---In STMFC@..., <tony@...> wrote :
Tony Thompson wrote:
Actually, be careful with this statement. The measured frictional resistance is vanishingly small between solid and roller bearings at all speeds above about 5 miles per hour. And even starting friction, certainly distinctly higher for solid bearings, is not a huge difference for days above about 50 degrees F (if memory serves on the temperature number). Of course on really cold days the difference could get huge.
The enormous advantage of roller bearings is not only the virtual absence of hot boxes, but the elimination of all the inspection and maintenance of solid bearings. In economic terms, this is the ball game.
Unfortunately the reduction in car inspection with the use of roller bearings also has created some problems.
As we all know, bearings, too, can and do fail, and the results are just as serious as when friction bearings fail.
And the life of bearings seems very difficult to predict. For example, my wife and I drive Volvos. I have two 1998
XC-70's and she a 2006. One of my XC-70's clocked 300,000 earlier this year and the left front wheel bearing
began to show signs of failing. My son and I changed all of them and found another that was also beginning to
go. With only 115,000 in hers my wife experienced the exact same problem with her left from wheel bearing
last month. Why mine lasted for 300,000 and hers barely over a third of that someone will have to explain to me.
But the point is the same, bearings ultimately fail whether they are solid or roller and the latter sometimes are
not checked enough, seeming from the false feeling that "roller bearings last forever". We wish!
Cordially, Don Valentine