BMW 2002 FAQ - scraping sunroof at speed, but not when standing still

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Thread Topic: scraping sunroof at speed, but not when standing still

Date: 7-4-08 01:34
From: jvermes in California

Subject: scraping sunroof at speed, but not when standing still

Tragedy.

I just bought a wonderful 1974 2002tii which checked out totally with a few very minor quirks. One quirk was that the sunroof was a bit sticky, but with care opened fine. The guy I bought it from (who had restored it) said he never used the sunroof and that the felt needed to be worn in if I wanted.

On the way from Southern California to my home in Northern California, I opened the sunroof and closed it several times at speed as conditions required.

When I got home, I noticed that the right and left edges of the sunroof paint were scraped, destroying the previously pristine nature of the car. My conclusion is that the aerodynamics of the sunroof causes it track wrong at speed, but standing still it tracks sufficiently well that there is no scraping, even when it is a bit sticky.

Obviously I want to get it fixed, but there's no point in painting and reinstalling the sunroof if it is somehow warped or can't be adjusted properly or something.

Any thoughts on how I should proceed?

Rgds
John

Date: 7-4-08 09:50 From: TobyB in Seattle Subject: Re: scraping sunroof at speed, but not when standing still
"Doctor, it hurts when I do this!" "Well, then, don't do it!" There's not a lot of vertical adjustment to the sunroof... and what there is, if I recall, is achieved by bending the roof lip... t _________________ I have a car disease. There is no cure. I'm not even managing the symptoms very well...

Date: 7-4-08 11:10
From: jvermes in California

Subject: Re: scraping sunroof at speed, but not when standing still

Your information is useful, thanks. There is felt that acts as weatherstripping as I think you know. The seller, who restored it, said he wasn't in the habit of using the sunroof, but demonstrated several times in his driveway that it opens, albeit somewhat stiffly. My assumption is that he had never tested it at speed after he installed it. His contention was that the felt hadn't been compressed and this may be true. He figured if I used it a few times, it would get better -- as it indeed did (and not because the sheetmetal of the roof got bent. As I said I suspect that the thickness of the felt combined with the non-wind-tunnel-tested aerodynamics together with the rapid airflow at speed caused the roof to press up against the lip marginally but enough to scratch.

So, the sunroof did not get scratched on opening when the car was parked, and I couldn't hear anything bad at speed because of wind noise. My assumption when opening at speed was not that I was damaging the roof of my new pride and joy, a possession of only a few hours, but rather that I was tamping the felt down as necessary. Indeed the roof slides nicely now. I am not a happy camper.

I call this a freakish problem, contingent on the speed as it is. I can't take the blame and I don't really blame the restorer. He did an A+++ job otherwise.

Calling me an idiot between the lines is really adding insult to injury; bad bedside manner, Doctor.

Date: 7-4-08 12:10
From: dubois in Hollister, (near SJ) California

Subject: Re: scraping sunroof at speed, but not when standing still

this is a long shot, but go inside your trunk and check to see if you have two curved vent tubes on the sides towards the firewall. These were removed (so I hear) by BMW on sunroof cars, because of similar problems. Before I knew this, I thought my sunroof car was missing it, common mistake to "retrofit" a car and causing more harm that good. Please report back, I am curious.

Also refer to this for adjustments, I believe there is some but not much...
http://www.bmw2002faq.com/component/option,com_forum/Itemid,50/page,viewtopic/t,294557/
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72 tii A4, 72 tii Alpina, 98 M3 coupe

Don't argue with anyone that will not consider the possibility of being wrong...
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