I've heard it's the glue that was used and I've also heard it's mosture that gets trapped underneath....but I'm curious as to what really causes the metal under vinyl roofs to rust/rot?

Also is this still a common problem with today's vinyl roofs?

Water.... :)

Actually that is factual but the reason is the vinyl tops get pinholes or have microscopic holes even when new. The water gets in the backing and the glue tends to have small pockets that hold water. Of course at the bottom and edges, where the material is cut, the backing can wick up water and I suspect that is why so many have rust at the edges.

Its very simple. The felt lining on the back of the top is nothing but a sponge. The sun draws water upward during evaporation. When the water touch's the felt edge of a vinyl top either along the trim molding edge, or worse yet, in the window channel where water lays , the sun then draws the water up, and under the top, trapping the water. Sealing the edge of the top, particularly in the window channel helps a lot. Cars in rainy environments, especially rainy then hot, like my beloved Florida, are the worst for vinyl tops. Daily 3PM summer sun showers, followed with blazing heat are death to vinyl top cars.

Wow....so I guess it's not really all that possible to have a vinyl top on your car without having rust issues underneath?

POR-15 or the other guys stuff before you primer it. Then use epoxy primer 2 coats then a glide coat. Armor cladding!!!

As I said, sealing the edge helps a lot.

Vinyl top cars got very poor paint prep on the roof area. Our Lemans looked like primer and some silver over spray. It's amazing that any of these cars survived. Had the roof been painted properly, there probably would not have been nearly as much damage from rust.

Keith is exactly right. At the factory the cars that were to have vinyl tops applied, they saved a lot of paint by only priming the roofs and the old lacquer primers would absorb moisture. There was a certain amount of overspray that got onto the primer.If the roofs had been properly refinished at the factory you would not see all the rust problems except maybe around the window clips.When the clips were installed they would scratch the primer and the rust problem would escalate. Yes you can have a vinyl top without the rust if the top is refinished properly.

Keith is exactly right. At the factory the cars that were to have vinyl tops applied, they saved a lot of paint by only priming the roofs and the old lacquer primers would absorb moisture. There was a certain amount of overspray that got onto the primer.If the roofs had been properly refinished at the factory you would not see all the rust problems except maybe around the window clips.When the clips were installed they would scratch the primer and the rust problem would escalate. Yes you can have a vinyl top without the rust if the top is refinished properly.

Exactly. Which is why I have ZERO hesitation about installing a vinyl top on my '69, which didn't originally have one.

Keith is exactly right. At the factory the cars that were to have vinyl tops applied, they saved a lot of paint by only priming the roofs and the old lacquer primers would absorb moisture. There was a certain amount of overspray that got onto the primer.If the roofs had been properly refinished at the factory you would not see all the rust problems except maybe around the window clips.When the clips were installed they would scratch the primer and the rust problem would escalate. Yes you can have a vinyl top without the rust if the top is refinished properly.

I agree. I'm even thinking that a primered top would have seen more damage without the vinyl. When it's time to do mine, I'll just make sure that all rust is gone, and that it gets a good paintjob under the vinyl.

Keith is exactly right. At the factory the cars that were to have vinyl tops applied, they saved a lot of paint by only priming the roofs and the old lacquer primers would absorb moisture. There was a certain amount of overspray that got onto the primer.If the roofs had been properly refinished at the factory you would not see all the rust problems except maybe around the window clips.When the clips were installed they would scratch the primer and the rust problem would escalate. Yes you can have a vinyl top without the rust if the top is refinished properly.

This makes sense as I've been informed primer is porous, or allows water to get to the surface of the bare metal and begin rust. And I'm sure having the primer moist 24 hours around the clock doesn't help it any.

Jesse#51, welcome and let me say it's a small world, if your area info is correct you don't live but maybe 10 miles or so north of me....just up 87....me I'm down here in Spring Lake. (I'm sure you know where that's at)

Actually that is factual but the reason is the vinyl tops get pinholes or have microscopic holes even when new. The water gets in the backing and the glue tends to have small pockets that hold water. Of course at the bottom and edges, where the material is cut, the backing can wick up water and I suspect that is why so many have rust at the edges.

I have heard of an original '67 Chevelle owned by a little old lady that religiously applied baby oil to her vinyl top. No water would get in. There were no bubbles, and it was as soft and supple as new, even when it was 30 years old. The late Skip Cain bought it from her. It was wearing original Mountain Green paint with a black roof, plus factory wires. I think Skip sold the car 10 years ago to somebody in Ohio.

Skip posted that several years ago about the baby oil. It obviously worked for the old lady. The old lady may also have kept the car inside. The sun is no friend of vinyl either. We finished and painted the roof on our '72 Lemans Sport like the rest of the car then added the new vinyl. These old cars, for the most part, don't sit out 12 months of the year any more so I'm not worried at all about rust under the vinyl. The vinyl gives the cars a neat nostalgia look that we like.

I have heard of an original '67 Chevelle owned by a little old lady that religiously applied baby oil to her vinyl top. No water would get in. There were no bubbles, and it was as soft and supple as new, even when it was 30 years old.

I use baby wipes to clean and preserve leather interiors. Works like a charm. Wouldn't be surprised if it works on vinyl as well.