Folding Bikes - Double Crank / Front Derailleur / BB on my Twenty

Currently in my quest for a UN72 Bottom Bracket, I seem to only be able to find 107mm spindle length.

If I were to cut off some of the BB shell , would I be able to use this BB with a Double Crank?

If so how much should I trim off?

What is the best way to trim the shell without fouling the existing threading in the shell?

Check out Sheldon Brown's site. He talks about cutting the bottom bracket shell. You can always get your bottom bracket rethreaded to a modern TPI so that you can use other bottom brackets. I am planning on doing this so that I can ditch my Sram Dual Drive and go with a double crank as well. The LBS guy that did the nice weld job on my Raleigh Twenty suggested it before I could even ask him about it. He said it's not a big deal and that he has done it before on other English Thread bikes without problems.
Juan

Juan, what has your experience been with the dual drive?

Ed, the dual drive is a solid performer. The only real problem I have with it is that when you're climbing in "the small ring" it feels like you're working a little harder than what you would if it wasn't an internal gear hub. I'm also trying to convert my Raleigh Twenty into more of a road bike, so I'm trying to make my bike lighter, especially the rolling components...internal hubs are heavy compared to regular hubs. If I were building a tourer or commute bike, I would leave the drivetrain as it is. In fact, when I build up my second project bike, which is for commuting and running to the local store, I am going to use an internal gear hub. So to answer your question, the dual drive is great. I just have a problem of "the right tool for the right job." Juan

He talks about cutting the bottom bracket shell. You can always get your bottom bracket rethreaded to a modern TPI so that you can use other bottom brackets.

I have done it on mine. I cutted the bottom bracket (to 68mm) and rethreaded it with a regular bb tap.

I then installed a BBun72 with a RX100 crank.

Look at my Twenty page (http://www.guybouchard.ca/twenty.htm)

I have done it on mine. I cutted the bottom bracket (to 68mm) and rethreaded it with a regular bb tap.

I then installed a BBun72 with a RX100 crank.

Look at my Twenty page (http://www.guybouchard.ca/twenty.htm)

Did you end up cutting an even amount from both sides?

From what i can remember and what i could see 2 minutes ago, i think i have removed most from the right side. By the way the Bottom Bracket is a Synchro where chainline is adjustable. I could have been able to do it with a regular Shimano BB. I had them on hand.

I really like my Twenty. Downside is folded package is not that small. My girlfriend old Dahon Speed is a neater package in the car boot.

Salut Guy,

I am curious to know what the "Folded" size of your 20 is after all the mods. I prefer machines that can fit inside a standard ATA approved suitcase. Not oversized luggage.

Enjoyed your info

Slim

Can't answer folded size right now. It is a lot bulkier than the Speed. It is a longer package. I think it could work great as a airline travel bike if you dismantle front and back, wheels and all. It could pack into a legal airline package i think.