Video time!

Here at Griggs Racing we understand your need for speed and heroic handling to achieve victory in the realm of competition motorsports.We understand it because we enjoy that feeling as well, so much so that we ourselves regularly give rides in our own cars to share the joy we have. We guess you could say we like to give back to our brothers and sisters in speed. So to give a taste of how our fully engineered and tested parts preform in the real world we submit this video for your viewing pleasure. (we suggest that this run be watched in full screen with good head phones or speakers)

This vehicle is a convertible which is owned by John Griggs and has a full GR40 kit including SLA, torque arm and watts linkage not to mention a little more oomph from the motor. the road is a CLOSED COURSE WITH SAFETY CREW AND A PROFESSIONAL DRIVER at the Virgina city hill climb a couple of years ago for the Ferrari club. John won... in his convertible mustang... with all due respect Mr. Enzo.  

Disclaimer! Do not attempt on public roads, without safety equipment, and a properly set up car.

TorqueArm Tech

Quick Facts about Torque Arm Kits

• Increases rear traction (forward bite)
• Decreases stopping distance significantly
• Engineered to maximize ground clearance
• Can be used without other rear suspension modifications
• Presets pinion angle
• Longer U-joint life
• The most driver friendly way to hook up power.

When used with a Panhard Bar or Watts Link the TorqueArm will substantially improve overall controllability of the vehicle regardless of power output because it:

• Allows for the removal of the rear upper control arms and quad-shocks on cars so equipped.
• Decreases snap-oversteer
• Corrects rear roll center location
• Decreases rear bind
• Inspires driver confidence

The TorqueArm when coupled with a Panhard bar or Watts link is the best in terms consistency of control and improved braking due to is constant and consistent tire loading regardless of ride height changes as the car encounters surface irregularities, cresting hills, etc. Compared to 3 link, 4 link, 5 link or IRS designs, the improvement in car control under power offsets any arguable merits of the other systems in a high powered rear drive vehicle that is without aid of high down-force aerodynamic devices. For this reason the same basic geometry is used on most Sprint Cars, Supermodifieds, Late Model Stock Cars, and other professional race cars around the world where rules allow.  

TorqueArm geometry would be used in more forms of road racing were it not for rules restrictions in various organizations such as TransAm, and NASCAR, or where aerodynamic packaging is the priority of design as in Indy cars and Formula 1.   

Griggs Racing was the innovator of TorqueArm design application to the Mustang in 1979, and has produced many versions and improvements since its inception.  Currently there is one basic off the shelf versions of Griggs Racing TorqueArms; Severe Duty. The severe Duty TorqueArm is intended for most applications; from street use on cars with stock engines and transmissions to cars with over 500 RWHP and sticky tires that are drag raced, brutally road raced, autocrossed, or similarly abused. The structure of the severe duty TorqueArm consists of the appropriate appendages for the model and axle used, attached securely to the severe Duty arm.

These are not hard and fast rules and when in doubt you should contact us for specific recommendations for your application.  The Severe Duty TorqueArm is the most popular and Bruce Griggs races his AIX cars on the severe Duty TorqueArm and his cars exceed the power level described above and still win while being completely durable race after race. If absolute durability regardless of abuse is the priority, you should choose the Severe Duty unit which is the most popular or contact engineering@griggsracing.com for a specific recommendation for your application.

FAQ's

We have gone to great lengths to develop Mustang chassis components that meet or exceed the output of modified power plants. In the following post we will outline those components and give you a blueprint for turning your Mustang into a world class sports car.


The Mustang’s chassis was designed in the mid-1970’s, during an oil crisis, to be an inexpensive sedan or station wagon (Fairmont/Zephyr) and not a sports car. It had to be light, cheap and easy to build. The unibody chassis, suspended by McPherson struts (state-of-the-art at the time) and a solid axle, did a pretty good job as a family truckster (cheap!) When the oil crunch eased and Ford stated to think about sports cars again, the only platform they had was the Fox. The new body style Mustang, born in 1979, was built out of revised station wagon parts. The Mustang was soldiered on, to the present day, with the same simple underpinnings.


