Remember, the recliner mechanism on a streetcar, stock or otherwise, is not supposed to fail and allow the driver to fall backwards, away from seatbelt restraints or airbags. There may have been cases where a seatback has failed, allowing a passenger to fall backwards and away from a rapidly crushing roof, but these situations are rare. OEM's have spent millions designing airbag and seatbelt safety systems that work with the occupants' upright in the stock designated position. Sparco designs aftermarket safety equipment that gives improved support and durability while driving, but everything they manufacture is designed to work together as a system. As can be seen in a Sparco equipped World Rally Championship car: seats, harness belts, steering wheels, and a roll cage are intricately engineered to all function together as one package. Be very careful and try to avoid arbitrarily throwing in pieces of safety equipment from different unproven manufacturers merely for grip.
Morita and Sparco USA warn our readers to be careful with their purchases, as not all seat construction is the same. During testing, Sparco has seen other brands' Taiwanese knock-off seats deform at 2g's of force, while Sparco's units have gone up to 15-28g's. To reiterate the point again, Sparco USA also repeatedly advocates the purchase and use of products that are homologated to meet certified FIA or TUV approvals.
Even with certified, quality components, it's up to the user to determine proper usage. When it comes to installing a slick, new suede covered deep-dish racing wheel, don't forget about what it is that you're loosing. Seatbelt restraint systems remain the primary occupant safety system, preventing passengers from bouncing around the cabin or flying out the window altogether, but airbags have really invaded the market. In fact, dual frontal airbags are easier to find on new cars than power windows or rear windshield wipers. Mandatory equipment on all new cars made since 1999, airbags are a secondary restraint system, in place to prevent belted drivers from hitting interior panels with their faces. As estimated by the NHTSA, the combination of airbags and seatbelts reduce the risk of serious head injury by an extra 20 percent over seatbelts alone. But remember, this is all considering airbags combined with stock three-point seatbelts. When using an airbag-less racing wheel, aftermarket manufacturers assume you will also be using a helmet and four-point or greater harnesses on a closed course. You'd be surprised by how much the human body can stretch during high-g deceleration. It is very possible to put your face into a steering wheel when used in conjunction with factory belts. There's a reason why even quality manufacturers like Sparco sell items bearing the disclaimer, "For off-road use only"
Harness belts are very popular add-on items, but the dangers in improper harness mounting often go unheard. If improperly mounted, spinal column damage, compressed vertebrae, crushing of the seat, or tearing of the harness itself could take place. One of the biggest keys to properly mounting harnesses is the angle of mounting and operation. Harnesses lap belts should be installed with an angle between 45-55 degrees above the seating surface, and shoulder belts should be between 5 degrees below and 30 degrees above the driver's shoulder. If the shoulder belt angle is too low, spinal compression during an accident is likely to occur, while if the belt angle is too high, belt slip is likely to occur, allowing the occupant to move forward, face first into the steering wheel. Diagrams and images displaying proper harness mounting angles as well as correct looping methods for installation are available on Sparco USA's website.