Let's talk anti-roll bars

[Ron Sutton]

Before we get into problems & solutions on your specific application … I want to share with you a viewpoint I use to make tuning easier … then outline terms & critical tuning concepts … so we’re on the same page.

We all know competition cars are COMPLEX. There are literally over 200 AREAS of things to TUNE in the suspension alone. I find what helps a Tuner/Crew Chief to become more confident is ... knowledge (of course) ... experience (of course) ... knowing what a mechanical change actually effects on track … and how each tuning change of affects other areas.

But also, as a Tuner/Crew Chief, having a viewpoint that makes all this complexity ... simpler to understand … provides clarity & builds confidence.



I have been fortunate to develop many crew chiefs over the years to work with me on my race teams. Teaching them everything they need to master is a long term commitment on my part & theirs. It takes years. But simplifying things help them grasp concepts quicker ... and develops confidence in their tuning decisions.

Let's simplify things first. Remember this little corny phrase: 4x4x2+2

It is short (like an acronym, but using numbers) for ALL the things that competition car Designers, Tuners & Crew Chiefs deal with. There are 4 key areas with 4 major ingredients, operating in 2 worlds … plus 2 wild cards. 4x4x2+2 is just a simple way to remind us what we're dealing with.

The 4 key areas are: power, braking, handling & aerodynamics (in no particular order.) Obviously these all play a role in the performance of the car … and in many cases affect each other.

Each Key area has 4 major ingredients that define it & of course affect it.

For power, the 4 major ingredients are:
Airflow
Fuel management
Spark control
Structure Design

For braking, the 4 major ingredients are:
Hydraulics
Leverage
CoF
Structure Design

For handling, the 4 major ingredients are:
Tires
Weight transfer … to and from tires
Geometry affecting … the tires
Structure Design

For aerodynamics, the 4 major ingredients are:
Force
Drag
Turbulence
Structure Design

When I said competition cars operate in two worlds, what I really mean is we do a lot of design, set up & tuning to the car in a “static state” … then go drive it HARD … and everything is affected & different when the car is in a "dynamic state" on track.

No pun intended, but the 2 wild cards are the track & the driver. The track environment is constantly changing, and good Tuners/Crew Chiefs tune to the changing conditions.

As long as we use human drivers, this will be a variable. Some drivers are more consistent & some less, but none of them are robots, so there will be inconsistencies. Some drivers are learning & improving, some not & even some declining in their abilities, but again, they are not static. Some drivers are more of a wild card than others.


I find, as long as we embrace these 4 key areas, understand the 4 major ingredients that define & affect them, remember the car is acting in a dynamic state on track & account for the 2 wild cards … the job of Tuner/Crew Chief gets more clear, less daunting and making tuning decisions becomes easier, quicker & more confidently.


----------------------------------------------------------------------------------------------

Let’s get on the same page with terms & critical tuning concepts.

Shorthand & Acronyms
IF = Inside Front Tire
IR = Inside Rear Tire
OF = Outside Front Tire
OR = Outside Rear Tire
*Inside means the tire on the inside of the corner, regardless of corner direction.
Outside is the tire on the outside of the corner.

ARB = Anti-Roll Bar
FRC = Front Roll Couple
RRC = Rear Roll Couple
TRS = Total Roll Stiffness
TAR = is those black round things the car rolls on. (Sorry, couldn’t resist)
WT = Weight Transfer

CG = Center of Gravity
RC = Roll Center
IC = Instant Center
RA = Roll Angle

----------------------------------------------------------------------------------------------

TERMS:

Total Roll Stiffness: is the mathematical calculation of the “roll resistance” built into the car with springs, ARB’s & their geometry. Stiffer springs & bigger ARB’s make this number go UP & the roll angle of the car to be less.

Roll Couple … front to rear … is expressing the roll stiffness separately & often in %. If we say the Front has 58% roll couple (then the rear automatically has 42%) … so the front suspension of the car is resisting roll more than the rear.

Roll Angle: is the amount the car “rolls” over from side-to-side in cornering, usually expressed in degrees.

