Front bumper mounting question

TodB

TodB

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I've removed my (Euro) front bumper a couple of times in the past mainly to get to the air dam to repair and/or paint. The 4 bolts, 2 for each frame rail, that hold the bumper in place are shorties where the head goes inside a slot within each rail. Its a bit of a pain making sure that all 4 bolts stay in there, don't fall out, fall inside the rail, etc. while getting the brackets lined up and onto them. Is there any harm drilling the bolt holes all the way through the frame rails and then just using longer bolts? Sure would be easier.
 
I'm not disagreeing that the factory solution is a pain, but I see an issue with your "drilling the bolt holes all the way through the frame rails" solution. Torqueing those bolts would crush the two sides of the frame together - not a lot, but enough to keep those bolts from staying tight.

To implement your solution properly, you'd need to weld spacer tubes between the frame sides to handle the compressive load.
 
Didn't think of that. I wouldn't think you would need to tighten the nuts enough to actually compress the frame rail sides?
 
HB Chris said:
The 73 uses a bolt thru the frames.
Click to expand...
Chris: OK, but is there a support between the vertical members on the 73's to handle the compressive load of the through bolts?

TodB said:
I wouldn't think you would need to tighten the nuts enough to actually compress the frame rail sides?
Click to expand...

Well, you're welcome to try it. But I'd use Loctite or a nylon locking nut to secure the nut; not a split lockwasher.
 
Last edited:
jmackro said:
Chris: OK, but is there a support between the vertical members on the 73's to handle the compressive load of the through bolts?



Well, you're welcome to try it. But I'd use Loctite or a nylon locking nut to secure the nut; not a split lockwasher.
Click to expand...
Not to my knowledge.
 
HB Chris said:
The 73 uses a bolt thru the frames.
Click to expand...
Not on my EU market may 73 e9 though.

And interesting topic, as I was fighting with the same bolts, I had to cut one before being able to extract it, as the side of the frame rail locking the bolt's square head, had squished into a round hole.
So I also need a solution; and I didn't consider the squashing effect. I will consider the tube. I Might also opt for nutserts.

If you decide to drill holes, remember to carefully extract the drilling debris from the inside of the frame rail with a magnet or air suction. They are the ideal starting point for rust.
And soak everything in your favorite paint after drilling and cleaning.
 
Tod,

Go ahead & drill. You could tack weld a sleeve if you’re so inclined, it would make reassembly much easier instead of looking for the hole through the frame rail.
 
There are cylindrical spacers welded on the US 1973 CS (mine as an example). I can upload photos later, but it is exactly what @jmackro postulates. Else, this 14 gauge metal frame rail would in fact hourglass in as the bolts are tightened.
 
Follow up. Here are photos of the 1973 US CS bumper attachment points. Sorry for the delay.

View from inside (engine bay):
20230113-1973 US bumper attachment inside.jpg


View from outside (wheel well):
20230113-1973 US bumper attachment outside.jpg
 
I get the feeling the idea is to bolt the brackets up separately from the bumper with the bolts loose so they have room to slot into the slots, then attach the bumper and make final adjustments. I removed the bumper without loosening the brackets from the bumper and I think it made things more difficult getting around the bolts that were in the frame rail.
 
as i remember, and i've only done this once, but i don't think you can make the final bumper to bracket attachments with the bumper in place ... especially with an air dam as there isn't much room to get the tools in behind the over-rider. i could be wrong, just going from memory ... but my car did have a dam in place ... but i was just trying to rework the rubber trim around the over-rider
 
That definitely makes sense which is why I didn’t try to loosen the bracket. I’ve seen photos of cars during restoration where the bumper brackets are mounted so it made me wonder.
 
On a 73 with the bigger bumper irons they must be secured to the bumper first and then introduced onto the frame rail which is why the thru-bolt is so much easier.
 
I guess I don’t know why you’d do this then. Glad I didn’t waste time on it!
 

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