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I have a peculiar problem. At about 135 – 140 MPH indicated, my car has a loud reverberation from the back deck. Sounds like its coming from inside the car. Above 140, the vibration goes away. When I first had this happen, I got major palpitations, stopped the car, but couldn’t find anything wrong. I initially thought it was the rear deck because it vibrates a lot anyway (I have the rear sunshade). But the last time this happened, I looked in the rear view mirror and it appeared that the rear window was oscillating in and out making the loud vibration! I was afraid my rear window was gonna blow out. I have forgotten my college physics, but it must be a resonant frequency or something since it only happens at that speed.

A Hamann roof spoiler is installed on the car. I like the way it looks but only installed it because I thought that a reputable company like Hamann would have thoroughly researched the effects (aerodynamics and such). However, I’m not so sure now. If it turns out to be the spoiler disturbing air flow, I will have it taken off. I would rather have function over form. Besides, with the rear window oscillating that much, it is dangerous.

Any thoughts on this? Anybody else have this spoiler?
Rayman
2003 M5
 

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Since I don't routinely drive at those speeds on highways (or most anywhere, really!), I can't speak from personal knowledge. However, the symptoms you describe (assuming you're not just playing with us) could well be attributed to your aftermarket roof spoiler. That part of the car is particularly sensitive to flow changes, though air flow changes generally don't require much. If you think about how easily the water running from your faucet changes flow and direction when you just barely touch it with your finger, you'll see what I mean. Air is a fluid and (for this purpose) behaves in much the same way. I suggest removing the spoiler. I would suggest then testing it again at speed but don't really want to encourage you to do something quite that illegal and dangerous! :M5launch:
 

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I would suggest then testing it again at speed but don't really want to encourage you to do something quite that illegal and dangerous!
I think most would agree that the point in buying an M5, or any other high performance sedan is to use it's amazing abilities. Even if you don't track the car, this can be achieved on the street relatively easily. I'm always amazed when people say, "where can you really use 400hp?". With the phenominal power of the M5, it takes only a small stretch of open freeway to reach those triple digit speeds. Remember, 130-140mph in an M5 is similar to 80 in a Honda Accord, it's extremely safe at high speds.

Ofcourse, I respect what you choose to do with your car regardless.

Travis
 
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