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Singlespeed & Fixed Gear "I still feel that variable gears are only for people over forty-five. Isn't it better to triumph by the strength of your muscles than by the artifice of a derailer? We are getting soft...As for me, give me a fixed gear!"-- Henri Desgrange (31 January 1865 - 16 August 1940)

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Old 07-17-08, 11:37 AM   #1
itschrisb
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Motobecane??

I have an old motobecane, the bottom bracket shell has 1957 engraved in it, im guessing thats the year it was built. I just learned about the french threading problems and it has me worried. Im going to convert it, well im hoping too. My biggest concern is the bb obviously. The headset is still in good shape and the other things like stem size dont seem to be that big of a deal. Right now the cranks on my bike have a square taper not spline. Would square tape arms fit on there such as the sugino RD crank arms? And using the existing bottom bracket im guessing ill have issues getting the chain lined up?
I looked on ebay and found french bb cups so do i need to buy a spindle and bearings and build my own bb that will better work with a track rear wheel spacing? Anyone that can help me that would be great. Is it worth doing or should i just look into a different frame and start with that?
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Old 07-17-08, 11:40 AM   #2
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Go see the master: http://sheldonbrown.com/velos.html
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Old 07-17-08, 11:56 AM   #3
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Ive read that, but i dont quite understand. Is the bb only a hassle if yours needs to be replaced? Or in order to run modern cranks you have to get a modern bb?
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Old 07-17-08, 12:10 PM   #4
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My biggest concern is the bb obviously. The headset is still in good shape and the other things like stem size dont seem to be that big of a deal. Right now the cranks on my bike have a square taper not spline. Would square tape arms fit on there such as the sugino RD crank arms? And using the existing bottom bracket im guessing ill have issues getting the chain lined up?
I looked on ebay and found french bb cups so do i need to buy a spindle and bearings and build my own bb that will better work with a track rear wheel spacing? Anyone that can help me that would be great. Is it worth doing or should i just look into a different frame and start with that?
Unless you're trying to preserve the frame as an antique wouldn't you just jam a normal bottom bracket into it and go?
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Old 07-17-08, 12:34 PM   #5
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Unless you're trying to preserve the frame as an antique wouldn't you just jam a normal bottom bracket into it and go?
If the threading is indeed French, then no. There are very few French threaded cartridge BBs on the market, and those that I know of (i.e. Phils) are crazy expensive.

It's not clear from the original post whether you already have an existing bottom bracket on the bike, though it sounds like the bike has cranks and presumably a BB as well? If it is there, it's almost certainly an adjustable (i.e. separate cups, bearings, and spindle) rather than a modern cartridge. In that case, you can save a lot of hassle by keeping the existing cups and just replacing the spindle. Check with your LBS and they should be able to get an appropriately sized spindle for ~$10 in order to line up your drivetrain. Cleaning and repacking the BB is very straightforward (plenty of online instructions), and you can replace the bearings if they're worn. If your cups are shot, you'll need to find new ones or go with a pricey cartridge BB, and that could be a deal breaker depending on how much you love this bike.

Good luck.
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Old 07-17-08, 12:43 PM   #6
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If the threading is indeed French, then no. There are very few French threaded cartridge BBs on the market, and those that I know of (i.e. Phils) are crazy expensive.
That's what I'm saying. I just bought an IRO BB and cross-threaded into my Motobecane. Sure it wrecked the frame's treads, but it works.
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Old 07-17-08, 01:06 PM   #7
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That's what I'm saying. I just bought an IRO BB and cross-threaded into my Motobecane. Sure it wrecked the frame's treads, but it works.
Didn't realize that's what you meant by jamming it in. Notably, many Motobecane BB's were Swiss thread, but I think they were French way back in the day, and this '57 may have French threads. I'm guessing you cross-threaded into a Swiss shell, since it has the same thread direction as ISO. If the OP's bike really has French threads, this wouldn't be possible.

Really, though, swapping the spindle is quite straightforward, and if the cups are in good shape, I'd go that route. If your cups are shot, you might also swing by a machine shop and see what they'd charge to fill and tap for ISO threads. This might be reasonably affordable, and it would make life a lot easier down the line.
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Old 07-17-08, 01:10 PM   #8
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yea right now the bike is complete and working just fine, cranks included. i dont really know how to tell if the cups are junk, they arent rusty or anything and the cranks spin fine. my main question is if i already have the complete orginial french bb can i use that with modern cranksets. from what ur saying it sounds like i just need to order the appropriate spindle and the LBS should be able to make everything work. im not looking to upgrade to if i dont have to since its my first fixie and is far from going to be top notch. im looking into getting the sugino rd messenger crankset, so to run that on the existing bb all i need is to get the spindle that fits the crankarms?
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Old 07-17-08, 01:39 PM   #9
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im looking into getting the sugino rd messenger crankset, so to run that on the existing bb all i need is to get the spindle that fits the crankarms?
Pretty much. If you really luck out, the new cranks will fit on the spindle and give a decent chainline. But the chances are pretty slim, and if these cranks are old enough, they may even be cottered, meaning you'll certainly need to replace the spindle when swapping cranks.

The cranks sound like they might be in decent shape -- do you really need to replace them? I still run the original crankset on my conversion, and though it did require finding a spindle for my chainline, I got off really cheap in the end and frankly I prefer my cranks over most modern options. Spacers and longer bolts can also give you some fine-tuning at the chainring, which could save you having to swap spindles at all.

