Bicycle Mechanics - French Frame
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09-24-06, 09:39 AM
So I picked up a 1978 Motobecane frame from a guy in town who was clearing out his basement.
It's a French standard headset with the awesome Swiss threaded bottom bracket.
I've done a little research on the issues that arise from that on Sheldon Brown's page, and the guy who gave it to me seemed to be quite knowledgeable about it too. In fact I have a sneaking suspicion that he posts on this forum occasionally.
I was recommended to solve the bottom bracket issue with a YST Threadless bottom bracket. And I have a spare fork off of a Raleigh Capri, that is british standard. I was told the fork will work, but I'm worried about potential issues concerning the rake. Does anyone have any experience with either the Threadless bottom brackets and/or using English forks on French frames? I'd like a little more information about the subject from several perspectives before I slap this thing together, which I plan on doing once the bottom bracket arrives.
09-24-06, 03:56 PM
A few months ago, I bought a Motobecane. I took it to the LBS & asked them to diagnose & repair a creak. They decided the BB needed replacing, and put an English-thread Shimano cartridge BB in. (They didn't know about Swiss threads although I pointed it out when I took it in.) It seemed to be crooked, so, another LBS chased the threads and put it in straight. Dozens of miles and several expert opinions later, it seems to be working fine and expectations are it should maybe go on working fine. (Sorry can't give you a higher-mileage report.) The expectation that it will continue to work well (even though the French/Swiss diameter is slightly larger than English) is because there's less axial load with a cartridge BB than with a cup-and-cone. See thread: http://www.bikeforums.net/showthread.php?t=216439.
I didn't mean for it to be done that way, but if it works, then fine.
On the way to reaching this conclusion, I asked & searched opinions about threadless BB's. They're troublesome, don't stand up to serious use, was what I read & heard.
Phil Wood makes (or made) a Swiss BB cartridge, but it's expensive.
09-24-06, 05:44 PM
Thanks, I couldn't find much info online about the quality of threadless bottom brackets. I've already ordered one and am planning on using it, since I don't want to drop much $ on this bike. The plan was to make it a fixed gear as this frame is much lighter than the bike i had converted to fixie. Plus the price was just right as this guy decided to give the frame away for free. Hopefully at best there won't be any weird issue, but at worst this could be a big problem on a fixed bike.
Another option was to tap it to english threading, but I'm very hesitant on that as there just seems like too many potential issues there with the skills of the person doing the job. I've heard it can be done fine, but I'm just too nervous about it.
09-24-06, 09:20 PM
another option is to tap it with Italian threading - which has a 1mm larger diameter. This will require a ream and then retap with the italian threads. Hard to find a shop with the tools I imagine.
Another option yet is a phil wood bottom bracket - available with swiss, french, raleigh, everything obscure threadings. This is expensive though.
Another option (cheaper) is to find a shimano un-72 or un-71 bottom bracket. The cups are removable and can be replaced with phil wood cups, which are a small portion of the whole PW BB cost. Finding something that works is preferable to permanently modifying a frame imho.
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