xanthochrome

I have a beautiful chrome Mark Nobilette light touring frame from ~1985 that was my mother's. I have been riding it for over a decade now but recently got a more modern road bike. This is still my commuter (I don't have a car) and I would like it to be its best commuter self, so I am considering a 650B conversion to get wider tires and rear fenders. I have already switched from the original 27" to 700C, but it's still a skinny tire, plastic 'origami' removable fender situation. I'm also a grad student and need to be budget-conscious, so don't want to put in a lot of money for not enough benefit, hence the sanity check.

The top of the crown where fenders would sit is 43mm, so I am thinking of the Honjo 43mm fenders and thus 650Bx32 tires. My current front tire is 700Cx23 and rear is 700Cx25, please see the photos for clearance (and ignore poorly-set brakes, I was measuring!). I expect I'll need the Tektro R559 long reach brakes to make this happen.

So, what do you all think? Does this sound sane and is it worth it? And any good sources on reasonably priced wheels? I've seen the Pacenti Brevets but those are more than I want to spend if possible. My current rear spacing is 126mm.

Thanks for the help in advance!

ThermionicScott 

Are you sure the original wheel size was 27"? Those tires look like a pretty snug fit as they are. I'd give 650x38B tires a try before resigning yourself to 32mm. Remember that the bottom bracket will be dropping as a part of this conversion...

zandoval 

Find another bike to convert... This ones a beauty as is!!!

ehcoplex 

Having recently converted a PX-10 to 650B (and loving it..), there are a few things to consider.
A 700c wheel with 23mm tires will have the diameter equivalent of 650B x 42mm, so as far as radial clearance if you run 32c you should be OK. The widest part of the tire on 650B will be (approximately) where the edge of the 700c rim is now, so you can use that to get a general check for width clearance between the stays and fork blades. My guess is that it might still be kinda tight for fenders, but might work.
But of course, the question remains is it worth it? It definitely was for my PX-10, as the wheels on it when I bought it were wrecked (and I wanted to learn to build wheels..), and I found some Mafac Raids for a good price. Personally I don't think I'd do such a conversion if 32c, or even 35c is as wide as I'd be able to use- I'd want 38 at least. But that's just me and where I live the roads are absolutely awful.

xanthochrome

When I first posted photos, people speculated that the frame was intended for 700C wheels but whoever actually set up the bike definitely did 27". I had to switch to the 700C because I couldn't inflate 27x1 Panaracers fully without rubbing -- I guess whichever tires my mom ran back in the day had a lower profile? I have those 27" wheels still - Wolber Super Champion Gentlemen 81s.

My thought with the 32s is that 32 + fenders would be more practical than 38s without, especially coming from 23/25s. Maybe that's an incorrect assessment? I checked on the BB: current BB-to-ground height is ~280mm/11" and bottom of the pedal in the worst case angle is 90mm/3.5", so I feel like losing 10-15mm/0.5" from the conversion should still be fine?

Thank you! That's also something I'm considering, but I definitely don't have room for 3 bikes right now

Yeah, I was measuring both the fork and the stays and it's about 40-45mm at the outermost edge of the tire and 50-55mm at the rim in both places, depending on where exactly things would hit. As I said above, I thought that 32 + fenders would be more practical than 38s without, especially since I'm coming from 23/25s. Do you disagree? Definitely it would feel more worth it if I had the parts around or the current wheels were toast, but that's not my current situation!

ThermionicScott 

Interesting! 27"x7/8" tires used to be a thing; wonder if that's what your mom used.​​​

Is that 280mm measured to the center of the bottom bracket shell, or to the bottom of it? Either way, you do have a little height to lose. (My 650B conversion is right around 265mm to the center.) And your choice of pedals should help obviate pedal strike.

kroozer 

Another option for a smaller diameter wheel is the 650A, also called 26x1-1/4. The rim diameter is 590 mm, which is just a bit larger than the 584 mm diameter of 650B. It will give you extra space for fenders and larger tires, and the brake reach is a bit less than for 650B. The Sun CR-18 rim and Panaracer Col de la Vie tire are both made in this size, they are affordable, high quality, and good-looking. The tire's actual width is about 35 mm. The downside is that the CR-18/CdlV combo is about the only decent option in this wheel size, but if that works for you, then you don't really need anything else. I have two sets of these. The first was for an English 3-speed, which is what they were originally designed for. The second set is on my Motobecane Grand Record, and I decided to get the 590's because the CR-18's were half the price of the cheapest 650B rims.

