Cause it's in the dreaded big ring, big cog position?

Well yes, as you say, that's the easy way. And (before I start my obligatory scoffing) I admit, there's a lot to be said for taking the easy way out (otherwise there wouldn't be a song about it).
And obviously there's something wonderfully elegant about a disk brake system where you can substitute any wheel set with approximately the same overall diameter.
Indeed, if the fatness of the tires is the only variable that has any effect on ride quality, you'll be in luck, because that'll be the only variable you'll experience.
So, as I say, this approach has a lot to recommend it.

On the other hand, disk brakes require heavy and more or less inflexible fork blades that (some experts argue) have a detrimental effect on ride quality. Now if you spend your whole ride worrying about whether your brakes are up to the task of stopping you, then the awesomeness of disk brakes is worth any cost.
I, however, am one of those guys who spends a lot of time pedaling and very little time braking, and it seems to me my brakes don't have to be awesome. They only have to be good enough. And rim brakes are good enough for me. They allow a lighter frame and more resiliant fork blades... And that seems more important to me than braking awesomeness.
At least in theory.

Threads like these made me try my first 650b conversion, now I have all sorts of wheel making equipment and 32mm tires feel "harsh."

I wouldn't hesitate to make a 650b roadie. I did one myself and love it. Take it on any paved road, never worry about hitting a bit of gravel. It's like driving a four wheel drive Porsche.

Regarding slamming a wheel all the way back in horizontal dropouts for max clearance, one may find that does not provide optimal shifting performance. It's a fine balance. I am now a big fan of vertical dropouts for fendered bikes.

But it's going to have 42mm tires.

Looks like panaracer has a pretty decent selection of 650b road tires. The gravel king 650b x 38c look like a fine tire and the weight is very good at 310 grams, https://www.panaracer.com/lineup/gravel.html

I haven't decided on the rims yet but I'll probably get the soma weymouth rims. They're siilver and they'll look right on a vintage bike. They look like pretty tough rims if a bit heavy at 580 grams, Weymouth Rim (700c & 650b) | SOMA Fabrications. Still I'd prefer something a bit lighter. I wish sun CR 18s came in 650b size.

I'll have to decide whether to use older hubs and stick with 126mm in the rear or stretch that frame to 130.

Have you heard about the new Pacenti Brevet rim? A bit pricy, but very light:
https://www.bikerumor.com/2016/10/25...rza-rims-2017/


I've been running Panaracer Pari-Moto 650x38b's (also a Pacenti design) on my conversion. Very nice tires. Light, supple, smooth, fast, but may not be the longest-lived. Don't have enough miles on them yet to know.


When/if I build up a "fancy" 650b bike I'll most likely use Brevets and Pari-Motos.


SP
OC, OR

I spent some time on the web sites of various suppliers and manufacturers and compile a list of 650b tires that are currently available, from 28mm to 50mm. Thought it might be useful.

https://valvejob.wordpress.com/2016/...-observations/

Those "Brevet" rims look really sharp. I'm planning to order a couple for future use before too long.

That's a really useful list, . I did not know that the schwable supreme touring tire came in a 650b. That's a great tire.

Sure, but that's only part of the equation. A lot of it really comes down to where you ride and how, and how much you weigh. I'm no lightweight - I ride a bike with 531 fork blades among the rest of the tubing on 38mm 650b Compass EL tires, and many times I'm happy to see the fork blades flex as much as they do. Micro versus macro. On smooth-ish pavement the distinction is minor at best, but that's not where it matters. Once things get rough you want that extra level of give.

Your idea for a XC MTB 650b x 42mm does sound like a blast, I'm just saying 42mm tires don't default you to a cushy cloud no matter where you are.

These do look really good. Which bike are they for?

That's the thing -- none of my bikes need new wheels, just wanna buy some of these.

Actually, I've gone this route four times, with good results. That said, the bikes I've converted were old-school 'limousine' frame MTBs with really long chainstays, and I converted them as city bikes & tourers:

The first was a '93 Trek 820, which I used as a test bed, mostly to see if I liked the result... (Sold in 2011)

The second was a larger size '91 Trek 820, which I still use as a touring bike (the frame is very similar to a Surly LHT)...

The third was my Univega 'FrankenRover' (Posted somewhere here in C&V), which I built up strictly as a townie (& to clear out spare parts from the previous two builds)... (Sold in 2015)

... And fourth- my Panasonic CB-620- wasn't so much a conversion as a restoration/ reversion, as the original Japanese (non-export) version, the Viatore CT, was actually a 650b rando. This frame was modernized at TiCycles here in Portland.

I have YET to do a 650b conversion despite how many years of planning and hoarding parts? I'm feeling a bit overwhelmed again with my bikes and bits sprawling all over the place. I sold my perfect 650b frame conversion a vintage trek a few years ago to someone planning to actually build a 650b for his wife. I have a frame that I was going to build 650b but I do not think the clearance is good for even 32mm cypres tires. Another bicycle in mid catastrophe could take up to 38mm. I am now thinking of a 650b conversion of my raleigh sports, or my raleigh sprite both of which are in bad shape. I had taken an old raleigh sports and built up new 650a wheels for some insane period correct reason. I used drum brakes and IGH hubs so this is a very heavy bike and in dire need of mechanical help. not a good project idea!
My husband however did a 650b conversion using some of my hoarded 650b parts. An 80's lower end japanese bianchi that has space for 38mm tires and my precious honjo fenders. Tekto silver long reach brakes, left everything else as is. He hated the ride of this bicycle with 700c wheels, but found 650b improved the ride considerably. I think it is a very fast and light bike which of course looks stunning.
My concerns are rims and brakes.

