Mysterious reinforcement rails between rear floor and trunk?

[stymee]

As I get more and more intimate with the structure of the 2002 unibody (I see it in my sleep), I have noticed a few things that seem to differ among cars/years. One that recently came to my attention, and kinda bugs me are two reinforcement rails that connect the rear floors to the trunk area. I noticed them while reading through Heist's thread. I believe his is a '74.

So I got to digging around some other threads and pictures, and they also appear to be present on the '74 from the my2002tii site

They are definitely absent on my car, which is a '72 but has had so much metal work done, I didn't know if they were just removed and never replaced.

And absent from the '76 from Tommy's Goodfellas thread.

And absent from this shot I found of a shell on a rotisserie, not sure what year it is.

I am assuming these were not intentionally removed from any of the pictured cars. Anyone know when and on what models these were added? If they did improve the rigidity of the unibody significantly, I may try to add some reinforcement similar to this as I stitch my rustoration back together.

If you have any pics handy of the underside of a '72 2002 (tii would be even better) I would love to see them.

P.S. I anyone minds me re-posting their pictures, let me know and I'll remove them.

[Mike Self]

added to the squarelight US cars to absorb and spread the crash loading for the 5 mph bumpers.

A 5 mph impact is pretty severe, and while the shock absorbers that the bumpers are mounted on will absorb some of the impact, the relatively light rear body structure of a 2002 will crumple once the shocks compress. And Federal requirements were for no damage to the body after the impact.

A 5 mph impact is 4 times as severe as the 2.5 mph impact requirement for the 1973 (only) model year; that's why the 73's could get by with reinforced bumper brackets and moving the bumpers further away from the body and no extra body shell reinforcements.

So it's reinforcements like those and the ones in the engine compartment that make US squarelight cars nearly 200 lbs heavier than roundies.

cheers

mike

[Harv]

Must have been added in 74 for rear impact to be transferred to the floor. Don't know why the 76 doesn't have them unless BMW changed their impact plan in some other way or ....?

John

[Tommy]

Must have been added in 74 for rear impact to be transferred to the floor. Don't know why the 76 doesn't have them unless BMW changed their impact plan in some other way or ....?

John

That's because the -76 in picture is a euro body. Those reinforcements along with quite a few others are only for big bumper US cars.

In euro models there isn't much structural difference between so called early and late models.

Tommy

[Preyupy]

The Turbos have them, even with the small bumbers.

[SteveJ]

I thought they added the reinforcments to keep the 2002 body from folding in half after adding those big-ass bumpers at either end in '74.

I guess I was partly right.

[Jaycen_PNW2002]

I don't believe this is a big bumper/small bumper issue. I had two 72s one had it the other didn't. One was a tii.

The two ceylon tiis done by Don Dethlefsen's shop both have those reinforcements.

http://www.thewerkshop.net/aboutUs/roundel/0702cover/

-J

[stymee]

Interesting! Thanks for the responses. I should have assumed it was done around the time they added the big bumpers. Tommy's euro body threw me for a loop. It sounds like the jury is still out a little bit, but I wonder if the '72 Ceylon mentioned was also a euro?

Just to piggy back on the original topic, did they add additional door reinforcement when they added the big bumpers? I have a passenger door that has some extra reinforcement and a kind of skirt at the bottom. This door is definitely not original to the car because it looks like it was Atlantik at one point (pretty color!). My driver door looks to be original, but only has the door skin and no bracing. The weight difference is significant. I guess having some extra protection for my passengers is the right thing to do.

[saaron]

Hey stymee

I have a 72 tii that is the euro version. It was summer '72 production. I can double-check, but I'm 99% sure my car doesn't have those reinforcements.

The story I had always heard was what Mike articulated.

I'll check the car later, and if it DOES have them, I'll re-post. But I don't think it does.

Scott

[Mike Self]

bottom) were also Federal side crash requirements. They were added either in 1974 or 75 to meet NTSHA requirements. Then after BMW ran out of non-reinforced doors in their spare parts stream, all the replacement doors for the US market were so equipped.

That shovel-shaped reinforcement at the bottom of the door makes it more difficult to clean and rustproof the seam inside the door where the skin meets the door's frame...

mike

[jgerock]

Here are two old pics of my late May 73tii. Looks like there are some reinforced areas under there.

[07GTIMYFAST]

Interesting most people agree they came in 74, but my 73 has them. regular ole sahara 73. I was under there yesterday looking at possible axle rubbing issues and where to run my 1/2" fuel lines.

[roadhog0]

If it means anything my 76 has them.... I thought they were on all 02's. The 74 parts car I had had them. You can sorta see them in this picture, they're doing their job and not bending.

[stymee]

Thanks all for the replies (and the pics, I especially like the one on the front loader). At least I can now assume that they weren't removed by one of the many hacks that have cut into my frankenbimmer. It would still be interesting to know for sure if they added them after a certain VIN.