Originally Posted by Mr. Fly

Brake: There are plenty of standard reach brakes nowadays. Tektro and Shimano both have them, although it may still be an issue since the mounting and clamping points for the Brompton are reversed.

Rear wheel: It's actually 110 mm. But yes, that's a bugger if you want a Chris King replacement.

Seatpost diameter: There are 31.8 mm seatposts around. Thomson makes one. But good luck finding such a long one!

Saddle clamp: The Pentaclip is actually a very fancy aluminum version of the steel saddle clamp that we have all along for as long as I can remember; I had one on my BMX bike in the 80's. They're $5 at your LBS, more typically used on older or cheaper bikes.

Chain tensioner: Yup. And there's no rear derailleur hanger to use an aftermarket one either.

Chainring BCD: The stock Brompton crank has a non-detachable chainring. BCD is really N/A.

BB size: The Brompton BB shell is standard 68mm English. It'll fit any standard English BB cup. And of course we all know that the spindle length is dependent on the crank used...
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