19/09/2013
When preparing a saloon car for performance driving, be it for track days or competitive rallying, the correct installation of safety equipment is paramount. Among the most critical components is the multi-point harness, designed to keep you securely in place during high-G manoeuvres or, crucially, in the event of an impact. A common query among enthusiasts revolves around the integration of these harnesses with a vehicle's roll cage, specifically, whether one can wrap the harness directly around the harness bar. The resounding answer is a confident yes, but with a vital caveat: this method is exclusively applicable to saloon harnesses featuring removable snap hooks on their shoulder straps. This seemingly minor detail opens up a world of benefits, transforming your harness installation into a safer, lighter, and more effective setup. Let's delve into the straightforward process and the significant advantages it brings.
The Unquestionable Advantages of Direct Mounting
Opting to wrap your saloon harness directly around the roll cage's harness bar isn't merely a matter of convenience; it’s a strategic choice that yields tangible safety and performance benefits. The traditional method often involves snap hooks attaching to eye bolts, which, while functional, can introduce inefficiencies. Direct mounting addresses these by optimising strap length, ensuring correct angles, and even contributing to crucial weight savings.
Optimised Strap Length and Reduced Elongation
One of the primary benefits stems from the ability to significantly shorten the effective length of the harness's rear straps. Saloon harnesses are typically manufactured with very long rear straps to accommodate various installation scenarios. However, roll cage harness bars are often positioned very close to the back of the seat, precisely where the harness passes through the seat's slots. By wrapping the harness directly, you eliminate any unnecessary slack.
Why is a shorter strap length so critical? In the event of a crash, the harness material, particularly polyester webbing, will experience a certain degree of elongation. Polyester webbing typically elongates at a rate of 3-5% under crash conditions. While this elongation is designed to absorb energy, excessive length means greater total elongation, which can lead to more forward movement of the occupant than desired. A shorter strap minimises this effect, ensuring you remain more securely restrained and reducing the potential for impact with the steering wheel or dashboard. This seemingly small reduction in movement can be the difference between a minor incident and a serious injury.
Achieving the Correct Strap Angle for Safety
Another crucial advantage of direct mounting is the ease with which you can achieve the manufacturer-recommended strap angle. The harness bar is usually level with, or very close to, the harness slots in the seat. This alignment is critical because it ensures the shoulder straps pull the occupant firmly back into the seat without exerting dangerous downward or upward forces on the spine during an impact. Manufacturers universally stipulate that rear harness straps should never be installed at an upward angle. The acceptable range for installation is typically between 0° and -30° (downwards from horizontal), with the optimum angle widely considered to be -10°. Installing straps at an incorrect angle, particularly upwards, can compress the spine in an impact, leading to severe injuries. Direct wrapping facilitates this ideal geometry, promoting occupant safety.
Significant Weight Savings
For those involved in competitive motorsport, every gram saved contributes to performance. By removing the snap hooks and eliminating the need for two eye bolts and two spreader plates per harness, a weight saving of approximately 450 grams can be achieved per harness. In a rally car, for instance, which typically features two harnesses, this saving doubles to nearly a kilogram. While this might seem marginal, cumulative weight savings across various components can significantly improve a vehicle's power-to-weight ratio, handling, and braking performance. It's a small change that contributes to a larger competitive edge.
Step-by-Step Guide: Direct Harness Installation
The process of directly mounting your saloon harness to the roll cage harness bar is surprisingly simple and requires no specialised tools beyond your hands. Follow these steps carefully to ensure a secure and safe installation.
Step 1: Detach the Snap Hook(s)
Begin by identifying the snap hooks on the rear shoulder strap(s) of your saloon harness. These are typically attached by wrapping the webbing around a metal bar or through a D-ring. To remove the snap hook, simply unwrap the webbing from around it. Ensure that the sliding adjuster bar, which is crucial for tensioning and securing the strap, remains on the strap. Do not remove this component, as it forms an integral part of the locking mechanism.
