since6

After following jamesdak's lovely conversion of his Fuji S 12 to 650B wheels with 42cm tires I wondered what other vintage frames could make this conversion? So If you have made this conversion please let me know the bike you converted and how the conversion is working out. Do include discussion of fender clearance and long reach brake choices.
Having moved to 650B wheels and 32cm tires on our tandem I really get what a difference a wide low pressure tire can make in both riding comfort and speed. I am considering building this conversion as a winter bike when there's lots of debris on the bike trail and bike lanes those wide tires make a big difference in safety.
Thanks for your thoughts and advice.

gugie 

The two things to look for are vertical clearance on the forks, and horizontal clearance in the chain stays. Without resorting to denting the chain stays, I typically look for long ones.

Early 70's bike boom Raleighs are good for this, as a general rule of thumb the later the model, the less likely they'll fit without modification.
Trek 620's
Motobecane Grand Record and Grand Jubilee - chainstays aren't as long, but they're dented

Those are some I've had experience with, I'm sure others will add to this list.

noglider 

I just received a set of 650B wheels with tires. I inserted them into my Lemond (Ti) frame, and it looks like they'll fit. The tires are 38mm wide, and I can't go any wider than that. I'm excited. It's a tight-clearance racing frame, and it rides great, but it's harsh. These tires won't be harsh.

VintageRide

Frankly I do not know of very many vintage frames that offer clearance for 42mm tires and fenders - the Fuji S10S, S12S as well as Ltd version and also the America from about 1978 - 1982 that are just about perfect especially if you are looking for a low trail Rando bike, which is what I did with my '81 S12S. I investigated quite a number of makes and there are not very many that offer low enough trail, if that is not important you may find a handful out there, getting frame dimensions and clearances is not easy, although there was a site that had listed quite a number of frames and had reasonably comprehensive information, the name escapes me at the moment however. That list allowed me to realize just how ideal these particularly Fujis where for a conversion. especially concerning bottom bracket drop and interference from the front wheel when peddling and turning.

63rickert

Anything older. When the narrow tire mania hit in the mid 70s it was complete and catastrophic across the entire industry. The bike business does not do anything halfway. If you look at pre-'75 it is not just a few models here and there that are readily converted, it would be practically everything.

gugie 

+1.

The OP wasn't asking about low trail, but those old Fuji's were practically made for 650b x 42's and handlebar bags.

The makes and years I mentioned mostly all require fork reraking to meet a low trail requirement.

due ruote 

ironwood

There is a long running thread on this forum devoted to 650B conversions. Treks from the early eighties can take 38mm wide tiresI recently converted a Zebakenko Record tour from 1978. It has low trail geometry and can take 650B x42mm Compass tires.

nlerner

I agree that if your goal is to run 42mm 650B tires (or wider as there are quite a few wider options now), your conversion possibilities are far more limited than if you want to run 38mm max tires. I'd suggest you browse through the 650B Google group (https://groups.google.com/forum/#!forum/650b) or do a search for "42mm conversion" in that group and see what comes up.

gugie 

If 42mm wide tires are your goal, I don't think a Sequoia would fit them without indenting the chainstays. @Andy_K might confirm this.

Andy_K 

I can neither confirm nor deny this. I think it depends on which model year Sequoia we're talking about. I'm pretty sure I read somewhere that they added more tire clearance in '83 or '84. I had 650x38 PariMotos on my '82 Sequoia. These tires plumped out to just under 40mm on my Velocity A23 rims. Surprisingly, the limiter on tire clearance was at the sides of the fork.



I think a 42 would probably fit in the back:



Of course, if you're just looking for a bike to use as a starting point, the Specialized Expedition (if you can find one) would probably be a better choice for tire clearance.

gugie 

Interesting, ID on the fork is rarely the limiter on vintage bike frames, from what I've seen.

since6

Thanks all and I will check into the 650B forum. As to tire width the 32cm tires on our tandem seem huge to me compared to the 28cm they replaced so 42cm was mostly drawn from the rebuild of the Fuji S12 S. I am sure that 38 cm will seem just at huge in comparison to the 32 cm we are running on our tandem, so don't limit suggestions to only 42cm capable vintage frames, a frame that would take a 38cm tire on a 650B rim would also fit my purpose of a very stable platform with comfort and speed for winter time riding and/or occasional hauling of groceries etc. I'll check and see what the 650B forums has to say too. Thanks

jlaw

My 1985 Trek 410 can clear a 650b x 38mm with no problem - about 5mm clearance on each side - the chain stays are the narrowest location - front fork and seat stays have more room. I could probably install 42mm wide tires, but the 38's ride very nicely at about 40psi. The tires I have are Panaracer Gravel Kings and they measure an honest 38mm.

If you haven't seen this reference, 'Bikeman' has some good advice about how to judge whether an existing frame is a good choice for for 650b conversion - tire clearance and brake reach are critical. If you measure the frame's tire clearance at 320mm from the axle location, then this should give you a good idea about how wide a 650b tire will clear.

650B Conversion Guidlines

beicster 

An 82 Trek 61x will easily clear a 38 and if you don't require a lot room for comfort, then I bet you could squeeze a 42 in. If you were willing to crimp the chainstays, you could easily add 42's. I was not willing.

Charles Wahl

Having been in a search for a vintage frame for 650B conversion, and bought several, I can confirm nlerner's advice: there are plenty of bikes that will take a 35 mm tire in the rear, many that will take 38 mm, and few that will take a 42 mm tire. As 63rickert observes, those are mostly frames built before the mid-70s.

