A tighter fit between the bearing inner race and the bearing post is a relatively easy way to reduce design-induced or manufacturing-induced vibe (For those of you who understand all the processes involved in machining and assembling all the bits, just think about the potential for vibe on a bimetal). Over time, a tight bearing post will tend to gall the more the bearing is removed and reinstalled, causing the bearing to bearing post interference to loosen up, thereby reducing its ability to to dampen the vibe.
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