Spring rate = pounds of linear force to compress the spring 1”.
Spring force = total amount of force (weight and/or weight transfer) on the spring.

Anti-Roll Bar, ARB, Sway Bar & Anti-Sway Bar … all mean the same thing. Kind of like “slim chance” & “fat chance” ...
ARB Rate = Pounds of torsional force to twist the ARB 5 degrees. (This has been corrected.)

Dive = is the front suspension compressing under braking & cornering forces.
Rise = can refer to either end of the car rising up.
Squat = refers to the car planting the rear end on launch or under acceleration
Roll = Side to side body rotation … aka body roll.
Pitch = Fore & aft body rotation. As when the front end dives & back end rises under braking or when the front end rises & the back end squats under acceleration.

Grip & Bite = are my slang terms for tire traction.


Track width = is center to center of the tread.
Tread width = is outside to outside of the tread.
A lot of people get those confused & our conversations get sidelined.
* The definitions for these 2 were swapped & has now been corrected

Rate = The rating of a device often expressed in pounds vs distance. A 450# spring takes 900# to compress 2”.
Rate = The speed at which something happens, often expressed in time vs distance. 3” per second. 85 mph.
* Yup, dual meanings.

----------------------------------------------------------------------------------------------

ASSUMPTIONS:

Let’s assume we’re not changing any ride heights, unless discussed. In race cars & many (but obviously not all) PT cars, the spring height is adjustable & if we make a spring rate change, we are putting the car back to the EXACT same ride heights, unless it is desired & discussed to change ride heights.

----------------------------------------------------------------------------------------------

20 CRITICAL TUNING CONCEPTS:

1. What you do WITH & TO the TIRES ... are the key to performance. Contact patch is the highest priority.

2. Geometry design, settings & changes should be to improve how the tires contact the road dynamically.

3. The design structure of every component affects how well that component handles forces inflicted upon it.

4. After the car is built, tires are selected & the geometry is optimum … most chassis tuning is to control the degree of weight transfer to achieve the traction goal.

5. Force (weight & weight transfer) applied to a tire adds grip to that tire. With the exception of aerodynamics, weight transfer from tire(s) to tire(s) is the primary force we have to work with.

6. Anti-Roll Bars primarily control how far the front or rear suspension (and therefore chassis) “rolls” under force, and only secondarily influences the rate of roll. Stiffer bars reduce roll angle, engaging the inside tires more.

7. Springs primarily control how far a suspension corner travels under force, and only secondarily influences the rate of travel. Shocks primarily control the rate of suspension corner travel under force, and only secondarily have influence on how far.

8. Springs, Shocks & Anti-Roll Bars need to work together “as a team” … with the springs’ primary role of controlling dive & rise, Anti-Roll Bars’ primary role of controlling roll & Shocks primarily role controlling the rate of both. They all affect each other, but if we choose the right tool for the job, we create a harmonious team.

9. I find in production based cars, we can go no faster through a corner than the front tires can grip. Balancing the rear tire grip to the front … for balanced neutral handling … is relatively easy … compared to the complexities of optimizing front tire grip.

10. The front tires need force, from weight transfer on corner entry, to provide front tire GRIP. Too little & the car pushes … too much & the car is loose on entry. The rear tires need force, from weight transfer on corner exit, to provide rear tire GRIP. Too little & the car is loose … too much & the car pushes on exit.

11. Tuning to allow a suspension corner … to compress quicker or farther … provides more force & therefore more grip to that tire … up to the limits of the tire. Tuning to allow a suspension corner … to extend/rebound quicker or farther … provides more force & therefore more grip to the opposite corner’s tire … up to the limits of the tire.

12. Softer springs allow more compression travel & therefore more force onto the tire … for MORE GRIP on that tire ... and less grip on the opposite tire. Stiffer springs reduce compression travel & therefore lessen force onto the tire … for LESS GRIP on that tire ... retaining more grip on the opposite tire.

