AO Silver Member
Join Date: Mar 2003
Inertia reel seat belts must have two independant means of locking according to safety regulations. No adjustment is possible on either.
The vehicle decelaration (crash sense) is by means of a stainless steel ball or similar device and the g-level is fixed by sled testing. This will not normally result in the belt getting tight, only the effect of locking on an incline.
The belt movement (web sensing) measures the speed that the belt is moving at when the torso is moving forwards by means of very small centrifugal weights mounted on the side of the spool. There will be manufacturing tollerances plus if the design is already too sensitive to small changes you can get the effect of the belt getting progressively tighter. Its inherant in the design of that particular belt design or type of manufacture but the webbing speed appears to have been set too low. Nothing can be done other than an "add-on" comfort device.
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