Trying to understand chassis tuning

[gran racing]

Chassis tuning has been a weak spot of my racing program and is something I would like to begin learning more about. Thus far, I have found the process to be very confusing and intimidating. Depending upon whom I speak with, I receive varying advice. What makes this especially confusing are the sources that provide conflicting information are all credible sources. (Thus my previous pyrometers vs. other tuning methods thread.) In the past I got the tire pressures and alignment in the general ballpark, but that’s about it. When I built my first car, I decided to go with a non-adjustable strut/shock package for multiple reasons. This was an excellent decision for me. I am now in the process of building a new ITB Prelude and just recently decided to upgrade my suspension, which will include having adjustable struts/shocks. I continue to struggle with how I can learn to properly tune my car.

I’ve spoken with some people about this learning process and they often either take for granted all of the information that goes along with this or do not recognize that some people will pick-up this type of material faster than others. During the past year I went out and purchased some books on how to tune a racecar, but a much of the content was way over my head. Once I get the new car together I have decided to hire someone with the knowledge to first properly corner weight / align the car then attend a test & tune day at Lime Rock (insert Kessler Engineering plug here). I plan to be involved with this and absorb as much as I can. Unfortunately I cannot afford to pay someone to go to every track I race at and also realize that tuning a racecar is an ongoing process. My goal right now is to begin understanding the basics of tuning. I do not have the desire to constantly be changing spring rates (it’s a major PITA on my car). I also can’t afford – time and money - to be attending numerous test and tune sessions. But I do have a tire pyrometer in this Spring’s budget. J

What other ways can you suggest that I can learn tuning basics? Are there any “tuning for dummies” books out there that a non-engineering type of person can easily comprehend? (I’ve have Going Faster, Tune to Win, and a few others.) I’m looking for information such as how to properly use the information a pyrometer provides, using tire pressures to tune, adjusting shock/strut settings, and etcetera. I’d also love to hear your suggestions on the basics techniques to tune a racecar, and if you have any special tips you can provide when tuning for a new track.

My other question is how I can better gauge what the car is doing? There are many of us who can drive the cars pretty quick but when it comes time to tell the tuner (even if it’s yourself) what the car is doing, we are not able to provide enough feedback. I’d like to be able to further develop this skill too. I know, lots of questions!

[Andy Bettencourt]

My other question is how I can better gauge what the car is doing? There are many of us who can drive the cars pretty quick but when it comes time to tell the tuner (even if it's yourself) what the car is doing, we are not able to provide enough feedback. I'd like to be able to further develop this skill too. I know, lots of questions!
[/b]

I will give you $.02 on this one. NHIS turns 1&2 are GREAT for testing and tuning. It's big enough and long enough to feel what is going on without other factors influencing your results. We try and learn what the car 'does' on corner entry, mid corner and corner exit. That info, plus what end of the car breaks away at steady state cornering first, is very telling as well.

Now you have a FWD car so you really need to get the car to rotate in the slow stuff and be balanced and predictable in the fast stuff. We typically tune our cars for the fastest sections of the track and work your way from there in terms of compromises. For instance, my Miata is extreamly right-turn-bias at LRP. Extra track is shifted to the left via spacers and cross weights reflect my goals. The results is an extremly quick car through Big Bend, the Uphill and the Downhill. The left hander is a throw-away IMHO, especially if you stay tight enough to be able to go flat through the right hander onto No-Name.

Each track will have it's optimal alignment for ultimate speed. You may have to invest in a seasons worth of teast and tunes before you can lock into spring/bars while tuning to each track with shocks and alignment. It ain't easy and it never ends. We keep detailed set-up books on each car for each driver.

