Does that sound reasonable or am I just talking nonsense?

 

[Philostang]

Indeed it would loosen the car up some. The whole point of the 25mm rear bar was that Sam mentioned when I talked to him no one was using the bottom hole in the Watts link because of too much push. I really just got all the squeaks out of the Watts link center pivot bolt, the prospect of bringing them back makes me nervous! It kind of defeats the purpose of having the rear roll center adjustment for a hole lower if you never use it right?

I'd reconsider that rear prop point. The purpose of an adjustable anything is to have range - not to insist on using the extreme ends of them. You adjust for what's needed.

I'm on the bottom hole of my Watts because I ended up there after starting in the middle (too loose in rear), then down one (better, still loose), then down, etc.... I found that to be best for me and the car. I don't have a push problem, but I'm also no longer on struts, so I've got a healthy surplus of front grip.

Of interest, SGDave has driven my car and thinks I should back off one point, because he likes a really loose rear end. I prefer things more balanced (with very controllable power-on oversteer), and I think the car is there with the rest of my set up. The point is that the adjustment points on that Watt's make pretty significant changes in the car's behavior. You should be finding the results out on your car's set up directly and comparing actual experience rather than assumption/expectation.

I'm sure you know this, but when doing this sort of tuning (a) have your priorities explicitly established, (b) develop a tuning plan that reflects those priorities (i.e. test/tune for priority #1, get it as best as you can, then with that foundation set, move to the next priority, wash/rinse/repeat), (c) at each test stage change only ONE thing at at time.

As an important aside, if you're letting "squeaks" influence your tuning, you're not tuning for performance. Don't take that the wrong way. I've done similar things: crisscrossing values and/or priorities and letting it get in the way of developing a viable tuning strategy. Talking with others can be a good way to address this. Sam has "set me straight" on more than one occasion with a single question. SGDave does it with more frequency.

Best,
-j

 

[cito]

All of the following comments are just my opinions, and need to be taken with a grain of salt because of that.

Within a reasonable scope of cars, the number one variable in times is the driver. You are well aware of this, but I thought I would say it to beat the horse deader. Most of the time when I understeer it is because of me and not my car.

Before you go spend any money, you might want to take some time and be very methodical about changes that you are able to make within the existing setup. If I were you, I would start with adjusting the air pressures in your tires and the stiffness settings of your dampers (not necessarily in that order). Go full stiff in the back once and see if that loosens things up. Go full soft in the front and see what that does, and then do those things vice versa, mixed, etc. Add pressure to the back, reduce it in the front, etc.

Joe Tharpe, who is a pretty talented driver, told me once that if you are going to mess with things mess with them in an exaggerated way to help you understand what the car is doing with the change. If you make adjustments slowly, it is hard to know whether the car is different because of the change or because of noise (i.e., driver variability). If you make an extreme change, it is easier to discern what the change did from what the noise is related to normal variability in driving. The best drivers are less variable. For a hack like me, there is significant variability related to my errors.

With your car, ESP is probably the way to go. You can basically do everything that Strano did to his car in ESP. Eventually, you could swap in a 5.0, or you could buy a complete mustang with the 5.0 and swap the parts from your car onto it.

Again, these are just my opinions. Conant is a good driver. Don't get too caught up in where your time is relative to him. He drives well and he knows that car better than I know my wife. Stick with it. This is all just for fun in the end.

 

[olds350]

I’m going to jump in here w/ some comments as well in regard to setting up a S197 for autox. Just to set my background, I’m running an ’08 bullitt w/ some suspension bolt-ons from the previous owner and I’ve added a few items myself, so this is not an optimal setup. Right now I’ve settled on the current settings…

> brenspeed 93 tune (but don’t like it due to non-linear throttle response)
> Addco front sway set to full stiff
> Strano 1” rear bar set to full soft ( think this is just a little too much bar for this car right now)
> Vogtland sport springs (not very stiff springs)
> adjustable panhard bar
> MM camber plates set to 2.5 neg
> 285/18 RS-3’s on 10” wheels. (Very heavy combo and this puts me in an ESP PAX which sucks, but the wheels were uber cheap)
> koni yellows, front set to 2.5 turns and rears set to ½ turn in autox trim.

