Plug for playing around with suspension settings
 

Ok guys,
I just want to put a plug in for playing around with suspension settings. I have been racing the same car for 6-7 years now. Over that time I have learned alot, but this past race weekend was an eyeopener for me.

I have been running our home track for years and back in 2002 I started racing there. In the first 2 years I would nearly always run faster each weekend. I hit a point where I ran one lap under 1:13 seconds. (1:12.9) It was a sort of peak of hitting a seeming un attainable number. I did not once, but around that time I would run other laps close to that.

Well then I took some time off from racing for family and stuff. I was still racing, but not as frequently. When I started back in 2005 I was just a bit off the pace I had prior. I put that down to being rusty. Well in the years since then I have been working getting in more races per year to pratice and trying to find that speed I had. I have been through alot of things and nothing seemed to work.

Well this past weekend I did something I should have done years ago. First step was to rebaseline the alignment and sway bars. I had recorded all my set-up, but never really changed it much. A little here and there, but I focued on driving. Well as I carefully when through it I notice some elements had drifted. I corrected them.

At the race weekend I went out in practice 1 for a baseline run. The intent was to do some real testing and make changes. As I needed to make the car handle better under trail braking. So I ran the car and got baseline feel. The car was good, but not perfect. Well over the years I have always tried to make a change based on how the car felt and then improve it to address that issue. This time I did something different. I felt the car had some understeer and lack of front end grip in that session in the mid corner, but was ok other wise. Normall I would never touch the front end or make it siffer since that would make the understeer worse. So what did I do? I made the front end stiffer with sway bars in spite of how it should have made the issue worse. 5 mm stiffer on the front bar. What would that do? Not really sure. Would it make the car worse? I did not really know, but figured I needed to try. Between seessions I went looking for an experienced racer for advice on set-up, but I could not find him. So I just made the change to see what happend.

Well the result was outstanding. It transformed the car by giving it tons of rear end grip allow me to trail brake deep. Despite gaining only 0.1 sec on lap time I knew the car was better. It also requried a tweak to my line to get best times. So next session out I tweaked the lines to get the car to roatate more at turn in using the brakes. I was finally running down at the 1:13.0 range where I had been all those years ago. I even ran my fastest lap every at a 1:12.866. It was amazing what 5mm of sway bars did to improve the car. I finally found that last few tenths I had lost and been searching for.

The amazing thing was that I found it by just rolling the dice on a change. Before this I always been afraid to scew-up the car with a suspension change. Now I just threw caution to the wind and made a change anyway.

So point is if you feel like you have plateaued at certain speed just make a change to the chassis. I need to be with a goal of doing xxx, but sometimes making a change will give you valuable information. If it does not work you can always go back.

However if you are afraid to change it you will never know what you maybe giving up. Heck I wish I had moved that sway bar by 5 mm two years ago.

Now my next race I will again make a change. Not sure what this one will be, but I will change something just to see what happens. I can always go back.

Joe,

I must say I admire your (early on) approach to just spend time concentrating on driving, something many folks I feel can benefit from rather that making a bunch of wholesale changes where the driver is more than likely the largest variable. Great stuff!

Increasing front wheel rate can give more front grip as you have experienced.

Chris early on I felt it was all driver. I did that for years, but what was amazing that I had fallen into that trap of it being all a driver for too long.

My biggest issue was lack of rear end grip under trail braking for one key corner. I would touch the brakes and corect the car. For years I have been driving it like that thinking my lack of pace was from me not driving the corner properly. So I would make little changes here and there, but nothing big. My other fear was making the car worse someplace else.

Well it turns out my problems under braking were due to softer front end roll rate. By going stiffer in fornt I allowed me to drive the car much easier in that trail braking decreasing radius corner. It did cause understeer elsewhere, but by adjusting turn in and driving line elsewhere I saw a net imporvment in lap times.

So my breaking out of the mold and just trying something was the key. I tend to think that as you learing you need to work on the driver first. However at some point you can be trying to drive around a problem that really needs to be resolved. The issue is that it can be hard to understand what change is needed to correct this problem. So sometimes you just need to change things and see what happens. It is all well and good to learn to drive around issues, but driving a bad car does not help either. The only way to know if the car could be better is change things. If you can make a change and feel it is also good way to learn more as this is key skill of a driver as I am sure you are well aware of.