[IPRESS]

Dave,
I have the same problem you have. I watch Jim Daniels, Jim Drago, and the Saferacer bunch adjusting setups at the track all the time. They are able to make their cars EASIER to drive fast. My car can go fast (as Saini) proved, but it is not EASY to drive fast.
I have a strong feeling that if given the right crew person to keep the car setup right, I can lay down some good laps. Now as far as feedback, I seem to be able to only relate the extremes. The little things that maybe I should notice slip past me. I need someone who feels them to tell me what I should look for.
I will give you an example: My last race weekend at Hallett, I had a large lead in the first 4 laps of the race on a half dry, half wt track. I made a mistake and hit a slick spot that resulted in me ending up on a tire wall. After inspecting and fixing body work and straightenuing out the front toe, (Forgot to check the rear DUH!) I was ready for the next day race (or so I thought.) I had one of my best drives ever, going from DFL to first in class. The car was wild to drive, the rear end was everywhere. Even in that state I just adjusted to make it through the corners that were loose and kept going. (I think my less then optimum usual setup paid off, as a hard to drive car didn't seem too different.) Ignorance is bliss!
Back at the race shop the guys took a look and couldn't believe I raced at all with the subframe bent.
The moral is, I need to do what you are talking about and LEARN about setup... for my own good.

Mac

[tnord]

i'm like Mac. I understand and feel what's going on with the car on a large scale, but the minute changes that need to be made to really make a miata go escape me. i was lucky enough to experience a car that was setup right a few weeks ago, and immediately after turning in for T1 i though "holy shit, THIS is what a car is supposed to feel like."

anyway....my advice to you is the same path i'm following. start at the beginning. chassis tuning at the highest level is way too complicated to understand right from the get go. start with a basic non-track dependent setup that will work pretty well everywhere. tune from there.

for example, i think changing your crossweights for left or right hand dominant tracks is the first and most basic step to chassis tuning. after that, i plan on messing with slight hints of tow in or out at front or rear for each track. after that, i'll move to left vs right camber.

however you decide to do it, only change one thing at a time until you know how that change affects the car, and where things change on the track. after that...move onto the next. don't try and do it all at once, it's way complicated.

[gran racing]

don't try and do it all at once, it's way complicated.[/b]

I believe this is one of my biggest issues and what makes the whole thing so intimidating to me.

[Bildon]

Dave,
Suspension setup is my strong point. I'd love to have a long chat with you. Could explain a lot.
Unfortunately my time is so damn limited these days.

If we're talking FWD & Hondas I'd recommend a few books in order of technical complexity:

The Front-Wheel Driving High Performance Advantage - Jack Doo
Publisher: Motorbooks Intl (July 1988)
ISBN-10: 0879382988

Good basics of FWD setup. A little dated but lots of good stuff for novice tuners.

How to Make Your Car Handle - Fred Puhn
Publisher: HP Trade (January 1, 1987)
ISBN-10: 0912656468

Old, much is outdated, but this is fairly comprehensive and easy to read and understand. I used to read this in college instead of studying ;-)

Competition Car Suspension: A practical handbook - Allan Staniforth
Publisher: Haynes Publishing; 4 edition (October 30, 2006)
ISBN-10: 1844253287

Tidbits of high tech mixed in with a lot of theory and geared more towards sports/formula cars. But good.

Race Car Engineering and Mechanics - Paul Van Valkenburgh
Publisher: SAE International; Rev Ed edition (November 2000)
ISBN-10: 0768007178

Very good. Broader than just suspension but it does have some excellent suspension sections and Paul is one of those guys we should all listen to. He has more experience than the entire ARRC paddock combined ;-p

There are more but these popped into my mind first.

[IPRESS]

Dave this is not FWD, but it may help.
http://forum.specmiata.com/cgi-bin/ultimat...42;t=000003;p=0 (http://forum.specmiata.com/cgi-bin/ultimatebb.cgi?ubb=get_topic;f=42;t=000003;p=0)

[spnkzss]

At our level you are going to have a hard time finding the little things. MOST of us can not drive well enough to stay within 1/10th EVERY lap.

[Despr8dave]

Good topic and just one of many of my weaker areas of racing also. I learned so much about minor adjustments when I ran circle tracks and was able to spend alot of time with many much more knowledgable and experienced racers. One of the best things was to have someone watch you in as many areas of the track as possible. Watch your turn ins, exits, speed compared to other cars, the angle of the front tires was another thing I never thought of, etc. Like Mac, one of my best experiences was at Hallett and turn one. I went down and watched some of the "local boys" and quickly learned I could go alot faster than I was. ( I love that place ). It's a never ending process and just because it worked at the same track last time, doesn't mean it will work this time................but man doesn't it feel so great when it is all set up sooooo right!


