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Old 06-22-2010, 08:16 PM   #1
Rudgers73
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Member#: 141433
Join Date: Feb 2007
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Location: Rochester, NY
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2006 Impreza 2.5i
Obsidian Black

Default Irritating noise I can't put my finger on

okay, so I need some help on this one:

06 2.5i
hybrid intake
stromung axle-back
17" rota SDRs
Sumitomo HTRZ-IIIs

I have noticed over the past couple of months that my car makes a cyclical drone that seems to hum back and forth or side-to-side. This only happens when I have 2 people in my back seat. I reach highway speed and the drone begins. At 60 mph is oscillates at about 1 Hz, at 70 mph only slightly more frequent. If I take my foot off the gas and let the car slowly decelerate it quiets down where I can't hear it anymore. If I have my foot on the gas to a point where my exhaust naturally resonates the sound buzzes throughout my whole car. I noticed today that if I am going around a sweeping curve the cyclical drone will change frequency and go away for a second like some sort of deconstructive interference. I'm not sure if it is a diff (rear or center), if it's my tires getting loud (it's my second season on them), or if having weight in the back seat is making something touch under the car where it normally doesn't. I recently lowered my car on eibach pro-kits and the noise in no different. I rotate my tires, have no odd wear, and checked for wheel bearings this weekend.

Any ideas??

Thanks
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Old 06-22-2010, 08:49 PM   #2
J-Chow
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Gray

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loose exhaust shields / bolts? Check if your rear sway bar endlinks are intact.
Any rear mudflaps scrapping due to low clearance?
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Old 06-22-2010, 09:01 PM   #3
kero
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Sometimes improperly worn tires can cause noises, especially when weight is put on them or you take turns that put weight on them. Check them out just to make sure.

When the weight is taken off, the treads are not as squished down, and the noise goes away, I had this issue once before and it was really poorly worn tires due to bad alignment after lowering the car.
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Old 06-22-2010, 09:14 PM   #4
Rudgers73
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Quote:
Originally Posted by J-Chow View Post
loose exhaust shields / bolts? Check if your rear sway bar endlinks are intact.
Any rear mudflaps scrapping due to low clearance?
definitely not mudflaps. I should check my endlinks, though. I will check heat shields when I'm under there, but it isn't anything close to the noise of a rattle so I doubt it's that.

Thanks for the idea man
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Old 06-22-2010, 09:16 PM   #5
Rudgers73
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Quote:
Originally Posted by kero View Post
Sometimes improperly worn tires can cause noises, especially when weight is put on them or you take turns that put weight on them. Check them out just to make sure.

When the weight is taken off, the treads are not as squished down, and the noise goes away, I had this issue once before and it was really poorly worn tires due to bad alignment after lowering the car.
I was thinking it could be the tires, but they look fine. And the sound was both there, and no different before I lowered the car. I was thinking of raising my tire pressure to 40 just for a day to see if there is a difference. I'll do that this week and see
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Old 06-22-2010, 10:37 PM   #6
kero
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^^ Don't raise your pressure to high 40 sounds kinda high to be honest. To high of pressure can cause crazy hard ride and poor handling and or emergency handling capabilities, etc. You don't want to be riding on stones.

Don't go by looks on your tires, take your hand and run them over the treads in both directions for all 4. This will alert you to any uneven wear that just looking might not show. Even slight uneven wear can cause road noise and humming and all sorts of odd sounds.
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Old 06-23-2010, 06:11 AM   #7
Rudgers73
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Quote:
Originally Posted by kero View Post
^^ Don't raise your pressure to high 40 sounds kinda high to be honest. To high of pressure can cause crazy hard ride and poor handling and or emergency handling capabilities, etc. You don't want to be riding on stones.

Don't go by looks on your tires, take your hand and run them over the treads in both directions for all 4. This will alert you to any uneven wear that just looking might not show. Even slight uneven wear can cause road noise and humming and all sorts of odd sounds.
I have a pretty good feel for tire pressure and wear since I have been autocrossing for 3 years. I reeeeeally don't think it's my tires. When I first got these tires I drove on them really aggressively and got some pretty serious feathering on the outside shoulders, but there was no noise or hum from them then. When I put them on this year I checked them out closely and the wear since rotating them has been very even. There is no cupping or flat spots and the feathering from the front tires has gone away since moving them to the rear. I don't think pumping them up to 40 psi will cause any serious issues for a trip to work and back. When I race I keep them at 45 on all corners and I have driven to events this way in the past. Yes, it does make the handling a little touchy, but I have a really good feel for my tires at higher pressure and plan on taking them right back down as soon I see if the noise is still there, different sounding, or gone.
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Old 06-23-2010, 06:50 AM   #8
silver2004impreza
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I think it's your tires. I've got the same ones on my car, and they make a sound like my bearings getting ready to explode. I know it's the tires though, because the noise goes away when I install my winter set of tires.

Speaking of which, if you've got another set of wheels and tires, just swap them for a test drive and see if the noise is still there or not.
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Old 06-23-2010, 08:45 AM   #9
Rudgers73
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ahh that's what I was looking for: someone with the same tires!

Like I said before, there is nothing wrong with the tires persay... but I would believe that they just get annoying as they get more worn down. Sounds like it's somethng I'll just have to deal with since I like the performance of these tire so much. I'll just have to make my exhaust louder to compensate haha

Thanks silver2004impreza
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