If you’re a Triumph TR6 owner, you know that the rear suspension is one of the car’s weak points. The original setup is prone to roll steer, which can make the car difficult to control when cornering. There are a number of ways to improve the TR6’s rear suspension, but one of the most effective is to install a Watts linkage.
A Watts linkage is a type of suspension that uses a single central pivot point to connect the axle to the chassis. This design eliminates the roll steer that is common in the TR6’s original suspension. As a result, the car is much more stable and predictable when cornering. Installing a Watts linkage is not a difficult job, and it can be done in a few hours with basic tools. However, it is important to note that a Watts linkage will not completely eliminate roll steer. The car will still have some roll steer, but it will be much less than with the original suspension.
In addition to installing a Watts linkage, there are a number of other things that you can do to improve the TR6’s rear suspension. These include:
Understanding Roll Steer and Its Impact
Roll steer is a phenomenon that occurs when a vehicle’s rear suspension experiences lateral forces, such as those encountered during cornering. As the vehicle rolls, the rear wheels move in relation to the body, causing the vehicle to either oversteer or understeer. This can have a significant impact on the vehicle’s handling and stability.
Oversteer
Oversteer occurs when the rear wheels move out of phase with the front wheels, causing the vehicle to rotate more than intended. This can be dangerous, as it can lead to the vehicle spinning out of control.
Understeer
Understeer occurs when the rear wheels move in phase with the front wheels, causing the vehicle to turn less than intended. This can also be problematic, as it can make the vehicle difficult to control and can lead to accidents.
Roll steer is influenced by a number of factors, including the vehicle’s suspension design, the tire compound, and the road conditions. By understanding the impact of roll steer, drivers can make adjustments to their driving style and vehicle setup to improve the handling and stability of their vehicles.
| Factor | Effect on Roll Steer |
|---|---|
| Suspension design | Controls the amount and direction of wheel movement |
| Tire compound | Affects the grip level and stiffness of the tire |
| Road conditions | Can alter the grip level and surface characteristics |
Factors Influencing Roll Steer in the TR6
What is Roll Steer?
Roll steer refers to the change in the toe-in or toe-out of a vehicle’s wheels as the vehicle rolls from side to side. In the case of the Triumph TR6, roll steer is caused primarily by the geometry of the rear suspension.
Geometry-Related Factors
The primary geometric factor influencing roll steer in the TR6 is the camber angle of the rear wheels. Camber angle refers to the inward or outward tilt of the wheels when viewed from the front or rear of the vehicle. In the TR6, negative camber is desirable, as it helps to keep the tires planted firmly on the ground during cornering. However, too much negative camber can lead to increased roll steer, as the wheels will toe-in more as the suspension compresses.
Other Factors
In addition to camber angle, several other geometric factors can affect roll steer in the TR6. These include:
| Factor | Effect |
|---|---|
| Toe-in | Positive toe-in can reduce roll steer, but it can also lead to increased tire wear. |
| Ride height | Lower ride heights can increase roll steer, as the suspension will have less travel before the wheels begin to toe-in. |
| Spring rates | Stiffer springs can reduce roll steer, as they will resist the suspension from compressing as much. |
| Anti-roll bar | An anti-roll bar can reduce roll steer by preventing the suspension from compressing on one side of the vehicle. |
Tuning the TR6 Rear Suspension for Reduced Roll Steer
Adjusting Toe-In
Roll steer is influenced by the toe-in of the rear wheels. Toe-in refers to the angle at which the front of the tires point inward relative to the rear. Increasing toe-in typically reduces roll steer, but excessive toe-in can lead to premature tire wear. The recommended toe-in setting for a TR6 is 0.06 to 0.12 degrees, or approximately 1/16 to 1/8 inch of toe-in per wheel.
Installing Adjustable Panhard Rod
A Panhard rod is a suspension component that connects the rear axle to the chassis. By installing an adjustable Panhard rod, you can fine-tune the lateral position of the rear axle, which affects roll steer. Moving the axle forward slightly can reduce roll steer, while moving it backward can increase roll steer. Start by adjusting the Panhard rod to center the rear axle in the wheel well, then make small adjustments as needed to minimize roll steer.
