The 24 Deadly Sins of Chassis Tuning

story by Don Alexander • Illustration by Ruben Cueto

Picture this: At the race track, you’re unloaded and ready to go for the first practice session. After the session is over, you feel lost because your car’s handling is way off. You make changes that should help, but in the next session, the car feels even worse. The same scenario continues for the remainder of the event, and you’re very unhappy with the result.

There is a good chance that one or more of the following chassis tuning sins is the culprit behind your situation. Any one of these problems can be your undoing; most racers are guilty of breaking several of the rules regularly. Here’s a primer to help you spot—and correct— these most common causes of bad handling. May you find salvation at the checkered flag.

Thou Shalt Have a Solid Baseline

One key to being fast and competitive is repeatability—and you cannot repeat results if you do not know where you started. That’s why you need a good chassis baseline. You can start with the baseline settings recommended by your chassis builder or suspension guy. If you have the experience, however, you can create your own. And best of all, if you have records from previous outings at the track you are headed to, you’ll have a head start.

You should at least record the following: frame heights, crossweight percentage, rear and left—side weight percentages, all four tire circumferences, fuel load, gear ratio, wing settings, spring rates (bar neutralized), shock valving, toe, alignment, pinion angle, Panhard bar height or Watt’s linkage settings, and any other settings than can affect the handling.

Thou Shalt Not Prepareth at the Track

This happens too often. You run out of time or have inadequate help before a test or race, so you end up preparing the car at the track—or at least finishing the job there.

It is very difficult to create a good setup at the track; you can do a much better job at the shop. And track time is expensive for a test day; wasting that time playing in the pits is not effective. If you’re prepping your car at the track during a race weekend, forget any chance of a good result.

Thou Will Taketh Tire Temperatures

Tire temperatures are your link to what goes on between the tire contact patch and the track surface. I find it difficult to make sound tuning decisions without tire temps. Tire temperatures should be taken religiously every time the car comes off the track—even after a race.

Thou Will Take Segment Times

Time around the track is gained in very small increments. Chassis adjustments can make a car faster (or slower) around the track, but may cost time in certain areas of the race track. Knowing this can add to the data available for you to make sound tuning choices.

The only way to accomplish this is to record times in several segments of the race track. (For example, timing how long it takes to get through a series of corners.) You don’t need to take times in every segment on every lap, but taking segments at various points for each session will prove very valuable, especially in testing.

Thou Shalt Not Have Excessive Crossweight

Crossweight, the measure of right front and left rear combined weight versus total car weight (both with driver), is a usefiJl tuning tool. In road racing or autocrossing situations, excessive crossweight will help handling in one direction but hurt in the other—and it hurts more one way than it helps the other way. Crossweight should be set at 50 percent, if possible, and never less than 49.5 percent or more than 50.5 percent.

Thou Shalt Keepeth Thine Records

This may be the most costly sin of all. There is just too much data to track if you don’t write everything down in an organized way. Even if you luck into a good setup, without records you will be unable to repeat it without going through the complete process all over again.

The best time to record notes is back in the shop after a race. If you have a good race setup, these notes will tell you how to get back to it the next time you race at that track under similar circumstances. And if the results were not so good, at least you know you need to do something different.

Thou Shalt Not Listen to Too Much Advice

Everyone is a setup expert, or so most people would have you believe. If you want to be successful, then you must learn enough to make your own tuning decisions within your own team. Listening to advice from others is one thing, but putting it to use is another.

Even if the person offering advice is very knowledgeable, that person likely does not know your situation, preferences, resources or needs. Most often, the person offering advice is less knowledgeable than you are, and usually only knows a couple of things that could cure your perceived problem.

Thou Will Haveth a Game Plan

Any plan is better than no plan at all. Take the time to create a game plan for each race, beginning with your realistic objectives, maintenance schedules, testing and race strategy. Remember that part of a good game plan is the flexibility to alter the plan as needed. Usually, no plan equals no result.

Thou Shall Determineth the Exact Problem

A handling problem can occur anywhere on the track. Is it corner entry, mid-turn or corner exit? Does it happen everywhere? If a problem occurs in one place, does it result in a different problem someplace else? The classic example of this situation is comer-entry understeer that a driver over-compensates for at the exit of the comer, creating an oversteer condition. The driver says the car is oversteering, but the real problem is the corner-entry push. Adjusting for the oversteer will make the problem worse.

