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996 CS howling sound from the back while driving


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Hi all,

First of all, I am a newbie here. I did some searches already. If I miss any post like this. Please kindly post a link in your reply post. By the way, I meant C2. No idea why I typed CS instead.

Ok, here is the story. My 2003 996 C2 has 21k miles on it. It has the sport chasis + the 18 wheels from the factory. Recently, I noticed a howling sound coming from the back of the car. Very noticeable around 20 to 40mph. Any speed faster than that, it kind of got drown out by the road noises.

Does anyone have any experiences similar to this?

If so, please post here.

Thanks! :)

Thomas

Edited by The Hoth
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Check the tires first - that is pretty low miles for a wheel bearing problem.

I have lowered the tire pressure from factory recommended spec to 32 front and 36 back. I wonder would low tire pressure generate noise like that.

By the way, how exactly could I check the tires? I mean, beside checking the tire pressure.

Edited by The Hoth
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The 911 is very particular about it's tires and tire pressure. Check the inside of the rear tires. I thought I had brand new tires on my 2000 model because of the tread I could see from the side. However, first rainstorm revealed a car that handled like on ice. Looked at the inside of the tire and it was bald.

Also, could just be that you are noticing tire sounds more now that you have had the car a little while.

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Are you sure factory spec is 32/36? I have 18" Porsche Sport Design wheels and the manual says 36/44. I wouldn't expect your 2003 model to be that different. The 32/36 in my manual is for 17" rims.

It has got to be the tire pressure. The noise started after I dropped the tire pressure.

You are right, the spec is 36/44. I read some posts on the internet saying the factory spec is too high, so I tried using the lower tire pressure. I use this new tire pressure for the past three days.

Hopefully, it did not damage the tires. :o

They are kind of expensive......

Edited by The Hoth
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I run 32/36 on my Bridgestone S03's. The car handles much better (for my driving style) at those pressures. So far I have not had any unusual wear pattern. But then I really don't expect to get much more than 10,000 miles out of the rears...

What is your tire size? 17" or 18". Factory or aftermarket?

Mine is 18 factory. I am going to increase the pressure to 36f and 44r. Hopefully, it will take care of the howling noise.

I will keep you guys posted.

Thanks for all your inputs.

:)

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Worn out tires could sound like a bad bearing. depends what tires you put in also. Bridgestone S03 are good quiet tires and michelins too. I had the old yokohama es100 on my Audi and I thought my bearing went bad, but it was just the tires. The pirellis I have right now OEM tires on the rears of my 03 C2(on the wear bar already) it's not as quiet as it used to be, but since the tires on this car is soooo expensive and wears out so fast I will wear it out just a little more. Can't wait to put on new tires/alignment and have that smooth quite ride.

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My 996 C2 had a similar problem, eventually traced to incorrect rear wheel alignment. The inside edges of the tyres had cupped and produced a wheel bearing like sound at around the same speed you mentioned, it decreased when the speed increased or as you said became less noticable. I had Bridgestone S02 at the time, new tyres and an alignment fixed the problem completely.

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My 996 C2 had a similar problem, eventually traced to incorrect rear wheel alignment. The inside edges of the tyres had cupped and produced a wheel bearing like sound at around the same speed you mentioned, it decreased when the speed increased or as you said became less noticable. I had Bridgestone S02 at the time, new tyres and an alignment fixed the problem completely.

Thanks for sharing your experience.

I've changed the tire pressure back to 36F and 44R. Now the noise is gone!

False alarm.

I guess I read some internet post for correct tire pressure and I mistook the 17" tire pressure for my 18".

Not too bright on this one. :rolleyes:

Thanks for all your reponses. Looking forward to hangout with you all in the forum. :D

Now I have to work up my courage to fix my wheels as I curbed my wheel a few months ago. It is still an eye sore.

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  • 2 months later...

The noise came back and got louder, so I replaced the tires with Bridgestone Potenza 050 Pole position. If I shut off the radio and listen carefully, there is still a little road noise which is normal for this type of tires. Now the difference is day and night.

Now I know for sure the noise came from the old Pilot Sport tires. I can't believe I have been driving on bad tires for such a long time.

Just got 03 996 back from dealership, new rear tires and 4 wheel balance took care of the howling.. Thanks to all I avoided the unnessary bearing replacement and saved $700.

Chris

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