Modifying Roll Center Height
The roll center is the imaginary point around which the vehicle rotates during cornering. Modifying the roll center height can significantly impact roll steer. Lowering the roll center height reduces roll steer, while raising it increases roll steer. One method of modifying the roll center height is to use different offset lower control arms. Lower control arms with a lower offset will lower the roll center height, while arms with a higher offset will raise it.
| Control Arm Offset | Roll Center Height |
|---|---|
| Lower | Lower |
| Higher | Higher |
It’s important to note that modifying the roll center height can also affect other suspension characteristics, such as camber gain and suspension stiffness. Therefore, it’s recommended to consult with a suspension specialist before making any significant changes to the roll center height.
Adjusting Spring Rates and Dampers
Adjusting the spring rates and dampers is another crucial aspect of improving roll steer. Stiffer springs will reduce body roll, thereby reducing the amount of roll steer. However, it’s important to find the right balance as excessively stiff springs can adversely affect ride comfort and handling.
Spring Rates
Spring rates are measured in pounds per inch (lb/in) and indicate the force required to compress the spring by one inch. Higher spring rates provide more resistance to compression, reducing body roll. When adjusting spring rates, it’s crucial to consider the vehicle’s weight, suspension geometry, and desired handling characteristics.
Dampers
Dampers, also known as shock absorbers, control the rebound and compression of the springs. They help dissipate energy, preventing excessive bouncing and oscillation. Adjustable dampers allow you fine-tune the damping force, optimizing the balance between handling and ride comfort.
Roll Stiffness and Oversteer
Adjusting spring rates and dampers can significantly impact roll stiffness, which is a measure of the vehicle’s resistance to body roll. Increasing roll stiffness can improve cornering performance, but it can also lead to oversteer, where the rear wheels lose traction during cornering.
| Spring Rate (lb/in) | Roll Stiffness (ft-lbs/deg) |
|---|---|
| 250 | 200 |
| 300 | 240 |
| 350 | 280 |
Optimizing Anti-Roll Bar and Suspension Geometry
Anti-Roll Bar Optimization
The thickness and diameter of the anti-roll bar influence the roll steer behavior. A thicker or larger diameter bar increases roll stiffness, reducing roll steer. However, excessively stiff bars can compromise ride quality and lateral grip.
Camber and Castor Adjustments
Camber refers to the angle of the wheels parallel to the ground. Increasing negative camber (tilting the top of the tire inwards) increases lateral grip but may induce roll oversteer. Castor, the angle of the steering axis, affects the self-centering tendency of the steering. Adjusting castor can influence the stability and responsiveness of the suspension.
Ride Height Adjustments
Adjusting the ride height modifies the wheelbase, ground clearance, and suspension geometry. Lowering the ride height generally reduces body roll and improves cornering grip, but it can also increase the risk of bottoming out.
Toe and Toe-In Adjustments
Toe refers to the alignment of the wheels relative to each other. Toe-in (when the front of the wheels point inwards) increases stability and turn-in response but can lead to increased tire wear. Toe-out (when the front of the wheels point outwards) improves traction but sacrifices stability.
Compression and Rebound Damping Adjustments
Compression damping controls the rate at which the suspension compresses, while rebound damping regulates the speed at which it extends. Adjusting these settings can significantly affect roll steer behavior. Increased compression damping reduces body roll, while increased rebound damping enhances stability and recovery from cornering.
| Adjustment | Effect on Roll Steer |
|---|---|
| Thicker Anti-Roll Bar | Reduces Roll Steer |
| Negative Camber | Increases Lateral Grip, Reduces Roll Steer |
| Increased Castor | Improves Stability, Neutralizes Roll Steer |
| Lowered Ride Height | Reduces Body Roll, Neutralizes Roll Steer |
| Increased Compression Damping | Reduces Body Roll, Neutralizes Roll Steer |
| Increased Rebound Damping | Improves Stability, Neutralizes Roll Steer |
Installing a Panhard Rod or Watt’s Linkage
Both a Panhard rod and a Watt’s linkage are effective solutions for improving the TR6 rear suspension roll steer. Here’s an overview of each option:
Panhard Rod
A Panhard rod is a simple and effective solution for eliminating roll steer. It consists of a rod that connects the axle to the chassis and is mounted parallel to the vehicle’s longitudinal axis. As the suspension compresses or rebounds, the Panhard rod prevents the axle from shifting laterally, maintaining proper wheel alignment.
