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In a nutshell, I've used plugs on a few occasions and they've all been serviceable and performance of the bike was virtually unaffected. If I grabbed a nail in the center of the tread on fairly new tires...I'm certainly not going to toss them away when they've got thousands of good miles left on them. If the sidewall was threatened, that would be a different story. If it's in the center of the tread, I'm plugging it and simultaneously saving myself money in the process.
the tires i have on my busa are the ones that come with it and i have around 38 3900miles on the bike and the tires look pretty good the side wall is fine and looks to have a good amount of tread left on the back tire