Charles Wahl

Hi folks,

Life has kept me away from bike projects awhile, but I'm thinking about converting a cosmetically ratty, structurally OK Raleigh International ('74) frame to 650B with moderately wide tires. I've measured it carefully: plenty of clearance between the fork blades under crown (45 mm +), but not so great between the round, non-indented chainstays behind the BB. To calculate what might be required, I measured some Pasela 35 mm tires mounted to 23 mm 700C rims, and find that the max. width of tire is at about 338 mm from axle. The frame has only 34 mm clear between stays at that distance from the middle of the rear dropouts (long Campagnolo type). I figured that, roughly, a 650B wheel, having BSD 38 mm less than a 700C, has maximum tire width at about 319 mm, where the frame has about 41 mm clearance between the stays.

Does that sound about right? If anyone with a set of, say, 42 mm wide tires mounted on reasonably wide (23 mm or more) rims would kindly measure theirs to confirm, I would appreciate the favor.

Ideally, I'd like to be able to mount and fender 42 mm wide tires. I've read about people "re-forming" chainstays somewhat, and am not opposed to paying a professional framemaker to do that, if it will solve the problem. I plan on several "fixes" and other changes too, like braze-on pivot bosses for centerpulls (no going back to 700C).



The black marks on the right chainstay are where I figure the max tire widths for 700C and 650B might be.

And for more general information, here's the original 2009 BF threadlet on this frame, with some more photos:
https://www.bikeforums.net/classic-vi...d-raleigh.html

Sorry, I find that I've never taken a decent set of photos myself. And I apologize for the "attachment" below -- having forgotten how to post photos from Flickr, I did this, and can't find a way to undo it.

gugie 

Charles,

I've contemplated exactly the same thing on my 73 International. I have a 73 Competition that was "reimagined" as 650b by Peter Weigle. It has plenty of room for 42's and fenders. His take is that the International fork crown is too narrow for 42's, but you could do 38's.

But I have a set of 650b wheels with Hetres on them, so why not take a look? My International is down to the frame right now anways, so off to the garage I go:

First, the JPW reconstructed Competition. I measure about 6-7mm clearance in the stays:


Now the International, same size wheels and tires. I measure just about 3mm clearance at the stays:


Here's a side view of the International with both wheels on. The front wheel has a bit over 5mm clearance side to side, which is adequate IMO. Radial clearance is fine for fenders as well, both front and rear.



Room for fenders? Arguable, radially, the front forks are plenty long enough for good fender clearance. The rear clearance tells another story. You'd have to crimp down the fenders significantly, shorten them, or cut out a lot of the sides to fit around the stays:



Bottom line? If you really want 42's and fenders on your International, you could do it. The 3mm clearance is a bit tight for my liking, also, I think the fenders at the stays would be narrower than the tire!

With all that in consideration, I'm planning on going with a slightly narrower tire. The 33.3's rode pretty dang smooth on this bike. Going a bit wider, 35-38 range would give you most of the 42 experience, IMO. Toe clip overlap with the fenders was pretty bad, if you care about such things.

So you and I are at about the same place! I'm also considering reraking the fork to lessen the trail a bit, as I really like the way the Competition handles with a handlebar bag, also on curvy downhills it seems to go exactly where I want it without thinking. I also would like to try brazing on some centerpull studs. This is a lot trickier than the cantis I've done in the past, alignment is much more critical.

Let me know how your project is going-some east-coast/west-coast knowledge sharing might helps us both! I'll post as I progress, please do the same!

Charles Wahl

Thank you very much for the comprehensive response. I don't really think there will be any problem with the fork; as I said, there's 45 mm clearance at the top, right under the fork crown which is amply high (363 mm from axle), and everything's wider from there on down. I'm not that needy in the clearance department; I ride a commuter that has similarly "width-challenged" rear chainstays, and have been doing OK with very little clearance. As long as the tire is relatively true (some aren't), and I set up with care, there's no practical problem. I just cope the fenders to fit around fork blades or chainstays -- Dremel with the sanding drum does that quite well, for plastic anyway.

Comparing my Int'l photos with your'n, I'd guess that your chainstay length is longer than on my frame. Mine is 43 CM from center of BB to center of dropout slot, along the chainstay. There's a lot of room between the tire and the BB in your photo. Unless the 650B tire doesn't have the sort of radius I've roughly calculated (which would be great), your frame's geometry and mine aren't that similar in this area.

What I'd really like is for someone to give me a bead on what the distance of max tire width location to axle is, on something like a Hetre. That way I'll have a better idea of how much the chainstay space needs to be increased.

rhm

Charles,

You probably don't have to worry about the fork or the seat stays. The clearance issue is at the chain stays.

650b rims with 42mm tires (Hetre), the widest point of the tire is around 320 or 325 mm from the axle (I measured without taking the wheel out of the frame, hence the imprecison) and the tire is round, so the wide part is large.

On my 650b conversion, a Holdsworth 531 special from about 1976, I measured this as 45mm. And it's enough. I have fenders and the wheels turn and it's all good, but the clearance on either side really is as little as 1-2 mm.

You can get more clearance by hammering a piece of steel pipe between the stays. On my Lambert I used the head of a hammer and beat it toward the bb with another hammer. I'm sure it weakens the stays, but I figured it doesn't weaken them enough to really matter.

nlerner

Charles, good to see you around these parts. I've fiddled a bit with converting Raleigh Int'ls to 650B, and the sticking point seemed to be BB height. The Int'l has a relatively low BB in the first place, so the conversion meant a really low BB. You might take some measurements about that.

I also endorse @gugie's recommendation for 38mm tires; lots of options in that size from Pacenti, Compass, Soma, and others, I believe.

gugie 

Wow, just measured my stays, I've got 46cm measured in the same manner. I can "choke up" to 43.5cm on the Campy dropouts. I find that the more I read about Raleighs of this vintage and how therea are significant differences from frame to frame, the more I believe it.

