"No ticket" (edited for different video clip)

'99 Box w/ 66K miles. I hear a low oscillating noise: womwomwomwom... Appears to change frequency with vehicle speed. So, I'm thinking either wheel bearings, or tires. Any experience with this type of noise? What would you start with first? I'm about to replace the suspension with a ROW M030 kit. Since most of the suspension components will be out of the way, may be the perfect opportunity to replace the wheel bearings. Hope to do that within the next month. However, if the wheel bearings aren't the problem, would rather use the money on some other area of the car that needs attention. Thoughts?



Edited 1 time(s). Last edit at 09/21/2011 06:32PM by bar10dah. (view changes)

... if you can make the sound change pitch and volume by swerving hard from side-to-side while the vehicle is moving it's the bearing.
If the noise remains more or less the same, kit's the tires.
Happy Boxstering,
Pedro

Pedro Bonilla
1998 Boxster 986 - 311,000+ miles: [www.PedrosGarage.com]
PCA National Club Racing Scrutineer - PCA National HPDE Instructor - PCA Technical Committee (Boxster/Cayman)

---

Racecar spelled backwards is Racecar

"Racing is life. Anything before or after is just waiting" ... Steve McQueen as Michael Delaney in "LeMans"

"If you wait, all that happens is that you get older"... Mario Andretti

"Being second is to be the first of the ones who lose" ... Ayrton Senna

...hope I don't get stopped for possible DUI from all the swerving I'm about to do!

The sound doesn't appear to follow the swerving, just the speed. So best guess is the wheel bearings aren't the culprit?

My rear tires seem to have plenty of tread on the outsides, but the centers are almost down to the wear bar. It's really really close! Probably in 1,000-2,000 miles I'll be ready for new rear tires. I guess I'll wait until then to see if the sound goes away. Then I'll do the ROW M030 install.

it's probably caused by running the tires over inflated.

I just bought the car and don't have any history. But when I picked it up, all four tires were at 32 psi. Per the inflation sticker, lowered the front to 29 and raised the rear to 36. However, when I noticed the centers of the rear were worn that much, I lowered the rears to 29.

The rears are supposed to be at 36 psi.

If you mean "the problem" being the noise. I would agree that underinflated tires might make noise.

If you mean "the problem" being the center tread wear. That would be overinflated tires.

[www.procarcare.com]

Since there car doesn't seem to have much in the way of service records and the fact that the front tires were overinflated and the rears underinflated, who knows how the previous owner looked after the car. My guess is that it was driven with the rear tires overinflated for some time by the previous owner.

Noticed the noise when the tires were at 32 PSI. Still heard the noise when inflated to 36 PSI. And heard again when lowered pressures to 29 PSI. Tomorrow, I'll inflate back up to 36 PSI and leave it.



Edited 1 time(s). Last edit at 09/23/2011 12:22AM by bar10dah. (view changes)

The design of modern wide tires, (30,40, 50, etc. series) requires proper (more) air pressure to push out the side walls to flatten the center of the tread. Low pressure will cause wear in the center. This is the opposite of older, narrow tires, (78, 80 series) where higher pressures will cause the tread to wear in the center. My Boxster with a lots of negative camber has more wear on the inside edges of the tires.

Ed B

Okay, so just to clarify, running lower pressure makes the centers wear faster?



Edited 1 time(s). Last edit at 09/23/2011 12:23AM by bar10dah. (view changes)

Yes, with modern low profile tires. With older narrow profile (ie 165 x 15) the opposite is true.

Ed B

Quote
Ed B
The design of modern wide tires, (30,40, 50, etc. series) requires proper (more) air pressure to push out the side walls to flatten the center of the tread. Low pressure will cause wear in the center. This is the opposite of older, narrow tires, (78, 80 series) where higher pressures will cause the tread to wear in the center. My Boxster with a lots of negative camber has more wear on the inside edges of the tires.

