In my case, I like to fine-tune a particular frame so I change handlebars often (I've accumulated spares over the years), leave them on a week then try another one and so on, until I get it right (different rise, angle of sweep, width, etc). Either that or I swap brakes... when I upgrade to a better one, the former brakes get trickled down to the other mtbs.

Lock-on grips has saved my sanity on many an occasion.

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