52telecaster

I've done a couple of conversions with similar clearance and if u trim the fender at the chain stays u will have no real issues. 38s is possible if u dimple the chain stays. Perhaps even without. Anyway I find 38s plenty big and frankly 32s are way nicer then 23s anyway. Everything u are doing is reversible so I see no issues with changing it. It'll be a wonderful ride I bet!

559 brakes on this

ironwood

The BB drop of 280 is probably a little too much for a 650Bx32 tire.

52telecaster

BB center to ground is under 260mm on my conversion and I have no pedal strike issues but I don't pedal through turns typically.

zandoval 

OK... At today's prices Just thinking about 500 USD or less. And that's nothing special or even period. I gotta think hard about this because in the future 27-1/4 or even 700c stuff will be too expensive or even hard to find.

60 USD New Long reach brake set
70 USD Fenders & Hardware
250 USD 650B Wheel Set
120 USD 650B tires

52telecaster

Significant chunk of change if u buy it all new for sure.

ThermionicScott 

I wouldn't worry too much about 700C going extinct in favor of 650B, if that's your thought process. 650B conversions are great for getting puffy tires into old road bikes, but they'll always be a niche compared to 700C bikes.

repechage

I think this bike was designed for 700c or tubulars.

from a cost basis, continue to run what you have.
for plushy 650c - different frame.
a middle tier Motobecane ? Look for a whole bike.

I think the chrome is going to be a lot of effort to keep in good shape over a winter, won't chip, rust? Weekly maintenance.

https://www.noozhawk.com/article/130...d5b4-247329828

ehcoplex 

I think you'll end up paying $80ish/ea for new 650B, rim-brake rims.... Pacenti, Velocity, V-O- they all seem around the same. Apparently the Sun CR-18 bargain work-horse rim was made in 650B but doesn't seem to be anymore. I ended up with the V-O 650B rims when they had their 20% off winter sale. Seems there was a time a few years ago when you could get a decent 650B rim-brake wheelset for $200, but I sure couldn't find anything at that price when I was looking (supply chain issues no doubt had something to do with it...). If you do find a reasonably priced set of 650B wheels I suspect they won't be 126mm for the rear, so you may have to respace... Or get rims and build up wheels using the hubs on there now. If you're willing to go with center-pull brakes you could probably find some long-reach Dia-Compe or Weinmann calipers for nothing (or next to nothing). A little time with some rubbing compound and simichrome and they can look like new. Fresh Koolstop pads and they'll stop you as well as anything.

It is a beautiful frame, and with 650B wheels and fenders it'll be a looker, that's for sure.

beicster 

Cycles Toussaint offers a nice set of 650b wheels for $169.00. I have a set and have had no problems so far. https://www.cyclestoussaint.com/coll...speed-clincher

ehcoplex 

With the usual caveat of you-get-what-you-pay-for, that's a pretty hard deal to beat! You'll have to respace the rear drop-outs, but that's a pretty simple procedure (less than $10 at the hardware store will get you all the 'tools' you really need).

ThermionicScott 

^ Respacing to 128mm is a good middle ground if you want to be able to throw in 126mm or 130mm wheels in the future.

52telecaster

Pretty easy to squeeze a 130 hub into a 126 frame without any adjustments. That wheel set is pretty intriguing.

bikemig 

I wish I hadn't seen this. That is tempting for a 650b conversion.

More expensive but these have "name" brand components; also 650b with a 130 OLD rear wheel. The velocity A23s are good rims and the shimano hubs are very good.

https://www.velomine.com/index.php?m...oducts_id=6367

Rooney 

I've used the Cycles Toussaint wheelset. True and rode well. Ended up getting a clicking that I couldn't figure out for a while. It turned out the hub needed to be cleaned and greased. Just installed them on a friend's Cannondale but rode them after the hub overhaul and wouldn't hesitate to buy another set. Definitely a good "intro to 650b" wheelset.

52telecaster

I built a set with a23s. An excellent riding rim.

52telecaster

Good to know

ehcoplex 

No kidding. IIRC they were 'out of stock' when I was looking a while back (actually seemed like silver rim-brake 650b wheel sets were out of stock everywhere...) so I ended up going with V-O rims and hubs and learning how to build wheels. I'm almost tempted to get a set of these just to have on hand for conversion 'testing' on other frames, etc....

52telecaster

I have some zac19 rims I built for 650b and use them as testers often. Hope someone buys those so we can all know. I know I can't build a set for that money.