I changed to studded winter tires (or wheels, actually) on my 2016 Toyota RAV4 hybrid 4 days ago. After driving the car about 200 km, it became apparent that the tire noise is unusually high and periodic. I don't remember having that much tire noise last winter. There is absolutely no steering wheel wobble. No noise on the summer tires, and no mechanical anomalies during tire swap that could explain the noise. The noise is definitely coming from tires, because it occurs also during electric drive. Noise volume and frequency become higher with higher speeds, and the strange noise is distinct from the usual stud noise.
While swapping the wheels, I rotated them, so the tires that used to be in front are now in rear and the tires that used to be in rear are now in front.
Pressures at 10 degrees Celsius (estimated, not measured) storage temperature were 2.48 bar (measured with a precision mechanical gauge), and recently temperature has been 0-5 degrees Celsius, so cold pressure should be 2.35 - 2.4 bar. This is bit higher than what the car manufacturer has specified (spec is 2.3 bar, measured cold, as usual), but I'm not sure if it's worth it to reduce the pressure, because the weather will soon become colder.
I checked the following things:
- Overall, I didn't see any immediately apparent damage in the tires.
- Wheel nuts should be tight. I have alloy wheels, and I re-torqued the nuts after driving 50-100 km (no nut was loose). I could perhaps check the torque again now that I have driven 200 km after changing the tires. I did overtighten the nuts by 7 Nm, as I tightened them to 110 Nm and only afterwards noticed the correct torque is 103 Nm.
- Direction of rotation is correct on both tires on the driver's side, so I can conclude direction of rotation should be correct on non-driver's side as well. I originally suspected this would be the cause, which is why I checked it.
What could be the cause of unusually high periodic tire noise? Is it possible that if a wheel weight has fallen out on the rear, there could be periodic tire noise with no steering wheel wobble?
Or is it possible that 0.05 - 0.1 bar higher pressure than what the manufacturer has recommended could cause major increase of tire noise?
It's of course possible also that I misestimated the storage temperature and it was 5 degrees Celsius instead of 10 degrees Celsius. That would mean pressure has been 2.42 - 2.48 bar in the recent weather conditions, being 0.12 - 0.18 bar higher than what the manufacturer has recommended.
I was planning to let a mechanic turn off that annoying tire pressure monitoring system (TPMS) light that turns on every time I swap the wheels, because the car doesn't have in memory both summer and winter sensors. The mechanic could at the same time check if there's something wrong in the tires. But before I do that, I would like to hear some opinions of what might be wrong.
If there's no apparent cause for the noise, I think I'm going to reduce the pressure very slightly.