Thou Shalt Not Have a Suspension Bind

Suspension binds create an inconsistent handling situation. If a bind is present, it is just about impossible to properly tune the suspension. If the car does not respond the way you think it should to suspension changes, check for bind in the suspension. Checking for binds should be part of your routine setup process.

Thou Shalt Not Have a Dead Shock

A bad shock can be very difficult to feel. Check the shocks if you cannot get the chassis tuned effectively. Feel for a dead spot or lack of resistance in both rebound and compression.

Thou Will Set Thine Car Up According to Driver Feel

Often, the fastest setup for a given car is too aggressive for a driver without some experience. When the suspension is too stiff, especially the shock valving, it is difficult for the driver to feel what the chassis is doing. The car reacts too quickly for the driver to sense what is occurring.

Softer springs and shocks, while slower for the experienced driver, may be faster for the inexperienced driver.

Thou Shalt Not Make Corner Weight Adjustments at Only One Corner

To adjust comer weight percentage, you must change frame height. Suspension geometry is designed to work best at a certain frame height, and changing the frame height can alter the suspension geometry in a negative manner.

Making one big change at one comer can cause this problem to happen. The trick is to make small changes at all four comers. Instead of putting a turn in the right front, put a quarter-turn in the right front and left rear, and take a quarter-turn out of the left front and right rear.

Thou Shalt Not Try to Cure Handling Problems With Only One Element

Any handling problem can be changed by adjusting several different parts on a car; it is ineffective to change only one or two items to improve the handling. Often engineers, whether their specialty be shocks, tires, springs, or whatever, will try to cure a problem by using what they know best.

This is often not the most effective way to solve a problem. It is important to look at the entire system as a whole, then make changes that suit the system best and offer the most favorable compromise.

Thou Shalt Not Make More Than One Change at a Time

While more than one suspension adjustment may be needed to cure a handling problem, it is always best to make only one change at a time. Make a change, and then go test.

Making more than one change at a time can produce results that are difficult to analyze. Which change helped, and did one change actually hurt?

Thou Shalt Not Stray From Recommended Frame Heights

This can cause binding in the suspension or, at a minimum, cause undesirable suspension geometry. Don’t stray too far from home.

Thou Will Carry a Consistant Fuel Load

Changing fuel load will always be a setup and tuning problem. As fuel is burned off, handling will change as the weight in your fuel cell changes. If you do not tune with a constant fuel load, your data will be inaccurate and the results misleading. No more than a two-gallon fluctuation is acceptable. One gallon is a better mark. Remember that each gallon of gas weighs about seven pounds.

Thou Will Establish Good Crew/Driver Communication

If the crew and/or driver are not sure of the concepts of tuning and are not clear about the language, all sorts of problems can occur. Everyone on the team needs to be on the same page.

Thou Will Control Over-driving

If a driver is over-driving the track or car setup, most of the data, whether from the driver or tire temperatures, will be less than accurate. Over-driving not only abuses the tires, but also masks real handling problems.

Thou Shalt Not Make Changes Which Are Too Big

If a change is too big, it can cause handling problems that are worse than the ones you already have. On the other hand, a change too small can be difficult to detect by the driver or on the stop- watch. Big changes include altering more than two numbers on shock valving, more than 15 percent in spring or bar rate, more than two percent crossweight or more than a 1/4-inch change in ride height.

Thou Must Understand the Whole System

Understanding the whole system is very important. The key is to understand how any change affects the tire contact load and traction. Always thinking in terms of tire contact patch load and traction will help you focus on making the best change possible for the situation.

Thou Must Recognize Changing Track Conditions

Track conditions constantly change. The car may get faster during the day even though the lap times are slower, because the track may be slowing more quickly than the car is getting faster. If in doubt, return to the starting setup to see how the track has changed.

Thou Shall Measure Accurately

Recording inaccurate measurements is as bad as not keeping place. This can lead to all kinds of problems.

Thou Will Not Chase Old Tires

At some point, tires get too hard to be fast. There is a point beyond which, no matter what you do, the car will not get faster. Chasing an old set of tires is ineffective.

About the Illustrator

Ruben Cueto is an illustrator with a unique style and a diverse clientele. After graduating from Long Beach State University, he has gone on to do artwork for Forbes, Information Week, NEA Today, and the Los Angeles Times.

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Comments

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Mister Fister
Mister Fister Reader
1/6/17 10:52 a.m.

I call bullshit on the big changes.