Cool story. Conventional wisdom would say a stiffer front bar would increase understeer. Why do you think your turn in improved?

So do you carry multiple sway bars? What have you found with alignments? Does the 944 like a little toe out or not?

That's what I was thinking.


More understeer in the suspension setup allowed for deeper trailbraking ... definitely makes sense.

Although as you noted, stiffening up the swaybar caused understeer elsewhere.

Stiffening up the front shocks in compression may help provide stability (increase understeer) during trailbraking, without having too much an effect on handling elsewhere in the corner.

Just a guess, but a stiffer bar also facilitates quicker weight transfer from loaded to unloaded wheel...and this can mean more lateral grip.

Good post Joe. As you know from my past posts on the spec forums, I too fight that trail braking instability. I have upgraded my rear bars but I too think I am still too soft up front, both spring and anti-roll.

I intend to do something about that this winter. My problems sound pretty identical to what you describe so hopefully I can get similar results. If only I could convince myself to spring for the Weltmeister adjustable sways... thos things are damn expensive.

I agree with Joe. You need to concentrate on driving first before anything else. Until you can do laps within a 0.1 sec, you will never be able to quantify what a suspension change does. Or any change for that matter. A certain change may "feel" better, but your times may be worse. The clock is the only guideline. It doesn't care how you feel.

Well this is the problem I think. People say 0.1.... that is wrong. Sure you need to be consistant, but not to that level. I am thinking more like 1 seconds consistancy is all that you need. You may or may not be able to see a lap time change, but you need to use feel.

Like I said first baseline session
best time 1:13.7 - (During the session I went full siff on Koni yellows) Impact was minimal, but there was only 1/4 turn left anyway.

After sway bar change
Best time 1:13.6 So did not seem like much, but I could FEEL the difference was vast. The reason I did not see a big lap time gain was two fold. Firstly I was not able to adjust the driving style to take advantage of the extra grip and to reduce the understeer it added. I felt it, but never got around to adjusting the driving. Secondly the track was very busy and traffic made it hard to push every lap in every corner.

Of course the next session I went out knowing what to expect from the car and what to try to change in driving style. Result was the improvement in lap times.


So you cannot use the stop watch all the time, but cause I cannot take into account other factors. So you need to use feel as an element. Also if you wait till you are perfect every single lap you may be forcing yourself to drive around a chassis issue. In fact lap time variablity could be a result of poor chassis balance. You are drivng harder to overcome some issue and that means lap times all all over the place.


IMHO when are you ready for tuning?

When you can feel what the car is doing at turn in, mid corner and track out. You have a chance. When you can put the car on the same line lap after lap even if the time are not always perfect you are ready. The other element you need is the ablilty to change a driving technique to maximize the change. If you can't trail brake then putting understeer in the car to aid in trail braking may be worse than anything. So just because you make a change does not mean you can approach each corner the same. Personally I still think I have 0.5 seconds out there somewhere. I just need to adjust things to fined it. I still don't believe I have my line optimized for the new levels of grip I have in the rear.

BTW... this tweaking of the bars makes believe adjustable sways are worth every penny. Making the change was easy to do between sessions and make a major difference. If the bars are not adjustable you lose one import element of chassis tuning. I care less about their actuall rate, but the adjustment is key.

One thing to consider is that what works at PIR may not work at another track. Last June my car ran well at Miller and I fully realize I may need to make some changes to make the car fast a miller for nationals. So while I dial it in for PIR Miller is very different due to 4-5 high speed turns take at the top of 3rd or bottom of 4th. In June I took them with tap of brakes and down to 3rd to get on the power early and control oversteer while adding some grip at turn in. I neve felt I was getting the all I could there and felt 4th was a better gear. However when I tried it once or twice I went off. So I ended up in 3rd and it worked alot better. Given the competition at the time it was perferable to run like than and stay on the road.

