Originally Posted by zaroba

Looking for a new front derailleur on amazon and seeing top and bottom swing. Never heard the terms before, and looking online it seems it just relates to the clamp being above or below the derailleur. Any I have had have the clamp above them so I guess it would make them bottom swing. Am I correct in guessing there's no difference in operation besides how it clamps to the frame and possibly whether the cable connects from underneath or above?

I'm also seeing different mm specifications, 35mm,31mm, 28mm, etc. What's that measurement?
Too wide for the chain width, way too short for the length. Is it the max travel distance when shifting gears?

Planning on ordering new wheels for one of my old bikes, are cassettes mostly universal?
I imagine there has been some variations over the years. I'm wondering if I should just buy a new cassette for the new rear wheel I'm getting for my 1970s Peugeot road bike in case the original cassette doesn't fit. But on that note, would any modern cassette fit the new wheel? Assuming the cassette doesn't have too many gears for the axle length of the wheel anyway.