Hi all, I'm working on my first fixed gear conversion and running into some snags. I'm building on an old Motobecane Nomade II frame that I nabbed on Craigslist. It's a really nice frame but I'm considering going for something else just due to the inconveniences I'm running into with it.

The old crankset on there has (I believe) a 52t outer ring and no inner ring, and I don't want to run 52x16 on this bike (I'm running 16 on the rear) so I feel like I'd have to either find an inner chainring to bolt on or a whole new crankset. It seems like both of these would be kind of a pain as the BCD for an inner ring on this set would be 122 (I've been hearing that this is somewhat rare) and the funky threading on Motobecanes would make a new crankset equally aggravating.

I love the frame but I feel like it's turning into a money pit and I'm wondering if I should just put the frame up for sale and find something that won't be such a hassle. On top of all this, the frame is a little large and I think I might like to ride something smaller. Any guidance and advice you guys can give would be a great help. Thanks.

If the BB is smooth and square taper, a new crankset shouldn't be an issue. The BB/spindle is the difficult/expensive part. Without some prior experience, the French stuff can be a bit maddening, but working through the hassle will be worth it in the long run as there are some really nice Frenchies to be had out there. sheldonbrown.com has the best info on French threading/sizing issues.

just go bigger on the back? It won't cost you very much to get a new cog.

Be manly, run 52x16.

I had a friend that ran 53x17.

I run a 53/18 on my fixed wheel roadie. It makes the ups a bit painful, but keeps me from spinning out or overheating my brakes on the long downs. It took a bit of getting used to, but I do feel manlier now...

Yeah, my friend decided he likes his knees, runs 48x17, now.

Haha, thanks for the replies guys. Maybe I will try 52x16, it just seemed a bit on the crazy side to me. I'll give it a shot at least; I can't wait to get this baby on the road.

52/16 = too manly for me

Is the BB square taper? If so, I'd just spring for an inexpensive crankset like Eighthinch, Origin 8 etc.

I'm pretty manly but a 52:16 is a little steep... I run a 52:19 on my roadie with a 17 on the flip for those perfect days when the road is flat and the wind is at my back.

I know girls that will outrun you, woman.

I'm a little lost here, what's wrong with buying a new cog?

Everything.

Do you think there will be a chainline issue? Maybe I'm just saying this because I just bought a Sugino xd crankset and un54 107 bb for my conversion and I'm running a kmc z510 1/8" chain and my drivetrain is still making noise and there still seems to be a slight chainline issue. It seems to be turning fine but it's cutting it really close. Kinda bummed but maybe it will work out.

Sorry for making this about me, I'm just bummed because I want to ride my bike. Anyways, if he is using the original BB and a track specific crank won't there be a chainline issue?

I usually just throw whatever crank/bb I have on and deal with the chainline by respacing/dishing the rear wheel. I just find it way easier that way in the end.

So I did a little tinkering today, and I've decided basically to wing it, get the bike rideable as soon as possible on the 52x16 just to see how it feels. I'm leaning toward the path of selling this frame pretty soon now. I don't know if I overestimated my own tallness or underestimated the tallness of the bike, but it's not the best fit and that handsome French charm only goes so far.

Incidentally, have you guys had any experience with EightInch frames? They seem almost too inexpensive, but I'm reading a pretty glowing review right now that has me thinking.

52x16 will be painful. just get an 18 cog and be done with it.

People are fond of the scrambler.

I run 52/17 and its a pretty nice ride.

swap out the cog, problem solved.

(if chain fits)

I'm going to wait on buying a new cog. I was screwing some things together in the garage last night and couldn't get the chain line right for the life of me. I know a shop where I might be able to find an inside ring that would fit, and that might just solve both my gearing and chain line problems in one fell swoop.

Okay. Fact one: Motos tend to be Swiss thread in the bottom bracket, not French. This means the fixed cup is reverse threaded. There thread pitch and diameter are the same as French. Sometimes (not always), you can thread in an English BB. They're different, but not as much as folks sometimes think (myself sometimes included). Try it if you have to (it may not work) but:

Fact two: most Motos were equipped with Japanese BB cups (Ie Sugino or Sakae) and replacement spindles are far easier to find than on other French makes; any old Japanese spindle will do. The walls of the cups are thicker on Japanese cups than most old Euro/French ones, so you cannot swap spindles between the two. Generally, old Japanese cups are marked somewhere with the maker's name, but I have an unmarked pair of swiss ones somewhere...

So a new crank may not be that aggravating, frankly. If you can find a Japanese crank and spindle, you're off to the races. Posting what the bike has on it (or pics) may be very helpful here. With an old moto, you would do better to trust the collective knowledge of the C&V board than here (although you'll get torched a bit for turning an old bike into a fixie, if you haven't done anything dumb-- like hack off all the braze ons with a dremel or rattlecan a perfectly good original paint job) you'll likely come out of the experience both intact and wiser.

Shops tend to be complete doofuses when dealing with old Frenchies, you'd have better luck bringing in a flying saucer for repair than an old Peugeot to your average bike shop.

Yes, you can get this working, but why bother? If the frame's too big and you're just going to flip it, then save the time and effort for the replacement bike that actually fits. If you were working on something you could just migrate over to the next bike, that might be different, but this sounds like a time suck to me.

Honestly I agree with you there, kyselad. I just want to get this bike rideable as soon as possible while I plan my next move. And it is basically rideable now, even though the chainline is a little off (just need to pick up some tubes). I don't see the sense in investing any more significant time/money/effort in it at this point. I think I'm just still partially seduced by its charm. It is a very handsome frame, I'd upload some pics if I had a camera.

And no, I have not hacked anything off and wouldn't even think of repainting this frame. I am opposed to plastic surgery.

I am happy to say that I just took my baby out for her maiden voyage around the block, and as soon as I started pedaling all of my concerns and trepidations basically melted away. It's 52x16 until further notice, gonna see about a chainring tomorrow. If that doesn't work out, maybe spacers and a bigger rear cog. Frame size is a little bigger than usual, gotta keep the saddle pretty low; **** it for now. Big girls need love too.

But god damn is it nice to ride that bike. 50% old parts from my garage, 50% new parts from the shop, 100% fun to ride. Thanks for all your help.