With the notable exception of dangerously unpredictable handling at the limit (fish-tailing), the current chassis works fairly well. After continual tweaking by Ford, the Mustang feels pretty racy to the average driver. But you wouldn't be reading this if you were the average driver. You may have discovered that Mustang cannot be driven near the limit. If you follow the steps laid out in this catalog, you can plan on owning a car that will pull over 1.0 G on a skid pad and outrun ZR-1s or Vipers in the Slalom without giving you white knuckles. By focusing on geometry and load management, we have developed a blueprint for building the perfect Mustang.


If you think this sounds an awful lot like Math and Physics, bear with us. Making a car perform well is an exercise in managing physical forces. The better you understand these forces, the easier it will be to build your pony-car without wasted time and money. Throughout this catalog, you'll see constant references to geometry and physics and information about roll centers, camber curves, anti-dive and anti-squat. Detailed explanations of all these terms are beyond the scope of this catalog, but where necessary, we have included engineering drawings to help illustrate why our changes are so effective. If you have more detailed questions about geometry changes for your application, please contact us. Our knowledgeable staff is always willing to explain the finer points to a valued customer. To save you the phone call for simpler stuff, we have answered some of the most common questions here.




What should I do first?


If you haven’t made any of the popular modifications to the suspension of your car you are actually ahead of the game. Lots of our competitors sell a set of shocks and stiff springs and sends a guy down the road, even though this can actually hurt performance. The first thing you should really do is to decide what your priorities are for the car: handling, drag strip launches or spirited street driving. Then, before you buy anything, read and understand the technical info in this blog. We have provided a lot of detail because if you understand the flaws of the stock Mustang, you'll probably wind up a customer. If you are careful about defining your goals, you can be sure that your project goes smoothly without wasted dollars on components that require replacement later on. If you can afford to build your entire chassis in one step, you should. You will save money on labor and have the best handling Mustang possible.


Your stuff sounds pretty racy. I just want my car to work better on the street do I really need all this stuff?


90% of our customers are streetcar owners. Our World Challenge and Drag Race customers are a small minority of our total sales. They buy our parts because we engineer our parts to do the best possible job of increasing grip within the confines of the production body and frame.
 
Since we are so focused on fixing geometry, our cars can be run with soft springs, shocks and sway bars for better performance on rough surfaces with more comfort.


How does the GR-40 Kit affect ride quality? One of my friends already bought springs and shocks and his car rides like a tractor.


Believe it or not, GR-40 cars ride about like a production Mustang. Our focus on high quality shocks, geometric perfection and suspension travel help us deliver ride-quality as good as stock. Our suspensions do, however, reduce the amount of insulation and compliance in the car, to improve its responsiveness. Your car will be a bit noisier over broken pavement or really bumpy surfaces, but in the words of Muscle Mustangs Technical Editor, John Hunkins, (who drove one of our cars from Texas to New Jersey during an east coast tropical storm), “The Griggs Racing approach is to restructure the basic geometry of the suspension from the ground up. By doing so ride harshness, jounce and dartiness at speed are practically eliminated....the GR-40 Mustang feels essentially stock in its ride quality....Other suspension systems have had us begging for mercy but the GR-40 provided a compliant comfortable ride.” (MM&FF, February 1996) We couldn't have said it better.


What about exhaust clearance? How do you guys get all that stuff to fit?


Exhaust clearance actually depends a lot on the car. Ford has very broad production tolerances for things like exhaust hangers and crossover tube location so some cars are easy to fit even with big tailpipes, other cars cause some problems. The problems, however, are really quite simple to resolve and each of our installers has the capacity to make the necessary changes.


I have heard TorqueArms create vibrations. Is this really a problem? If so, can you guys fix it?


TorqueArms do not create vibrations, but they may transmit existing vibrations. 98% of the vibration problem we encounter are the result of poor balance factors within with the original drive shaft. The installation of a high quality lightweight unit (which we offer) will usually sort things out.
 
