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Discussion Starter · #1 ·
Just reading on the MGExperience forum how some owners of the later "rubber bumper" MGBs remove the bumper covers, remove the steel energy absorbing bumpers, duplicate them in PVC, and reassemble everything. Saves about 18 lbs of weight on each end of the car. Has anyone ever done such an operation to a Mk II Supra?

I might have done this if it had occured to me while I had things apart for painting a few years ago. Now I don't think I want to disassemble my car again to perform the task, but I am curious if anyone here has tried it.

Bob
 

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Sounds like a great idea - take a 40 year old car and make the crash structure even worse 🙄🙄🙄
 
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Sure if you don't mind having no bumper when you crash (y) Might as well remove the seat belts as well.
 
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On the other hand if maybe if all you were doing was autocross it might actually save someone's life. Sometimes competitors get bored and distracted while taking their turn working the corners. :whistle:

When I retire I want to build a spray booth and teach myself how to paint and I thought those MGBs might be a good car to practice on. There's not a lot of surface area to have to "do over" a bunch of times and the rubber bumper ones can still be found for cheap. They almost all need paint and a little body work anyway and there's chrome bumper conversion kits. The last thing I'd want to do is put those ugly black rubber bumpers back on.
 

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Discussion Starter · #5 · (Edited)
Well, everyone is entitled to their opinion, but for those of you who are not as mature as me, you may not remember that the idea of the "5 mile per hour" bumpers was not to offer any added protection to passengers in the event of a serious crash, it was to lessen the insurance claim amounts in the event of a low speed impact. The big heavy hunk of steel absorbed the impact and all the body shop had to do was repaint the cover and you would be back in business. Passenger safety in a serious crash is accomplished by the "crush zones" built into the unit body structure. I believe the thinking of the MG owners is that a collector car that is only driven a few thousand miles a year, and never parallel parked, can perhaps get away without having the actual steel reinforcements inside the cover.

I own two MG's, and I was never a fan of the rubber bumpers, but if they are painted body color they don't actually look too bad, especially on the GT.

BTW, please disregard the Costa Rica flag; I am on vacation but will be back in the U.S.A. next week.

Bob
 

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The giant steel bumper reinforcement is not for '5 mph' protection. It helps to distribute the crash load into the unibody properly so it can absorb as much energy as possible, even if the impact is only over a small area and/or not close to the front crash structure of the car. That's why it's so heavy. But it's your neck.
 

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Discussion Starter · #7 ·
I quote Paul Niedermeyer from Curbside Classics:

"One of the all-time most controversial new regulations during that regulation-happy period of the 70s was the 5 mile bumper. A response to rapidly increasing repair costs due to the extravagant styling and resulting minimal bumper protection of so many cars during the 60s, the 5 mile bumper was implemented for MY 1974, and required that there be no damage to the car’s lights, safety equipment and engine in angled 5 mph impacts. For MY 1979, the standards were raised further, to zero-damage. Controversially, the standards were lowered in 1982 to 2.5 mph, where they still stand, similar to the international standard."

I stand by the original reason for the heavy, obtrusive bumpers that began appearing in the mid '70's. The regulation was intended to reduce insurance claim costs in relatively slow speed impacts, NOT to offer any additional protection in the event of a serious crash. If they did anything to help reduce injury to passengers in a serious crash, then that was all well and good, but it was NOT the reason for the regulations. You may do a search for an article in the January, 1975 Road & Track that discusses the issue in depth.

So we may agree to disagree. I guess the answer to my original question is a resounding "NO", no one on this forum has contemplated removing or in fact removed the heavy internal structure and replaced it with something lighter, either for better handling and acceleration on the track or for the slightly better fuel economy that a lighter car would exhibit.

