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Seat Backs and Downward Shoulderbelt Angle
Regarding spinal compression and the downward angle of the belts. Very early in an accident (forward or rear), the body is compressed down in the seat padding putting the shoulders inline with the top of the seat back (if it is not there or below already). This transfers the downward load of the belts away from the shoulder and to the seatback. The QuickFit belts are all car specific. The traditional Rallye 3 and Rally 4 belts have a vehicle certification list (we are the ONLY company with such a list). To be certified for a vehicle, Schroth calculates the geometry of all belt mounting angles to ensure that they do not exceed 45 degree downward angle and also to verify the mounting points can be properly accessed for mounting. We also test the specific seats with a downward load test (developed by Schroth) to ensure that the seat back will take the downward angle forces (about 3,500 lbs). All BMW, Audi, VW, Mini, Subaru WRX/STI and a few others can pass this test. Many SAAB, Volvo, and some Merecedes did not pass this test. It is not a failure of seat design just that to be safe in normal use this level of seatback strength is not normally needed.