The remaining problems are generally the result of a well-meaning installer trying to shim the TorqueArm to create a high-performance pinion angle. There is no such thing! The TorqueArm installation sets the pinion angle, and prevents it from changing under load. If the TorqueArm is installed, as delivered without modification, a car in good condition should not vibrate. However, variations between individual cars may require adjustment to driveline angles–which is a simple procedure.


My street car is supercharged, develops 500 ft./lbs. of torque and traction is terrible. Will the TorqueArm really fix it?
If anybody tells you they can prevent a street tire from spinning on a car with that kind of power, look elsewhere for the truth. It just isn't possible. We can give you the best possible improvement in forward bite that does not compromise the street ability of the car. Mark Ray Motorsport of Charlotte, NC, has a street strip car, which makes 495 ft./lbs. from its Vortech-boosted engine, has run 1.53 60 ft. times on its 8 inch slicks. This kind of time is typical from cars with larger 10 inch slicks! 
Moreover, the car launches and runs perfectly straight and is totally consistent. Our testing with radial street tires show consistent reductions of .2 to .3 seconds over any other rear suspension system.
 
You'll still have some wheel spin, but your car will be predictable and easy to drive.


I have heard all about the GR-40 system. I think I understand it but I have heard you have to do the whole system at once if you want to avoid understeer problems. I can’t afford to spend that kind of money in one chunk. Can the system be done in stages?


Modifications can be done one at a time or in stages. Please call us if you wish to discuss a customized kit. Each additional stage will increase your car’s performance even more than the last, and the total combination gives an unbelievable level of grip and balance. 

Call for details on our three-stage method. Either way, with a little planning you can get exactly what you want, save money and keep your car fun to drive at every step of the way.

The GR40 Suspension System

Why the stock Mustang suspension doesn't work and how Griggs Racing fixes it

In the beginning Fox bodied and SN-95 Mustangs feel so good. There's the easy V-8 power, the light steering and quick handling. Compared to other street cars the Mustang is ready and nimble, a joy to drive.
But for the ever-learning enthusiast there comes a day when that magic Mustang sunshine dims. Often it's because another, modified Mustang showed you its taillights, or perhaps you took your Mustang to the drag strip or slalom. You begin to notice things, like how the rear end seems so inconsistent. At the strip the car never seems to launch the same, and when you get what feels like that rare perfect launch, the tires blow off just as soon as the car gets rolling. Your front tires grind off their outer front edges long before the rest of the tread shows any real wear. Start whipping around freeway ramps faster and your Mustang begins to feel unsure; you find yourself waiting for the rear end to snap out unexpectedly. Ultimately, your Mustang feels more over-powered and less capable than simply fast.

All products are abused on the track prior to making it to the street.

Those first moments of insecurity about your Mustang's white-knuckled handling at the limit, or its fickle appetite for traction at the strip are not your imagination hitting the rev limiter. Those are the first realizations the Mustang chassis is far from delivering the confident handling its high-output powertrain deserves.

At Griggs Racing we've dissected the Mustang chassis and suspension to identify its shortcomings and engineer cures. Our fix for the Fox and SN95 chassis Mustang is no quick medicine; it's a fundamental change in the suspension geometry that yields a fundamental handling improvement. Our suspension is also adaptable to a huge range of Mustang performance. From the street, to the strip, road course or slalom circuit, our re-engineered GR-40 suspension system provides the stable, consistent, responsive platform you need. It's only shortcoming is it has to be experienced to be believed.

So what are the issues working against you in the Fox and SN95 chassis Mustang? For starters, the unibody structure is lightly built, with insufficient rigidity. High torque and cornering loads deform the structure, causing the suspension to lose precision, doubly so with convertibles. Welding in reinforcing structure is the cure.

Knowing where to reinforce the structure is important, as indiscriminately adding braces wastes money and adds weight without gaining meaningful increases in rigidity. By twisting a Mustang unibody on a frame table, we learned the main problem is in the middle of the car. Ford counts heavily on the rocker panels as the primary structure between the firewall and rear wheelhouses, especially with the '79-'04 cars. This lets the front and rear axle forces to twist the car far too easily.

