albrt 

I'm wondering how hard it would be to do a 650B conversion on a Peugeot that was probably designed for 650Bs to begin with.

I bought an approximately 1981 Peugeot Competition just to fiddle around with and see what it was like. This is a mid-range bike with 531 triangle and probably generic stays and fork. I haven't done much yet except wipe off the dust, service the gritty bottom bracket, and swap out the 27" wheels for 700s.



It came with 27" wheels that I think are original for the American market. The tires were skinny and stiff, and the bike was not particularly nice to ride. I put some old 1 1/4 Paselas on it, and they barely fit. The chain stays have nice big dimples for fat tires, but they are nowhere near where they would need to be for a 27" wheel. Here is what they look like with 700x35 tires:




Looking at where the dimples are, I think this frame was built for the Continental market to accommodate 650B touring tires, but then they slapped 27" wheels on it and shipped it to America. Does that sound plausible?

The bike is already nicer to ride with the 700x35s on it, but if I'm going to get the bike its own set of wheels I think I'd prefer to go all the way to the 650Bs. It seems to me all I would need (besides the wheels) is a longer set of brake calipers. The ones that are on the bike have some room, but not 23 mm.

So my questions for the forum are: what sort of calipers am I looking for, does anybody have some, and am I missing anything here?

bikemig 

No, the bike was not built around 650b wheels but was built around 700c wheels. This looks to be an 80s PKN 10 (perhaps an '82). It's a very good bike and yes the fork and rear triangle would be hi tensile steel whereas the main triangle is Reynolds 531. The catalogs are available online

By the 80s, Peugeot was using a dropout that worked either with Simplex or Campy/Shimano/Suntour/etc. so you have a lot of choices with rear derailleurs. I don't remember offhand the bcd of that crank but you can get an 86 bcd stronglight crank and run it either as a triple or a "compact crank." That's what I did on my 1982 Peugeot PXN 10.

albrt 

The Simplex derailleur actually works surprisingly well. I had to remove the adjusting screws completely and move the wheel all the way to the back of the dropouts to get the Paselas to fit. I thought it would affect the functioning of the derailleur, but if anything it works a little better.

Catnap 

For a 650B conversion, you need Tektro R559 long-reach calipers: https://tektro-usa.com/product/r559-long-reach/

You can also use Dia-Compe DC-750 centerpulls, or MX-806 side-pulls.

albrt 

Looks like I would also need wheels. I stopped by the big co-op across town and no dice on 650B road bike wheels.

Or I could build the wheels - I have a few nice old hubs if I can find some rims.

kroozer 

I don't think the conversion to 650B wheels will be all that difficult, although the wheels themselves (especially rims) can be expensive if you want a vintage look. That bike looks like it was designed as a racer, and early 80's racers usually had rather tight clearances. I would think long-reach brakes like Mafac Racer's or Weinmann 750's would have enough reach for 650B wheels on a frame like that. Tight clearances will also limit your tire size. You can probably fit 650Bx38mm tires, although very few road frames (like, none) of that era can take 650Bx42mm. So basically you're looking at doing all this to increase your tire width from 35mm to 38mm, and that's assuming the brakes will reach and the tires will fit. Cushy 650B wheels are nice, but on frames not built for them it's a crap shoot. You never really know for sure if it's going to work until you actually put on the components.

Nwvlvtnr 

If you can build wheels Sun Rims CR18 in 26 1 3/8” (ISO 590) size are a great value and only 6 mm larger in Diameter than 650b’s. Same sized used by most English 3 speeds. While selection is more limited these mostly use 35 mm tires.

Dia Compe or Wienmann 750 center pulls are common and work really well, there are also a lot of Caliper brakes meant for BMX bikes that would work.

Have a look at Porkchopbmx.com for brakes and if you’re building a budget wheel they offer reasonably priced spokes in custom lengths.

albrt 

Yeah, I bought this bike just to fiddle with it, was not originally thinking about a 650B conversion. But with those big dimples in the chain stays located right where the bulge of a 650B tire would be, I kinda think I can't resist. I'm a co-op guy so I always find a deal on parts somehow. And I suspect I could fit 42s in there.

