Roof Rattle...no Hum...

(With apologies to Bono)


I have to admit that my roof rattles -- actually it makes a really loud cracking sound over a decent bump, and is pretty quiet otherwise. The rubber isn't bad around it. I swear I keep looking for one of the folding struts from my old 911 targa top to not be quite locked into place -- just senility creeping in, but that's the same sound -- last heard 22 years ago.

Any typical fix for this? I guess I could take photos of the rubber -- As I sit here, I am wondering if it's the metal edge of the top making contact with the top of the window(s) glass or the top of the channel... I'll have to drive it tomorrow with the windows down.

While I'm posting, my car only has lap belts, and a buddy came by to drive it yesterday and called me a "moron" for not installing shoulder belts or racing harnesses. You know, when I think about the downside, maybe the gov't had a point. Anyone know how to do this with minimum impact, photos of an aftermarket job, or someone near NYC who can do it and do it well???

 

It's the clamp that holds the roof in place, most likely on one side. Next time you're driving manipulate the locking mechanism and you will most likely find the rattle. Been there, done that.

 

I added a question about adding shoulder belts or harnesses above. Any ideas?

 

Are the lap belts on reels? Our car has the original lap and shoulder belts that were mandated in the UK in '74. No reels, but that's not much of a problem since I'm the only one who drives the car.

I sent photos of mine to a guy in the UK who was replacing his. Whoever did them (he posted photos) came up with a very reasonable facsimile.

I'm pretty sure that some US cars did have inertial reel lap and shoulder belts, so something like that might be your best bet. For sure somebody here has that set-up...

Definitely a good idea to add shoulder belts. I think that racing harnesses might be a bit much.

 

It may be the locating pins. Part of the roof. They have a wrench end, try a turn or two. Worked on mine.

 

the belts have nothing to do with the rattle (which i know you know). adding shoulder belts aren't necessary.

as for the rattle, the rubber, the targa bushings (fitted into the frame around the windshield), and the clamps should reduce the problem. but remember, these cars weren't sound proof from day one. with the top off, the noise isn't noticable. with the top on, the rain or other weather noise was designed to block it out. only kidding, however, these cars were designed with the roof being an emergency roof. it was designed to prevent water infiltration, not sound proofing.

 

Since you don't have shoulder belts, this might be a little more work. I think it was at Superformance in the UK that I saw a cross bar that mounts where the shoulder belts mount just behind the top of the seats. The racing harnesses were attached to this cross bar. It was really nice. I'm thinking of doing this in my car once she's back.

 

I'm going to search for photos,... would like to see what "factory" shoulder belts looked like, and how they were mounted

 

Mrony,
For the rattles and squeaks that are so common with the Dino roof, try silicone lube spray on a rag and apply to all surfaces that contact the leading edge and trailing edge of the roof. Also apply a bit of chassis or bearing grease to the hook part of the latch on the trailing edge of the roof. That's the hook that holds the roof in place in two locations on the trailing edge of the roof. Finally, I place a short piece of 3/8" (O.D.) hose in the drain gutter of the roll bar where the notch is for the roof . . . see the pictures. You want hose that has just enough resilience to snug-up the top against the body at all contact points.

For alternatives to factory seat belts/shoulder harnesses, which I agree are pretty minimal for aggressive driving, I installed a "period" 4-point system that works well. When I got serious about track days with the FCA many years ago, I bought a set of Simpson belts and installed as shown in the attached pictures. That's an 0.090" band of Al, paint matte black, tucked under the vinyl covered facia plate just below the rear window. There are several bolts that go through the firewall with nuts showing in the engine compartment.

Hope this helps,

Bill
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The instalation looks fantastic. Do you know which aluminum alloy was used? If it was 6061-T6, .092" thick aluminum I'm not certain it would perform as you would hope. Approximating the actual dimensions, the restraint system would probably fail during a fairly moderate accident developing a 25g force and on a 180 lb person. Below is a finite element analysis showing just one upper connection point.
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Here are those photos of the OE belts on our RHD UK car. As previously mentioned, no reels. Adjustable by hand.
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The material used is the key. Just because the sizes are similar does not mean the strength is equivalent. The factory uses a steel alloy in their design which has a much higher tensile strength than comon aluminum alloys. What you must ensure is the strength of the anchorage is at least as strong as the belt web material. I believe the belts have a breaking strength of 6000 lbs. In the analysis above, the applied load was only 1125 lbs. The only way to know for sure is to perform some destructive testing. I'm not trying to be critical, just want you to be safe.

 

Thanks for the FEA . . . for free! I just checked the material with a magnet and it's not Al as I had thought . . . it's been about 14 yrs since designed and installed by an independent Ferrari shop. A true analysis would have to include the rest of the system which the visible band of metal attaches to - - the firewall, connectors and well-aged belts. Fortunately, I never dinged the Dino during those years on the track. Sure was great fun and a wonderful learning experience on Watkins Glen, Pocono, Summit Point, Rockingham, Roebling Road and Road Atlanta. S/N 08118 is now back to a show quality road car with an A/C that actually works pretty good. Took a Platinum Award and Best 2-Series Dino (The Dino Ferrari Award) in 2006 at the FCA Annual Meet. My wife and I spent last Fri - Sun driving the back roads of MD, PA and WV for about 600 miles with 20 other Ferrraris and miscellaneous sporty types. Great fun with the FCA Mid-Atlantic Region!

I notice you also have a 74 GTS (your user name). What S/N? Tell me about it.

Bill

 

Bolted through the firewall are probably going to be the best alternative. This isn't intended for the track, but for at least some measure of shoulder restraint for general driving. The matte metal looks pretty unobtrusive. When I take the car in for paint, I'll see if the shop can handle this...