Regarding the BB condition, the best way to tell is simply to pull off the non-drive side cup and look (the drive side cup is a big pain to remove and can just stay in if it's in decent shape). Be ready to catch the loose bearings. Clean the grease out and check for excessive wear (grooves, pitting, etc.) on the cups, bearings, and spindle. If it's running fine as-is, everything's probably in good enough shape, but it's probably worth disassembling so you know what you're dealing with and so you know it's properly packed with grease.
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Old 07-17-08, 07:07 PM   #10
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The only reason i was going to replace them is bc i thought i had to in order to get a good chain line. That and i was told that stock cranksets arent strong enough for fixed gear riding. I definitly wouldnt mind polishing mine up or painting them black. They look nice. Ill take it to the LBS and see what he thinks. Thats how i found out about French threads i had no idea. Good thing i stopped by there.
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Old 07-17-08, 07:18 PM   #11
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heres a picture, i can get a better one of the crank itself if it helps any.
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Old 07-17-08, 08:12 PM   #12
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ride it as is. find a better option to convert or just get a real track bike.
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Old 07-17-08, 08:31 PM   #13
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That bike is much newer than I was thinking and quite possibly has a Swiss BB, not that it's any easier to replace Swiss cups vs French. It also doesn't look like it has cottered cranks after all; you can easily tell by looking for a cotter holding the crank arm onto the spindle.

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The only reason i was going to replace them is bc i thought i had to in order to get a good chain line. That and i was told that stock cranksets arent strong enough for fixed gear riding.
Your chainline up front is a function of cranks, chainring placement (i.e. which position you're using on the crank arms and whether you're mounting the ring inboard or outboard), and BB/spindle. You can certainly get a good chainline with the existing cranks, quite possibly with very little adjustment. Just measure to see where it is on each of the existing chainrings and then go from there in deciding what (if anything) to change up.

There's absolutely nothing wrong with older cranks if they're not damaged (or cottered), and whoever told you they're not strong enough to ride fixed is full of crap. Proper track bikes require tougher and stiffer goodies, and somehow this notion seems to have extended to all things fixed in the minds of some folks. Bust aside from that, the RDs are just repackaged road cranks anyway. Skip the hype and stick with the character; I agree those are nice lookin' cranks, classier than the RDs by a long shot in my opinion.
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Old 07-17-08, 08:33 PM   #14
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ride it as is. find a better option to convert or just get a real track bike.
Why does the OP need a track bike?
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Old 07-17-08, 08:40 PM   #15
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Yea im not really sure if its from 1957, i was looking on the hubs, the front one is an Normandy with 05 81 stamped on it and the back one is an Atom with ?? 81 stamped on it. Its also made with 2040 tubing which from what ive read makes it somewhere in the 70's. I wish their was a serial number decoder of some sort. What exactly does a cottered crank look like? This has a little 14mm bolt that threads on the spindle after you take that off there pretty much is just a spindle and a crank arm.
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Old 07-17-08, 09:24 PM   #16
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What exactly does a cottered crank look like? This has a little 14mm bolt that threads on the spindle after you take that off there pretty much is just a spindle and a crank arm.
Then it's not cottered. Check online if you need info on disassembling and servicing the BB. Park Tools' website is a good start -- just look up "adjustable" bottom brackets.
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Old 07-17-08, 10:00 PM   #17
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Thanks so much for all the help. Ill start looking into servicing my bb.
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Old 07-17-08, 10:36 PM   #18
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Built two Motos recently using existing BB or Yellow Bike(French BB's are pretty easy to spot in the bins). Both had good chainline, one required reversing the axle, but otherwise no problems. Just wait 'til you try to upgrade the stem, that's when things get a little hectic. I love the ride of French bikes, but if you find some parts, hoard them forever...
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Old 07-17-08, 10:44 PM   #19
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Well thats good to hear, i was really worried at first bc i really want everything to work out. The guy at the bike shop made it seem like im pretty much s*** out of luck bc i have french threading. But im glad that i got all of this information and found that there are ways to upgrade if needed. Aside from bottom brackets what other things are different on french bikes. Stems,forks,headseats. Anything else? And how much of a PIA are those things? Thanks
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Old 07-17-08, 11:11 PM   #20
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Well thats good to hear, i was really worried at first bc i really want everything to work out. The guy at the bike shop made it seem like im pretty much s*** out of luck bc i have french threading. But im glad that i got all of this information and found that there are ways to upgrade if needed. Aside from bottom brackets what other things are different on french bikes. Stems,forks,headseats. Anything else? And how much of a PIA are those things? Thanks
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That link pretty much says it all.
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Old 07-18-08, 12:40 AM   #21
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Alright ill read up, thanks again for everything
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Old 07-18-08, 03:58 AM   #22
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I just overhauled the BB on my peugeot. As long as all the BB parts clean up nice and spin freely once put together, you should be just fine.
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Old 07-18-08, 08:10 AM   #23
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im gunna do that when i paint my frame. Anyone make a homemade crank arm puller or do you have to put the tool?
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Old 07-18-08, 09:28 AM   #24
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I picked up a crank puller at my lbs for a little less than 10 bucks. Well worth avoiding the headache.
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Old 07-18-08, 09:37 AM   #25
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yea thats what i figured, thanks again
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