Naturally, a full roll cage will cure this, but that solution is cumbersome and expensive on street cars. More practically, a dual-plane brace to provide triangulation of the floor pan is required; we do this with our Full Frame Kit.

The mid-car twist also explains why we don't offer g-load and strut tower braces. By strengthening one end of the car they actually increase the mid-car twist.

An even larger concern is found in the rear suspension. Ford uses a 4-link design, but with the upper two control arms angled heavily outward. This means the lower and upper rear control arms are not parallel, so as the suspension moves the upper arms are twisted in their bushings. During performance driving this quickly leads to a near total binding of the rear suspension, called roll bind. With the axle bound, it acts like a giant anti-sway bar, causing the rear roll stiffness to skyrocket and the overloaded rear tires to loose traction and spin. This is why the rear end snaps into uncontrollable fishtailing when cornering, and it is also why the rear tires break loose at the drag strip once the body starts rising from the initial power hit.

2005+ Griggs Racing TorqueArm and Panhard Bar

Ford addresses the roll bind by fitting the upper arms with very soft bushings, a sloppy fix, to say the least. Our cure is to fit a torque arm and either a Panhard bar or Watts link to provide the necessary axle location, then remove the stock upper arms. Roll bind is then impossible, and the tires freely follow the pavement.

You may have noticed we use two locating devices, the Torque-Arm, and either a Panhard Bar or Watts link, to do the job Ford uses just the upper control arms for. This is to separate control of the fore-and-aft engine and braking loads from the lateral suspension loads. More precise suspension control is then possible.

GR40 Watts Link

Additionally, the rear roll center is now defined by the Panhard bar or Watts link instead of the upper control arm angle as Ford had it. Stock the Mustang's rear roll center is far too high, which overloads the outside rear tire and causes oversteer. By lowering the rear roll center with the Panhard bar or Watts link we get the rear tires to carry more of the load so the rear end will stick longer.
More compromised geometry is found in the front suspension, a point made abundantly clear when driving a car with the rear suspension fixed and the front suspension stock. Ford built the Mustang with generous steering axis (king pin) inclination, which requires equal amounts of caster to keep the tires flat to the ground when turned. Unfortunately, Ford gave the Mustang only minimal caster, a condition we reverse with caster plates and redesigned K-member.

GR40 SLA System

Also at the front, Ford's tall ride height comes into play. Lowering the entire car benefits the center of gravity, but causes the front suspension geometry to lower the front roll center well below ground level. Combined with the tall rear roll center, this results in a roll couple (the relationship between the front and rear roll stiffness, of which roll centers play a part), to heavily load the front tires. Imagine trying to drive your Mustang around a corner with the front end squashed below ground level and the rear end raised a yard or so in the air; obviously the car would be trying to turn using just its front tires. That's about what the stock suspension tries to do. Lowering the rear roll center with the Panhard bar or Watts link helps this condition, of course, but we also raise the front roll center, accomplished by relocating the points where the front suspension attaches to the chassis. Moving the suspension pickup points is done by redesigning the K-member, which is the crossmember the front suspension attaches to. Redesigning the K-member also allows us to add more anti-dive to the front suspension help correct the lack of caster.

Ackermann is also a concern on stock Mustangs. Ackermann is the steering geometry that steers the inside front tire more than the outside tire, a necessary condition as the inside tire follows a smaller diameter turn radius. With the Mustang, Ford actually ended up providing reverse Ackermann, meaning the front tires toe-in slightly when turned. We also cure this with our K-member.
So, did Ford really goof terribly on the Mustang? Well, not by accident. By selling a relatively high-powered, inexpensive car into the youth market, Ford wanted a car that signed off in the handling department so soon that only the fool-hardy would get in high-speed trouble with it. In short, Ford designed the Mustang for inexpert drivers.

Unfortunately, dumbing-down the chassis is a common manufacturing tactic in the affordable performance car market. That is why it is so difficult to describe the incredible improvement a complete chassis re-engineering provides; few enthusiasts have experienced the huge thrill of piloting a powerful V-8 machine that starts, sticks and stops as well as it's engine goes. Once you've wheeled a GR40 car, however, you'll be one of the few.