On 03/06/16 03:40, Joerg wrote:



I was thinking about the material used in the seals. On MTB that is
usually rubber and on road bikes often some sort of fiber. Very small,
so the seal itself would likely burn up.



I have never seen a fibre "seal" used on any bicycle bearing. All of
the seals I've seen are rubber, and they most certainly do not "burn up".


It has more surface area than heat sinks used for integrated circuits
which need to dissipate tens of watts, and FAR better airflow than you
find inside most electronic equipment as well.

And 2% of 200 is 4, by the way.


But you have four bearings, so 1W each.


I used an on line estimator of bearing losses by SKF some time ago, to
find out what they estimate bearing loses to be for a typical double
sealed cartridge bearing as used in the wheels I had at the time. The
bearings have a rubber seal on both sides. If I remember correctly, the
loses per bearing were in the order of 0.5W at a road speed of 50km/h.
0.1W of that was rolling friction. I.e. sticky grease and friction in
the ball cage. 0.4W was from the seal friction.

So a total of about 1W per wheel at 50km/h. Hardly enough to raise the
bearing temperature by some detectible level above ambient - even if the
bike was stationary and being pedalled on rollers!

--
JS