Ed B

I've never heard of wider tires wearing the center tread more quickly due to low pressure. I have heard that it might happen if you put wide tires onto too narrow a wheel.

It's true that as you raise air pressure, it pushes out the sides more, but it also pushes the center part of the tire (tread) out more, whether it's wide or narrow tires.

Not a Porsche but years ago my Honda CRX developed a womwom. At highway speeds it sounded like I had a Sopwith Camel chasing me. The rear hub assemblies with the bearings were integral to the trailing arms so they got changed out and goodbye noise. Out of round tires can do something similar. Any sign of scalloping? (Tread blocks individually worn unevenly,)

Minus 40 degrees... Is that Fahrenheit or Celsius?



Edited 1 time(s). Last edit at 09/21/2011 09:19PM by Laz. (view changes)

But I'll look again tomorrow.

The lowest I can recall anyone here setting them at is 33. If there's still enough tread, just set the pressure to at least 34-5 and change them when you see minimum safe tread. And if they're only summer spec tires, don't drive in snow. If you don't know already, summer tires can snap suddenly even on dry pavement below about 45 F.

Minus 40 degrees... Is that Fahrenheit or Celsius?

Both just after about a minute

[www.youtube.com]

[www.youtube.com]



Edited 1 time(s). Last edit at 09/21/2011 09:13PM by Laz. (view changes)

Minus 40 degrees... Is that Fahrenheit or Celsius?

Went through this on a RAV4 with OE tires that had plenty of tread and no unusual wear patterns. The tires were amazingly loud to the point where conversations were difficult, so with only 7K on them I had them rebalanced--wha-la--greatly reduced noise.

Since your tires sound like they are due for replacement, re balancing would seem to be unnecessary, but would keep this in mind as the miles mount up on the replacement tires.

I just had the tires rebalanced a week ago. Hunter Road Force. I'm still hearing the oscillating noise. I'm thinking I'm just going to inflate to 29 front and 36 rear and start pricing new rear tires (fronts appear pretty new, lots of tread left). I can't tell if the noise is coming from the front or the rear, so I'll just start with the rears and see what happens.

Thanks all for the help! I appreciate the flow of ideas.

Quote
bar10dah
I just had the tires rebalanced a week ago. Hunter Road Force. I'm still hearing the oscillating noise. I'm thinking I'm just going to inflate to 29 front and 36 rear and start pricing new rear tires (fronts appear pretty new, lots of tread left). I can't tell if the noise is coming from the front or the rear, so I'll just start with the rears and see what happens.

Thanks all for the help! I appreciate the flow of ideas.

I literally replaced my 2 rear tires today and just drove it home. It's amazing how much quieter it is. I had noticed, as wear became worse, noise became louder, also picked up a little vibration at the last 500 miles or so. 17,500 miles on them and they were down to the cords on the inside right tire. Cut it a little close!

I just replaced my rear tires today and took the car out for a test drive. That low oscillating sound is gone!! Wohoo!

I have Cooper Zeon 2SX on the front with 8/32 left. I figure I'd get some BFG G-Force Sport for the rears this time around. By the time I'll need new tires again, I'll get matching front/rears, maybe even with new wheels. I really like the brush face silver RW-5 from roderickwheels.com but they only come in 19". I'd like to stick with 18" for my '99 Box. But if I do go with the 19"s, what do I need to do to make them fit correctly? Spacers?

BTW, the tires I replaced were 2/32 in the centers and 5/32 on the outsides.

I'm *so* relieved it wasn't wheel bearings...

On my 2000S last year I spent a couple of months messing with tire pressure and rotating tires etc.trying to chased down a similar sound.
I replaced the wheel bearing on the rear drivers side and it was like having a new car!

My car had about 95K miles but is a similar year as yours. Replacing bearings on these cars is not unusual.

BTW, I got mine at Autohausaz for $39.

dghii
2000 Boxster S 6speed 112k miles