I've been on a tear this Summer to reseal my '66 big cars to make them as quiet as they can be. Quixotic quest maybe, but I'm getting there.

On the big cars, in the 60's, GM used sponge rubber roof rail seals on the hardtops and a harder rubber seal with metal insert in the convertibles. Yesterday I compared my used Metro brand convertible roof rails to the Steele roof rails and noticed some differences on the bench. I thought some of you convertible people might be interested in seeing them side by side.

Overall the Steele pieces use thicker rubber, are longer lengths (good for an Olds 98), wider on top, have a slightly longer ear that hangs down on the outside of the window to have water drip on the outside. But they are a cruder casting than the metro stuff. Metro on the other hand is a more detailed casting, but the rubber is thinner and the pieces are smaller in many dimensions. On the Metro parts the metal skeleton adjustment slots are better placed and slightly larger than Steele. Metro is definitely more adjustable.

Smaller thinner seals on a convertible means more potential for gaps which allow in water, air and noise. Thicker rubber allows for more range of error. Thicker rubber may also seal longer and tighter against windows.

Drivers Side front molding from the underside:

Steele part is thicker and slightly bigger, but a cruder casting. Metro is a better looking part, but a bit smaller. The front of this casting is complex - it seals the vent window, driver front window and windshield.

Drivers side front molding view from the top:

Steele piece has thicker rubber where the vent window meets the convertible top and interface is longer too.

Comparing driver's side molded ends where top meets the windshield.

Some wind noise in convertibles can be attributed to where the top, vent window & windshield all come together. A good seal here should help quiet things down & keep things dry

Comparing the casting thickness of the driver's side middle pieces. Viewed from the end:

I'm hoping the thicker rubber casting of the Steele piece will create a better seal against my convertible windows.


Looking at the middle pieces from the underside. Here the quality of the Metro casting is evident in the bumpers they cast in to keep glass from hitting retaining screws, but those bumpers also create a window top edge gap. Steele has no bumpers, but in exchange for a theoretically tighter seal between glass top edge and roofrail you take on the risk of glass on metal...

Metro has a higher quality casting, but thickness & underside flatness of Steele may perform better.

Aim to seal the window inside glass against the rubber:
At the risk of going on too long about this stuff, I'm concluding that the main wind/noise seal for GM windows in the 60's was not the top of the glass, but rather the inside glass against the rubber bulb seal or convertible flap seal as seen here.

For years I'd tried to get the top nice & tight against the window glass top edge, but I'm arriving at the view that the real seal deal is getting window inward pressure on the seals just right. Of course this requires adjusting windows, and not just messing with roof rails and rubber, so it's natural to try to get it close just by fixing the top parts and avoiding the work (often a day or more) to get the windows really right. Last week I did the windows on the 66 Starfire coupe, it took me 2.5 days more or less. Not dying to burn that on the convertible, but I'd also like to fix it while my learnings from the hardtop are fresh.

For now my parts are simply screwed to the top frame until I've adjusted the windows to the new seals. Once I'm happy with the new seal placement & window interface, I'll put some 3M seal caulk on the top of the rubber to water seal it against the underside to the top frame like GM did. Main message here is don't glue the seals down until you _know_ you're happy with how they sit in/out, fore/after and against your windows.

Hope this isn't more about convertible roof rails than you ever wanted to know.

Chris

 

Hi Chris, I'm currently looking to replace the door seals on my Vista Cruiser and was looking for info on steele vs metro quality when I found your really interesting post. I also have have a '66 Cadillac Eldorado, which I had retried, with a new top and seals. That was some years back for various reasons I have hardly driven the car since. In any case, the top looks very nice but there is plenty of wind noise, including from the front header. There is also more road noise that I'd expect from a Cadillac, which seems to emanate from the rear quarters, though pinpointing a sound source can be tricky. One obvious question at the outset is how quiet this convertibles should have been when they rolled out of the factory. Sometimes contemporary road tests give a clue but I haven't seen any references to this subject on 60's GM droptops.

So I would be very interested to know how you get on! Robert

 

Sorry for the late response, I’m on house projects at the moment.

Wind noise is part of having a convertible. The top is fabric: the price you pay for top-down flexibility.

I’ve spent days & days on the convertible wind noise problem. Maybe weeks. Modern cars have made us spoiled. In the 60’s the standards for what was a “fast” car, a “quiet” car, etc. were simply lower than what we enjoy today. They were not bad, but not as good as today.

