Nearly There: Motobecane 650B Conversion

Well, the Motobecane Grand Jubile 650B conversion is nearly there. I still have a few odds and ends to complete - install toe clips and straps, wrap the bars, get some fenders, etc. - but it's definitely rideable at this point.

I've taken the bike for a short spin around the neighborhood to sort things out. It seems to handle nicely, and felt pretty good over the old brick-paved streets near my home (they're like the Akron version of cobblestones -- Akron pavé, if you will).

The red/black/gold color scheme is a favorite of mine. The paint looks pretty good from a few feet back, but up close there are lots of chips, scratches, and touchups to be seen. Never mind that for now. I'm not sure what the angles are on this frame, but the head angle looks fairly steep, and there's not a lot of fork rake. I could be wrong, but it seems to me that earlier versions of this model had a slacker head angle and more rake. Funny thing, though - the '77 catalog lists the Grand Jubile as a touring model. It's probably closer to that now than it was when new. I ordered some fenders from Velo-Orange, which I think will cap this project off nicely.

I did end up cutting about ¾ inch off the ends of the bars, which seems to work well with the bar-end shifters, and makes them look a little more "normal" to my eye. I used Dia Compe 750 center pull brakes on the front and rear, with Velo-Orange pads. The pads are not quite at the bottom of the slots in front - but are pretty much there in back. I still need to wrap the bars (I'll use Tressostar black cotton tape with a coat of shellac) but I won't do that until I'm sure about the reach to the bars and the brake lever placement, etc.

Lots of space in the back. Fitting fenders shouldn't be a problem. For the cable hanger in back, I found a new-old-stock Shimano hanger with a built-in quick release. There's a similar quick release hanger on the front, but marked Dia Compe. Yes - my brake levers have quick releases built in, too. Used together, the brakes open up as wide as possible to let a wheel and a fat tire out easily. To run the brake cable housing along the top tube I needed to use cable clamps. Fun fact: French bikes use a 26mm top tube and most cable clamps are made for 25.4. I had some nice old Shimano ones that appear to be stainless steel instead of chromed, but they wouldn't quite work - the clamps themselves are flexible and seemed like they'd fit, but the supplied screws weren't long enough. I searched though my spare parts and found longer screws that happened to be the right thread and diameter. Yay!

This view tells me I need to remove a little excess cable housing - the "loops" look a bit big to me.

I did it again. Another SunTour Vx - this time it's the medium-cage "S" model. The bike would have originally come with a Cyclone derailleur set - but the Vx is reasonably light, looks pretty cool, and is darn near indestructible. Notice that the frame was built with SunTour dropouts. Older versions of the Grand Jubile used Huret Jubilee derailleurs, and I assume the Huret dropouts as well - and the derailleur hangers on those are not compatible with most of today's derailleurs (at least not without some modifications). SunTour and Shimano both settled on the Campagnolo-style derailleur hanger some time back in the '60s or early '70s, which pretty much made that the de-facto standard for the industry.

Up front, I have the SunTour ARX, a nice-shifting but under-appreciated front derailleur. I used the same Vx/ARX combination on one of the bikes I built for my daughters. I got the VO crank slightly used for a fraction of the price of new (the version with drilled rings would have been a nice touch, but that's how it goes). MKS Sylvan pedals have the right vintage appeal.

Always Brooks saddles.

I know I included the catalog and specs in an earlier post, but it's worth seeing again.

Being my first 650B conversion project, I tried to keep the investment low. I got the frame pretty cheap, raided my parts bins or bought lightly used parts wherever possible, and went with budget-friendly new parts where needed. I'll have to get a sense of how much I like the bike, and make sure the fit (and everything else) works for me. For one thing, I did go with a 25" frame (I normally ride 24") based on some recommendations from people who've done similar conversions. Going down a wheel size lowers everything enough that I can still straddle the top tube just fine - but I do wonder about the length/reach. We'll see how that works.

If I decide I really like it and want to stick with it, I do have some thoughts about things I might do with it later - like maybe sending the frame out for new paint and having some braze-ons added, such as brake pivots (either for direct-mounting the center pulls, or possibly cantilevers), and cable guides/stops, etc. But I'll want to ride it as-is for a while before I make any decisions like that.

Here are the full specs:

Frame: 1977 Motobecane Grand Jubile, Vitus 172 chrome-moly tubing throughout, 25".
Wheels: SunTour Vx hubs, Grand Bois rims, 36 Sapim double-butted spokes.
Tires: Pacenti Pari-Moto 38mm
Rear Derailleur: SunTour Vx-S
Front Derailleur: SunTour ARX
Shift Levers: SunTour BarCon ratcheting bar-end levers
Freewheel: SunTour Pro Compe, 5-speed, 14-28
Crank: Velo-Orange, 48/34
Pedals: MKS Sylvan
Bottom Bracket: IRD QB-55 with Swiss-threaded cups.
Headset: Velo-Orange (French threaded)
Stem: Nitto Technomic, 9cm
Handlebars: Velo-Orange "Course," Maes-bend
Brake Levers: Dia Compe 204Q (with quick release)
Brakes: Dia Compe DC750, with Velo-Orange pads.
Seatpost: Kalloy Uno, 26.4mm
Saddle: Brooks B-17

I'll get more pictures posted and a ride report when the last bits are finished.