Cycles Toussaint has a pretty nice 650B frame for $525 and it will accept tires up to 42mm.


Review: https://stonehog.com/2014/03/03/init...routier-notes/


Frame: Velo Routier Version 2 650B Low Trail Frame (with braze-ons) | Cycles Toussaint

I'm late to the conversation, but I've done a bunch of 650B conversions over the past 6-7 years. My first was actually my most ambitious and most successful-- I'm still riding that one regularly. It's a 1984 Shogun tourer made for 27" wheels, and had a very high bottom bracket, handily lending itself to conversion. I had the usual braze-ons added (extra eyelets, bottle mounts, and canti posts, and provisions for internal wiring), had the whole thing powder coated in cream, and built it up as a 650B randonneur-style bike. It fits 42mm wide 650B tires with very little room to spare:



The bike wasn't perfect for this setup and didn't do well for long rides with a front load, so I reconfigured it as an around-town porteur-style bike, and the difference in riding position transformed the feel of the bike. It works really well in this configuration and I've been using it in this form for a few years:



I built this new Soma Buena Vista frameset up for my wife using 650B wheels right from the start (no modifications necessary... gobs of tire clearance for 42mm tires... just needed long-reach brakes), and it has been her errand bike for the past six years. It has a low bottom bracket, so I might not recommend this frame for 650B road riding unless you were to go with shorter cranks. It's had a few changes and swap-outs since then, but it still retains its 650B format:



Since then I've added 650B purpose built frames to my fleet (Rawland Stag and a Jeff Lyon L'Avecaise custom), but haven't played around with more conversions.

With my Holdsworth being cut apart and brazed back together under [MENTION=381793]gugie[/MENTION]'s skilled hands, I have been without a 650b bike for a few months. It turns out this is a very good way to determine whether you like the whole 650b thing; and I found absence does indeed bring an old cliche to mind.

So I took this old Bottecchia frame --early 1970's, either a Professional or Giro d'Italia model, I think they were the same frame with different components-- and built it up with some more or less correct parts, and some later stuff. Here's what they looked like in the sales literature 45 years ago:



Weinmann ZAC19 rims, 42 mm Hetres fit under Bluemels Lightweight fenders. The front brake is an Altenburger Syncron, an early version of the dual pivot sidepull. The rear brake is a Tektro 559 and even so I had to make a drop bolt for it. I believe there is a longer version of the Altenburger that will fit there. Mounting the Velo Orange rack on the fork was a mindboggling pain in the neck. To be fair, I guess that's the fender's fault.








I think I'm going to have to switch the fenders to VO aluminum ones so I can put a light on the rear fender. For now, there's a Planet Bike dynamo headlight on the handlebar, but I'll probably change that, too. I don't like having the light on the handlebar.

Nice to see you post again [MENTION=137164]southpawboston[/MENTION], and nice looking conversion rhm.

So the kool-aid tastes good, huh, Rudi?

Here's a new one I built up recently, similar idea to version 2 of Anton's Shogan up above...



It was a fairly beat up old Trek 420. I swapped the fork with one that came from a Rawland Stag, and added braze-ons for MAFAC Raid brakes, rack mounting, different brake cable routing, dyno powered lights front and back, and a few other details.



It's not quite done yet. I think I'll probably thread the steerer and switch to a quill stem for purely aesthetic reasons. I also plan to eventually replace the Soma porteur rack with something a little lighter and more elegant that I'll build myself when I find some time.

Another beautiful job, Steve! You and Gugie have inspired me, this summer I aim to get some brazing equipment and start experimenting. I'd love to take some old 531 frames and refurbish them into purpose-modified (is that a phrase?) 650b machines.

Are those the Compass centerpull braze on posts?

Let me know when you're getting ready to start and I'll tell you what not to do!

Keep your eyes open for a used oxy-acetylene setup with tanks. The bits are pretty inexpensive, but those Compass posts are a bit pricy compared to cantilevers.

Wasn't this featured in the most recent Bicycle Quarterly issue? Also--the article talked about affordable 650b conversions, but it didn't say how much the project cost! After reading the article I had a mental tally well into the $thousands...

Thanks!

Yes, I used the Compass posts. There are a couple other alternatives. Fer instance, this fellow built his own posts by combining the studs from a mafac center mount bracket with the bases from standard canti mounts. The other alternative is to befriend someone with a lathe and have them make them for you. Considering the other options, the Compass posts seem well worth the price.

A warning to you... The metal work thing is addictive!

This is new one, similar to the one featured in BQ.

Different people definitely have different ideas of what "budget" means. The idea was that the bike was comparable to a custom fully integrated all road bike. To have one of those built will generally cost $3,000 or more just for the frame and fork. Add a 2 - 3 thousand more for a rack, wheels, components, etc. I built the Frek featured in BQ (the complete bike) for about $1,500 including the cost of the original bike. I already had some of the parts in my spare parts supply, but I was also able to use quite a bit from the original bike.

So, you're right. $1,500 isn't exactly a "budget" bike. But I think it's a pretty reasonable price for a bike that offers about 95% of the functionality of a custom fully integrated all road bike. Here's where I'm obliged to tack on the "YMMV" qualifier.