I love making big changes to see if that's where the problem is, and then bracketing in to somewhere in between.

WildScotsRacing
WildScotsRacing Dork
1/6/17 3:28 p.m.

I think having a baseline is one of the best tuning tools there is. When things start to get stupid, and what should have been the correct adjustment doesn't have the effect you thought it would, re-setting to the known basically correct-but-untuned settings can point to the problem. This logic works for a great many things other than suspension.

Knurled
Knurled MegaDork
1/6/17 4:59 p.m.

"Don't try to tune something that binds"

AKA - Don't try to tune an RX-7. The front suspension binds by design and the rear suspension binds by design. That's why the racers back in the day basically made it so stiff that it couldn't move (a suspension that can't move, can't move badly) and adjusted handling with alignment. Or just drove around the problems.

This is why I am infuriated by Techno Toy Tuning or whatever their name is. They may know Toyotas but they certainly don't understand Mazdas. They make a lot of parts for RX-7s that either don't address any real problem, or they actively make the chassis' problems worse. They actually sell Heim-jointed rear suspension links as an upgrade, when non-compliant bushings is exactly the last thing you want in the rear suspension. Absolutely unforgivable!

Stefan
Stefan MegaDork
1/6/17 6:06 p.m.

In reply to Knurled:

I've tried to explain this to people when they attempt to "tune" whatever chassis they have.

Nothing like adding stiffer bushings to a sway bar that is essentially a cross-connected torsion bar. Or worse making this bar larger.

Its also interesting to note how many people relate body roll and responsiveness to "good handling" especially after watching professional race cars bouncing around on super stiff suspension, not realizing that much of that is due to the amount of aerodynamically induced load that is placed on the suspension and that maintaining the car's ride height is very important for under car aerodynamics.

sesto elemento
sesto elemento SuperDork
1/7/17 11:00 a.m.
Knurled wrote: "Don't try to tune something that binds" AKA - Don't try to tune an RX-7. The front suspension binds by design and the rear suspension binds by design. That's why the racers back in the day basically made it so stiff that it couldn't move (a suspension that can't move, can't move badly) and adjusted handling with alignment. Or just drove around the problems. This is why I am infuriated by Techno Toy Tuning or whatever their name is. They may know Toyotas but they certainly don't understand Mazdas. They make a lot of parts for RX-7s that either don't address any real problem, or they actively make the chassis' problems worse. They actually sell Heim-jointed rear suspension links as an *upgrade*, when non-compliant bushings is exactly the last thing you want in the rear suspension. Absolutely unforgivable!

Why wouldn't you want accurate, controlled movement in your rear suspension? Or is that sarcasm?

snailmont5oh
snailmont5oh Reader
1/7/17 11:56 a.m.
sesto elemento wrote:
Knurled wrote: "Don't try to tune something that binds" AKA - Don't try to tune an RX-7. The front suspension binds by design and the rear suspension binds by design. That's why the racers back in the day basically made it so stiff that it couldn't move (a suspension that can't move, can't move badly) and adjusted handling with alignment. Or just drove around the problems. This is why I am infuriated by Techno Toy Tuning or whatever their name is. They may know Toyotas but they certainly don't understand Mazdas. They make a lot of parts for RX-7s that either don't address any real problem, or they actively make the chassis' problems worse. They actually sell Heim-jointed rear suspension links as an *upgrade*, when non-compliant bushings is exactly the last thing you want in the rear suspension. Absolutely unforgivable!

Why wouldn't you want accurate, controlled movement in your rear suspension? Or is that sarcasm?

Assuming that this question is serious and not sarcastic:

Yes, accurate and controlled movement is important, when a system is designed to move properly. The problem occurs when a manufacturer makes compromises, usually for packaging or for cost. Many times, the link lengths or the design of the linkage keeps it from moving freely throughout the range of motion that it would move through under normal operation. The solution that is normally used is to install soft bushings, which makes the links "variable length". That's okay for getting groceries, but not good when you start to really put a load on things. People install stiff bushings to help that problem, but now the design issues show up, and you end up with two suspension rates. The first little bit of roll is controlled by the springs and dampers, but then the linkage binds, and the roll stiffness can increase by orders of magnitude. At this point, you are basically driving a different car. If you aren't expecting it (and sometimes if you are), it can cause bad things to happen from a car control standpoint.

rslifkin
rslifkin Dork
1/7/17 3:39 p.m.

