Jj, where are you located in the left coast/prc?

I don't have an issue if people post stuff from my books as long as they say where it came from.

There was one person on here who claimed some of my pictures as his own and I got on him about that but that was the only problem I've had.

Ironic how NONE of the above requirements were met in this case, it was not transformative, it was not "commented upon", it was not "criticized". It appeared to me the main end result here, intended or not, was the post precluded the OP from purchasing the quoted authors book and getting his desired information from authors copyrighted graph, rather then a generic formula, IMO.

Ostrich's don't miss much either, you can quote me on that.

Tony and AndyF, this is not about you guys.

I would disagree that none of those conditions were met. One could say the posting of the graph transformed the conversation from one of "go read this" to a graphic example of what needs to be achieved. Part of commentary in the discussion to direct the OP to a document that would assist in his goals. Removing the graph and additional commentary, we are left with the references below to Mike Martin's work without divulging the entirety of the chapter contents or methods, thus providing limited purpose. As such, the OP will need to do additional research on the topic, which may lead them to a search for this or any of the other books mentioned in the thread as the OP says he now has some reading to do. So I'd say we fell within fair use guide lines as described in the definition above.

jcc-

The information presented in Mike Martin's book (the theoretical handling line and formulas) was originally presented in one of the Mopar Oval Track books, which I believe is now out of print.

I'll let ya'll decide how that plays into the copyright discussion.

My main issue with the theoretical handling line is the formula is never clearly stated in either book. And working backwards from some of the suggested setups in the oval track book doesn't give consistent results. My main issue is if the wheel rates of springs are truly supposed to be doubled. No one spells it out in either book.

Regardless, the theory is sound.

But changing roll centers, etc, would change the line. And the original line was developed for circle track mopar B bodies if I remember correctly. So maybe the line is a little different for an A body.

So really, if one wants to go all the way, you need a complete chassis setup program (or to go hire someone like Ron Sutton to do it for you).

The formula as I've used it:

Percentage of Front Roll Bias: Front Roll Couple / (Front Roll Couple + Rear Roll Couple)

Front Roll Couple = (Torsion bar wheel rate * 2) + rear sway bar wheel rate
Rear Roll Couple = (Leaf Spring wheel rate * 2) + rear sway bar wheel rate

Torsion Bar wheel rate = listed rate
Front Sway Bar wheel rate Opt 1 = rate as quoted from Hellwig or Hotchkis
Front Sway Bar wheel rate Opt 2 = sway bar rate * (Motion Ratio^2)
Motion Ratio: (sway bar attachment point from pivot point) / (ball joint from pivot point)
Leaf spring wheel rate = (listed rate) * ((leaf spring width / track width)^2) * 2
Rear Sway Bar wheel rate Opt 1 = *not sure if Hellwig & Hotchkis quoted numbers are wheel rate or sway bar rate - will need to measure and calculate old way*
Rear Sway Bar wheel rate Opt 2 = sway bar rate * (sway bar end link width / track width)^2

solid sway bar rate = 500,000D^4 / (0.4244*A^2*B + 0.2264*C^3)
A = Main bar centerline to end link - 90* (think ~8.5")
B = Main bar width (think ~30")
C = Main bar centerline to end link - at whatever angle the bar is (think ~10")
D = Main bar diameter (think 1.25)
*if bar is hollow, calculate rate for solid of that size, then subtract rate of a bar that would be the diameter of the hollow diameter
*sway bar rate formula from the Fred Puhn book - How To Make Your Car Handle.

Further credit to TC@HP2 - we've had a few email conversations about the theoretical handling line. There was even some discussion of making an excel for everyone to use, but we never did. Maybe TC@HP2 will still do that?


If you're serious about doing some of the number crunching on your own, you should look at getting the following:
-How to Make Your Car Handle - Fred Puhn
-How to Build the Ultimate Super Street Mopar - Mike Martin
-Mopar Oval Track book - I think the Mopar Oval Track Modifications book (available at Mancini)


Still, at the end of the day, the above formulas will only get you close. Be prepared to fine tune the combo (i.e. - buy more springs, sway bars, etc). If you work with Ron Sutton or one of the newer suspension setup programs that requires more inputs, then you can probably nail setup from the start. Those programs or Ron will require measurements every attachment point in your suspension.

