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Alloy jockey wheels a waste of time and money?
Probably, depends what you're trying to achieve. Jockey wheels would be the first (and quite likely last) place I'd choose ceramic bearings on a bike, so if you're swapping to ceramics and they happen to be wrapped in aluminium wheels, there's no harm. There might be some hysteresis losses in the plastic ones, so if you're after a few mW of marginal gain it would certainly be worth measuring to see if metal ones made a difference. The corollary is that metal ones are almost certain to be noisier.
Alloy jockey wheels a waste of time and money? They seem to be all over eBay but RDs come with the rubbery ones