Finding source of a little drag

The "Timken" part on RockAuto has pictures of a bearing stamped with Koyo:

More Information for TIMKEN HA590064

 

Apparently Timken is Koyo, or the other way around, at least most of the time. See this discussion:

 

TPMS is working and in any case all the pressures have been checked a couple of times with a gauge. Faster and easier to get the pressures that way than hauling out a laptop and cable. This isn't a low pressure issue. The tire shop obtained 3 of the tires from one source and the last one from another. They all have the same manufacturing date. The tire on the wheel which is a little hot is probably the odd one out, because it was (a little) dirty, while the others were clean. Never heard of a tire which runs hot at normal pressures though, but I suppose it's possible.

6F between tires may not be functionally significant but it is statistically significant. That is many standard deviations from the mean of the other three temperatures. Those temps were always really close, a fraction of a degree separating them, and the meter probably isn't even accurate to those small differences.

 

Agreed. But identical tires under nearly identical conditions should heat up the same amount.

The two front tires are each carrying very nearly the same weight, are at 35 PSI, and travel nearly identical paths, yet the one on the left is heating up more than the one on the right. The one on the right is heating up the same amount as the two on the back, and those are carrying less weight, at 33 PSI, and still traveling nearly the same paths. I can imagine a defective tire running hotter than the others, but think it more likely to be a wheel bearing or brake issue. This weekend I will try to swap the front wheels, which will either indicate a tire level problem or rule it out after the next long drive.

 

The difference in temperature seems to be slowly going up. This past Saturday it was a full 10F between that wheel and the other. Didn't have a chance to swap the front tires until today, then took it for a 20 minute drive. It was cloudy, so no direct sun to heat up one side or the other. Measured these temps right after coming off the highway:

location (spoke near hub) (on rotor through spokes)
D Front 82.4 87.2
P Front 71.6 70.8
D Rear 70.3 NA
P Rear 74.4 NA

So it stays in the corner and doesn't move with the tire. It would have been really peculiar if it had.

When the car was up on jack stands the front passenger side wheel rotated more freely than did the front driver side wheel. Odd that either would turn at all since it was in Park, but maybe that's how it works when the axles are hanging? I looked closely at the brakes and didn't see scoring or anything jammed between the shield and the brake. The pads on both sides looked about the same, both in their thickness and their position on the rotor (that is, they both seemed to be right on the rotor, but no way that I could see a tiny gap which was present on one and not the other.) I'm thinking slightly dragging brake rather than bad bearing, since the rotor was hotter than the wheel on one side, and the same or other way around on the other. Questionable logic since the hub and the rotor are bolted together.

The 3.1 degree F difference in back suggests that maybe it is time to empty the dust out of the drums again. Or that might be just statistics - those 3 lower values have a mean of 72.1 and a std deviation of 1.71.