OK, so I was changing my license plate and I noticed what looks like a valve stem from a tire in the body of my car behind the rear bumper. It has a label that says 25-200PSI. Anyone know what this is for? My car is a 67 coupe.
Air shocks were simply to raise the rear of the car for tire clearance and improved load carrying ability. They helped to stiffen the rear in cornering to some degree. I had em on my 67 FB. Some like em, some don't.
Years ago before gas shocks were really good folks used them to keep the inner fender from rubbing the tires when going over large bumps and dips in the road (i.e. railroad tracks). You could also put more air in them to get a jacked up look. Some folks believed they helped w/traction. Also you have some adjust ability of ride quality. One well known brand is Gabriel HiJackers.
Disadvantages
I have heard that the air shocks have cracked the upper shock mounts, although I have not experienced it.
After a few years they tend to leak air either due to bladder failure (not so common) or the lines are broken and leak. Sometimes the seals in the unions leak as well so you must keep adding air every week or so.
I replaced mine w/ some KYB gas shocks which are really good considering the price. The air shocks leaked a little at the unions but I wanted to replace them w/ a quality gas shock and wasn't too concerned w/ a "smooth" ride.
+1, the Schrader valve behind the bumper was for air shocks.
A '65 notchback I had got Skyjackers put in at some point and they were terrible. They did leak, but they were still harsh even when the air was gone. I had a friend in high school that also had them under his '65 Olds Cutlass it was like riding in a truck. In fact, that's the only place I think they belong; under a truck.