When replacing any bushing, etc. with a different material or a heim joint, it's always important to look at how it moves as the suspension cycles. You want to pick the type of joint / bushing that will allow it to move as freely as possible in the directions it needs to move and as little as possible in other directions.

Binding is definitely a common issue with sway bars. The common stick-type sway bar end links with sandwich bushings at each end (shown below) bind horribly on any suspension that isn't very short travel. In the case of my Jeep, the suspension behaved drastically better after removing the binding-prone rear sway bar setup and swapping in stiffer rear springs to re-gain the lost roll stiffness. Overall handling balance was about the same, but it was more predictable and rode better too.

Tom1200
Tom1200 HalfDork
1/7/17 4:16 p.m.

The tough thing for this article it has to deal with generalities;

Newbie to mid level drivers tend to crank the rebound on dampers and use higher spring rates as it gives instant feed back rather than leaving them softer where they build more grip but have less feel. Now if the car has a big splitter and rear wing throw that out the window because maintianing optimal ride heights net more lap time than that what you would gain with suspension compliance.

@mister fister yeah sometimes making big changes will at least get you out of the woods / pointed in the right direction BUT I've raced several cars and bikes that have a narrow range.

The aspect of the article I whole heartedly agree with is write everything down and take as many notes as you can.

Knurled
Knurled MegaDork
1/7/17 5:30 p.m.
sesto elemento wrote:
Knurled wrote: "Don't try to tune something that binds" AKA - Don't try to tune an RX-7. The front suspension binds by design and the rear suspension binds by design. That's why the racers back in the day basically made it so stiff that it couldn't move (a suspension that can't move, can't move badly) and adjusted handling with alignment. Or just drove around the problems. This is why I am infuriated by Techno Toy Tuning or whatever their name is. They may know Toyotas but they certainly don't understand Mazdas. They make a lot of parts for RX-7s that either don't address any real problem, or they actively make the chassis' problems worse. They actually sell Heim-jointed rear suspension links as an *upgrade*, when non-compliant bushings is exactly the last thing you want in the rear suspension. Absolutely unforgivable!

Why wouldn't you want accurate, controlled movement in your rear suspension? Or is that sarcasm?

If you replaced all of the suspension links with Heims, the suspension will only want to move straight up and down. There are serious geometrical issues in the 4-link and compliant rubber is required if you want the suspension to articulate. This is a large reason why the cars had a habit of ripping the upper mounts off of the chassis and/or twisting the rearend housings so the pinion angle points up, if they were driven hard.

Bored one day with a stock chassis and with the springs out, I unbolted one upper link and articulated the axle. The link was something like 2" too short when drooped and 1.5" too long when compressed, supporting the axle in its center. If you don't have soft rubber bushings in the rear suspension, there will be nothing to allow that misalignment but chassis flex and rear axle twist, and the handling gets... scary. Now that I have a stock chassis again, I may make a YouTube video demonstrating this.

This is exactly my point - the parts that this company sells are not designed with the car's quirks at all, but they prey on the uninformed consumer who sees something shiny and makes sense on the surface (compliance is bad, right?) so they go for it. And that, IMO, is scamming people.

That is only one example, and the most dangerous. Most of the product they sell for the Mazdas is inherently flawed in one way or another. Sadly, all of the "traditional" aftermarket for these cars is long gone since they're too old/rare/outclassed to be viably competitive cars anymore, so all you have left is this hard-parker junk.

sesto elemento
sesto elemento SuperDork
1/7/17 7:33 p.m.

Thanks for clarifying, I wasn't familiar with the car in question's suspension design.

Knurled
Knurled MegaDork
1/7/17 7:52 p.m.

In reply to sesto elemento:

You're welcome. I may be a little overenthusiastic about it, but people selling snake oil is something that REALLY gets my goat.

And the chassis does work wonderfully once you go with a 3 link arrangement, the old E/Production method of eliminating bind. Call the 3rd link a "traction bar" (legal mod) and replace the upper links' bushings with roll bar padding (bushing material is free) and suddenly there's no more binding in the suspension and you can TUNE it, instead of stiffening everything up so much it doesn't move...

freetors
freetors New Reader
1/7/17 8:43 p.m.
Knurled wrote:
sesto elemento wrote:
Knurled wrote: "Don't try to tune something that binds" AKA - Don't try to tune an RX-7. The front suspension binds by design and the rear suspension binds by design. That's why the racers back in the day basically made it so stiff that it couldn't move (a suspension that can't move, can't move badly) and adjusted handling with alignment. Or just drove around the problems. This is why I am infuriated by Techno Toy Tuning or whatever their name is. They may know Toyotas but they certainly don't understand Mazdas. They make a lot of parts for RX-7s that either don't address any real problem, or they actively make the chassis' problems worse. They actually sell Heim-jointed rear suspension links as an *upgrade*, when non-compliant bushings is exactly the last thing you want in the rear suspension. Absolutely unforgivable!

