Bottom Bracket Sizes and a "fix"
Standard "English" bottom bracket shells come in 2 widths: 68mm and 73mm
Italian is 70mm
Let's not discuss French and Swiss bottom brackets, right now...
The Raleigh Twenty bottom bracket shell is approximately 78mm.
I've used a few 68mm cartridge bbs in 73mm frames, so I figured that I could use a 73 in the 78mm frame.
When I built the Evil Twenty (which Phatatude posted about on 9/29/08), I took a 122.5mm (spindle length) by 73mm Shimano UN52, and threaded the non-drive cup deep into the frame, until it snugged the body of the bb. The alloy cup I used lacked the ring which you find at the end of the threads on the plastic cups, so it threaded right in.
If you have the plastic cup, filing that ring off will alow the cup to thread fully into the frame with distorting.
DISCLAIMER: I haven't put any significant miles on this bike. I built it for an art show, this coming Friday, and have only test-ridden it around the neighborhood for a few miles. Time will tell if this conversion will hold up. As I said, it has worked with standard mtb frames, in the past, so it should work just fine in this instance.
Also, I think a longer spindle (127.5mm) would be required to use a more modern crank. The 122.5 just worked with the old-school SR crank I used.
Check here for more details: http://grinderswheels.blogspot.com/2...il-twenty.html