I’ve had a very hard time getting the car to stop over steering over the past year and it’s taken me a while to get to the point to where the car is fairly neutral. I think I’m finally there and just playing w/ tire pressures now and driving style. I’m finding that subtle adjustments between 36-38 is just about where I need to run the bullitt. Going to run the stock tune in order to keep the throttle more linear. All at once throttle plays hell on an autox course and brings the rear around much too quickly.

@ Whiskey 11, I did find it interesting that you were still having push issues w/ the sway bars. I think setting up the rear softer than the front is the only way to drive a S197 car. Please post back up when you find the magic setting. I’d be interested in knowing where you set the sway bars. I had been thinking about buying the Strano front bar, but playing w/ tire pressures really helps balance out the car. Amazing what 2lb difference can make between the front and rears.

 

[Sam Strano]

This is becoming overly complicated, as most things on the 'net seem to.

First, there is no requirement you run the Watts in the lowest hole. In fact I ran my RC all the way *UP*. Second you have options on both bars to free the car up... down on the front, up on the back, or even *both*. Thirdly many folks seem to think there is a particular magic number with camber and all that.. there isn't. I run way less than what some others seem to think you have to have. And given that this car is also a street car, you don't want like -4 anyway.

The answers are all right in front of you, and they are simple. Either soften the front bar, or stiffen the rear, of raise the RC height some, maybe even some combination of 2 or 3 if you want to go nuts. What's so complicated?

 

[Sam Strano]

@ Whiskey 11, I did find it interesting that you were still having push issues w/ the sway bars. I think setting up the rear softer than the front is the only way to drive a S197 car. Please post back up when you find the magic setting. I’d be interested in knowing where you set the sway bars. I had been thinking about buying the Strano front bar, but playing w/ tire pressures really helps balance out the car. Amazing what 2lb difference can make between the front and rears.

Again there is magic setting. The driver, the style, the mistakes, the tires, the alignment all play in.

I quoted this mostly to address the comment "I did find it interesting that you were still having push issues w/ the sway bars." Why? He's got the rear Roll center slammed, the front bar full stiff and the rear not. The idea behind the size of the bars I run, and their being adjustable is be able to tune both with and without a watts link. Having the bars doesn't mean the bars are set best for him or you, or Joe-Bob. I have my thoughts and things I like, others have different opinions.

 

[Whiskey11]

I am constantly reminded of why I love this website!

I have a tendency to over think and spend too much time thinking on the right way to do things and spend too little time tinkering. It's an annoying flaw in my character.

I think based on what has been said here I will leave the front bar as is. The last thing the front of this car needs is less spring rate to slow down the change in directions. The rear bar has another notch of adjustment stiffer I might as well use it and see what happens. If it ends up being too much I can drop it back down and raise the rear roll center again and go raise the rear tire pressure to dial out the remaining push. Not enough, I can still raise the rear roll center and play with tire pressures anyway.

I guess I was looking for an answer to "What is the right way to go about this?" and the answer was "Every way" which was admittedly surprising!

 

[Sam Strano]

Assumptions, you are making them. You dont' want to soften the bar because it slow down direction change, when you have shock left and shocks are what control the roll rate (bars and springs the roll amount).

This is why I am constantly reminded of why I can't stand most sites. The answer "every way" isn't correct. The fact is all those ways can free a car up, but they do it in different ways. What's best is which way works best for you.....

 

[DILYSI Dave]

To Sam's point, test test test. Or run lots of events and keep your wrenches handy. Either works.

My gut feeling is that I would keep the front stiff, keep the rear stiffness relatively soft, and mess with the watts with the goal of helping it dance without hurting the ability to put down power on corner exit, but that's just a gut feeling. I also think that camber bolts are worth playing with. IIRC the Eibach ones are $25 per pair give or take, and I think Sam sells them. It's a cheap way to learn if you're leaving something on the table, even if you are worried about them slipping. If nothing else, it can tell you whether buying the plates will be money well spent.