I like your optimism Steptoe and obviously it's based on experience. But my little experience with a failed one that i hadn't even touched suggests to me they're a bloody failure waiting to happen. If the bike is secondhand, there's no knowledge of the treatment they've had. I wish I'd known how vulnerable they are, I'd have changed them. I'd always recommend changing them. Is whole big PITA if they fail out on the road...easily ruin a day and more.There is no need to fit new Q/D's if your old ones are fine. If you're clumsy and break things then you're just as likely to break new ones as easily as the old ones. I see bikes all the time with their original 10+ year old Q/D's still working perfectly, use plenty of grease and don't force them.
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