Quote:
Originally Posted by bobbecky
I’m pretty sure the rpm of the bearing will be the exact same rpm as the tire/wheel assembly, regardless of the size of the tire.
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EXACTLY THE SAME !!!!!
Many people have no idea how fast wheel bearings spin. Most are surprised when the find out how "slow they really go"....
Here's how to figure the RPM:
The diameter x pi = circumference (typically results are in inches).
There are 5280' in a mile so that's 5280x12x= 63,360 inches in a mile.
Divide 63360 by the circumference and that will give you revolutions per mile.
At 60 MPH, it's a "direct comparison",
So, a 16" tire that has a 31" diameter would have a 97.4" circumference (31x3.1416=97.389)
63360/97.4=650 revolutions per mile = 650 RPM at 60MPH....
So, it's not the same as 100PSI blowing across a dry bearing causing it to spin at 1200RPM as the needle bearings "rattle around in the bearing cages"... I can't give you an exact figure, but if you've ever used a blow gun to spin dry bearings, they will "whir until they shreek" and I'd guess they are spinning somewhere significantly greater than 1000RPM as the sound changes from "shreek to shrill"... (I know, very unscientific descriptors for RPM)....
The point of all this: Wheel bearings on a trailer being towed at 60MPH only spin around 650-700 RPM and a dry bearing, spinning on your fingers by compressed air is probably spinning 3 times that fast with nothing to absorb the vibrations as the needle bearings rattle around in the bearing cages. That can't be "a good thing for reliability"......