I have read the Fred Puhn book, but wasn't aware of the Mopar Oval track book. I'd expect it to be biased to left turn-only cars though, right?

I understand that the Op didn't want an answer so much as a few suggestions on how to figure it out for himself. That is impressive to see...most people just want to copy from someone else since it is much easier.

Yes, the neutral handling line was compiled by Mopar engineers in the early 70s and was used in developing the Kit Car program through the late '70s. It was copied and expanded by Mike Martin into his book in '84. The Martin books are out of print now and can only be found at swap meets and Amazon. The Mopar Oval Track book is still publish, and like Mopar's Engine or Chassis books, contains a lot of good data. However, while some of it is becoming dated, some is still relevant, and you have to understand how to sort it out.

I thought Martin provided a good basic of roll couple calculations. The Mopar books, not so much on the calculations but they do provide piles of other data. However, I have only read Martin's 1984 book "Mopar Suspensions" and not his 1988 book "Ultimate Super Street Mopar" so I do not know if his last book was repackaging of the first, all new material, or a combo of the two. In the first book, Martin did not get into the Nth degree details of adjusting rates by motion ratios. He simply stated overalls, which, if that's all you used, could be a more simple way to arrive at a number for a relevant starting point, but would definitely shift the neutral line one way or the other from what Martin published.

Martin does point out right on that page posted above that there are many contributing factors that will impact the relative position of the neutral line. Even Mopar said that that the line can have a wide range of variables but it can be used to create the fastest route to a starting position of parts that handle reasonably well compared to simple trial and error.

While the original observed data was all B body stock cars at Atlanta, verification of the data was done across multiple tracks, including road courses, and applied to the kit Car program which had a several different wheel base lengths and weight breaks it was involved in. So the theory is sound and is applicable to any chassis regardless of wheelbase, weight, or application.

Uhcoog1 your format right above does seem to cover everything necessary to arrive at some good numbers with the most precise calculations. Like you, I've used multiple books to understand the variables and develop the formulas I have. From my Chevy and Ford days, I have an extensive collection of Steve Smith Racing books that have developed many similar methods that seem to have picked up where Mopar and Martin left off.

The thing about geometry in a stock based suspension is that it applies to both left and right turning cars. The transition to an oval track car is accomplished by weight bias, wheel offsets, spring rates, and shock rates. Typically you want the suspension motion to be symetrical from side to side to avoid radical unsettling and create predictable handling should the car get unweighted or turned around, which happens often. So it is very easy to apply oval track theory it to a street car that turns left and right. All you do is equalize everything left and right.

But even with a formula, you have some homework to do and further tuning will be required. Or, like Uhcoog1 says, you contact Ron Sutton and he does all this work for you, on your car, with your preferences in mind. Or spend a few hundred $$ on a software app that you can plug all the variables in to.

This is a great thread, but it looks like there is a typo in the formula. I'm not real sure, but it looks odd to me, so I thought I'd ask.

In the Front Roll Couple formula, it says to add the REAR sway bar wheel rate.
That's supposed to be, add the FRONT sway bar wheel rate, correct?


Tav

Nope, makes sense to me...

So then the front sway bar rate doesn't affect the front roll couple?

Still seems odd.

He included a formula on how to calculate the front sway bar rate, but then didn't use that front bar rate in either roll couple formula.

You are correct, that is a typo. Front roll couple should be front springs and front sway bar, rear roll couple is rear springs and rear sway bar.

THANKS!
Previously I had just duplicated the stock setups, but it's become apparent that there's room for improvement, even without drastically changing the cars original appearance.
I've been studying up, and this thread has been quite helpful.

Best I could determine was that there was no single Neutral line for all situations, but rather a line that could be established and used for guidance. I summarized this here http://www.heritech.org/cuda/mgcudah.html regarding my own car. If interested in the spreadsheet contact me off-list.

