Eric Wallgren wrote:Speedrings or no, it's virtually impossible to preload your skateboard bearings.
Eric, I know a guy who is a bearing engineer, and not only does his bearing company (California Bearing) provide bearings to NASA and private industry, but he also orders a specific NMB bearing to market as a skate bearing since he himself is a skater. His opinion on the speedring and preload issues is this:
=====
"It use to be and still is general skate theory to use spacers and tighen up your wheels real snug. The spacer will force the ball track to ride against raceway shoulder (duplexing/Preloading)adding stability and elliminating the "loose Play" however, adds friction. From an Engineering and skaters point of view, I think for street skating, the pounding, jumping off rails, etc., I would use spacers with the nut snug to elliminate the "Loose Play"... The bearings will "share the load" in the wheel giving the bearing/wheel more strength and stabilty, will handle more of a beating but you will give up speed, quickness and the bearings will wear faster.
....But for me, (Im strickly a Vert/Pool skater) and other Vert skaters I recommend a different setup. For Vert the bearing application is different than street skating. You want stability and strength when your street skating, but VERT, halfpipes, pools, etc. you want speed and quickness. Rather than running the bearings as a "Duplexed Preloaded Set" mentioned above, you want the bearings to run as independant high speed radial bearings with Low starting and running torque. Dont use the Spacers and only tighten the wheel bolt, lightly snug, to eliminate most of the slop. Sometimes if too loose it seams like you dont need bearings but when you stand on it and add 120 or more pounds of load and get traveling in one or more directions, the bearings will rotate and the inner ring will not spin on the axle, but you dont want alot of "loose play' or "slop" either. Lightly snug !!! By not tightning the the nut too tight, the bearings will have less preload and will run like a "high speed radial" bearing."
===
I guess the question is whether for slalom the stability is more important or if speed is. If the use of 8mm axles takes away the typical axle slop anyway, then perhaps there is no reason to run the spacers and washers at all since you'd get speed that way (and not need the stability).
The only way to get excessive preload would be to omit the spacers, or apply so much pressure by over torquing the wheels nuts that you collapsed the spacer.
Here's what Ron of California Bearings says on preload:
==
"A 608 has about a 7-9 pound max preload limit. 608's in Precision Duplex Pair applications like pairs I supply to NASA for the cameras on the outside of the space station, have just a 4-5 lb Preload. Anymore than that the bearings will fail to turn and wear extremly fast. Tighten that nut down real hard and you could add 20-30 lbs of preload !!! Bottomline......I think spacers preload the bearings too much for VERT skaters but is good for the Street Skaters where speed and quickness isnt as much of an issue as stability and strenghth."
==
Me again. I'm totally convinced that the 8mm axles are the way to go, I'm just confused on running spacers and rings or not. Any further comments?
BTW, if you guys haven't tried them, you might want to try the NMB bearings from California Bearing (or you can get them from skatelab). They test every bearing they can get their hands on vs. the NMB - so that if they find something better they can source that one instead. So far, the NMB is tops. Here is a review of the Biltins, for example:
"I just checked out these Biltin Bearings. Not bad for inexpensive Chinese. There are no inner ring steps, No labryinth Seal or inner ring design. By the way the so-called ABEC 7 bearing measured out to ABEC 3 tolerances in my lab. As far as I can tell, the ABEC 3 , 5 and 7 sold by Biltins are the EXACT same bearing. Maybe they dont even know it and their bearing supplier is just slipping ABEC 3's past them Certifying to ABEC 7. These Biltins ARE NOT ABEC 7. Im sorry , its true. Not a bad concept to manufacture the bearings with extended inner rings to eliminate the spacer and washers. However, This has nothing to do with how "fast" or smooth the bearings are. I tested them against the NMB SuperPrecision Bearing and the starting and running torque values were double!! on the Biltin bearings versus the NMB Bearing. That means the biltin bearings take more energy to get up to speed and stay at top speed. The NMB Bearing really blew away the Biltins on the Running Torque test. That means the Biltins slow down faster while the NMB SPS Bearing holds its speed with little or no effort. I wont even get into the Smoothness test which the NMB bearing obviously has the lowest values of any 608 Ive Tested and Inspected."
I think they sell the NMB skate bearing direct for $23, retail is like $30 or something at Skatelab and other shops. And for the record, I have no connection to those guys other than being a satisfied customer. Their webpage on that NMB bearing is
http://www.californiabearing.com/skate.htm
-Slim