13. Optimum roll angle works & loads both sides of the car’s tires “closer to even” ... within the optimum tire heat range … providing a consistent "long run set-up" & optimum cornering traction throughout a multi-lap event. Long run set-ups typically take ½ a lap to a whole lap for the tires to “come in” 100%.

14. Higher roll angles work better in tight corners but suffer in high speed corners. Lower roll angles work better in high speed corners but suffer in tight corners. The goal on a road course with various tight & high speed corners … is to find the best balance & compromise that produces the quickest lap times.

15. Too much roll angle overworks the outside tires in corners & underworks the inside tires. Too little roll angle underworks the outside tires in a corner. Excessive roll angle works the outside tires too much … may provide an “ok” short run set-up … but will be “knife edgy” to drive on long runs. The tire heat up quicker & go away quicker. If it has way too much roll angle … the car loses grip as the inside tires are not being utilized.

16. Too little roll angle produces less than optimum grip. The car feels “skatey” to drive … like it’s “on top of the track.” The outside tires are not getting enough load from force, therefore not gripping enough. Tires heat up slower & car gets better very slowly over a long run as tires gain heat.

17. I learned early that tuning is NOT linear 2 directions with stops at the ends. A car can be loose because it has too little roll angle in the rear & is not properly loading the outside rear tire ... or loose because it has too much roll angle in the rear & is not properly loading the inside rear tire. A car can be pushy because it has too little roll angle in the front & is not properly loading the outside front tire ... or pushy because it has too much roll angle in the front & is not properly loading the inside front tire.

18. The car’s Center of Gravity acts as a lever on the Roll Center … separately front & rear. Higher CG’s and/or lower RC’s increases roll angle. Lower CG’s and/or higher RC’s decrease roll angle. Getting the front & rear of the car to roll similar is desired. Getting them to roll exactly the same is not, because …

19. Goal: To have optimum grip on all tires and disengage the inside rear tire (to a degree) to turn well … then re-engage the inside rear tire (to a higher degree) for maximum forward bite on exit. So, on entry & mid-corner, the car needs to roll less in the front to keep both front tires engaged for optimum front end grip, while allowing the car to roll slightly more in the rear to disengage the inside rear tire, to a small degree, to turn better. For optimal exit, the car will have more roll in the front & less in the rear to re-engage the inside rear tire to a higher degree than it was on entry & exit, for maximum forward bite (traction) on exit.

20. Don’t forget the role & affects the engine, gears, brakes, driver & track conditions each have on handling.


----------------------------------------------------------------------------------------------

After you have read this ... and have time to digest it ... the cause of your handling challenges may become more clear. Regardless, I'll be back tomorrow with what i think is an explanation for your particular issues.



If anyone has any questions, feel free to chime in on this thread.

Ron Sutton

[Tomswheels]

[Ron.in.SoCal]

"TAR = is those black round things the car rolls on. (Sorry, couldn’t resist)"

That's a NASCAR term right? As in, "Last pitstop he took two TARs!"

Ron such a pleasure to watch you in action. Keep going Sir!

[Ron Sutton]

"TAR = is those black round things the car rolls on. (Sorry, couldn’t resist)"

That's a NASCAR term right? As in, "Last pitstop he took two TARs!"

Ron such a pleasure to watch you in action. Keep going Sir!

No, Ron ... that's a drag racing term I picked up in the South. After the race was over ... talking with racer buddies over several adult beverages ... a friend said he was having problems with tar. I said, we used to also. But now we put WD-40 on the fenderwells before runs, and the tar doesn't stick. He looked at me like I was drunk ... no comment ... and said, "No Ron. I having problems getting my tars to hook up."

Oh.

[Ron Sutton]

Tom,

Tom ....


Tom ... you going to be ok?

[Tomswheels]

Awesome stuff. Trying to figure out how to get my Torsion bars and leaf springs to understand it all...