The fattest part of my Hetres are about 317mm +/-2 from the axle. The tires are mounted on SOMA Weymouths (24.4mm width). My other bike uses 25mm VO Diagonales, width measurement of the tire is essentially the same. Your guesstimate of 319mm is pretty dang close.

Keep in mind that the actual OD of Hetres is probably 41mm (per Jan Heine, YMMV). If you want Hetres or similar width tire, you'd have to dent the stays, I think. That's the bad news. The good news is I'm now looking at my long chain stays as allowing me to think twice about tire width!

Also, concerning fenders-rather than cope them around the stays, why not bend them to match? Rereading an old Bicycle Quarterly with Mssr. Weigle's instructions, I did this on a current build (early 70's Fuji "The Finest"), and am quite happy with the look. Take a peek at my first photo of my Competition, Peter formed the fenders on it, I really like the way it turned out. Just another way to accomplish the same effect.

Charles Wahl

Thank you, Rudi, Gugie and Neal. I figured about 319 mm or so, but good to know it may be larger than that. I had fleetingly made a mental note to measure/calculate the BB height. This raises another question, I guess: what's the "practical" diameter difference between, say, a 27" rim with a 1" or 1-1/4" tire, and a 650B rim with a 42 mm tire? A larger tire at lower pressure will, seems to me, have more "drop" when loaded; but using a narrower 650B tire is going to have a smaller diameter than a wider tire on the same rim. So is there a good way to figure out how much lower the BB will be than it was on the stock bike? Maybe I'm overthinking, and just need to build a 650B wheelset, and try it out.

One other factoid: this is a frame on the larger side (the way I like them) with 62 cm/24.5" CTT seat tube -- would that have an effect on the BB height, compared to a 57 or smaller? I'm statistically in the latter range stature-wise, but somehow feel more comfortable on the taller frames. And of course, I can't change that about the Raleigh.

If I were using metal fenders, I'd certainly consider bending them, so as not to lose or interrupt the edge roll; with plastic, I think that coping them works fine.

Road Fan

Hi, Charles! Nice project, I wish I had an International to convert!

I went down the same route when setting up my Terraferma, but did not save the info. If you're still noodling over this later in the week, I'll have time to get out the tape measure.

rhm

For the BB height, I'd stick with the math; estimate the height of the axle by adding the tire size to the rim radius. I realize this is an estimate, but I figure it won't be too far off. So by this logic...
700x25c tire 25+311=336
650b Hetre 42+292=334
650b Lierre 38+292=330

So yes, your BB will be a little lower than you're used to. If this scares you, you might consider shorter crank arms. If you're already running 165's this is easier said than done.

Did the 24.5" International come with longer crank arms than the next smaller size? If so, then perhaps the BB height was higher to accommodate the longer crank arms... but I'm guessing they were all shipped with 170's and the BB height was the same across all sizes.

Charles Wahl

I appreciate your figures, Rudi. This confirm that my impulse to go with a 42 mm tire is a better goal than settling for 650B and narrower, or 700 C and narrower still: maximize the wheel diameter and tire width too, for optimal result. Right now, my commuter has a 33 mm tire on the rear, and a 36 on the front, for this reason. I actually have two other frames that could be used for such a conversion: PX10 LE (no Nervex Pro lugset) or a Jeunet frame; but they're both 63.5 cm tall, with longer top tubes than the Int'l. So for the time being, I'm going to focus on the latter. I've wanted to have it repainted anyway, but before I commit to that, I need to figure out what else I want to do with it. I'm comfortable with 170 mm cranks, so I'm going to stick with that, too.

gugie 

Charles, can you get your hands on a set of 650b's with Hetres mounted? Your figures and logic look quite right, but not a bad thing to have a reality check. I imagine your framebuilder might have a set? There's always a nice weekend drive to the center of the 650b conversion universe in Old Lyme, Connecticut...

Sir_Name 

Here's a good link for some of the above info (seems like you guys have it well in hand, though):
https://www.bikeman.com/bikeman-blog...sion-guidlines

Best of luck, I'm mostly complete with a similar project. I wound up with 38s (Loup Loup Pass extralight) and they ride beautifully.

repechage

My 22.5" International came factory with 172.5's.
The smaller frames got 170's.
Don't know about the larger sizes not did they modify the BB drop to compensate.
I never considered my frame to have a low bottom bracket.

gugie 

I find I never know too much that I can't learn something new. Thanks for the link!

ThermionicScott 

Have you tried the Hetres, too? I haven't done anything with 650B yet, so I wonder how much "extra" you get with Hetres, now that there are a couple of good options in the 38mm size.

gugie 

Myself, only Hetres, but the plethora of new 650b offerings give me reason to build anew.

Sir_Name 

I have not tried 42s yet. My measurements said I could just fit a set on this frameset with barely adequate clearance, though once the wheels were built just enough didn't seem enough. Looking at air volume between tire sizes, going from 38 to 42 on a 650B rim is ~comparable to going from 23 to 25 on a 700C rim (in terms of percent increase in air volume if I got the math right). So, it'll be noticeable if you trust the numbers alone.

Honestly, I was a bit bummed when I decided it'd be wise to play it safe and order 38s. I got over it after the first ride. They're plenty 'fast' on the road, and transitioning to dirt or gravel doesn't take any real thought. The ride off road is eye-opening going from knobbies on a rigid MTB.

In terms of how much "extra" you would get with Hetres over 38s, I'd bet it's a bit, but obviously not nearly as much as going from 28s or 32s to 38s. Maybe someone with firsthand experience with 38s vs 42s has more to add.