Quote:
Originally Posted by Robert986
What I mean is, in a roll over I doubt I want to be sitting fixed in a harness without a proper roll Cage. Just wanted some advise on wether it was reasonable to do it with only a roll bar with proper broomstick-clearance.
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There are two different issues; one, the strength of the car in a roll-over; two, the safety equipment provisioned for the driver.
The Boxster has reinforced boron tubes within the A-pillar next to the windshield to strengthen the windshield frame. This, along with the stock roll hoops provide acceptable roll-over protection on the street.
The stock safety equipment provided to the driver is the 3-pt belt and a certain amount of assumed head clearance. Of course, people come in many different heights and some very tall drivers may not have adequate head clearance in a stock Boxster.
The BK extension is intended to maintain a reasonable amount of head clearance while wearing a helmet and the broom stick test is intended to verify the clearance.
A 5/6 pt harness provides quite a bit of additional safety in that it addresses submarining (sliding under the lap belt) and firmly keeps the driver in the seat in an incident. The stock Boxster seats are not compatible with a 5/6 pt harness so you'll also need to install a proper sport or racing seat for use with a 5/6 pt harness. And as others have said, it is important to use a proper neck device when using 5/6 pt harnesses to protect your neck.
Of course, a dedicated roll cage adds immensely to the overall strength of the chassis and its ability to withstand a roll over. However, these are not entirely practical for a street driven car.
Thus, if you wear a helmet, it is important to maintain adequate head clearance via passing the broomstick test. Install the BK extension if needed to pass the broomstick test.
Proper head clearance must also be maintained with a full roll cage. It is not unheard of for a driver to have to lower the seat in order to maintain sufficient head clearance in a car with a full roll cage.
That addresses the car portion and any of these configurations (stock, BK extension, or full roll cage) can be used with a proper driver restraint system.
For a driver restraint system, you can either use the stock 3-pt belts/no neck restraint/any seat (stock or upgraded)
OR use 5/6 pt belts/neck restraint/upgraded seat. When you get to this point, it's kind of an all or nothing sort of deal since the 5/6-pt harness, neck restraint, and upgraded seat all have to be in place for the whole restraint system to work properly and safely.
Using only single parts of the upgraded driver restraint system (like a 5/6 pt harness with a stock seat) could be more dangerous than just keeping the stock 3-pt belts and stock seat.
BTW, you can keep the stock 3-pt belt for use with the upgraded seat to maintain proper safety on the street when you're not wearing a helmet or using the 5/6 pt harness/neck restraint.
The roll cage is typically added when the risk of car-to-car contact is increased such as during wheel-to-wheel racing. In a typical DE, the structure of the event (point by or controlled passing, no side-by-side driving, etc) keeps the risk of car-to-car contact at an acceptable level.
The safest configuration is clearly a full roll cage, racing seat, 5/6 pt harness, and a head/neck device. But this may not be acceptable for a car driven on the street and will create other tradeoff's.
It is entirely acceptable to use 5/6 pt belts/neck restraint/upgraded seat with the stock roll hoops or a BK extension. This is part of what used to be known as the "BSX" configuration and was often used by drivers who track their street driven cars a lot. I used this configuration for two years before I built my car into a full Spec Boxster.
Of course, only you can determine what "safe" means to you and your family. Think it over and then select equipment accordingly.