What is the importance of EXACT bearing spacers?

[Glenn S]

What is the precise dimension for a bearing spacer in the Avalon’s and Cambria hub?

Are all bearings milled the same? Meaning would all bearings sit in the hub seat the same and require the same spacer for an exact fit?

At the 3DM-SPORT.COM website it says to use 10mm, but I’ve been told by your sales staff to use a .400 inch spacer from any local skate shop.

<img src=http://www.3dm-sport.com/art/wheels_avalon_ortho.gif>

.400” equals 10.16mm

If the space between the bearings is actually 10mm exact, how important is that extra .16mm?

Would an extra .16mm mean that it would not let the bearing sit completely in its hub seat? And again do all bearings sit exactly the same in the hub seat?

The reason I ask this is because Michael Dong posted some comments at “ncdsa.com” that I’d like to quote here about bearing spacers to hear further discussion on this topic.

Michael Dong:

“This brings up another thing that hopefully some smart manufacturer will address. The current bearing spacers are in need of improvement. First, it would be nice if the material was steel rather than aluminum. Those crappy aluminum spacers start mashing down over time and you eventually get an undersized spacer. The width of spacers varies HUGELY. I've measured 0.100 differences in a handful of spacers. A good idea if you are buying spacers at a shop is to bring a pair of calipers and only buy the ones between 0.400 and 0.405. This is also really nice at a race when time is short and you need to choose among a handful of spacers. The other method is to put a random spacer in, put your bearings in and then swear because your wheel won't spin because you just put in an undersized spacer. Repeat until you find one where your wheel will spin freely. This a fun way to eat up the short practice time and get you really frustrated right before qualifying.

It would also be interesting to know what the wheel manufacturers use for a spacer dimension. I know from talking to Chris Chaput that 0.4" is supposedly the standard. Then I look at the 3DM-SPORT.COM website and it says they use 10mm spacers. Using undersized spacers will put an axial pre-load on the bearing so the wheel doesn't spin freely. Oversize them and you may get wheel slop with the wheels sliding from side to side from the slop now introduced in the bearing pocket.

I know a lot of skaters who would pay for a high quality, racing quality steel spacer (ground bearing surfaces would be nice).”

Comments anyone?

Here are some measurment conversions:
10mm = 0.393700784015748031496062992126"
.400" = 10.16mm
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Note: In the above 3DM-SPORT.COM website picture it has now been changed to .400", where it used to say 10mm.

<font size=-1>[ This Message was edited by: glenn on 2003-06-17 13:25 ]</font>

[Howard Gordon]

Our website is wrong (thanks for noting this) - the correct spacing is 0.400", not 10mm (which is 0.394"). If you contact any of the manufacturers of spacers and order 10mm, you'll receive 0.400". We get spacers from Sure-grip, I haven't noted variation of more than 0.002", though that's from a limited set of measurements.

Note that the wheel hubs are not precision machined (they're poured urethane) which likely have variations of a few thousandths, so there is no point in getting too carried away on precision, though variations in excess of 0.004-0.005" may be noticeable.

[John Gilmour]

Have you noticed any wheels to "tick" when rolling? Would putting some grphite in the bearing seats help this?

[Howard Gordon]

Yes, I've noticed this with Avalon wheels in combination with some bearings (Ousts in particular). It may be due to the wide outer lip profile of the Avalon producing a higher side load on the bearings - some bearings produce a sound as a result, probably from flexing or realignment of the ball bearing cage. I found that when I changed to a different type of bearing, the sound went away. If it's due to flexing of the metal, additional lubricant probably won't help, but it's certainly worth a try.