Why wouldn't you want accurate, controlled movement in your rear suspension? Or is that sarcasm?

If you replaced all of the suspension links with Heims, the suspension will only want to move straight up and down. There are serious geometrical issues in the 4-link and compliant rubber is required if you want the suspension to articulate. This is a large reason why the cars had a habit of ripping the upper mounts off of the chassis and/or twisting the rearend housings so the pinion angle points up, if they were driven hard.

Bored one day with a stock chassis and with the springs out, I unbolted one upper link and articulated the axle. The link was something like 2" too short when drooped and 1.5" too long when compressed, supporting the axle in its center. If you don't have soft rubber bushings in the rear suspension, there will be nothing to allow that misalignment but chassis flex and rear axle twist, and the handling gets... scary. Now that I have a stock chassis again, I may make a YouTube video demonstrating this.

This is exactly my point - the parts that this company sells are not designed with the car's quirks at all, but they prey on the uninformed consumer who sees something shiny and makes sense on the surface (compliance is bad, right?) so they go for it. And that, IMO, is scamming people.

That is only one example, and the most dangerous. Most of the product they sell for the Mazdas is inherently flawed in one way or another. Sadly, all of the "traditional" aftermarket for these cars is long gone since they're too old/rare/outclassed to be viably competitive cars anymore, so all you have left is this hard-parker junk.

The things you say about the RX7 suspension are interesting to me. From what I gather in your posts they are a basically a 4-link on a live axle, is that correct? I've always understood that normal triangulated 4-links don't have any bind at all when using rod-ends and will move freely in roll and bump to the limits of suspension or rod end travel. I have even modeled this on solidworks and the axle moves freely. It is also my understanding that parallel four links like drag cars are guaranteed to bind in roll. It is my understanding that introducing normal bushings like an OEM would are what actually introduce binding, ala the mustang "quadrabind". Although these are my beliefs about four links, I still have a piece of reservation in me that accepts there could be more special cases from link length/angles/etc that turns a four link into a useless bind monster. This is a special interest to me since I would someday like to replace the leaf springs on my MGB with a four link (Satchell) someday in the future.

Do you have a good picture or diagram of how these RX7s are laid out?

snailmont5oh
snailmont5oh Reader
1/7/17 9:16 p.m.

All of my experience is in the Ford Fox chassis, with its extremely crappy triangulated 4-link rear suspension. And, while I never actually tried it myself, I'm given to understand that putting rod ends on both ends of all the arms will cause a bind in roll because the plan view rod lengths are not the same. I switched to a 3-link/Watts setup (with all rod ends, except for the rear lower control arm bushings-they're Delrin) to get around that problem. The rear seems to not have roll bind issues.

freetors
freetors New Reader
1/9/17 5:39 p.m.
snailmont5oh wrote: All of my experience is in the Ford Fox chassis, with its extremely crappy triangulated 4-link rear suspension. And, while I never actually tried it myself, I'm given to understand that putting rod ends on both ends of all the arms will cause a bind in roll because the plan view rod lengths are not the same. I switched to a 3-link/Watts setup (with all rod ends, except for the rear lower control arm bushings-they're Delrin) to get around that problem. The rear seems to not have roll bind issues.

See I've always been led to believe that the bind with the rubber bushed 4-link was caused by the fact that rubber bushings really only like to flex in one direction, twisting. While a single rubber bushing on its own can generally accommodate multidirectional motion, an entire collection of rubber bushings as used in a 4-link are all kind of fighting each other as the suspension moves.

Are you saying that it binds because the upper and lower pairs of links are not the same length, or all links are different lengths. Either way it should still work in theory.

Also, what kind of bushings does it use OEM? Are they bonded "metalastic" or free spinning? I can definitely see how someone might confuse suspension bind for bonded bushings winding up.

Knurled
Knurled MegaDork
1/10/17 8:34 a.m.
freetors wrote: Do you have a good picture or diagram of how these RX7s are laid out?

