john,
this is a very good ad, it states very clearly that, bearing bore and the finished I.D. of the sleeve insert are machined to a tolerance of + or - 5 tenthousanths (.0005) of an inch. This is a very critical procedure that is performed by skilled machinists using precision CNC equipment. We are one of only a few shops currently offering this critical modification.
This along with two other main factors is why Harley went away from the old school Timken setup. The other two crucial factors are, heat and rpm's. the Timken's because they have to be preloaded are susceptible to thermal growth. its a fine line to get it setup correctly, when the engine is cold the preload is loose, but as the engine heats up the preload on the bearings increases as well. If you ever put an old style Timken wheel bearing on, you remember that you had to tighten them up and roll the wheel to seat the rollers, and then back off the nut so you had just a little play in the wheel. that was to allow for thermal growth of the bearings and subsequently the preload on these bearings. if you try to make the preload too tight when the bearings are cold, you will fry them when they heat up to operating conditions. Even if you get the preload right for normal operating conditions, exceed the operating temps and you start getting too much preload again. its just not
a great setup for all operating conditions, there has to be a compromise somewhere. Next, the fact that there is more rollers in contact (as you stated above) is a good thing, but there are drawbacks to this as well. more contact = more heat and more drag. these bearings are very strong granted, but they have the most rolling drag of any bearing on the market, making them very inefficient and robbing you of ponies, and because of this they also have the lowest max rpm rating of any bearing style available. so for me the whole idea of switching to these bearing for a high performance application is like "Jumbo shrimp" an oxymoron to the highest degree. If I were building a high performance bike I would go to a belt driven open primary that can handle the torque. you guys want the best of both worlds a stock looking monster HP sleeper. as the saying goes you cant have your cake and eat it too. Harley made these changes to save money yes, but they are also trying to keep the technology moving forward, as production tolerances increase as well as engine rpm's there needed to be a bearing change to accommodate this, for all operating conditions. the Timken's just don't cut the mustard. The roller bearing can take the heat and the rpm's better and are not as susceptible to thermal growth, but I agree that they should have added the outboard support from day one. Whoever made this change was looking in the right direction, but didn't think through all of the forces involved or was trying to save HD money at our expense, and as one of our members so eloquently put it, someone at HD should be bent over a knee and SPANKED REPEATEDLY.
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Topic: Crankshaft Bearing Upgrade (Read 10604 times)