Originally Posted by macfly
Why does Scroth strongly discourages the use of a five-point harness, the tightness of the Elise may merit it. ?
I can't speak for Schroth, but I'd guess that their concerns are captured by the following post I made in a different thread elsewhere in this forum...
I think there's a lot of confusion about what it means to "submarine". I see two ways that load can be transferred off the hip bones (a hard point of contact) to the abdominal wall (a soft point of contact that puts one's organs at risk) in the event of an accident.
The first is when, at the moment of impact, the body is thrown forward and when the lapbelt tightens, the hipbones slide under the belt. Intuitively, it seems reasonable that the more vertical the seat, the less likely this will happen. Fair enough, although that does NOT mean that a vertical seat such as is found in the Elise will necessarily protect you from submarining. I've not seen any data to evaluate this issue, and until I do, I would much rather assume the risk is there (and be wrong) than assume there's no risk (and find out the hard way).
However, I think another cause of submarining lies with everything that happens BEFORE the moment of impact. I've worn 4-point belts in lots of cars, including Elises, and I've observed the lapbelt to shift upward by a substantial amount just as a function of tightening the shoulder belts. The same thing has happened when I've shifted around in the seat, braked hard for a corner and put pressure on the shoulder straps, or cornered hard and leaned into the straps. Plus, belts can loosen after a few minutes into a hard track session. If the lapbelt creeps up enough before the moment of impact, then it won't take much for you to submarine, even if your seat is nearly vertical.
Bottom line is that I think (and Schroth clearly believes) that if you're concerned enough to install a harness in the first place, it's worth (i) installing a 6-point harness and (ii) using a HANS device. Again, others may have their own opinions, and everyone's got to do what they're comfortable with.