Thanks you, I enjoyed reading that.

OK, I have another question about one of the formulas.
"Front Roll Couple = (Torsion bar wheel rate * 2) + front sway bar wheel rate"

I see that it's torsion bar wheel rate times 2.
I imagine that's because there are two torsion bars & two wheels.
That makes sense.

I see that it's front sway bar wheel rate.
That's the sway bar rate for a single front wheel.

Since there are two front wheels, should it be front sway bar wheel rate time 2?

In some respects, you can go crazy trying to make things better, by observation. NOT that they can't be improved upon.

As for the A-body handling, check out "The Green Brick" which "Mopar Action" built and road raced with great success. Not sure were it might be online, but it's an interesting read! Especially when they went to Road Atlanta!

To get an idea of Chrysler suspension geometry, there are some factory training manuals online at either OnlineImperialClub or MyMopar.com. In that book, you'll understand that Chrysler engineers knew about "controlling the contact patch", even back in the 1950s. Plus, an explanation of camber angles in cornering!

As for spring rates, f/r, there were some excellent articles in the old "Car Life" magazine, circa 1966. About how the f/r stiffness balance affects how the car bounces and comes to "flat" after a road disturbance. This orientation keeps the car more level and comfortable in general driving, such that one end doesn't bounce more than the other, with good shock absorbers.

There was a graphic of a car encountering a dip and how soon the car would be level again. "Number of bounces" at each end. This relates to spring AND shock absorber issues . . . AND can vary with speed.

Back when I was driving the '66 Newport all the time, with a good set of HD shocks (first the Chrysler "MAECO" stamped factory HD shocks and later a pair of Gabriel Strider adjustable shocks on the front), the car was flat and stable "at speed" and pleasantly firm otherwise. The observed natural cruising speed on the highway was the 75-90mph range. Faster, it felt "busy", slower it felt "bored".

Until you spend "road time" with a torsion bar Chrysler product, you cant really feel how good they are, by observation. I mean on a trip of several hours, not just going across town. Keying into the engine response/throttle input, the way you don't have to slow down for corners, the confidence of the 11x3" drum brakes, and other aspects of the driving experience.

Go into www.allpar.com and read the sections of the Chrysler "squads" and LAPD testing. Quite outstanding, even in the later 1950s!

Chrysler didn't like to use a rear sway bar for many years. They chose to use stiffer rear leaf springs to help with that rear roll stiffness issue. But in the "Police and Taxi" section of the 1970 parts book, there is a listing for a rear sway bar with the note "LAPD". Not sure if they co-opted the Helwig rear sway bar (aftermarket).

The first rear sway bars were on the radial tire cars circa 1974, B & C body in particular.

Pontiac used rear bars on their GTOs and such first, then Chevy came out with their F-41 package for many cars, which helped handling a good bit.

In a 1969 issue of "Car Life" magazine, they did an article on "Power Cars", which were full-size cars with larger engines. In that time frame, they had a test corner where they had a camera set up to picture the front suspension and tire/pavement interface. It clearly showed how the Chrysler products had superior front suspension geometry to the other cars, which greatly aided their cornering performance.

As the MasterTech book shows, the outside wheel goes into negative camber such that the outside tire is better braced to take the added load. The inside tire goes into positive camber, to help with the cornering load, too. GM and Ford geometries kept the tire perpendicular to the body, so that as the car leaned into the corner, the tire was not perpendicular to the road surface, resulting in greater outer tire wear and decreased cornering performance. ONE reason the rear bar and less lean made so much difference in their handling!

What has not been mentioned here is tire pressure bias f/r. Factories generally wanted an understeering car, so the front tire pressures are generally lower than the rear (especially in the C-body wagons! and when "full load" is planned for.

What I found, going back to the tire's load and excess load potential at a particular tire pressure . . . one of the "Car Life articles on tires had a chart of tire pressure and tire load by tire size (in 2psi increments between 24psi and 32psi, the pressure ranges back then). On a Chrysler C-body (or others) with a 55/45 f/r weight distribution, here's the strategy I prototyped and found to work well for me . . . proceed at your own risk.

