Attn: For those who track their car's ......... - The Unofficial BMW M5 Messageboard (m5board.com)

FAST 5 · 19th August 2004, 05:58

I was on WWW.SPARCOUSA.COM and took notice of the fact, that they have numerous EVO type harness bars, which would allow the driver/passenger to install & use 4, 5 and 6 point harness straps in the mentioned vehicles. I know there was interest and many inquiries over time to determine whether or not a harness bar exists and if it could be implemented for our E39 M5 sedan. If those who are interested contacted the SPARCO company, located in CA., perhaps they would consider fabricating a harness bar for the E39 M5 sedan. Many guys here track the M5 car on a frequent basis, si i thought this would be a good idea to have a harness bar designed by a well known company.
Get in touch with SPARCO and make this request! Come on guys!!!
Thanks.

PS If SPARCO does decide to make a harness bar for the E39 M5, Im sure were will be more than enough guys to get a Group Buy to take place with the company and buy the harness bar in volume.

Bob Uenaka · 19th August 2004, 11:28

I've thought about upgrading the belts for track use but decided against it after talking to a BMWCCA instructor. He pointed out to me that the racing style harness systems while great for track driving, are potentially more dangerous when used without a roll bar. He would only use one if a roll bar was also installed. It does make sense that in a roll over situation, you would not want to be strapped in upright without a roll bar.

RRoberts · 19th August 2004, 17:44

We all agree that the best driver restraint for the track starts with a solidly mounted roll bar/cage having a horizontal bar directly behind the driver's seat and positioned about 1-2 inches below the top of the driver's shoulders. This will allow 3 in. wide shoulder harnesses to be rigidly attached and not allow excessive stretch under impact load. The lap belts should be positioned below and behind the driver's pelvis on either side - preferably mounted to the cage if possible, and the anti-submarine belts should be anchored to the floor (I prefer a tube welded between the seat mounts) a few inches behind the driver's crotch. This latter will require cutting the driver's seat cushion to reach the floor. Modern race cars will have this setup, plus a form-fitting, solidly-mounted seat that has the needed apertures for belt mounting plus locates the shoulder belts so as to prevent slipping off the shoulder. Some harnesses are now sold for HANS use, with 2 in. wide sections of the shoulder belts where they run on top of the HANS device. I personally have no trouble with use of the HANS device with the standard 3 in. wide shoulder straps.

The gist of the above is that a standard race harness system is not designed to be mounted with excessive (more than about 6 in.) length between the driver's shoulder and the mounting point on the roll bar/cage. There are enough horror stories out there that one needs to be quite careful to not let this length get too long. This is the problem with many harness bars, that are designed as a compromise to minimize cutting up the interior of what is basically a street car. I have seen harness bars that are located 18 in. behind the seat, and too far below the top of the shoulders besides. One has to be real careful here.

The other alternative for occassional track use of a street car is the Schroth 4-point belt system that was designed and proof tested for specific car models, including the E39. These belts are not race car systems, but clip into the existing car 3-point safety belt anchors (plus additional anchors on the outside of the front seats and on each side in the rear). In this case, the harness system is intended to provide an amount of controlled extension under impact load, and relies on this effect to prevent/limit submarining when adjusted properly (there is no sub belt). These belts are tested and demonstrated to meet DOT restraint standards for the specific car model (which is different from being DOT approved). It is tempting, when examining the product, to think that we can make our own for lots less money but how can we be sure the home made belts would work correctly, given that the shoulder harness free length rule is violated big-time by the Schroth design.

I don't mean to sound like a Schroth salesperson here, but wanted to point out that there is an engineered product already on the market that is aimed at street cars that see the track only once in a while. Of course, it doesn't matter how well a restraint system functions under impact if you never crash.

Beyond the safety considerations, a firmly tightened driver restraint system will improve your driving. Steering and brake control, and your ability to feel the tires and suspension working, is greatly enhanced if the drivers body does not move relative to the car under cornering and braking loads. Late model 3-point belts, with inertia locks and explosive pre-tensioners, may provide good protection in an accident but are not able to be kept consistently tight for track use.