Watt’s Linkage
A Watt’s linkage is a more complex but also more effective solution for roll steer. It consists of two parallel rods that connect the axle to the chassis at two different points. As the suspension compresses or rebounds, the Watt’s linkage allows the axle to move vertically while preventing lateral movement. This results in even more precise wheel alignment than a Panhard rod.
Comparison of Panhard Rod and Watt’s Linkage
The following table summarizes the key differences between Panhard rods and Watt’s linkages:
| Feature | Panhard Rod | Watt’s Linkage |
|---|---|---|
| Complexity | Simple | Complex |
| Effectiveness | Effective | More effective |
| Cost | Less expensive | More expensive |
| Installation | Easier | More difficult |
Effects of Rear Toe Settings on Roll Steer
Rear toe settings significantly impact roll steer characteristics. Here’s a more detailed explanation:
Toe-In
Toe-in (positive toe) reduces roll steer in most cases. This is because it creates a greater distance between the outside tire’s contact patch and the pivot axis during roll, reducing the effect of steering on the outside rear wheel. Toe-in is often used to counteract the “toe-out on roll” inherent in most suspension designs.
Toe-Out
Toe-out (negative toe) increases roll steer. In this case, the distance between the outside tire’s contact patch and the pivot axis during roll is reduced, amplifying the effect of steering on the outside rear wheel. Toe-out can be useful in situations where additional roll steer is desired, such as reducing understeer or improving cornering stability.
Rear Toe-In/Toe-Out Balance
The optimal rear toe settings depend on the vehicle’s specific characteristics and the desired handling balance. Balancing the rear toe-in and toe-out values can fine-tune roll steer, allowing for adjustments to understeer/oversteer tendencies and optimizing cornering performance.
| Toe Setting | Effect on Roll Steer |
|---|---|
| Toe-In | Reduces roll steer |
| Toe-Out | Increases roll steer |
Maintaining Proper Wheel Alignment
Proper wheel alignment is crucial for a well-handling Triumph TR6. It ensures that the wheels are perpendicular to the ground and parallel to each other, reducing tire wear and improving handling and stability. Adjusting Toe: Toe refers to the inward or outward angle of the wheels when viewed from above. Correct toe settings vary depending on the specific TR6 model and tire size, but typically fall within a range of 0 to 0.25 degrees of toe-in. Front-end alignment shops typically use a laser or electronic equipment to set toe accurately.
Adjusting Camber: Camber measures the inward or outward tilt of the wheels when viewed from the front or rear. Ideal camber settings for the TR6 vary slightly depending on the model and desired handling characteristics, but generally range from negative 0.5 degrees to negative 1.5 degrees. Negative camber helps maintain tire contact with the road during cornering and improves responsiveness.
Adjusting Caster: Caster is the angle between the steering axis and a vertical line drawn through the center of the wheel. While not as critical as toe and camber, caster settings slightly influence handling and stability. Adjusting caster is often performed to compensate for other suspension modifications or to fine-tune the vehicle’s behavior.
| Alignment Parameter | Range |
|---|---|
| Toe | 0 to 0.25 degrees toe-in |
| Camber | -0.5 to -1.5 degrees negative camber |
| Caster | Varies, typically within 0 to 2 degrees positive caster |
Regular wheel alignment checks and adjustments are recommended to maintain optimal handling and tire life for your Triumph TR6. It’s important to note that alignment specifications may vary slightly between different TR6 models and years. Refer to your vehicle’s service manual or consult with a qualified alignment technician for the specific alignment parameters applicable to your TR6.
Considerations for Street Versus Track Applications
The primary difference between street and track applications lies in the level of performance required. On the street, komfort is paramount. On the track, handling is king. This difference drives the following considerations:
Street Applications
- Softer Springs: Provide a more comfortable ride on uneven road surfaces.
- Less Roll Stiffness: Allows for more body roll in corners, reducing discomfort.
- Lower Ride Height: Slightly lower than stock for improved handling without compromising ground clearance.
Track Applications
- Stiffer Springs: Enhance handling by reducing body roll and providing more precise turn-in.
- More Roll Stiffness: Limits body roll, allowing for faster cornering speeds.
- Lower Ride Height: Significantly lower than stock for improved aerodynamics and stability.
9. Roll Center Adjustment
The roll center is the point at which the suspension forces act on the chassis. Adjusting the roll center can significantly alter the roll steer characteristics of the TR6. Here’s a deeper dive into the impact of roll center adjustment:
Raising the Roll Center
- Decreases Roll Steer Effect: Reduces the amount of rear-end “tuck” under braking, improving stability.
