Bearings Discussion

by Surazak Uawithya (Zak)

I don't think that oil and grease will be much different in terms of rolling resistance. If you get two bearings otherwise identical but one oiled and one greased, and spin them, the oiled one will spin longer. However once you add the wheel the difference becomes less noticeable. Add in a skater and his associated air resistance (air resistance is proportional to speed squared) and rolling resistance of the wheel on the skating surface and the difference between oiled and greased bearings is largely irrelevant. There are too many factors at work here. Packing too much grease in a bearing is bad, as is not enough. A light oil e.g. GT85 (with added PTFE) is probably the fastest option, but will require the most re-oiling, grease is the most maintenance free, and the best if you insist on skating in the wet. I've got Terminator ABEC 5 bearings which I have recently cleaned out and oiled with Duckham's Hypergrade "borrowed" from my mate's car, and I don't think that I can get more spin out of my bearings than that. Personally I think that if you get a grade 1 haircut (lowers air resistance) and have a good shit before you go out (makes you lighter, and more comfortable) you will notice a bigger improvement in your skating than the oil/grease debate.

In theory the higher the ABEC number, the better the bearing, but as you all know one brand of ABEC 3 can be as good as another's ABEC 5. What you also have to look at is the material that they are made from. All bearings will get warm through heavy skating. This heat causes the bearings to expand, consequently changing all of the fine tolerances that they were originally made to. I understand that some speed skaters run their bearings dry. To me this makes no sense. Cyclists tried this many moons ago, found out that it was crap, and went back to lubricating their bearings, Although not before a few people seized up their wheels as they overheated. Sure they will spin fine when you've just put them on, but if they are un-lubricated surely their operating temperature is higher because there is nothing to reduce the friction in the bearing. If the operating temperature is higher than there is greater heat distortion due to thermal expansion hence increased friction. I have heard that titanium bearings are good as their rate of expansion is supposedly much less than that of steel. Which means that they expand less at for the same temperature change, hence run smoother and quicker. I have no solid evidence to support this, and have no intention of looking through data books to find the relative  thermal expansion co-efficients because I'm not that dull. But the principle makes sound engineering sense.

One other thing to look at is the bearing surfaces and the bearings themselves. Most bearings have 7 balls, a few like BSB V8's have 8. This is better as the skaters weight is spread over a larger number of bearings, so less distortion happens. A step up from this, often used in the cycling and cars, is to go for roller bearings. These use short sections from a solid bar rather than balls. The advantage of these is that in a ball bearing the contact areas are quite small. Take a hockey ball, put it on a flat table and look how much is actually touching the table. With a roller bearing instead of having a contact point that is only a spot, you have an entire strip running along the width of the bearing. This will come into its own in in high load situations e.g.. landing big air on aggressive skates. Also you have to look at what material the bearing is made from. If the bearing and the surfaces it runs on are made from bog standard mild steel, after a couple of weeks of playing hockey the bearings will no longer be perfectly spherical so they will no spin so well. At the other end of the scale you have bearings coated in titanium nitride. This material are very hard so your bearing will stay perfectly spherical for much longer. Most bearings are made from a hard alloy of steel imaginatively named "bearing steel". 

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