Am looking at doing a 650b conversion. Several bikes in my current stable don't meet any or all of the criteria for a successful conversion. I am widening my search and need some help from those of you that might know. Do touring bikes of the 80's as a general rule (by design) have a lower bottom bracket height? Should I eliminate 80's tourers from my search as possible candidates for a 650b conversion?
TIA

Yes Touring bikes generally have a lower BB by comparison to Road bikes.

I'd recommend not overthinking it. I've converted a Varsity to 26" and a World Voyageur to 650B and found it way easier to just do it and worry later than to stress all the little details.

Stupid question.... with 650B, do the larger tires make up much of the height lost from 700c rims??

Depends on how fat a 650B you go with , but yes it does make up for some of that height lost. The fatter you go, the moreso.

I can measure tonight and put some numbers to that statement.

That's not a stupid question, Matt. A 700c x 23mm tire is pretty close to a 650b x 38mm tire in diameter.

Good to know.

I must be over thinking this conversion thing. The few I have tried lowered the bottom bracket too much and I am concerned about pedal strike but they were all 27 to 650b. I will narrow my search to 700 to 650b and see if I have any success.
thanks

Zaphod and myself have both converted 1973 World Voyageurs from 27" x 1 1/4" to 650b x 42mm. Member southpawboston converted an 80s Shogun touring bike from 27" to 650B. His required the moving of the cantilever posts, but it worked out very well.

Dueling World Voyageurs!!!

Pedal strike can be pretty easily avoided by just not pedaling through sharp turns/cornering with the inside crank arm in the 6 o'clock position.

I have a frame I'm converting to 650b which is easy because the fork and chainstays have never been finalized. Trying to figure out what tires to use, the selection seems underwhelming

Yeah, it's pretty much a non-issue if you've done any fixed gear riding.

That's an enviable position to be in. Since building my World Voyageur I've wanted a Frame with a short wheelbase, vertical dropouts and clearance for 650Bx42.

If you're going for new tires there's a few...The GB Hetres being the fattest, then Pacenti Pari-Motos at 38, Panaracer Col-De-La-Vie 38's, and Grand Bois Cypres 32's.

For my money I'd do a 650a (590mm) conversion. Lots of tires available at inexpensive prices but rim choice is slim atmo.

I've got a 650A bike and I wouldn't do it for tire choices. The only good tire for that size is the Col-De-la-Vie IMHO. Those Schwalbe tires are garbage.

There was a thread here a couple years back "650A vs 650B, trying to make sense of it all" which made some very strong arguments for 650a. Also, here's a list of about two dozen tires in 650a, for those looking for alternatives to the 650b route.

I have considered it since buying 650a wheels by mistake a while back. But for the whole reason I want to do 650Bs is the 42mm tires

You know, I'm glad I ran across this... I am looking to do a 650B conversion for my Miyata 1200, but am finding it hard to find anything cheap (I usually build all of my stuff for very cheap... it just takes a while). I wanted something nicer than CR18s to lace to an ultegra wheelset, but I don't know if that is justifiable. I'm just going to use the bike as a commuter anyway. If I had a 650B I'm not convinced I would spring for GB tires anyways... I'd probably do the CDLVs.

But then again... saying that you have a 650B is so cool.

If you dig around eBay you can find 650a rims other than CR-18s. I know CR-18s are pretty pedestrian, but in polished form they are a decent, strong rim for the money. Like you say, you don't have 650b bragging rights, but your wallet will likely be thicker than the guy with the 650b's.

I would like the biggest tire possible, so I guess I should plan for 42. I have become a fan of longer chainstays for climbing on slick roads with steep grades. There is a limit though.

I have a pair of Velocity Synergy rims coming in, rear hub is going to be XT 135mm, and front is going to be a Sanyo dynohub. All in silver so hopefully it doesn't detract from the vintage look too much. The frame is the modern Columbus SL, standard tubing sizes.

Because 650Bs are cool. Imagine, a bike that is as much at home on a long stretch of paved road as it is on a fire trail.

Theres a set of new 650B hoops for 60 on the bay right now.

Thanks for all the info guys.
I am over thinking all this.
I am moving forward and everything and anything is fair game.
I just needed some reassurance the 27" is doable.

that's what made me want one. I was looking through Peter Wiegel's pictures, and he has some where he has taken his 650b bike down some singletrack. I always liked doing that. One spring, I had my racing bike up to the axles in mud on one small road. That was fun.

I'm coming from the other side, thinking of converting my vintage 26" hardtail/rigid fork MTB to a more of a roadie/firetrail bike with drop bars, bar-end shifters and different tires. Advantage there is a huge number of rim/tire choices. What are the advantages of a 650b over this setup?

You have the experts in this thread (of which I certainly am not)... but from what I gather, there is nothing inherently/physically better about 650B vs a 26". When you convert a 700c road bike to 650B though, you get that road geometry with the pneumatic comfort of the puffy tires. You also free up room for fenders. From my experience converting rigid MTBs/hybrids to drop bars, the handling and fit is kind of odd. Lots of people have done it and have had good results though.

EDIT: fenders, not comfort