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WHAT THE INDUSTRY DOESN'T WANT YOU TO KNOW The other day I was comparing trucks and axels looking for significant differences that would substantiate the price increase in some of the models. Can someone explain to me why axel diameters are .308-.310 while inside diameters of bearings are .315+/-.0002. Now this is great for assembly purposes, but totally defeats the accuracy of the bearings. The bearing must rely on the nuts to square it up, but there is nothing to guarantee concentricity or run-out. I don't like the fact that they expect a mass machined nut to square up the bearing but I was pissed that they would let me spend $40.00 plus on some name brand abec 7's to be left to the mercy of a "slop- fit". Some of these bearings are made to an accuracy of 98 millionths or less, and we're led to believe this extra cash that we're laying out will benefit us somehow. I needed to know if anyone was talking about this or was it some industry joke and these punk-ass suits were laughing at us all the way to the bank. Well after perusing the net for a few hours I found one place in Australia that was willing to tell it like it is. This company specializes in miniature precision bearings for hobbies and the machine industry, and if your not going to buy bearings from me this is the next best place to get them. The following is an excerpt from their web page for skaters. Read it and you'll come to the same conclusion we did "the suits are laughing at us all the way to the bank". At the bottom there is a link to, MINIATURE BEARINGS AUSTRALIA PTY LTD., the prices are good and I know they are honest. What are the grades of bearings available in order. How different are the grades? OK, but don't forget that you really do not need to waste money on anything higher than ABEC 1 or ABEC 3 for skateboarding applications. It should also be pointed out that the precision grade only tells us how close the bearings dimensional tolerances are (that is, how close the bearing is to the stated size). There are many other factors relating to the quality of a bearing, and many of these factors will have much more of an impact on your skateboarding experience than the ABEC Grade of the bearing. From Lowest to Highest ABEC 1 Approximately equal to ISO P0 ABEC 3 Approximately equal to ISO P6 ABEC 5 Approximately equal to ISO P5 ABEC 7 Approximately equal to ISO P4 ABEC 9 Approximately equal to ISO P2 There are a number of factors covered by the ABEC grades, but to give you an idea we will just examine one of these factors - the eccentricity (out of roundness) of the track in the inner ring. For an ABEC 1 (lowest grade) bearing, the maximum eccentricity allowable is 0.0075 mm (0.000295"). This is quite precise - more than precise enough for skates and skateboards. The figures for the other ABEC grades are 0.005 mm (0.000197") for ABEC 3, 0.0035 mm (0.000138") for ABEC 5, 0.0025 mm (0.000098") for ABEC 7, and 0.0012 mm (0.000047") for ABEC 9. If used in high precision, high speed machinery (see above), these minute variations can make a difference. The fact is that no matter which of these bearings you use in skates or skate boards, after 5 - 10 minutes of use the tracks won't just be eccentric, they will become irregular (albeit minutely) enough to be practically indistinguishable from one another. Your high priced ABEC 9 bearing might as well be a 50 cent ABEC 1 cheapie. What will be the result of using these higher grade bearings in Skating Applications? The most noticeable result is that you will end up with less money in your wallet and the people that sold you the bearings will be eating out at restaurants at your expense for a few days. Under the following conditions, you may notice an improved performance. (a) You spend a lot of money (i.e. thousands of dollars) to have your equipment (wheels and board) redesigned and manufactured to suit these high precision bearings. You will need to use some type of shock absorber that allows for absolutely no vibration. (b) You will have to be prepared to skate on a perfectly smooth surface and make no attempts to use your feet to propel yourself. (Doing so would cause shock loads to the bearings and any extra precision would be lost very quickly). (c) After you work out how you are going to achieve the above two criteria, you may (and that is only "may") experience a better result than using ABEC 1 bearings after you attain a speed of about 310 KPH (195 MPH) with 52mm wheels and grease lubrication. MINIATURE BEARINGS AUSTRALIA PTY LTD A full copy of this article can be found at http://www.minibearings.com.au/skate.htm#13 SFS Conclusion: If you want them we'll sell them to you, but don't say we didn't warn you. |
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