David

[Renaultfool]

I really loved this book; The Front-Wheel Driving High Performance Advantage - Jack Doo. There is a picture of one of my old cars, #89, at the bottom of page 31! Cool to be published.

[CaptainWho]

This might sound nuts, but get a larger scale remote control car, say 1:5 or 1:6 scale. AFAIK, all of them will have fully adjustable suspension. The smaller scales are harder to learn setup from, because so much of the action happens effectively instantaneously. With the larger scale cars, you can actually see the car float around on the suspension.

The big reason you can learn a lot about setup with R/C is that you can run boatloads of laps in little time for little ongoing expense.

But some of it is counterintuitive. As an example, we were trying to tune my 1:10 scale electric buggy one day years ago. It wouldn't fly flat off a jump, regardless of what I did with the throttle while in the air. And the type was known to fly well and land well. Mine kept doing endos. We kept making it softer and softer, thinking the rear suspension was launching it. Wrong. It was so soft at the beginning, and we just made it worse for a while, that the rear end was slapping the ramp and the rebound from that slap was causing the endos.

Now, hopefully, you'll never have to deal with suspension problems causing endos in an SCCA amateur race. But the R/C can help you work out in your mind the way different changes affect the car's handling.

Some of the better simulators with high fidelity physics models can do the same thing for you, if you intentionally go in and exercise the physics model.

[gran racing]

Doug, that doesn't sound crazy.

Someone my wife knows is very into local circle track racing and does quite well for himself. I've been thinking of starting to attend some of his races and see what I might be able to learn. Since they only turn left :rolleyes:, how much of what they do would transition over to road racing?

Here's an idea for someone - develop a class to coach people on how to tune a racecar.

[Andy Bettencourt]

Here's an idea for someone - develop a class to coach people on how to tune a racecar.
[/b]

I think you will find that this already exists on a one-on-one basis. One of Nick's favorite things is a test and tune day with customers.

[gran racing]

Yeah, I realize it exists on a one-to-one basis but I know that I can't possibly absorb everything in one test and tune day and can't afford many more (financially or days off from work). I could however make time during evenings or weekends to take "how to tune" classes. I could picture someone even doing this type of training over the web / conference calls with a small group of people and make it interactive, or in person at a site. It would offer various classes and levels from beginner tuners on up. Now only if I knew how to tune cars. :rolleyes:

[924Guy]

Hrrmmmm.... I think I'd weigh in on the side of 1-on-1 instruction/test-n-tune, not because I've done it and benefitted from it, but because of the following.

I think that chassis setup, just like driving technique, is something that simply can't be learned all at once. You can neither sit down, read a book all about it, and KNOW how to tune your chassis any more than you can sit down, read a book by Prost or the like, and KNOW how to drive fast.

It's a set of skills that you have to experience to understand, and yet you need experience to understand the higher concepts! Even with an experienced guide, the right information has to be handed out at the right time, in the right phrasing, or it might as well be written in Swahili. Concurrent with that, if the student isn't properly focused on the right lesson at the right time, again no progress can be made.

I'm no expert at chassis setup, so I'll offer the car construction example instead; it does me no good to be advising a rookie about the basics of building a safe and reliable racecar if they're bugging me for details on head prep for max HP. Likewise, until they understand how the suspension is even supposed to function (a real oddity on the 924/944 rear axle), it's gibberish for me to discuss the finer points of tweaking camber and torsion bars.

So there's still no substitute for direct hands-on experience. The next best thing is to have someone who knows what they're doing be completely responsible for the setup, and you don't touch it - you learn to drive it anyway.

I can do 1:19's in my ITB 924 at Waterford Hills (within 1 sec of lap record). I'm assisting a rookie get his ITB 924 up to speed; in line with that, I provide settings and assistance in setup for the chassis. Until he can get his car into the 1:22's, he's best off not to change those, but rather to focus on using what he's got. Maybe at that point, he'll be working the tires enough that we'll start taking tire temps. But not till then.

Just my perspective...

[ddewhurst]

***develop a class to coach people on how to tune a racecar.***

Dave, as I read these posts & do some thinking I remember that my son went to a oval car tune seminar at Indy 3-4 years ago that was strictly oval. next time I talk with him I'll ask what org. put on the seminar.