[Matt@BOS]

Ron, hopefully this isn't too confusing, but in place of setup 2, I actually had two setups with minor differences which mostly drove the same.

setup 3:
Front Springs: 550#
Front Sway Bar: 447#
Rear Springs: 300#
Rear Sway Bar: 402#
Notes: I arrived at a set up I was reasonably happy with. last setup with AFCO shocks on all corners

setup 3.5
Front Springs: 575# (Now with JRI shocks up front)
Front Sway Bar: 447#
Rear Springs: 300#
Rear Sway Bar: 402#
Notes: I arrived at a set up I was reasonably happy with. I ran the same little track at Adams Motorsports track in Riverside (autocross sized) before and after making the changes, and found the JRIs to be slightly quicker. I have driven the track many times, and I was a bit quicker with the JRIs. Perhaps it was just confidence but I felt like the JRIs functioned better through quick transitions and gave better turn in feel. I had to back compression off of the AFCOs to get them to respond the way I wanted them to in 180 degree slow speed, tight corners, which left me with a car that felt a little numb and was slightly slower to react in slalom situations, but otherwise worked well. It is probably pointless rambling about that since I've changed out the shocks, and we don't know have dyno sheets of the afcos, but more information never hurt, right?

I will have to go look for the shock dyno charts on the JRIs, if I don't have them I can always call DSE.

Matt

[Ron Sutton]

Thanks for the update Matt. I'll create an updated sheet, so as we discuss how changes affect the car ... you & I can refer back to actual setups you had.

I'm hoping Rod & Tom join in the conversation as well, with their experiences.

[Ron Sutton]

Awesome stuff. Trying to figure out how to get my Torsion bars and leaf springs to understand it all...

Ain't no big thing. A spring is a spring, regardless of how man shaped it. If you think of it this way, it all makes sense.

A. We are always working to get the 4 tires to optimize contact patch.
B. There is a roll angle the car is happy at for each corner ... and a best compromise for the various corners of a track.

Have you added a track bar to your leaf springs?

[Ron Sutton]

For clarity sake, Matt … please read this and make sure I am interpreting your writings correctly. If not, copy, paste & edit into the next post.

----------------------------------------------------------------------------------------------

Your car is a 1969 Camaro with 454 LS7 (gen IV), T56 Magnum, 3.73 gears, 18x9 and 18x11.5 wheels with 275/35 F, 315/30 R tires. DSE subframe and quadralink. 3500lbs with a full tank, sans driver. 51/49 F/R weight distribution, with “close” cross weights” & narrower front than rear track width.

You have had basic 5 suspension set-ups:

#1
Front Springs: 450#
Front Sway Bar: 447#
Rear Springs: 250#
Rear Sway Bar: 344#
Notes: The car had pretty good bite and turn in, but it was wearing the outside tires badly and it was the tire was being overloaded because it would skip, or hop once before taking a set.

#2
Front Springs: 450#
Front Sway Bar: 447#
Rear Springs: 250#
Rear Sway Bar: 402#
Notes: I stiffened the rear, only to notice that I now had decent initial turn in with terrible mid corner push turning into transitional oversteer, making the car really loose putting power down.

#3
Front Springs: 550#
Front Sway Bar: 447#
Rear Springs: 300#
Rear Sway Bar: 402#
Notes: I arrived at a set up I was reasonably happy with. last setup with AFCO shocks on all corners

#3.5:
Front Springs: 575# (Now with JRI shocks up front)
Front Sway Bar: 447#
Rear Springs: 300#
Rear Sway Bar: 402#
Notes: I arrived at a set up I was reasonably happy with. I ran the same little track at Adams Motorsports track in Riverside (autocross sized) before and after making the changes, and found the JRIs to be slightly quicker. I have driven the track many times, and I was a bit quicker with the JRIs. Perhaps it was just confidence but I felt like the JRIs functioned better through quick transitions and gave better turn in feel. I had to back compression off of the AFCOs to get them to respond the way I wanted them to in 180 degree slow speed, tight corners, which left me with a car that felt a little numb and was slightly slower to react in slalom situations, but otherwise worked well. It is probably pointless rambling about that since I've changed out the shocks, and we don't know have dyno sheets of the afcos, but more information never hurt, right?