Simply put, today’s engineering is better, even accounting for cars which were built to a price. The designs have changed, new seals are better (owing mostly to bulb seals), & almost all new car windows now roll up into door frames. Then those door frames seal very well against the vehicle body (with more bulb seals). In the 60’s the windows sealed against questionably firm rubber seals which eventually harden, crack & create voids.Roof rail rubber voids create noise.

Ignoring the top for a minute, I can report with a little confidence that the ventipane (wing windows) also create noise in the driver’s ear. I have a ‘66 Starfire coupe (hardtop) whose doors & windows are nearly identical to my 98 convertible, allowing for the difference between hardtops & convertibles.

Enough b*tching. Let’s get on to solutions / improvements:

1) Fresh roof rail rubber helps. Hopefully the notes above help you.

2) Fresh top may help too: top fabrics these days either shrink fast or are made just a bit too small for the factory top frames. I’ve gone through 2 top fabrics looking for a quieter car. One was a Caddy spec top which was supposed to fit an Oldsmobile 98 (reasonable assertion - the frame parts are the same across brands). It was too narrow by at least. 1-2” which was just enough to cause the fabric to sit above the frame rails. Then the inside/outside pressure differential pulls the top upwards (ballooning) and suddenly you have wind noise coming in from a top-to-frame gap at highway speed. Ugh. That top was done by Convertible Service in San Gabriel, CA. They did a great job. It just didn’t really cover my top frame properly. If you go by factory specs, what they did should have worked. But it didn’t for me, due to noise or my frame is out-of-whack.

So I kept hunting for better.

3) My local guy replaced the specialist top with a fabric from Eaton’s (East Coast somewhere). It’s better, but still too narrow for the frame to allow the top wires to pull the fabric _below_ the frame rails and hold it tight. After 2 tops in 15 years, at this point, I suspect my frame rails are wrong are t3o wide, or otherwise misadjusted. If you follow the factory literature, I’ve adjusted the Front Header Seal, Male Hinge, Roof Rails and on & on.

In the end I’m getting used to “Well standards were different then”.

4) I have insulated my top with some additional 3” flap seals from Trimlok. The idea was to use the flap seals connected to the frame rails to stop noise getting in. That helped. They’re pretty much an inverted U to squeeze the frame rails with metal staples and the flap variably seals to the top that moves. Installation is easy: you cut lengths of the flap seal that match your frame rail part and tuck the flaps in. Eventually they stay where you want ‘em, but in the early going you want to pay attention to watching the flaps go where you want them.

5) You can also add a layer of 1/8” closed cell foam hidden between the top fabric & an extra black fabric inner liner. My local guy sewed up an inner liner and put the foam between. It’s just in the front section, not middle or rear, but the foam and liner help. If you look at modern convertibles, you can’t get away from windows rolling up into the top frame roof rail rubber by design. But what the modern cars have is more layers for quiet. We can add these, selectively, but too much and your top wont sit flat in the well when it’s down.

6) I’ve had 1/4” shims between my top frames & roof rail rubber for years to force the rubber down onto the window tops. That helps.

7) Over the past few months, I’ve decided that the real “seal” deal or quiet seal is not the top edge against the roof rail. The real seal deal (aka what drives the quiet) is the inside vertical edge of the window against the roof rail vertical seal. Specifically not the top edge.

Hope that helps
Chris

 

Thanks Chris, I look forward to trying some of these fixes. Apart from the '66 Eldo, I have a '64 GTO which needs a complete body rest, so getting it as right as possible is on the agenda too. I have had several classic Mustang droptops and plenty of wind noise with the top up was always a given, but I never tried to address that. Top down was better and you could drive through rain and stay dry - the catch was you couldn't stop without getting wet! I've also owned a modern Mustang. Wind noise there was pretty much absent. As you say, one of the immediately noticeable differences is that moderns have an inner lining, with a completely hidden frame. The question of 'Was it like that out of the showroom, or has it deteriorated with age?', applies to almost every aspect of of our hobby other than appearance. Contemporary road tests can supply a few clues though. Some '60's Mopar convertibles were criticised for wind noise with the top up. On the other hand, when Car & Driver tested a '64 (I think) T-Bird convertible, they remarked on the absence of wind noise. (T-Birds and Continentals did of course have unique top mechanism). Closer to home, one of the mags tested an early '70's Vista Cruiser, and noted that it was extremely quiet, wind noise included. That car was a factory special, upgraded to 4 4 2 spec, so was hand built and unrepresentative of what rolled off the assembly line But it does show what could be achieved back in the day. I'm wondering what new seals will do for mine!