Originally Posted by northstar1960
1 i don't think grease expansion plays a part in this and have never had issue with such . temps should not get to hot and if they do you may have other issues .
2 on grease compatibility don't think there's an issue there either
this is all imo
You may be correct and I've spent some time thinking about the expansion thing over the years. I carry a high quality infrared thermometer with me. Whenever I stop, I'll shoot the tires, and wheels close to the hubs, mostly to see if any one wheel/tire is hotter than the others. When we have left the house on cool days of around 40 degrees F, and then drive through a few hills and stop, the tire temps will be in the 125 F range, and the hubs a few degrees warmer. Now those temps are not worrisome to me, but it is a 300% increase in temp. I should probably check to see what the coefficient of expansion is for wheel bearing grease, but it's probably pretty low, so I tend to agree with your statement, but I'm still a little more comfortable by not packing the hub cavity full. Given the right temps, grease will flow.
As to grease compatibility, I've never had an issue, but when I pull hubs to repack, I'll remove all of the old grease and discard. Especially on vehicles. I have a Scag zero turn lawnmower and they strongly state to not mix grease for the blade spindles, but those things are spinning around 18,000 rpm which is a little faster than vehicle wheels...lol Does anyone know the rpm of a 16" trailer tire at 65 mph?