#4
Front Springs: 575#
Front Sway Bar: 447#
Rear Springs: 275#
Rear Sway Bar: 402#
Additional Changes: Put JRI Shocks on the rear & Falken Tires all the way around
Notes: These changes gave me understeer that was most noticeable on turn in, but the functioning rear shocks greatly fixed traction issues as I used to start losing traction on auto crosses mid way through a straight since the rear springs wasn't being controlled.

#5
Front Springs: 700#
Front Sway Bar: 295#
Rear Springs: 275#
Rear Sway Bar: 402#
Additional Changes: Put JRI Shocks on the rear & Falken Tires all the way around
Notes: These changes seemed to increase the amount of understeer into transitional oversteer that I experienced & ended up with a car that seemed to put power down exceptionally well but exhibited more understeer, especially applying power with slight steering input.


Do I have this correct ?


Ron Sutton

[Matt@BOS]

I mentioned earlier that I was widening the front track width, but never got into specifics. It is a pretty big change. I just picked up a set of widened Fiberglass fenders which should allow me to move the wheels out 1.5" per side from what I have now. It should allow me to run a roughly 71"/70" front to rear track. My car is out getting getting the rear center section fixed after all of the ring gear bolts fell out, for a second time. So, I can't measure for sure, but the other Camaros in the shop allowed me to work backwards to those numbers, and I kind of cringed when I figured out what they probably are.

So, let me pose one more question for you, and hopefully we aren't getting ahead of ourselves too much, but this relates back to one of Rod's questions. Can we get into undersquare versus square front to rear tire widths, and how they affect turn in?

[Matt@BOS]

Oh, and yes, the latest sheet of setups is correct and includes all of the combinations I've I ran on autocrosses. I did go out to Big Willow, and have a few notes on that setup but for the sake of focus, I haven't included those notes.

[Ron Sutton]

Matt,

When you say "71"/70" front to rear" ... that's not track width, that's tread width ... or you really have a WIDE car.

Small difference in measuring ... big difference in how it affects the car. If your tires were the same width ... even though the measurements are outside-to-outside & need to be center-to-center ... the ratio of 1" wider in front would be fine.

If you make your car have a "tread width" of 71" front & 70" rear ... with your 275/35 Front tires on 18x9 wheels, which have around 9.8" tread on the ground and your 315/30 Rear tires on 18x11.5 wheels have about 11.8" of tread on the ground ... that would make the front track width 61.2" ... and your rear track width 58.2" .... 3" wider in the front .... hmmmmmm ... wrong direction ... will make the car push like a dump truck ... not good. Let's discuss this along with everything else.

To discuss how the car has been handling ... we need to clarify the track width the car has now.

Next steps ....

1. Measure center of tread to center of tread ... front & back ... and post the #'s.
* (or outside of tread on one & inside of tread on the other)

2. Provide me with accurate tire tread width numbers for future calculations.



If anyone has any questions, feel free to chime in on this thread.

Ron Sutton

[Ron Sutton]

Can we get into undersquare versus square front to rear tire widths, and how they affect turn in?

Any time you widen the front track width ... and leave the rear track width the same ... You are tightening the car on Corner Entry & Exit ... meaning you're adding more rear tire grip. If the car was pushing already .. the push will get worse. The same would be true if you left the front track width alone and narrowed the rear track width.

The handling in the center of the corner ... also known as the "roll through zone", where you're off the brake & haven't picked up the throttle yet ... can have different results. If the car had too much Roll Angle ... the wider front track width may help reduce the roll angle & load the IF tire more, adding grip to the front end of the car, helping it to turn better.

On the other hand, if the car already had the correct Roll Angle or too little Roll Angle ... and the IF tire was already loaded & doing it's job ... the wider front track width will reduce the roll angle even more & unfortunately may load the IR tire to a higher degree (bad) adding grip to the rear end of the car ... contributing to a tight or push condition.

Read my long winded "book" in post #21 ... then read this again ... and let your mind digest it some. Let me know when you're ready to pick up the conversation again, and if you had any "Ah Ha" moments.


If anyone has any questions, feel free to chime in on this thread.

