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      06-08-2009, 01:22 PM   #1
Driftaholic
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Z4 Roadster Stock Roll Bar and the use of a Harness

Greetings,

I use my Z4 Roadster for DE, Autocross, and Drift events. Would you please share with me what you know regarding the stock Roll Bar and how much protection it provides in case of a roll over? With my helmet on, I am ¼” below the edge of the bar.

My Z4 has leather seats. I use my knees to support my body while cornering. By the end of a session, both knees ache. I am considering a harness and I have the following questions:

1- My understanding is that using a harness without a roll cage is dangerous. This is because stock seatbelts are designed to allow the body to submarine in case of a roll over. With the harness, the body is not going anywhere; therefore, you need the roll cage to ensure that your head does not get injured. Is my understanding correct? Does it apply to the Z4 with extendable roll bars?

2-If the harness is possible, is there a harness bar for the Z4 Roadster? If not, are there good mounting points?

I know a full cage is the correct solution, however, I am not ready for one yet as my Z4 is still mainly a street car.

I look forward to your replies.

Thanks in advance.
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      06-08-2009, 02:19 PM   #2
jragan
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You know if your goal is to give you more stability in the seat, there are multiple ways of using your OEM seat belt provide this without adding anything extra...
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      06-08-2009, 03:56 PM   #3
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Thanks.

Other than trying the CG lock, what do you suggest?
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      06-09-2009, 07:56 AM   #4
DerekSelmanRacing
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I have the M sport seats and a CG lock in our car and it's not too bad. Considerable improvement over the std sport seat and seat belt.

The next step for me on our dual street/track car might be a different seat but we do about 6-8 weekends a year and I think I'm adequate now.
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      06-09-2009, 10:03 AM   #5
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With completely stock seat belt and ///M Sport seats, I'm able to completely lock myself into my seat so I can't move anything but my arms, legs, and head. It's great for stability on a tight track.

What I do (requires power seats):
  1. Move the seat well back from your normal driving position.
  2. Latch your seat belt.
  3. Pull all the slack out of the lap belt, and as tight accross your lap and chest as you can and feed all slack into the tension mechanism (so your hand with the belt in it ends up near your outside shoulder...don't let go).
  4. Now jerk out/down so the retention mechanism latches and hold pressure against it so it stays latched.
  5. Using a free hand, hit the power forward button on your seat and move it to your track driving position.
If you did it "right", the belt should now be approaching uncomfortably tight with you held against the seat. There should not be enough play anywhere such that the belt could unlock itself.

This technique works wonders for me.
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      06-09-2009, 10:28 AM   #6
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Thanks,

I do that to secure a child seat but I did not think of doing it to secure my 200lb. I will give it a try. I am drifting at 80mph. Hopefully this works.

Any thoughts regarding the stock roll bars and how much protection they provide?
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