Not offhand, and I don't do the GIS/hotlink game at work. It's a semi-parallel 4 link, the lower links are parallel to each other, the uppers are not parallel to each other in plan view, maybe 2" further out at the rear. Uppers and lowers are parallel at ride height in side view. The uppers are also almost half the length of the lowers.

There is also a Watts link for lateral location, and its mounting is somewhat too high for good handling. (This is why properly engineered lowering springs don't go very low in the rear, and are generally 10-20% softer than stock. Roll stiffness goes up greatly as suspension compresses, the opposite of the front)

freetors
freetors New Reader
1/10/17 9:07 p.m.
Knurled wrote:
freetors wrote: Do you have a good picture or diagram of how these RX7s are laid out?

Not offhand, and I don't do the GIS/hotlink game at work. It's a semi-parallel 4 link, the lower links are parallel to each other, the uppers are not parallel to each other in plan view, maybe 2" further out at the rear. Uppers and lowers are parallel at ride height in side view. The uppers are also almost half the length of the lowers.

There is also a Watts link for lateral location, and its mounting is somewhat too high for good handling. (This is why properly engineered lowering springs don't go very low in the rear, and are generally 10-20% softer than stock. Roll stiffness goes up greatly as suspension compresses, the opposite of the front)

It sounds like they intended to have have a triangulated 4-link, ran into packaging constraints, and then gave it some half assed geometry to make it fit. Then they must have figured out the axle was poorly constrained side to side and the forces imposed on the angled links were huge because of not enough angle between them. To fix that they put on a half assed watts link which overconstrained the whole darn thing...

Huckleberry
Huckleberry MegaDork
1/10/17 9:25 p.m.

24 seems like a lot of deadly sins. Even fictional biblical types knew to keep that E36 M3 to 10 or less. And 7 of those were total bullshyt.

Imagine I wrote an article for Vogue called "The 2247 Ways You Are berkeleying Wrong". Technically, it could be correct but there is probably a common theme the author missed that could maybe have a root cause, no?

You guys used to be a step above click-bait or, if you weren't - it wasn't retarded. WTF?

Marjorie Suddard
Marjorie Suddard General Manager
1/12/17 2:41 p.m.

Uh, stow your anger there, Huck. The article is from 1999--before clickbait was even invented.

Margie

4cylndrfury
4cylndrfury MegaDork
1/12/17 3:32 p.m.

lol...by '99, we had hardly figured out how to make interweb pr0n work. What we've learned since then will shock you!

snailmont5oh
snailmont5oh Reader
1/12/17 4:23 p.m.
freetors wrote: See I've always been led to believe that the bind with the rubber bushed 4-link was caused by the fact that rubber bushings really only like to flex in one direction, twisting. While a single rubber bushing on its own can generally accommodate multidirectional motion, an entire collection of rubber bushings as used in a 4-link are all kind of fighting each other as the suspension moves. Are you saying that it binds because the upper and lower pairs of links are not the same length, or all links are different lengths. Either way it should still work in theory. Also, what kind of bushings does it use OEM? Are they bonded "metalastic" or free spinning? I can definitely see how someone might confuse suspension bind for bonded bushings winding up.

The OEM bushings were bonded.

Here's the sequence of events that took place in my car, a Fairmont:

Original suspension: squatty, floppy. Crap.

Step 1: Install lowering springs. Lower, floppy. Crap.

Step 2: Install "polygraphite" bushings on rear in stock arms (because they don't need lubed all the time like regular polyurethane. Result: Initial turn-in understeer, then snap oversteer.

Step 3: Replace rear lower control arms with arms that have a rod end at the front, and a solid Delrin bushing at the back (supposed to keep the axle side-to-side under control). Result: not as much wheel hop, still snaps loose on cornering.

Step 4: Install adjustable length rear upper control arms with rod ends on the body side and poly bushings on the axle side. Result: oil-canning of the rear seat floor depending on acceleration load or braking! Wicked loose.

Step 5: Remove upper control arms, replace with forward-facing single arm with rod ends. Install Watts link with rod ends. Result: hoses poorly driven C-4 Vettes, keeps up with well driven C-4s, average C-5s and Spec Miatas. On 225-50 tires, exhibits throttle-off oversteer that settles, then plants, when throttle is increased, until the tires spin.

So, the short version of the story is that roll bind isn't bad with soft factory bushings, is horrible the stiffer you make the stock setup, and goes away if you fix the design. I think that the factory bushings deflect in length and twisting.

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