Another issue is brake reach. Unless you're willing to go the braze-on mounting boss route, Compass or Mafac Raid will only go to 80 mm reach when mounted to standard fork crown and brake bridge holes. Many of the older frames that will take a wider tire also have pretty long reach: made for centerpull brakes, often 27" rims, and so forth.


The best candidate I think that I have, dimension-wise is a 1974 Peugeot PX-10 with 50 mm+ clearance between rear chain stays, and fairly short brake reach; but it's also not my favorite. Runner up in that department is a recently purchased Motobécane Le Champion, 1972 or so, with 47 mm and slightly more reach. UNICORN ALERT - delusional statement: An unexpected bonus that came with it, though, was a Universal 61 centerpull that appears to have about 80 mm reach. I didn't know those existed. As gugie has observed, Raleighs seem to be highly variable; and frames with longer chainstays (like 44.5 cm) usually have better clearance for accommodating a 650B tire.


EDIT: must have been those mushrooms I ate; remeasured this caliper, and it appears to have 72 mm reach max., as documented in some Universal catalog.

63rickert

Couple of points. You want clearance, not just possibility of shoehorning a wheel in. Most tires stretch over time. All Japanese nylon casing clinchers stretch over time. There is batch variation. You can buy the same make and model of tire and next time it's bigger. You might rebuild a wheel with a different rim, a wider rim, and suddenly you ate another bit of clearance. Or the same width rim, but the hook and bead seat are a little different and the tire mounts bigger. Spokes don't break as frequently as they once did, they still break. Now what is your clearance?

Smaller wheels ride harsher. Smaller diameter means the wheel goes deeper into that rut. Big wheel bridges over gaps that smaller wheels fall into. You need at 42mm of 650 tire to get roughly similar comfort to a 700x35. Raising the question why not simply get a bike that handles 700x35. And for those riding Gatorhosen, Armadillos, or Marathons, your bike rides like a tank because of those tires. If you take a ride on Hetres of course it feels great. Put Marathons on a 650 wheel instead of Hetres and you have a tank again. Put Compass or Vittoria on the bike you already got and feel the comfort. Is this trip necessary?

Bikeman guidelines noted above tell me that if I ground a pedal I'm surefire going to crash. Funny, I grounded a pedal on Sunday and here I am. Back in racing days, when we raced on widish pedals with toeclips, everyone who raced wore down the bottom corner of their Campy pedals. When the bearings were visible it was time to buy new pedals. And no one noticed a thing. You'd have 100 guys going through a crit corner and every one tagged their pedal. And no one crashed. No one even noticed. Too much going on to notice a little thing like pedal strike. If you ride big wide flat pedals you might ground a pedal once in a while. If you ride skinny one-sided clipless pedals you may never ground a pedal. It ain't likely. Of course bikes with low bottom brackets handle far better, have less wind resistance, tuck into the draft of the rider ahead better. But we can't have those bikes anymore because some blogger invented the myth of pedal strike. Your 650 wheel is 19mm less radius than a 700. The tire you will put on that smaller wheel will have approx 5-15mm greater radius. The bottom bracket with 650 is not that much lower. And getting a lower bracket is one of the totally unqualifiedly excellent things about a 650 conversion. No production bike and darn few customs ever had a bracket that was too low to handle a 700>650 conversion.

jamesdak 

You know as I sit here thinking about it I bet my old mid 80s Orbea Cabestany would fit a pretty wide 650b setup. It's all ready got a ton of room running a fat 700 x 30c tire. Hmmmm...













The problem may be finding one in the states as Orbea was not importing them then. I don't know how this one got here. I'll also freely admit that the build quality is much less than the Fuji. It sure is fast though.

Andy_K 

Dfrost 

nlerner

since6

Thanks all, it's kind of like being Santa. I'm gathering my list and checking it twice, lol. But seriously this is what makes this forum, such a wealth of knowledge shared.

Now the most important thing, be patient, wait for the right condition frame and right size. That latter will be the hardest part, lots of big frames found so far, but medium frame? Again "be patient" must be the mantra.

But be ready too.

VintageRide

Do give serious consideration to one of those Fuji S12S and variants I mentioned, very stable, predictable and nice riding bikes that really only need Dia Compe 750 center pull brakes to convert, and once you have tried 42mm tires you may not want to go back. Great for gravel roads and trails and even with 175mm crank arms and wide MKS Sylvan pedals under normal cornering pedal strike is a non issue. It is true that these bikes seem to have been designed for 650b, especially a front load but are fine without it. Here is my conversion, purchased as a frame and built up. I had it cold set at the rear for 135mm hub spacing ( Shimano XT ) as I had the wheel set beforehand, currently using Shimano 9 speed ( 11-34T ) with a combination of Shimano Mountain derailleurs ( XT ) and Campagnolo Ergo 10 speed shifters.

I might spring for some TA Cylotouriste triple cranks and an older Shimano Mountain rear derailleur one day just because I like the look of them. I spent a good amount of money on components but do not regret it as the bike, though not particularly light, just works so well and feels lighter.

dweenk

I used a Raleigh Olympian. I bought a pair of inexpensive Tektro long reach brakes to hit the rims.

gugie 

+1

I've only had one conversion that I felt the BB was too low, but it was still rideable. It was an older Velo Orange lugged frame, riding the gap between not very tall speed bumps in a parking lot I would hit them if I forgot to just freewheel over.

Pedal strike is probably over-rated, so is toe-clip overlap. If I were building a custom frame I'd take both into consideration, but it's not that big a deal to most riders.