How to push in bumpers on a US-spec GTS/GTB

I pushed the front and rear US-spec bumpers inward this weekend on my US-spec 1983 308 QV.

There are several threads here on how to do it, but the directions are piecemeal, so thought I’d document the process here. I am no expert; this is just a description of how I did it (I took no photos). I certainly will not say anything about whether doing this is safe or not. Hopefully others have more content to contribute.

First off, the reason why there are no detailed threads is because the process is very straightforward.

>>>Rear bumper<<<
The goal here is to remove the two solid aluminum spacers between the bumper shocks and the bumper. These spacers are 1 ½” thick, and by removing them, you move the bumper 1 ½” inward. That is enough. The shocks themselves are difficult to shorten because they are enclosed under the rear trunk and getting to them would require removing lots of stuff, drilling rivets etc. 1 ½” is pretty optimal actually.

The process I used to remove the rear spacers is as follows:
- Remove exhaust cover
- Remove bumper
- Remove aluminum blocks
- Cut 1 ½” lengths of steel tubing as spacers to keep the bumper nuts on the threaded area of the bumper studs. (I used ¾” electrical conduit.)
- Replace rear bumper
- Slide on steel tubing spacers
- Replace nuts (consider using new Nyloc nuts). Use washers.
- Replace exhaust cover

>>> Front Bumper <<<
The goal here is to remove the front shocks and shorten them by compressing them. An alternative is to buy solid replacement brackets from MAcarbon. “Brian Harper” has pushed-in his shocks and “BLACKHORSE” has used the MAcarbon brackets. I had thought Brian Harper’s front was pushed in further than BLACKHORSE’s, Ferr Parts gave me a good price on a set of used shocks, so I did the drill and compress method. The reality is that Brian Harper’s are pushed in about the same as BLACKHORSE’s (and now mine) so, if I were to do it again, I would have bought the MAcarbon brackets.

The process to replace the front shocks is as follows:
- Raise headlights and disconnect battery
- Remove front grille
- Unplug the signal light pigtails on either side of the bumper
- Remove bumper
- Remove front shocks
- Replace front shocks with shortened ones (see below). Consider using new Nyloc nuts.
- Replace bumper (consider using new Nyloc nuts)
- Reconnect signal light pigtails
- Replace grille (consider using new Nyloc nuts)
- Reconnect battery

The process to shortening a pair of factory shocks is as follows:
- Drill a hole in the top of the shock roughly in the middle of the tube. This is the place where you will drill completely through later to secure the shock in a compressed position. Be prepared for a high-pressure mist bomb of mineral oil. Also be prepared for major oil drippage (see below). It gets everywhere; it’s as though it can drip upward.
- Using a wood vice (you need a 11” jaw opening), compress the shock to the desired length.
- (I assume all shocks are the same dimensions but you might compress the shocks at this point and rough fit them to measure how much you need to compress them for your car.) (My factory shocks were 10 7/8” total length and I shortened them to 9 1/8” which is 1 ¾” shorter. This is extremely tight: I did not have a mm to spare.)
- Drill through the entire shock starting at the hole you originally drilled for pressure relief.
- Insert a bolt through the hole and secure with a Nyloc nut.

Some tips:
- Keep some slack on the large vertical rear bolt (should have a Nyloc nut) on the front shocks. If fully tight, you cannot move the bumper up and down for height adjustment. Slack the nuts for the U-bracket to move the bumper up and down to get it even left to right. It’s a fiddly process.
- Check all grille hardware. I was shocked that two critical bolts on mine had loosened to finger tight. I replace all nuts with Nyloc (5mm dia 1.0 thread pitch). I know “somebody” who actually had their grille fall off; I can easily understand how this can happen.
- People claim they have done all this work within 3 hours. They are much better home mechanics than me. I struggled with wrenching nuts in many very confined quarters and spent a lot of time getting the bumper nicely leveled.

Regard the oil spill, both of the shocks I got from Ferr were identical looking. However, when I drilled the first one I just got a burst of dry air. When I drilled the second one, I got a lot of oil spray and dripping. Fortunately, prior threads had warned me of this and I had the shock fully wrapped as I drilled it. It is amazing though, how much oil just kept on dripping from the darned shock; it wouldn’t stop.

Bumper weights were as follows:
- Rear bumper: 39.2 lbs
- Front bumper: 40.3 lbs

 

It will be interesting to see if it works. 1.) I think once you look at the layout, you may find its not really possible to wrap a hose clamp around the shock to compress it. 2.) I'm skeptical that a hose clamp could provide sufficient compressive force. These shocks are supposed to stop a 3,000 lb car from 5 mph within the shock's 2 inches of travel. Must be pretty high pressure inside. 3.) If held in compressed position, over the years the high pressure gas would probably leak out making it unlikely the shock would spring back to original performance.

 

Personally, I think it now looks GREAT. As in: extremely happy. Call me conservative, but I like the idea that I have I-beams rather than fiberglass as bumpers.

There are three reasons why I did it the way I did:
1.) I wanted to keep it as a reversible change.
2.) I wanted to ensure I pushed the front bumper in as far as it can possibly go. (Technically, it could go farther in if one were willing to trim a bit of (non-structural) chassis).
3.) I kinda like taking things apart just to see what's inside.

I didn't take "before" shots, but there are a few of the result.
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It would be interesting to see some photos of the result. Particularly, it would be interesting to see a photo that shows how far the rear bumper pushes in with the shock drilled rather than by removing the aluminum spacers.

It would also be interesting to see photos of the front and rear bumpers of a factory euro car. Anyone?

 

I can answer my own question regarding the Euro bumpers. "-CD-" had posted some clear bumper shots of his magnificent Euro GTB.

It looks like the Euro bumper extends a little less than a pushed-in USA bumper, but the bigger difference is that the front of the Euro bumper is angled at the same slope and is flush with the marker lights. The USA bumper has a flat front. To my eye, the Euro is aesthetically better, but the pushed-in USA bumper comes acceptably close.

The rear bumper however is considerably different. The Euro considerably shorter. A big difference is the requirement for the exhaust cover on the USA model, which makes it impossible to imitate the Euro profile.

I will get flamed for saying this, but I am okay with the USA exhaust cover. The exhaust cover implies the car has such a big engine "package" that it has to hang under the car.
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Thanks for the kudos. We big-bumpered 308 owners can be self-conscious. Happily, a little bumper tuck goes a long way.

It makes a BIG difference, doesn't it?

Great idea using nut extenders; I wish I had used them.

 

There are several people who are reporting that they don't have the 1 1/2" spacers.

Now that you've pushed in the rear shocks, is the bumper now even with the exhaust cover or does it still extend beyond it? If it still extends beyond, that would probably mean you have a different length of rear shock than the cars with spacers. The spacers are so easy to remove though, that I suspect they were just removed at a prior time.

It would be great if you could post a photo of your rear bumper now that the rear shocks are pushed in.