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Bottom bracket for Motobecane(5 posts)

Bottom bracket for Motobecanechopper
Sep 13, 2002 10:00 AM
I'm looking at buying a late 70's early 80's Motobecane frame. I'm assuming it has unique French threading and that I'll need a special bottom bracket for it. Are these hard to find? Are they expensive? I know Phil Wood carries them but if they are too expensive I'll pass on the frame.

Thanks.
re: Bottom bracket for Motobecanecurlybike
Sep 13, 2002 10:05 AM
In that period, French bikes could have either French or English bb threads. There are still French bbs around. I have 2 Campy on the shelf. The Phils can be had for around $100. If the frame is not 531, it is probably not worth the trouble.
It's probably swiss thread..........Dave Hickey
Sep 13, 2002 10:22 AM
Go to EBay cycling and do a search under "French". They have BB's all the time. I might be mistaken, but didn't Motobecanes from that period have Swiss BB's?

Here is what the expert says: From Sheldon Brown

French-thread bottom bracket cups use 35mm x 1mm threads. They are getting hard to find. If you have a French bicycle with sound bottom bracket cups, you may want to re-use them, even if you wind up changing the axle. Since French bottom brackets are normally the usual 68mm width, British/I.S.O. bottom bracket axles will sometimes work.
French bottom bracket cups usually have thinner walls than Japanese ones, so the bearing ridges on the spindles are farther apart. If you use a standard Japanese spindle, the adjustable cup won't be able to screw in far enough to snug up the bearings, or if it does, it will sink into the bottom bracket shell so that you won't be able to install the lockring.

The good news is that a Japanese spindle made for an Italian size (70 mm) bottom bracket will usually fit! In the Sugino marking system, these are the spindles that are marked with a "5" code. Spindles for 68 mm bbs have codes beginning with 3. This trick often makes it possible to upgrade an older bike from cotterd to cotterless cranks at a reasonable cost.

Cartridge bottom brackets are not generally available in French thread, although Phil Wood retaining rings are avaialable in French size. Phil Wood rings work with both Phil Wood bottom brackets and Shimano UN72 units.

French-thread bottom brackets, like Italian, use regular right threading on both sides. This means that the fixed cup will have a tendency to loosen up in use. The best prevention is to make sure it is really tight. In some cases, a thread adhesive may even be called for.

Some French bicycles, notably many Motobécane models, used Swiss thread bottom brackets. These have the same thread and diameter as French, but use a left thread for the fixed cup. This makes life interesting when you need to remove the fixed cup and don't know which way to turn it. Good luck.

Newer french bicycles commonly use Italian or British/I.S.O. bottom brackets.
It is Swiss Threaded.grzy
Sep 13, 2002 1:32 PM
Got several Moto's from that era and Swiss threading is the standard. Best advice is to get a Phil unit and the Swiss rings - this is what I did about 20 years ago when I wrecked and the BB hasn't been serviced since!! You may get lucky and find a Swiss threaded BB somewhere, but don't count on it. In the end you can take the Phil BB from another bike or transfer it to another bike and just swap out the rings. You also need the special tool for insertion & removal, plus they use a special loctite formulation to keep everything in place. Call them up - they're quite helpful. Be advised that almost every part of the Moto frame will have special size requirements, by todays standards: headset, BB, stem, and seatpost.
swiss threaded. also:Alexx
Sep 14, 2002 5:08 AM
don't forget that old french bikes used different heasets and stems, too. your choices in those sizes will be severely limited.