Bob
 

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The 5mph part is the plastic bumper and the foam absorber and has nothing to do with the steel beam inside. You take new cars apart there is still a beam under there and looks very similar. These days they can be made from extruded aluminum or some I've seen heavy composite ones as well. Putting some PVC pipe from home depot isn't going to do crap in a crash. Originally when they first started doing these requirements they had big shock absorbers and pushed the bumpers so there was room for the shock to move. Most street cars have always had bumpers going back to the brass era. Just look up offset crash tests when they first started doing these and the impact was outside of the bumper beams.
 
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Yep, the 5mph bumpers on my 1979 Cadillac have steel shock absorbers that look like taken from a railroad car. The Supra bumpers don't look anything like that but at least the rear bumper is really heavy (I had to lift it out when doing the part resto on my blue Supra.The front steel bumper structure is fixed to the car if I remember correctly and won't slide out like the rear one.
 

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On the mk2, I'd assume because the front steel bumper beam makes up a significant portion of the left to right reinforcement of the frame in front of the firewall, removing it may reduce the torsional stiffness of the chassis so much it would negate any benefits. For the rear, it's not the best place to drop weight in a car that's already a bit front heavy and traction limited.
 

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Discussion Starter · #11 ·
"The 5mph part is the plastic bumper and the foam absorber and has nothing to do with the steel beam inside. "

Before the 5 mph bumpers were mandated, cars did NOT have huge, heavy steel beams inside the bumpers. The bumpers WERE the steel beams. And they were bolted directly to the frame, not mounted on shock absorbing pistons. Did car companies suddenly decide to add heavy beams out of some sudden feeling that they needed to do more for the stiffness of the structure or passenger safety? No, they did it due to the fact that congress mandated bumpers that would withstand a 5 mph low speed impact without damage in order to reduce insurance claim costs.

And that is all that I have to say about that!

Bob
 

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On the mk2, the bumpers are the steel beams, bolted direct to the frame. The outer painted cover is just that, a bumper cover.
 

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The bumpers WERE the steel beams. And they were bolted directly to the frame, not mounted on shock absorbing pistons.
Just like the bumpers on the Supra. Steel beams bolted directly to the frame, with energy absorbing foam and a plastic cover on top of it to meet the 5 mph requirements. There are no shock absorbing pistons.

That said, Toyota did change their cars for the varying safety market standards for many cars during the 1980-2000'ish era. For instance, the doors have added reinforcements on North American cars, and the bumpers were frequently different. On the AE86, the front bumpers everywhere except North America and the Middle East have no rebar, the plastic bumper is just bolted straight to the frame with a small bumper bracket, front and rear. It would be interesting to see the higher speed crash test data between the Japan-spec and North American-spec cars. That said, my anecdotal experience is that the North American bumpers generally cause increased repair costs, as a corner impact will cause lesser damage to both frame rails/fender aprons, etc., instead of more damage to just the one side.

The Supra/Celica XX uses the same bumper arrangement globally, so they didn't just add the extra bumpers to the car only to meet North American standards. They also used them in markets that didn't require them, despite doing so for many other cars. Perhaps there was some benefit beyond meeting those local requirements. Not sure.

Personally, it does not seem worth the 30 lb weight savings if the car still looks exactly the same. It's just wouldn't be enough weight loss for me to undertake such an endeavour, but I reckon your mileage may vary.

Jeff
 

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On the other hand if maybe if all you were doing was autocross it might actually save someone's life. Sometimes competitors get bored and distracted while taking their turn working the corners. :whistle:

When I retire I want to build a spray booth and teach myself how to paint and I thought those MGBs might be a good car to practice on. There's not a lot of surface area to have to "do over" a bunch of times and the rubber bumper ones can still be found for cheap. They almost all need paint and a little body work anyway and there's chrome bumper conversion kits. The last thing I'd want to do is put those ugly black rubber bumpers back on.
I've got a little Opel GT you can practice on right down i35 :D
 

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Open GT is on the list. I always click on the links when I see one listed for sale anywhere nearby. But as to painting one, its going to be a while till I can retire and build my "barndominium" with a separate room.
 
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