Now for nationals this year I expect to nee to fine 5-6+ seconds (on a 3:32 lap) to get where I need to be. I fully expect what works at PIR will not be optimal for Miller so I am planning on being ready to adjust the bars to get the balance I need. The adjsutable welts are a key to doing that since I won't have time to put in new springs (although I could bring a spare set if I really wanted)

Nice post and food for thought. Very timely, as I'm just getting back into the track thing here. I've always done my own work, and felt my car drives/handles well. But next month, I'm taking her to Jae Lee at Mirage Intl for some professional work (raised spindles, shock re-valving, balance and some camber work up front). I've realized my knowledge and ability is limited, and it will be nice to get someone with his experience to get a baseline set up. From there, some tweaks may be in order over time, as you've noted.

That's exactly what I use DE's for. At wvery DE i make it a point to make major changes in setup just learn what will happen (shocks, bars and even springs). That way when there I have a problem I know how to fix it. I can also feel when I have "nailed" the setup.

Also like you I have found stiffer front bar can sometimes reduce understeer at turn in. Stiffer platform can provide less "falling over" and quicken response.

Well,
I edit my earlier post since I did not convey my problems.

My major issue was an inablity to trail brake in a key area on the track. Every time I hit the brakes the back end would step out of line and I would correcting the car at 90 mph. This make me very work very hard in this corner. I feared a much stiffer front end due to it causing too much understeer everywhere else. For years I just tried to drive around the issue or adjust it with rear toe. I knew if the toe was off it would be bad. Anyway this time I just made the front end stiffer not worring about what it might do elsewhere on the track. I figured I would try it inspite of having understeer in the morning.

The result was in fact more understeer in places, but I learned that I could adapt my line to minimize that and the gain in stablity in trail braking more than made up for that understeer.

In the end sometime you just need to make a change and see what happens rather than worring about it in fact making the car worse. It could do that, but when it does just change it back.

Joe,

Maybe next race you should try moving your bar in the opposite direction, reversing you camber settings and letting all the air out of your tires...just a suggestion...from the back of the pack....:evilgrin:

Well, if the suspension setting is way off, you will definitely be able to feel that and know something isn't right. For instance, disconnecting the rear sway would definitely feel wrong. You wouldn't really need to measure laps times to know that that was a bad change.

I was talking more about subtle changes. Stuff that has the potential for changing lap times just a few tenths. So let's say you make a change in the sway bar setting that has the potential for a 0.2 sec improvement or detriment. My belief is that you need to be twice as accurate as that to measure it (sort of based on the Nyquist sampling theory). So in that case, you would need to do laps within 0.1 sec to be able to accurately measure the effect of the change, and conclude that was a good move or not.

I agree that some changes, although may make the car faster, also might make it scary to drive. There's a confidence factor that goes into the equation. Or a change doesn't suit the driver's driving style. That happens all the time in F1 where teammates get the same setup, but one driver can't get the lap times from it because it doesn't suit their style. Then there's changes that make the car faster, but tire wear suffers. It just goes on and on. Setup is one big compromise.

That's what make this whole sport so much fun and challenging. In a spec series, suspension setup is one of the few weapons you have against your opponent. It's the one thing you can control. Therefore it's important to maximize it's potential.

I have to agree that you need to get the times at a track you are very familar with, down to under .25seconds. There are times when as a group we are all with in hundreths of a second and that one last tenth is hard to find. If someone runs .25 second faster, we all get together and bag on them for using new hoosiers, or turning up the boost or something. Ive made changes that made the car borderline unsafe to drive, but my times didnt suffer. Im sure many of us drive around problems our cars have. I remember a story of Mark Anderson giving his car at Willow Springs to a well known pro to get feedback on his car. Mark usually wins or finishes in the top 2-3 in POC races . He runs 1:23.xx in this car, yet the Pro came back and said that the car was "undriveable". :).
I think its really important to test new settings, something Ive not been able to do in recent years. I admire your effort to find out what might work better. Somethings counter intuitive might actually improve things.

With your issues showing problems during "trail braking", had you tried lowering the rear brake bias?
softening up your rear springs, swaybar, lower rebound, change tire pressures, etc etc. There are so many things I would like to try, but never get enough test time to be bold enough to make radical changes. Heck, I think i have two blown out shocks and IM scared to fix them, figuring the car is good enough now, i would hate to have to find the time to retune. :)

Great topic of discussion.

mk