Shrunken bumpers

[wwilkins]

Has anyone heard of the bumpers on our cars shrinking? My 1978 front and back bumpers are just a little bit narrower than the car. It looks like they shrunk but I am new to fiberglass so I could be wrong. Why would the bumpers shrink but not the rest of the car?

Bill

 

[JohnZ]

Different materials, different expansion/contraction coefficients; the body panels are fiberglass, and the bumper covers are reaction-injection-molded reinforced urethane.

 

[paintdaddy]

I am confused on what there made of .If they are fiberglass they are probably just a poor fit as most of the aftermarket bumpers are.The factory bumpers do get distorted ,wavy and misshapen over time.

 

[Gary42]

I am confused on what there made of .If they are fiberglass they are probably just a poor fit as most of the aftermarket bumpers are.The factory bumpers do get distorted ,wavy and misshapen over time.

The polyurethane bumpers on 73 to 82 Vettes annoy the hell out of me...have for years. I undertsnad the need to find a solution to federally mandated crash standards, but geez, other manufacturters found ways to deal with this without resorting to this terrible material. We've all seen otherwise gorgeous Vettes marred by their wavy, gooey bumpers. It's a shame. If I had a soft-nosed shark, I think I'd have to get the fiberglass replacements in order to be happy. Actually, it was one of the key factors in my decision to go for a pre-73 Vette.

 

[Paul Borowski]

For some reason, and it may have been the "mix" of the urethane that GM used any particular year, but some "rubber bumper" years hold up better than others. It also depends on how the car was stored, sat out in the sun, in a hot climate vs cool, etc. 1976 seems to be a year where they "lost" their bumpers alot. I've seen and judged alot of '78's where it looks like the area above the tailights is "caving in". This is very obvious especially on '78 Silver Anniversary cars. My '74 has the original bumpers, as does my '80, but my '75's front and rear bumpers came apart three years ago and I installed both a front and rear TrueFlex bumper. They came out very nice, however I had to modify a good bit to what is behind them because the bumper WOULD NOT fit over the factory crash dampening material unless I had trimmed it.