Step 2: Wrap Around the Harness Bar
With the snap hook removed, take the end of the strap and feed it under the harness bar of your roll cage. Then, bring the strap back up and thread it through the sliding adjuster bar. It is imperative that this sliding bar is positioned as close as possible to the harness bar. This proximity is vital for the integrity of the subsequent locking loop and to prevent any unwanted slippage under load.
Step 3: Create the Locking Loop
This is arguably the most critical step in the process, forming the 'locking loop' that secures the harness to the bar. Once the strap has passed through the sliding bar (as per Step 2), it now needs to be looped back through the same sliding bar, effectively creating a double-back. When viewed from the side, the profile of the strap and sliding bar should resemble a 'Z' or 'S' shape, where the strap enters the slider, wraps around the bar, and then re-enters the slider from the opposite side. This creates friction and a self-tightening mechanism that prevents the strap from pulling free. Double-check this configuration meticulously.
Step 4: Manage Excess Strap
After creating the locking loop and ensuring the strap is properly tensioned, you will likely have a significant amount of excess strap, especially given the length of typical saloon harnesses. It is essential to have at least 10-15cm of excess strap as a 'tail' beyond the sliding adjuster. This ensures there's ample material for the locking loop to function correctly and provides a margin of safety. Any remaining excess can be neatly rolled up and secured out of the way using a cable tie or dedicated strap tidy. This prevents the tail from flapping around, getting caught, or distracting the driver during spirited driving.
Critical Safety Precautions and Best Practices
While the direct mounting method offers significant advantages, its effectiveness and your safety depend entirely on meticulous attention to detail and adherence to crucial safety precautions. Overlooking any of these can compromise the harness's ability to protect you.
Webbing Clearance and Abrasion Prevention
It is absolutely imperative that the harness webbing passes smoothly through any seat openings or harness guides. There must be no danger of the webbing rubbing against sharp edges, seat mounts, or any part of the vehicle structure. Any form of abrasion, even minor, will weaken the webbing over time and could lead to premature failure in a crash. Regularly inspect the webbing for signs of fraying or wear, especially at points of contact. If any sharp edges are present, they must be filed down, covered with protective material, or the installation method adjusted.
The Importance of the 3-Bar Slide Position
As mentioned in the installation steps, the 3-bar slide (or sliding adjuster bar) must be located as close as possible to the harness bar. A loose or distant 3-bar slide allows for excessive strap movement and can lead to slippage, reducing the effectiveness of the locking loop. This slippage can compromise the harness's ability to hold you securely, particularly under dynamic loads.
Verifying the Final Locking Loop
The final locking loop, created in Step 3, is the cornerstone of this installation method's security. It's surprisingly easy to forget or improperly execute this crucial step, especially when rushing. Always double-check, and even triple-check, that the strap has been correctly looped back through the sliding bar, creating the secure, self-tightening mechanism. A quick visual inspection and a firm tug on the strap should confirm its integrity.
Understanding Webbing Elongation
As discussed, polyester webbing elongates by 3-5% during a crash. While this is a safety feature, a shorter strap minimises the total elongation, thereby reducing occupant excursion. This reinforces the benefit of direct mounting, which naturally results in shorter strap lengths compared to installations using eye bolts and longer connecting straps.
Crossing Shoulder Straps for Stability
In some installations, particularly when the roll cage is located more than 50cm behind the seat, it is strongly recommended that the shoulder straps be crossed over. This means the left shoulder strap connects to the right side of the harness bar, and the right strap connects to the left. Crossing the straps significantly aids lateral stability during a crash or high-G cornering, preventing the occupant from sliding sideways within the seat. This is especially beneficial in vehicles with less supportive seats or where the harness bar is further away.
Maintaining the Correct Angle: Never Upwards
Reiterating a critical point: the shoulder straps must never be installed at an upward angle from the seat slots to the harness bar. This can cause spinal compression injuries in an impact. The acceptable angle range is between 0° (horizontal) and -30° (downwards), with the optimum being -10°. Always ensure your harness bar is positioned correctly relative to your seat for ideal geometry.