Ron Sutton

[Matt@BOS]

Hey Ron, here is what you wrote:

Track width = is outside to outside of the tread.
Tread width = is center to center of the tread.

It sounds like you meant to write the opposite, no?

So, let me take another stab at this,
overall width is currently 68"/70"
That would make the tread width closer to 67"/69"
and the track width would then be 57.2" front and 57.2" rear

With the widened front fenders I was planning on adding more front tire, so instead of a 9" wheel I would be moving up to a 10.5" or possibly 11" wheel. This would allow me to run a 295 or 315 front tire, depending on brands. Falken only makes a 295/40, which is too tall, so I would be looking to run their 315/30/18s all the way around.

I believe this would change things to:
58.2" front, 57.2" rear track width.

Again these numbers are approximate because the car isn't in front of me, but if it is fine with you, let's run with these numbers. I can always work backwards and plug in the actual numbers later, right?

[Ron Sutton]

Hey Ron, here is what you wrote:

Track width = is outside to outside of the tread.
Tread width = is center to center of the tread.

It sounds like you meant to write the opposite, no?
Hmm. I went back & looked to fix it & can't find the error. I found the error in post #21 & corrected it. Thanks for catching it.

Regardless, Track width is center to center of the tread ... and Tread width is outside to outside of the tread.


So, let me take another stab at this,
overall width is currently 68"/70"
That would make the tread width closer to 67"/69"
and the track width would then be 57.2" front and 57.2" rear
You're on the right track. My math says 56.6" front & 57.0" rear.

I'm using these #'s which are "in the ballpark" ...
275/35 Front tires on 18x9 wheels should work out to 10.6" overall & 9.8" tread on the ground
315/30 Rear tires on 18x11.5 wheels should work out to 12.4" overall & 11.8" of tread on the ground
* Again, when you get your car back, measure everything "for real" & we'll work from those #s.




With the widened front fenders I was planning on adding more front tire, so instead of a 9" wheel I would be moving up to a 10.5" or possibly 11" wheel. This would allow me to run a 295 or 315 front tire, depending on brands. Falken only makes a 295/40, which is too tall, so I would be looking to run their 315/30/18s all the way around.
OMG ... this would be a great move ... because 1 of the issues your current set-up has is the small fronts & big rears.

But if the front track width goes past 58.0" ... or 1" more than the rear ... you may compound your tuning challenges.

Assuming you're going from a 9" wheel to an 11" wheel, the back spacing will need to be .3" MORE than your current front wheels. That would place .3" of the additional 2.0" of tire width on the inside, closer to the frame & 1.7" of the additional 2.0" of tire width on the outside, closer to the fender. My suggestion is this is the MAX I would push the tires & wheels out. This creates a 58.0" track width

I feel optimum would be back spacing .5" MORE than your current front wheels. That would place .5" of the additional 2.0" of tire width is on the inside closer to the frame & 1.5" of the additional 2.0" of tire width is on the outside closer to the fender. This creates a 57.6" track width ... .6 or 6/10 of an inch wider than the rear.



I believe this would change things to:
58.2" front, 57.2" rear track width.

Again these numbers are approximate because the car isn't in front of me, but if it is fine with you, let's run with these numbers. I can always work backwards and plug in the actual numbers later, right?

Yes, let's run with these numbers & the concept ... and work out actual numbers when you have your car back.

[Matt@BOS]

Well, I can't go inboard with the front wheels anymore without seriously limiting steering, but I can go out .25 inches per side in the rear if that would help.

[Ron Sutton]

Well, I can't go inboard with the front wheels anymore without seriously limiting steering, but I can go out .25 inches per side in the rear if that would help.

Awesome. That should make the front track width 58.6" and the rear track width 57.5" ... give or take until you measure your car for real.

2 questions ...

1. Have you read Post #21 thoroughly yet?
2. If so, are you getting ideas of why your car is pushing with bigger rear sway bars?


Ron Sutton

[QuarterD25]

Mind blowen....

[Ron Sutton]

Mind blowen....

Sorry ...