[JimLill]

http://www.ricracing.com/new_page_7%20chassis.htm

[latebrake]

oh please!!! you people are so damn stupid. :bash_1_: act like grown men for once. all you need is a volcano, a witch doctor and a virgin. lower her down into the thing and let the doctor do his dance and sing. nothing to it. black art tuning always works for me. i am running out of virgins though. :D

keep good records. sooner or later someone can read them and tell you something useful. i gave up and just do a netural car and have fun. :birra:

[TimM ITB]

Hey Dave;

When I started on my "development road" with the VW A3, AFTER I spent the first year losing my mind and a good chunk of my retirement savings in wasted tires, I learned a few things:

1. IF you are going to seek advice from "those in the know" - stick with ONE way of doing things and make ALL of your adjustments, etc listening to that one voice. My mistake was that I kept asking lots of different folks for input, and each camp had their own perspective on how things should be tuned on a suspension. Examples - lower the ride height VS. raise the ride height / stiff springs in the front and soft in the rear, plus a big sway bar in the rear VS. soft springs in the front and stiff springs in the rear with a wimpy sway bar / lower pressures in the front tires and higher in the rears VS. the same pressure on all four ............. The problem was that I kept trying a little from Column A, and a little from Column B, etc!!!! What a mess!!! The car would push like a pig and then snap the rear end around!!! So, the lesson - try one method of setup, and if it doesn't work, move on. Never mix.

2. Any adjustments that you make - MAKE ONE AT A TIME!!! This may seem like common sense, so that you can address one specific input with a corresponding result, but with track time at a premium, not many test days, etc.........the temptation to make more than one adjustment is very easy to fall for. I fell for it. It was a waste of time and money. Don't do it!!

3. Any adjustments that you make, make them big enough so that you can FEEL a difference! At the outset, I was trying little changes to each of my settings (camber, tire pressures, spring rates, etc) and looking for the change. But there are SO many other variables out there on the track - even on test days - that it was very difficult for me to gauge ANY difference in my car when I was making minor changes. Example - when I added 25# of rear spring to my car at a NHIS test day - I couldn't tell if it was me in the oval driving differently, or was I imagining a change, or what?? So I tried 50#. But, there were other people very close to me in the oval during that session seemingly on every lap, so I was more worried about them than "feeling" the car. Couldn't tell if there was a change or not. Went to 100# more springs in the rear and WHHOOOOEEEE!! The car did rotate!! So, I dropped it back down again to 75# and it felt glued to the asphalt - lower push, and very driveable. The point is, within the bounds of safety, make enough change to make sure that you can feel it.

That's all I got! I am still learning at every track - at every race!

Good luck and have fun!

later,

Tim M

[JLawton]

Here's an idea for someone - develop a class to coach people on how to tune a racecar.
[/b]


Come to ITA, you can get schooled like the rest of us every weekend........ <_<


I&#39;m in the same boat as you Dave. I still have a lot to learn. But the one thing that really helped was getting into a car that was built 10/10ths and set up near perfect. You need to know what a great set-up feels like before you can figure out how to get there. (Yogi Berra has NOTHIN&#39; on me!!)

[rick88civic]

More on this subject. I am running a 1990 ITA Civic with Koni shortend, and valved. The problem is bottoming the suspension, specifically the left front upper balljoint hitting the tower. Hit with 1000# springs in front, no front sway, progressive in back with 800# springs, 5 1/2 " ride height. Springs to stiff car bounced. Raised car to 6 1/4 dropped to 800# front and 600 # back. Still hit left front balljoint but not as bad.
I would like to keep this spring setup but the car will not rotate under these conditions. I don&#39;t want to put the front bar on because of a bad push. If I lower the car, hence lower the CG the car should not roll as much but I am afraid of bottoming again. This happens on hard rights. How can I fix? I cannot drastically change corner weights but would this help. HAs anyone installed sway so that it does not catch until car rolls to a certain point? Might be snappy when that occurs. Thoughts?