Preventing Lateral Strap Movement on the Bar
During aggressive driving, particularly when cornering hard, there's a tendency for shoulder straps to slide laterally along the harness bar. This can lead to uneven loading, discomfort, and potentially compromise the harness's effectiveness. To prevent this, a simple yet effective solution is to solder a wire loop or create a robust guide on the harness bar for each strap. This loop should be wide enough for the harness webbing to pass through smoothly but narrow enough to restrict significant side-to-side movement. This ensures the straps remain correctly spaced and tensioned, even under dynamic conditions.
Comparative Analysis: Direct Wrap vs. Snap Hook Installation
To further illustrate the advantages, let's compare the two common methods of harness installation for saloon cars:
| Feature | Direct Wrap Installation | Snap Hook & Eye Bolt Installation |
|---|---|---|
| Strap Length | Shorter, optimised length | Potentially longer, more slack |
| Elongation in Crash | Reduced total elongation | Greater total elongation potential |
| Angle Optimisation | Easier to achieve -10° optimum | Requires careful eye bolt placement |
| Weight | Lighter (~450g saving/harness) | Heavier (snap hooks, eye bolts, plates) |
| Complexity of Parts | Fewer components | More components (eye bolts, spreader plates) |
| Installation Ease | Simple, quick once understood | Requires drilling/securing eye bolts |
| Lateral Movement Prevention | Can be easily managed with guides | Can still slide if not secured |
| Required Harness Type | Saloon with removable snap hooks | Any harness with snap hooks |
Frequently Asked Questions (FAQs)
Can a roll cage be used for racing harness installation?
Yes, absolutely. Roll cages are designed with safety in mind, and many are specifically homologated by their manufacturers for the purpose of mounting racing harnesses. However, it is crucial that any bars used for shoulder belt mounting are indeed specified and certified by the roll cage manufacturer for such use. Always refer to the roll cage manufacturer's documentation and homologation papers to ensure compliance and safety. Using non-specified points can compromise the integrity of the roll cage or the effectiveness of the harness.
Do I need a harness if I roll a car?
While a standard 3-point seatbelt offers significant protection in many scenarios, a multi-point racing harness provides a superior level of occupant restraint, especially in the event of a roll-over or high-energy impact. In a roll-over, a standard belt might allow for more vertical movement, which could bring your head closer to a collapsing roof. A properly installed multi-point harness keeps you firmly upright and securely positioned within the safety cell of the car, significantly reducing the risk of head, neck, and spinal injuries. While you can still use a good quality locking 3-point belt for everyday driving (which offers more freedom of movement for reaching the glovebox, for example), for dedicated track or competition use, a multi-point harness offers unparalleled safety.
What is the optimum angle for harness shoulder straps?
The optimum angle for harness shoulder straps, measured from horizontal at the point they exit the seat to the harness bar, is -10° (ten degrees downwards). An acceptable range is typically between 0° (horizontal) and -30° (thirty degrees downwards). It is critical that the straps never go upwards from the seat to the harness bar, as this can cause severe spinal compression in an impact.
Can I use this direct wrap method with any harness?
No, this method is only suitable for saloon harnesses that feature removable snap hooks on their shoulder straps. If the snap hooks are permanently sewn into the webbing, this direct wrap technique cannot be performed.
How often should I inspect my harness?
It is recommended to inspect your harness regularly, ideally before every track day or competition event. Look for any signs of wear, fraying, cuts, or abrasion on the webbing. Check the condition of all buckles, adjusters, and stitching. Any harness that has been involved in an impact, even a minor one, should be replaced immediately, as its structural integrity may be compromised even if no visible damage is present. Harnesses also have an expiry date, typically printed on a label, after which they should be replaced regardless of their apparent condition.
Conclusion
The direct mounting of a saloon harness to a roll cage harness bar is a highly effective and beneficial modification for any performance vehicle. By understanding and meticulously following the simple steps, coupled with a keen awareness of the critical safety precautions, you can significantly enhance your safety, reduce vehicle weight, and optimise the performance of your restraint system. This seemingly small adjustment contributes immensely to your overall security and confidence when pushing the limits on the track or rally stage. Always prioritise safety, ensure your equipment is correctly installed, and never compromise on the details when it comes to occupant protection.
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