Hi, i want to put a double chainset on a brompton for manual change (by hand no front derailleur) i wanted a 28t/ 48t or something but theyre hard to find especially with max 170mm length and square taper and the one i found was too expensive... Can i get something like this Sunrace FCM30 28 38 48 Bicycle Chain Wheel 170mm Crank Arms | eBay and remove the middle ring? Or will there be a big gap in the rings? Or are these triple cranks "fatter" and effect the fold?

Thanks

Or could the inner chainring on this be removed? SR Suntour CW13 XCT 8 Speed MTB Chainset 170mm WHI | eBay

Removing the inner ring is the best way to go.

So a triple with the inner chainring removed is an acceptable double?

Yes. Ideally, you'd use a shorter spindle to improve the chainline, but in practice it seldom matters much.

I've seen people remove the middle ring and put the 48 in its position. The shifting was friction and wasn't terrible. The cranks where typically shimano 110/74 triples from the late 80s and early 90s. If you're shifting by hand what do you gain by removing the middle ring?

Yeah thats what im trying to find out with this thread... Does the triple chainring make it poke out more? Is the bit the square axle goes in fatter on a triple and effect the bikes fold? Or is it because of chainline? Its a brompton with a 3 speed sturmey hub and a 50t right now and geared so high superman would struggle uphill.... Heres more info if anyone has time to help https://bromptontalk.wikispaces.com/Twin+Chainwheels .... Ive never found a mention of a triple on a brompton... Im hoping that suntour crank will work with a 42/32 and the smallest taken off?

Thanks a lot for the responses

That suntour crank you linked to looks like it might have the chainrings are riveted in place so it's not easy (or possible) to swap them into the configuration you want to. Some cranks are made with more or less offset depending on their intended use and an old 110/74 was designed to be used a double or triple so it has less offset than a newer MTB style triple does, at least in my experience. In theory if you take the inner ring off any triple you should be able to use a shorter BB to bring the crank closer. In your case I would measure the chainline and try to get the front rings to split the difference of the 3 speed's chainline.

While they aren't cheap, one of Velo-Orange's randonneur style wide range doubles might do the trick. They do a 30-46 chain ring combo on a smaller than normal bolt circle which would be more elegant and probably give a tighter chainline than kludging a triple.