Rick Jarrett
ITA racer

[Xian]

More on this subject. I am running a 1990 ITA Civic with Koni shortend, and valved. The problem is bottoming the suspension, specifically the left front upper balljoint hitting the tower. Hit with 1000# springs in front, no front sway, progressive in back with 800# springs, 5 1/2 " ride height. Springs to stiff car bounced. Raised car to 6 1/4 dropped to 800# front and 600 # back. Still hit left front balljoint but not as bad.
I would like to keep this spring setup but the car will not rotate under these conditions. I don&#39;t want to put the front bar on because of a bad push. If I lower the car, hence lower the CG the car should not roll as much but I am afraid of bottoming again. This happens on hard rights. How can I fix? I cannot drastically change corner weights but would this help. HAs anyone installed sway so that it does not catch until car rolls to a certain point? Might be snappy when that occurs. Thoughts?

Rick Jarrett
ITA racer
[/b]
Sounds to me like the issue isn&#39;t in spring rate but instead in bumpstop length. How much of the stock bumpstop do you have on the front left corner? You should be using just over half of it... any less and if you hit a big enough bump, it will cause the upper control arm to hit the frame. FWIW, I had my car set up by OPM and am running 500#F spings without any push or bottoming problems (also on shortened/revalved Koni&#39;s) with no front bar.

Christian

edit:
are you running a rear bar? Also, have you looked into running a softer front rate and stiffer rear rate?

[rick88civic]

Full bumpstop in place.

[mattbatson]

Now, I&#39;m not running a civic...but a suzuki swift.

It is a fwd though, so same principals may apply.

I am running stiffer springs in the rear then the front. My koni&#39;s are also adjusted almost full stiff on the rear. And much softer rebound for the front....
I run a stock rear bar, and no front sway bar....

Even before the welded diff, I had no problem with rotation...(open diff)
Now with the welded, it handles like a RWD :P plenty of rotation...

I also dont have it lowered as far as possible...I rarely hit the bumpstops.

This set up has been pretty effective so far, as I rarely give up anything in the corners...
So, perhaps trying softer front and stiffer rear is a method to try? And, maybe raising it all around half an inch?

[Xian]

Full bumpstop in place.
[/b]
Weird. Are you positive that the upper ball joint is hitting the shock tower? Are you able to see the "circle" mark that it leaves or is it something that you&#39;re just hearing from within the car?

I&#39;m running about a half bump stop on both front corner without excessive bottoming problems. Yeah, if I really pound a curb i can hear it bottom out and every once in a while the upper ball joint will hit the shock tower but it&#39;s not upsetting to the chassis.

RE: the lack of rotation. I imagine that a large part of this is due to the spring rates front to rear and the rest of it might be due to the low-ish ride height in the rear (too much camber as a by product of ride height). My car also has a fair bit of rake in it&#39;s setup (front ride height 5.25" at the rocker panel and 6.25" rear). 500# front springs 700# rear with no front bar and a 3/4" Suspension Techniques rear bar. Maybe try significantly increasing the rear roll stiffness and decreasing rear camber to get the rear end to loosen up.

As always, my $0.02.

Christian

[rick88civic]

Definitely is hitting nice imprint in tower. A little more bar in back I don&#39;t think will make a difference. I am already lifting inside tire off ground at entry all the way to exit. If I raise the back I will be moving the CG towards the front, which will load the left front tire even more.

[Xian]

Definitely is hitting nice imprint in tower. A little more bar in back I don&#39;t think will make a difference. I am already lifting inside tire off ground at entry all the way to exit. If I raise the back I will be moving the CG towards the front, which will load the left front tire even more.
[/b]
I understand that raising the rear will shift grip forward but in doing so it will also loosen the car up for you and should get rid of the push you mentioned initially. I&#39;m really not sure why you&#39;re having the problems with bottoming on the front... other people I know running similiar setups to mine on the 88-91 Civic chassis don&#39;t seem to have excessive bottoming problems either :shrug:

[rick88civic]

I have also talked to other people who do not have a problem of bottoming. I did run a heavy spring in back on a good smooth track but the track i have been running the heavy spring made the car bounce all over the place, although it was fast it was handful with plenty of rotation. By shifting weight forward i would think it would load the left front even more were it would go beyound the tires grip capability. The push in the car with the current setup is probably the best it has ever been. I thought of raising the left front hence putting more weight on right rear and get the rotaion by putting more bar in the car. The only problem is that by raiseing left fron the static load would be greater on that tire but the transfer should be less. Actually raising the left rear would transfer weight to right front which should give beter front end bite and loosing the left rear for rotation. Any thoughts?