Installing 3-Point Sparco Harness in E90

[jenk_man]

I'm enjoying the days at the track and decided to install a Sparco 3-point belt using the mount between the rear seat bottom and top, but I can't figure out where to put the eye bolts for each side of the front seat. Has anyone done one of these installs before?

[///My5UV]

Dang, I was about to tell you not to screw around with that and just use a Schroth quick-fit pro...then I saw that they still don't offer a E9x application :-(

I have fitted harnesses with eye bolts in other cars, but not my E90... A bolt-in mount is usually much easier to fit if the stock points are suitable. I'll take a quick look at my car and see...

I will also take this opportunity to say... don't use those belts at the track! I think they're find for autocross, but I'd rather spend a few extra bucks to get the Schrotch belts with the anti-submarine loops, like the Rallye 3 ASM, or ideally, a Profi-II ASM FE that you can add the 5th and 6th points to down the road and has a better quality camlock. That's what we put in my wife's Z3 and it was fantastic, but we had to get custom seat mounts fabricated to attach the lower 4 points. (The upper two points were wrapped onto the roll bar, and it had racing seats with holes for the anti-sub straps but that's another story.)


Edit: took a look, and you definitely can't use the stock front seat belt points which is probably why Schroth doesn't offer a quick-fit. The bolts that hold down the back of the seat rails would probably work, but only with bolt-in tails... to mount the eyebolts for the snap-in tails you'd have to drill the floor and there's not much room to spare, which could make it tough to include the reinforcing plates you'd want.
I don't know the specs on the seat rail mounting bolts so I can't promise they're strong enough to take the load of a seat belt but the best bet would be to sandwich the mounting eyes between the seat rail and the floor, and cut back the carpet (you don't have to remove it completely, just cut a couple slits so it can be folded back) so that it's a metal-to-metal sandwich without any wiggle anywhere. Only tight-fitting bolts without any play will perform as intended.

Again, I don't recommend those sparcos for track use since they present a greater risk of submarining than stock belts, and of course, I haven't been able to evaluate the strength of the seat rail bolts and floor to know that they'll take the load from a seat belt in an accident. One particular worry is that the bolts are smaller than the mounting eyes even on a bolt-in tail, so it might not perform correctly in an accident.

Because of the hassle and liability of doing stuff like this, alot of folks tracking street cars just use something like the CG Lock instead.

[jenk_man]

Thanks, that's very helpful information. I'm not so sure about the seat rails either. For safety sake, I'll probably use the OEM belt combined with the Sparco to hold me in the seat. It's all a learning experience at this point.

[phusion974]

If your using a 3 point harness I would highly recommend strapping the harness to a roll bar.

[///My5UV]

I worry about trying to use both belts. I don't know exactly what could go wrong, but it just seems unwise. As to the Sparcos in general, I worry that the twin shoulder straps are going to pull upwards on the lap belts in an frontal accident, and unless you sit very upright, your body is going to squeeze under the lap belts like the inside of a tube of toothpaste, with all that implies for your internal organs. If you insist on using those Sparcos, be sure you tighten the lap belt first (this is where you get most of the benefit anyway) and leave the shoulder straps as loose as you can.

[piloto]

DO NOT ATTACH IT TO THE LATCH ANCHORS!!!!!

Sorry for yelling, but wanted to be sure that I got your attention. Do not do this. If you get into an accident, you're going to compress your spine (after your break the seatback structure). I've explained it in some detail in this post (another forum): see posts #31 and #33 for my more detailed explanations. If you want more details, PM me. I'll sketch a simple diagram to show how it would compress your spine. There's a reason why there's not only an FAA madate, but all major aircraft OEMs like Boeing/Airbus have criteria ensuring the shoulder belt angle on pilot seats is above zero (relative to a horizontal line). It's the same exact concept in a car.

One of the posters on the other forum has probably the best suggestion, which was to track the seat all the way back, get the belt tight, and then move the seat forward slowly.

[FStop7]

http://www.cg-lock.com/index.html ?

[M3SQRD]

I agree, don't mess with a three-point harness and get a CG lock instead. If you've never used a CG lock before you'll be amazed by how effective it is at holding you in place.

[itf joegun]

Originally Posted by dbarnes

I agree, don't mess with a three-point harness and get a CG lock instead. If you've never used a CG lock before you'll be amazed by how effective it is at holding you in place.

+1

Works perfect for trackday use!

[jenk_man]

Thanks again, sounds like the CG Lock is the best bet. Looking forward to the next event at Thunderhill.

[///My5UV]

Glad to hear you'll try the CG lock first! I probably need to pick one up myself... I wish I'd had one for PCD since I'm not used to putting that much strain on my left leg anymore.