- Decreases Rear Grip: Slightly reduces grip by raising the weight distribution at the rear of the car.
Lowering the Roll Center
- Increases Roll Steer Effect: Exaggerates the rear-end “tuck” under braking, providing more rotation.
- Increases Rear Grip: Enhances grip by increasing the weight distribution at the rear of the car.
| Adjustment | Roll Steer Effect | Rear Grip |
|---|---|---|
| Raise Roll Center | Decrease | Decrease |
| Lower Roll Center | Increase | Increase |
Practical Tips for DIY Suspension Modifications
1. Inspect and Replace Worn Components
Start by thoroughly inspecting all the suspension components for wear and damage. Worn-out bushings, ball joints, and shock absorbers can contribute to excessive roll steer. Replace any worn or damaged components to improve suspension performance.
2. Adjust Toe-in
Proper toe-in settings play a crucial role in minimizing roll steer. Have the alignment checked and adjusted by a qualified mechanic to ensure it’s within the recommended specifications.
3. Enhance Lateral Stability
Installing a sway bar can significantly reduce body lean and improve handling. Choose a sway bar with appropriate stiffness to reduce roll steer and enhance stability.
4. Lower the Vehicle
Lowering the vehicle’s ride height lowers the center of gravity, which helps reduce roll and improves suspension efficiency. However, it’s crucial to ensure that there’s sufficient clearance between the tires and the body.
5. Install Stiffer Springs
Stiffer springs can reduce body roll and improve suspension responsiveness. Consider upgrading to stiffer springs to minimize roll steer and enhance handling capabilities.
6. Upgrade Shock Absorbers
Installing high-performance shock absorbers with adjustable damping can help control suspension movement and reduce roll steer. Choose shock absorbers that are designed specifically for the TR6 rear suspension.
7. Modify Panhard Rod
A modified or fabricated Panhard rod can help to eliminate lateral axle movement, which can contribute to roll steer. Consider installing an adjustable Panhard rod to fine-tune the suspension geometry.
8. Add Caster to Front Wheels
Increasing the caster angle of the front wheels can help improve stability and reduce roll steer. Adjust the castor settings by installing custom camber plates or adjustable control arms.
9. Use Wider Tires
Wider tires provide more contact surface area, increasing grip and reducing roll steer. Consider upgrading to wider tires to improve handling and cornering capabilities.
10. Fine-tune Suspension Settings
Once you’ve implemented the above modifications, it’s crucial to fine-tune the suspension settings for optimal performance. This involves adjusting the sway bar, shock absorber damping, and alignment to find the best balance between handling and stability. A professional mechanic or racing specialist can assist you with this process to maximize the TR6’s rear suspension performance.
How To Improve The TR6 Rear Suspension Roll Steer
Roll steer is a phenomenon that occurs when the rear wheels of a vehicle steer in a different direction than the front wheels, typically when the vehicle is cornering. This can be caused by several factors, including the design of the suspension, the tire pressures, and the alignment of the wheels.
In the case of the TR6, the rear suspension is designed with a solid rear axle, which means that the wheels are not independently suspended. This can lead to roll steer if the axle is not properly aligned, or if the tire pressures are not equal.
To improve the TR6 rear suspension roll steer, there are a few things that can be done. First, the axle should be aligned to the chassis. This can be done by a professional mechanic or by using a do-it-yourself alignment kit. Second, the tire pressures should be checked and adjusted to the manufacturer’s specifications.
In addition to these measures, there are also a few aftermarket parts that can be installed to improve the TR6 rear suspension roll steer. These parts include adjustable rear control arms and a Panhard rod. Adjustable rear control arms allow the axle to be adjusted to the correct position, while a Panhard rod helps to keep the axle from moving side-to-side.
People Also Ask
What is roll steer?
Roll steer is a phenomenon that occurs when the rear wheels of a vehicle steer in a different direction than the front wheels, typically when the vehicle is cornering.
What causes roll steer?
Roll steer can be caused by several factors, including the design of the suspension, the tire pressures, and the alignment of the wheels.
How can I improve the TR6 rear suspension roll steer?
There are a few things that can be done to improve the TR6 rear suspension roll steer, including aligning the axle, adjusting the tire pressures, and installing aftermarket parts such as adjustable rear control arms and a Panhard rod.
