Seatbelt Question: Will 944 Rear 3 Point belts work in the front of the 911

[Tidybuoy]

My 911's seat belts are old and tired and piratically choke me.

My 944 has perfect, never used, rear 3-point belts and I'm wondering if anyone knows if these would fit the 911 (for use in the front).

I will take the time to compare but I thought I might ask in case anyone has tried this. The 944 belts have never been used and they retract perfectly as if it were a brand new car. I'm thinking that the only issue might be the length as everything else appears the same. I don't mind donating the 944 belts as only a "small" midget could fit in the back of the 944 - it's much smaller than the 944.

Thanks in advance........Vern

[Tidybuoy]

Anyone? I'm bumping this up because I find that I get few responses when I post questions at night. Of course, that's the only time my brain is working so that's when I think of things to ask

[emac]

Vern they will. You will have to drill out one hole on the piller no big deal I did it about ten years ago so my 63 yr old brain is a little foggy. It took about one hour
Ernie 81 sc

[emac]

Vern let me take back what I posted. I replaced mine with FRONT belts. Sorry
Ernie

[RWebb]

I think I'd rather trust my life to a stock belt that is not too old

[Walt Fricke]

You should be able to figure this out with some measuring and testing. Will the metal part that clips into the center holder fit what you have? If not, can you transfer the 944 equivalent?

I assume the 944 part has the retractor box, as does the 911? If so, look at how that is mounted - memory says one bolt, plus a locating pin or the like. The mounting thread sizes are standard (an SAE thread, no less), so that should work, and the outside end mount on the rocker area ought to bolt right up.

How about the D ring up high on the B pillar? Is there one on the 944 stuff already?

I have had the retractors apart. Which means I have a set of retractors which don't work any more, as I could never get them back together properly. So I would advise against disassembling them for any reason. There probably is a way to do it, so a guy could replace old nylon belts with new ones. But I could not figure it out - winding up the spring always ended up getting away from me.

[Tidybuoy]

I'm not too worried about using non-stock belts as these were either made or sourced by Porsche - just a different model. These belts come from my '88 944 with 42k miles and have never once been used by a person. They have been used ocasionally to hold an ice chest in place but otherwise they are in like-new condition and retract like a modern new car.

I suppose one issue could be the angle that the belt mounts as the 911 retractors are vertical and the rear 944's are at a slant mounting position - I'm not sure if the internal weight is moved to accomodate the mounting position.

I will remove from the car and compare to the 911 - and if this works it will be a great solution for me.

Vern

[dad911]

Front Belts sold here: Pelican Parts - Product Information: 928-803-126-09-OEM

I would be very concerned that a different angle would change how they work/lock in a collision.

[Walt Fricke]

You can figure out if angles matter easily enough. When you have the 944s out, just hold at an angle and pull.

I think the latch mechanism works in two ways. One is inertial, as in some kind of pendulum inside, which swings forward under decelleration. If the decel is hard enough, the reel locks. Since changing the angle is going to work on a pendulum the same as decel would, basically, that can be an issue. But you have to test it.

The other way I am pretty sure they work is by how fast the reel is rotating. There must be some centrifugal pawls in there, so if you yank on it it will catch. I've been testing cars during DE tech this way for many years, and they will catch. That ought not to be affected by angles.

[RWebb]

Originally Posted by Tidybuoy

These belts come from my '88 944 ...

Here is the real concern -- the age of the webbing.

Are they safe? Dunno.

Do you want to find out? No.

[Walt Fricke]

Webbing aging is an issue which lacks well researched answers.

UV will damage webbing, though it damages the area exposed, and not beyond. Like sun bleaching. Mountain climbers know to be wary of the strength of old pieces of webbing used as rappel anchors and the like - they are right out in the sun (especially if at high altitude) for roughly half their lives (well, somewhat less as the sun and shade move).

The U.S. Army's Natick laboratory, during WWII, did some testing on nylon climbing rope's reaction to UV. Showed it lost strength. Webbing, with more surface to mass, is going to degrade faster than rope. Modern climbing ropes, with a non-load bearing outer sheath, ought not to lose much strength at all due to weathering.

In the mid-90s, the race seat belt manufacturers showed the SFI some test data from somewhere which showed nylon lost at least half its strength in two years. This was presented as new knowledge, which promptly prejudiced me against the science skils of these people. No mention was made of testing of actual seat belts, whose date of manufacture is easy to know because it has long been marked for competition belts. I take this to mean none was done. Knowing how this testing tends to be done, I suspect the two year test was not on anything like seat belt material, and was probably an accellerated UV testing at higher intensities but over less than two full years. But it would still amount, nominally, to leaving a belt outside for two years in a sunny climate. But this "new" test result was the basis for SFI's change in their approvals - they are not good only for two years. The SCCA, which has been in the racing business a long time, did not follow. Neither did PCA, and some other sanctioning bodies, and used five years as a standard.

The FIA, which also has standards, uses five or six years as their standard. Because some organizations accept the SFI 2 year standard for SFI rated belts, but will accept the FIA standard for a longer time, some belt manufacturers have had their belts approved by both agencies. A 2.5 times difference between what these agencies think is safe for racing use at the highest levels.

Where does this put a street car's belts? Well, hard to say because I don't know of anyone who has taken old belts and pulled them till they broke and recorded the results. I used to have indirect access to a lab with this kind of equipment, but it doesn't do that kind of thing any more (all it takes is a strain gauge with a telltale if old school, and a hydraulic puller, and you do a destructive test). I keep hoping I'll luck into this, as I have some 25 year old belts which would be fine subjects, although they spent the last 15-20 years in my crawl space far from any UV).

But the UV exposure is going to vary a lot. How much does window glass attenuate UV?

If a belt is not discolored, I'd be inclined to think it probably is OK. If it has gotten stiff, I'd be inclined to believe it has lost strength. Unused rear seat belting is not apt to be worn.

Pelican, in technical notes or whatnot on their belts, suggests that if the belt had held an occupant in an accident, it should be replaced, as it has been permanently stretched. That is not quite true. Like many other materials, nylon has an elastic limit, and a plastic limit. If the elastic limit is not exceeded, it isn't losing significant strength and retains its length. Generally, in hard impacts where the belt earned its keep, you can see (on competition belts) an area near adjusters which has melted some. That is a good sign that its days are done.

I've been griping about all this for years (sorry about that). I once asked if anyone knew of an incident where a belt had failed. Yes, there was Dale E, but his belt was improperly mounted, and did not fail because its inherent strength was exceeded. Someone found a report of a helicopter crash in Canada where the belt failed. Plastic vs glass UV transmission difference? Bubble front helicopter? And I think it failed at the single part of the Y shoulder harness configuration typically used so the inertial reel can be used on the shoulder harness in that application, though that might be the same force as you'd see with a standard passenger car belt.

Otherwise, despite all the highway wrecks, and all the Saturday Night racer wrecks, and all the track stuff, when has one seen or heard of a seat belt failure?

Even with 25 - 40 year old belts which were original on our timeless Porsches?

[RWebb]

There is an old thread where I reported that NHTSA and IIHS did not know the answer.

I do replace the entire seat belt and spool assembly every 20 years on my vehicles - safety.

Now, regular glass has a sharp change in the transmittance at 350 to 300 nm -nearly completely opaque to anything shorter than UV-A. Not sure re auto glass...

[Fastdog911]

talk to Steve at www.Seatbeltplanet.com as he made a set of new retractable front belts for my 70 with no drilling required. I did have to use a different vinyl panel that hides the retractor. He will ask for the dimensions etc. Was not to hip on betting my life on 42 year old belt material .