rubber bumpers
11-08-2008, 06:31 AM
#1
Heel & Toe
Thread Starter
Member Since: Nov 2008
Posts: 19
Likes: 0
Received 0 Likes
on
0 Posts
rubber bumpers
As I stated in my "New Guy" post I have a 74 corvette convertable that has had a garage life all these years. Why would the rubber bumpers crack? Car has never been hit in 10,000 miles. Looks like they shank. Is this common?
11-08-2008, 07:52 AM
#3
Team Owner
Member Since: Sep 2006
Location: Westminster Maryland
Posts: 30,173
Likes: 0
Received 2,878 Likes
on
2,515 Posts
Hi M,
I had a new 68 GTO with an 'Endura' front bumper. Most people thought they were really neat but there were problems from the beginning.
I think the Corvette bumpers of a few years later were a different material but I do remember them not fitting very well and the paint not matching too well, either. Maybe yours are actually pretty good for a 34 year bumper that wasn't 'great' when new.
Regards,
Alan
I had a new 68 GTO with an 'Endura' front bumper. Most people thought they were really neat but there were problems from the beginning.
I think the Corvette bumpers of a few years later were a different material but I do remember them not fitting very well and the paint not matching too well, either. Maybe yours are actually pretty good for a 34 year bumper that wasn't 'great' when new.
Regards,
Alan
11-08-2008, 08:47 AM
#4
Race Director
The 73,74 and 75 urethane bumpers all tend to do this. I know of cars that have had the bumpers crumble and fall off in a pile on the floor while sitting parked in a garage. This has nothing to do with climate, mileage, abuse or anything else I know of, except maybe age. The 73-75 cars used a black urethane material, in 76, GM changed the formula used to produce the urethane. The 76 and newer urethane is yellow in color and seems to last just about forever. I don't know of any thing that can be done to keep this from happening to black urethane bumpers. I had a customer with a 74 that he was having painted, His front bumper had disintigrated and I was able to talk him into a Tru-Flex fiberglas front bumper, but he insisted on re-using his original, urethane rear bumper. It didn't last 6 months before it fell apart.
As far as Alan's comment about the paint not usually matching on the urethane parts, I was told that the early "flex" agents caused this. Flex agents were added to the paint to keep it from cracking as the bumper flexed. This seemed to get worse with time, too. I have found that periodic polishing (not waxing) of the original paint on the bumpers of my 81, brings them back to a closer match to the body, for awhile anyway.
As far as Alan's comment about the paint not usually matching on the urethane parts, I was told that the early "flex" agents caused this. Flex agents were added to the paint to keep it from cracking as the bumper flexed. This seemed to get worse with time, too. I have found that periodic polishing (not waxing) of the original paint on the bumpers of my 81, brings them back to a closer match to the body, for awhile anyway.
11-08-2008, 12:14 PM
#8
Team Owner
Member Since: Sep 2006
Location: Westminster Maryland
Posts: 30,173
Likes: 0
Received 2,878 Likes
on
2,515 Posts
Didn't the paint have 'flex agent' in it? Maybe this is why it 'faded' even with the car sitting inside.
I've faded somewhat since 1974 and I've spent most of that time inside.
Regards,
Alan
I've faded somewhat since 1974 and I've spent most of that time inside.
Regards,
Alan
11-08-2008, 10:41 PM
#10
Racer
My '74 has been garaged all it's life. Time will take a toll on urethane bumpers. I replaced both front and rear with fiberglass on the advise of a local Corvette Restoration Shop.
Mike
Mike
11-09-2008, 11:00 AM
#11
Safety Car
I think this a a normal occurence with original bumpers. They seem to get dry rot, and decay as a normal process of the material breaking down over time.
kdf
kdf
11-09-2008, 03:27 PM
#13
Intermediate
Happened to Both of mine on a '74
I recommend the Toledo Pro Tru-Flex bumpers they are easy to install even if you are a rookie. And if yours is falling apart remove the C-O-R-V-E-T-T-E letters from the bumper they are like $80+ to replace for the real OEM ones. (Don't get the imported ones) I lost my letters (C-O-R-V) when a chunk of my bumper fell off on the road.
11-09-2008, 08:32 PM
#15
Melting Slicks
11-10-2008, 07:29 AM
#16
Heel & Toe
Thread Starter
Member Since: Nov 2008
Posts: 19
Likes: 0
Received 0 Likes
on
0 Posts
11-10-2008, 08:04 AM
#17
Race Director
Member Since: Apr 1999
Location: CORVETTE 77 385 C.I. TEXAS
Posts: 11,520
Likes: 0
Received 12 Likes
on
12 Posts
The 73,74 and 75 urethane bumpers all tend to do this. I know of cars that have had the bumpers crumble and fall off in a pile on the floor while sitting parked in a garage. This has nothing to do with climate, mileage, abuse or anything else I know of, except maybe age. The 73-75 cars used a black urethane material, in 76, GM changed the formula used to produce the urethane. The 76 and newer urethane is yellow in color and seems to last just about forever. I don't know of any thing that can be done to keep this from happening to black urethane bumpers. ...
As far as Alan's comment about the paint not usually matching on the urethane parts, I was told that the early "flex" agents caused this. Flex agents were added to the paint to keep it from cracking as the bumper flexed.
As far as Alan's comment about the paint not usually matching on the urethane parts, I was told that the early "flex" agents caused this. Flex agents were added to the paint to keep it from cracking as the bumper flexed.
