We swapped tires on the STI at a local Subaru dealer two weeks ago. Days later the tire pressure warning lit up. A check of tire pressures confirmed they were to spec. We checked the tires regularly for several days. No change. TPMS light still on. Meanwhile, we made arrangements to get it back to the dealer.
Today, while driving around town with the windows down, we heard a noise. Clap-clap. We could not reproduce the sound consistently. It seemed to originate near the rear wheel and was most common from 5-15 mph. We heard it in a straight line. We heard it while turning.
There were never more than three claps at a time, but the silence between them ranged from seconds to minutes. One editor described the noise as dropping a marble on concrete. Another thought it sounded like a valve stem cap falling on the driveway. Then we realized what was happening.
We understand its not easy to diagnose from words alone, but can you figure out our problem? Conclusion to follow....
Mike Schmidt, Vehicle Testing Manager @ 20,045 miles
aspman26 says:
03:32 PM, 03/16/09
Sounds like a tire pressure sensor rolling around inside the tire, occasionally getting stuck against the rubber before rolling again. Just my 0.02
joefrompa says:
03:36 PM, 03/16/09
TPMS light on = Either a sensor problem or your rolling diameters have changed enough to induce a problem.
Since it doesn't seem to be a tire pressure issue or tire issue, I'm going with a loose TPMS sensor inside the wheel. Not super loose though.
Joe
Mad_Science says:
04:25 PM, 03/16/09
Sensor flopping around in the wheel would be my first guess.
...but since 2 people said that already, I'll go a different route: what about the pickup for those sensors?
I'm guessing it's in the wheel well or somewhere on the suspension. Maybe it got knocked loose?
ampim says:
04:54 PM, 03/16/09
I'd bet good money on a loose TPM sensor. Anything greater than 15 mph, and the wheel would be spinning so fast that the centripetal force would keep the errant sensor pressed against the tire.
ddoouugg says:
07:11 PM, 03/16/09
The tire gnome wants out!
altimadude00 says:
08:59 PM, 03/16/09
Someone put their two cents in your tire?
pengwin says:
09:10 PM, 03/16/09
Hamster.
stingray454 says:
07:17 AM, 03/17/09
Loose wheel lug nuts?
arm51 says:
07:45 AM, 03/17/09
I agree with the rest; TPMS sensor fell out and is held on to the inside of the tire at higher speeds, but falls off and clatters around at lower speeds.
gcsads1 says:
08:02 AM, 03/17/09
'ampim' I hate to be a physics nerd but it is centrifugal force that would be in effect here. Centrifugal force is outward, centripetal force is inward. Centrifugal force is actually reactive to centripetal force. I have to go clean my pocket protector now.