s2k_9000rpm

I'm curious as to which is actually safer to use. I want to upgrade to a harness setup, but not if stock is safer. Does anyone have info on this???

CoralDoc

This is not a simple question, so here's a long answer.

Disclaimer - I am not a safety engineer, just an S2000 enthusiast that has read a lot of literature from harness manufacturers and posts on racing web boards. I invite our more knowledgable members to provide criticism, correction or support to the following.

If you are running the stock roll hoops, the consensus is that the stock seatbelt is safer. Restraint systems in modern automobiles are very effective and are designed to decrease the likelihood of injury or death, but cannot protect against all foreseeable scenarios. Here are two with an armchair comparison of the stock and 4-point systems:

Rollover
In a rollover, the A-pillar and roll hoops are designed to leave some room between the passenger compartment and the ground. However, ever notice how low the stock roll hoops are? Obviously, if your body stays in driving position it is possible that your head will hit the ground. However, the stock 3-point system allows lateral movement that has been reported to prevent head injury in these types of accidents. If you were wearing a 4-point harness, lateral movement would be limited, increasing risk of severe injury to the head and neck in a rollover accident. That is why 4-, 5-, and 6-point harnesses should only be mounted in cars that have a roll structure that extends above the head (or helmet).

Frontal Impact
In this scenario, the primary OEM restraint is the 3-point seatbelt. It, combined with the airbag, is designed to distribute the energy of the impact to the strongest parts of your body and over a wide area. Our 3-point belt also has belt pre-tensioners that reduce forward movement. A properly installed 4-point harness will distribute crash forces over a larger surface area of the body, but you lose the pre-tensioning benefit. There is also the increased risk of submarining as compared to the stock seatbelt system ( see below).

It is very difficult to properly install a 4-point harness in the S2000. The main problems are secure mounting of the shoulder straps and prevention of submarining under the lap belt. The only way I know of to correctly mount the shoulder straps is with an aftermarket rollbar that allows the attachment of the shoulder strap mounts high enough. It is important for the shoulder straps to extend rearward at no more than a 15 degree downward angle from the horizontal. If the shoulder straps are mounted improperly (e.g. looping the strap over the shoulder and down to a floor mount) you greatly increase the risk of severe injury from spinal compression. Submarining is a concern with a 4-point harness system for 2 reasons. 1) Since the shoulder straps pull up on the lapbelt, it is possible to raise the lap belt above the pelvic crest bones and onto the abdomen. If the lap belt is too high, serious injury can occur to internal organs. That's why 5 and 6-point systems are used in racecar restraint systems. However, it is not possible to use these anti-submarine straps without the installation of an aftermarket seat that allows the straps to pass directly down to the floor. It is not safe to loop the anti-submarine belt over the front of the seatbecause it does not provide the correct downward force and still allows submarining. 2) A 3-point system allows some chest rotation. The right side of the chest moves forward in an accident, decreasing the tendency to slide under the lapbelt. In all but one 4-point systems, this rotation in prevented increasing submarining risk. Schroth makes a 4-point harness with an anti-submarine feature that does allow some chest rotation and decreases submarine risk.

I am putting together a post on my experience mounting a harness in my car. Look for it in the Racing and Competition forum.

pfb

The primary advantage of a racing harness in a street car is that it holds you firmly in your seat, so that you may focus on driving rather than bracing yourself so you don't slide around on the leather.

As CoralDoc already pointed out, there are some *significant* safety risks when using one in a street car, especially a roadster!

dlq04

CoralDoc, excellent summation.

s2k_9000rpm

thanks for the input, i think i'm going to install the harness and keep the stock set up. i'll only use the harness for canyon runs and such, but use the seat belt for everyday use. thank again for the information.

turbo_pwr

Some how I don't think you comprehended the information that was relayed to you. To use harnesses during canyon runs/aggressive driving, where you are more likely to make a mistake and rollover is wrong.

s2k_9000rpm

as far as aggressive driving, i drive like a winnie, but i'd like to sit put in my seat. day to day driving i'm probably more prone to a serious accident.

CoralDoc

s2k_9000 - Can you correctly answer one simple question: How do you plan on mounting the shoulder straps to the chassis?

I spent a lot of effort synthesizing and reporting information, but it still sounds like you don't understand what I'm saying. Let me be clear - it is unsafe to install harness systems in the S2000 unless you have sufficient rollover protection and specially fabricated mounting points. It doesn't matter if you're commuting, driving on the track or driving like a weenie just going down the street for milk, accidents happen and we all want you to be as safe as possible. Please continue to use the OEM 3-point seatbelts.

Ztec

Joshua, as usual you impress me with your explanations
I am purchasing the Cusco 5 point roll bar from Bulletproofs group buy, what are your thought on a good harness system and can it be used with the stock seats? I am planning on new seats as soon as the funds are available!
Nick

dlq04

S2k 9000rpm, I can tell that I rode in a S2000 that had an original seat (passenger side) with a harness system and it was damn scary... once around the track and I was screaming to get out! Listen carefully to what's being said here.