Besides, I already have a bunch of upper middling early eighties road bikes with normal size tires.

albrt 

I'm sure it was sold to Americans as a racer. The geometry looks sort of like a racer when it has big wheels on it, especially the 27s with narrow tires. But it's kind of beefy and stiff, and it has eyelets and slackish angles. It's really a classic example of the 80s sport/tourer all-around mid-range bike. I bet the geometry will look a lot more like a touring bike if it has smaller wheels.

mgopack42 

albrt If you want something still French (kind of) i have this huret / sachs stuff circa 1990. make me an offer. this is how we all would have upgraded our bikes back in the day if we were going french.
huret sachs mini group

jdawginsc 

Thats definitely a cool group for sure. After seeing it and looking at Velobase, I wondered if that was a freewheel group that a brifter could shift.

bikemig 

Simplex rear derailleurs are good and by the 80s Simplex had moved away from delrin. Simplex RDs typically (but not always) have good capacity. Your RD should be able to handle 28 teeth and I wouldn't be surprised if it can handle up to 30 teeth.

I think you have the Simplex SX410T RD, in which case it can handle 30 teeth if properly adjusted:

https://velobase.com/ViewComponent.a...280cc&Enum=108

bikemig 

Yes it is a racing bike but the Pugs did not go all in with short reach brakes and no eyelets which was all the rage in the 80s. These bikes used standard reach brakes, eyelets, and can take a decent volume tire. I'm not convinced it's a good 650b candidate so you will want to take some measurements. Also I'll bet you can run a 32c tire which, while not as wide as a 38c that you may be able to run on a 650b (depending on clearance), is a pretty good all around size.

I'm a fan of Huret Sachs stuff and ran it on my primary road bike. That said, your group is 8 speed which is an issue for the OP since the bike is set at 126 OLD. The rear triangle can be spread but the OP would have to deal with this (and the rear wheel will need a different axle, the wheel will need to be properly centered, etc.).

I also do not think that is what people did back in the day if going with a French bike or at least that was not my experience working in a shop during this era. The later Simplex stuff was fine. YMMV.

albrt 

Thanks for the offer with the Huret/Sachs group, but I'm happy with the Simplex group. The only thing I probably want to do is try the 650B wheels, which will apparently take a while. For now the bike is riding well with the temporary 700x35s.

Catnap 

Cycles Toussaint has the cheapest complete 650B wheelset for rim brakes. I bought a pair and they are high quality, no complaints at all:
https://www.cyclestoussaint.com/coll...speed-clincher

albrt 

Thanks, that is a reasonable price. What is shipping like from Alberta?

Catnap 

I'm not the seller, Cycles Toussaint is, so go to their website and get a shipping quote. They are based in Calgary, Alberta so I assume it will be pretty reasonable.

albrt 

Thanks, I was just hoping you might remember whether your shipping was a big number or a small number.

JohnDThompson 

The crank appears to be a Stronglight 104bis:

https://velobase.com/ViewComponent.a...m=115&AbsPos=9
It has a 122mm BCD, like the older mod. 93 crank, so smallest ring is 37T. These are hard to find, even more so than 122mm BCD rings in general, although someone made reproduction 37T rings to fit that BCD. There is an online store in the UK, IIRC, that stocks some 122mm BCD rings, otherwise eBay may be your best bet.

bikemig 

The 37 tooth reproduction rings comes from one of our forum members. https://www.redclovercomponents.com/

albrt 

Vermont is Canada for all practical purposes. Well, except the electoral college I guess.

albrt 

Thanks for this - the crank is Peugeot branded. The extractor threads are standard 22 mm. I tried Stronglight and TA first and they were way too big. I am pretty happy with the existing gearing - the temp wheel has a Maeda 14-32 freewheel and the Simplex derailleur is handling the big cog like a champ. I might buy a Red Clover triplizer if I take up trail riding. Which I might be inspired to do if I end up with a gen-yoo-wine imitation French randonneur bike with 650B wheels.

JohnDThompson 

Stronglight changed from 23.35mm extractor thread to 22mm in 1982.

Catnap 

i came into a huge stash of NOS 122 BCD rings, that I sold off to a reseller. He's got them on Ebay here: https://www.ebay.com/itm/115801948184

albrt 

So I finally got a set of 650(b) wheels, tires, and tubes put together. The wheels are the Kill Wood wheels featured in a separate thread.




Go ahead and keep telling me those factory dimples on the chain stays were not intended for 650b tires, and I will go ahead and keep not believing you. The brake caliper mounts are positioned to accommodate 650b's perfectly with Weinmann 730 calipers. I have no problem believing that most of these bikes were sold with 700 or 27" wheels, but they were pretty clearly intended to be convertible to randonneurs.