Just my $0.02

Regards, Dick Roberts

pmiranda · 19th August 2004, 20:25

"The other alternative for occassional track use of a street car is the Schroth 4-point belt system"

I got the clip-ins for my M3 and they're pretty good. Took under half an hour to put in the necessary extra attachment points (at factory-reinforced bolt locations) and they clip in and out in a few minutes.
They have an anti-submarining "patch" in the inboard shoulder belt that will lengthen in an impact to allow your torso to roll forward and in a bit, which should prevent you from "oozing" down through the lap belts (which would cause nasty internal injuries). This may also provide enough movement to prevent spinal cord injuries in the event of a rollover that crushes the roof, but I don't know for sure and they don't seem to claim that that is the case.
The only thing I don't like about them is that (unlike a 5 or 6 point) you have to tighten the lap belts pretty hard to keep them from riding up when you tighten the shoulder belts.
They are pretty inconvient on the street since you can't move your torso at all when properly tightened, so I only use them at the track.

As with any shoulder harness where the tails go more than 18 inches from the seat back, the shoulder belts cross before attaching to their rear anchor points, which should provide enough inward tension on the shoulder belts to keep them from sliding off of your shoulders. Additionally they are only meant to be used with the shoulder belts running inside the headrest slides, and the webbing is sewn together where the belts cross.

I adjust the seat back and bottom angles to make sure the angle down to the rear belt anchor points is not beyond the maximum 18 degrees (I think--- I'd need to check the documentation that came with the belts to be sure) from perpendicular to the seat back. (Actually to have enough room to wear a helmet in my M3 I have to run the seat back a bit anyway since it has a sunroof.)

Overall a great compromise if you don't want to put a roll bar in your car.

[EDIT: forgot to add one more thing]
I found the shoulder belts would rub on my neck and be very annoying so I bought a set of harness pads. They come in 2" and 3" widths to accomodate either size of belts. I assume they are not HANS-compatible, but neither are 4-point harnesses AFAIK. That reminds me... I need to get a neck roll...

mottati · 19th August 2004, 20:33

I think installing a harness bar might be a bit over the top for me, in my M5. It's a street/passenger car first, a track toy a distant second. I'd be concerned having a sturdy metal bar in the passenger compartment with kids riding in the back seat etc.

That said, I do use the schroth 4 point "clip in" system that RRoberts mentions. It really does allow you to use your efforts to drive, rather than exerting so much energy to stay planted in your seat. It's an easy in/out system too. Bob, i've heard that 'you'll be trapped upright in a roll over, debate' with other instructors and I don't buy it. There is no way I could resist the gravitational and centrifigal (dont think that's spelled right) forces at work to lean my body over across the seat if the car was rolling. Additionally, the stock seat back will break away, in a severe collision (i don't know if thats by design). Additionally #2 the a pillar structure is pretty darn strong. I've seen maybe 5 roll overs in the past 10 years at CCA schools, the roof has maintained itself in all cases.

Now, as i'm getting older and less imortal, i do think of these things more, especially now that i'm the instructor sitting in the passenger seat. I might be hesitant to strap myself in with a harness in a student's car, and i remember it being the rare instructor who would use My harness when i was a student.
I was recently offered one of those "C/G locks" to try, and have it installed in my M5. It basically locks the seatbelt, to keep you more securely planted, yet would still allow some movement of your upper body if needed. I'll see how I like it in a couple of weeks at thunderhill.

M5Kid · 19th August 2004, 20:46

mottati,

I would like to hear your comments on the CG Lock vs. the 4-point Schroth harness after you get somet time to test it.

Thanks,

Travis

mottati · 19th August 2004, 20:50

Quote:

Originally Posted by M5Kid

mottati,
I would like to hear your comments on the CG Lock vs. the 4-point Schroth harness after you get somet time to test it.
Thanks,Travis

I'll report back after the 27/28th....

Mike

Redshift · 19th August 2004, 23:35

I have seen a lot of folks using the Schroth harnesses and they seem like a well-engineered product. Personally, I use CG-Lock and it works perfectly. I've been a passenger in the M5 while on track and without a CG-Lock and it was unbearable. As a driver, I would be unable to drive quickly without it. And it retains all functions and features of the factory seat belts. Personally, I would say this is the best overall solution to keep you planted and safe without installing full-out harnesses and rollbars/cages.