The minimum tire pressure for "high speed driving" (in the owner's manual) was 4psi over "normal". That meant 28psi in the tires. Adding in the correction factor for the front being heavier, by the pressure/weight carrying/tire size chart, adding 2psi to the front balances out the load which each tire sees, proportionally. For a 60/40 split, a 4psi front bias yields the same situation. Key thing is that EACH tire had the same static percentage load it supports. That would mean that each tire should "slip" at the same time in a corner, as a car with a 50/50 f/r weight situation. i.e., "neutral" handling, rather than the front sliding first (understeer.

Understeer, for the masses, is deemed "safer" as you'll hear tire noise before you get into trouble and, as a result, slow down to a safer cornering speed. In a Mercury Marquis I rented in '97, that speed was 25mph in a city setting with Michelin Symmetry radials. Any Valiant would out-handle that car!

One thing on many Chrysler suspensions. When factory a/c was ordered, the front torsion bars were upgraded to the HD bars due to the added extra weight. Just the bars, not the shocks. The full HD suspension added the shocks and heavier rear springs/shocks to the mix. That's the way it was on the C-body cars. Check the respective service manual for specs.

Using the f/r tire pressure bias I mentioned also tends to result in greater tire life. Reason is that EACH tire tread is flat against the road surface. No wearing on the edges from too-low air pressure, no wearing in the center from too much air pressure.

One other thing you can do to check the contact patch is to be on a dry concrete surface and with the car parked, turn the wheels from lock to lock. Then back the car up a foot or so and check the resultant rubber marks left on the concrete. With the factory alignment settings, with the 2+psi pressure bias in the front, it should be a solid patch.

With the wider tires and rim width of more modern times, such a solid patch might not be possible, but with the 5.5 and 6.0 inch wide wheels of the 1960s, it worked fine for me.

From the luck which "Mopar Action" had with The Green Brick Valiant 2-dr sedan on the road course, it proves that a stock Chrysler suspension can be easily upgraded to handle very well with few modifications. But then, this was in the 1980s, well before the hyper-touring orientation came along.

KEY thing is chassis/body stiffness. Chrysler's UniBody was a better "unit body" than GM knew how to build, back then. Ford too. This stiffness helped give the suspension a stable place to work.

The assymetrical rear leaf spring configuration helps in acceleration performance, as did the r/l spring stiffness bias on the HP cars of the '60s.

And then there are shock absorbers! Of which we have fewer options than in the 1970s! And then there are some new options, too.

One of the things which, to me, made Chrysler products such great cars was the "Torsion Bar Feel" (which encompasses the whole gamut of their suspension design orientations). It was the greater high speed handling which made Chrysler products the desired vehicles of so many state police and other law enforcement agencies. Check out the "It's a Wild, Wild, Wild World" video and watch the several Chrysler products in the "racing" scenes. Watch the suspension dynamics at work on those cars, even a '62 Imperial convertible.

Also, find the "On The Test Track with the 1957s" video on YouTube where 1957 Chrysler cars were compared to "the competition" from GM. It's easy to see how much better the Chryslers were! And how much flex were in some of the GM body/frame cars in an unexpected encounter with a train track crossing in the country.

To me, when you start putting new k-frames and even frames under a Chrysler product, with the lowered ride height and 8-10" wide wheels, to me the great chassis feel of the stock Chrysler chassis is lost. Be that as it may, but I suspect lots of money can be spent for a very specific gain in a specific application. You can spend money, get "the look" and performance increases, which leaves the only reason to have a Chrysler product to be its styling rather than otherwise . . . for which a Camaro would do the same thing.

Sorry for the length, but these are the things I've researched and pondered over for a good while, but I still believe that what the factory provided is better than some might suspect or realize. Others might not agree, which I respect.

CBODY67

THanks for the detailed post.I appreciated it.

Yes, thanks for sharing all that info!