650b Conversion

On a bit of a whim I bought this Tom Board roadie. Nice lugs, seems to be 531, mix of Campy Triomphe, C-Record and early Athena.

The English guy I bought it off had three bikes built by Tom Board that he’s sold recently in Sydney - including a fillet brazed MAX one that looked pretty sweet.

The only catch with this frame is the ridiculous rear clearance. Space for a 20c tyre, and even that has been rubbing. Not going to make for a very useful bike.

Spirito suggested a 650b conversion; this page is a great starter: 650B Conversion Guidlines

I’m basically sold. I was planning to build up a practical, comfortable road bike as an alternative from the carbon one. Big tyres and gravel ability would actually be great. Old style would be nice, e.g. Suntour barcons, Mafac centrepulls, Brooks etc.

But as Blakey indicated, chainstay clearance is a problem. With a 584 rim I think I could fit a 28mm at best. Do 28mm 650b tyres exist or does this defeat the purpose? Clearance in the fork and seat stays would be fine for bigger tyres.

Options I can think of:
a) Crimp the chainstays, maybe like this: Improving chainstay tire clearance, post production.
The chainstays are currently not crimped but quite ovalised, only 18mm wide. Bad idea?

b) Perhaps Peter Bundy can re-braze some long forward facing dropouts in. Would require new paint. Maybe if I was getting that done I’d ask for mudguard brazings, rack mounts… $$$… is it worth it? It could do with new paint anyway.

Meanwhile, PM me if you’re interested in any of the Campy parts. Here are some photos I took in the rain, before I’d cleaned anything: https://picasaweb.google.com/112403672217167595940/TomBoard?noredirect=1

Chainstay clearance issues foiled my Vitus 650b porteur ambitions. Otherwise I could have made something truly wacky.

Brazing horizontal drops may help the issue some but I wouldn’t bother with fender eyelets as it’s unlikely you’ll have room to create enough clearance on an already tight frame.

Crimping the chainstays can be tricky and I’d leave it only if you’re sure it’s needed, will work and are set on a tyre size/position.

As mentioned I’ve got some 650b’s in the shed with 32c tyres. Don’t wish to sell them but happy to loan out so you can test. Worth trying and can be made to work … you’d find out within a minute. Chainstay clearance will be the issue and at that point you can weigh up whether indenting the stays is worth opting for.

a lazy guess: current wheel diameter (622mm + 20 + 20) is 662mm, 650b’s with 32mm (31mm actual) would come to 646mm (584mm + 31 + 31mm). 16mm divided by two would suggest the tyre will be drawn further back 8mm.

Btw, that’s some tight clearance … back to the days when builders (especially brits) were building “fag” paper clearances. It’s cool in terms of period curiousity or point of difference but it can make for a tricky or impractical choice for a daily rider. The top mounted aero shift levers is another tricky situation but there’s more options for that smaller problem.

I’d grab Spizza’s wheels and test fit them for clearance (check BB drop at the same time, might be too low). There’s nothing narrower than a 32mm in 650B. 650C/26" will be too small and too much drop.

If you have acceptable clearances elsewhere and only the ST is the issue, get Peter to dimple the ST like Paconi did to Horatio’s Duarte.

Looking at the photos, the fork has plenty of clearance, front wheel to DT is fine, the seatstays are fine, I reckon a dimpling of the ST and chainstays and you’ll be golden for 700x23/25. Better than spending far too much money on new dropouts / new paint.

My tyre clearance issues on the Frezoni are at the brake arms, to get more clearance I’d have to go to single pivots/centrepulls, or less chunky DPs than the SRAM ones.

I would clean it up with the parts that you have first and then see how it goes. Give everyhting a good clean, try to get the 23mm tyres sorted, new cables, brake pads, bar tape, chain, a comfy saddle. Then you have not over committed, and you will soon know what you need and don’t need to sort out. My 2c.

(Nice find too!)

Just got back from a visit to Spirito’s bike cave. (cavern?)

There’s no way fat tyres are going to fit without some serious changes to the chain stays. So no 650b. Pity, but I might try it on another frame at some stage.

Blakey, you’re right, dimpling the seat tube looks the best option. I didn’t realise the famous Duarte had had it done. If I can fit a 23 in there I’ll be happy, or better, a 25.

In the meantime I’ve got some fresh 20c tyres from Spirito so I can at least test the bike out and see how it rides.

Cool to see you again … Sweet frame :wink: Nicely finished, and distinctly sharper than most Aussie built frames from the same era.

As you mentioned I think crimping the seat tube will get you that smidge more room needed. It has some of the shortest chainstays I’ve ever seen … if I recall correctly 38.5cm.

As Carlin suggests see how it rolls and if you like it, then play it from there re: modifications and kitting it with parts you’d like.

I love this thread

Forgot to say, go with whoever is confident of dimpling the frame without issue. Shouldn’t be too hard but not easy either. The dimple will be around the butt transition and the front derailleur braze on is around the same region which will make it tricky to support.

In the meantime keep the 650b hope alive for another frame. Here’s a beautiful conversion of a 70’s Raleigh by the Master J.P. Weigle. I like the balance of form and you can see the long stays help drag the wheel back enough for the fat 42mm tyres + fenders. Quite inspiring !!

JPW is on another plane (heh planing!) level though, he only converts a very narrow range of Raleigh frames, and moves the bridges and fits canti mounts, so they’re more involved than your garden variety conversion. Stunning work though.

Yes, and he knows how to have fun with it too. I like this one the best … Capella lugs which were only used by Raleigh for a few years, sloping fork crown … shows he thinks outside the box re: tyre/fender spacing and a play on words between the Raleigh models International and Super Course … + a custom rack, canti studs etc etc … just dead sexy.

Nice rack!

This thread is directly related to my interest and future ‘light wieght’ porteur project.

Anyone here done any 26" -> 650b conversions?

I’ve seen a few Surly LHT that have been done…

I think the surly LHT is lucky (or by design?) in that the canti studs are in just the right spot to allow the pads to hit both 584 and 559mm rims, 12.5mm apart, (unlike the 19mm of 622 to 584). Plus it has clearance for fat 26" tyres, so the larger OD isn’t an issue, likewise the BB gets higher (OHNO HORATIO), so no increased pedal strike.

Definitely not guaranteed to work.

Yeah I guess the brake reach is the hardest thing with both 700c and 26" conversions.

Although I thought that tyre clearance would be less of an issue as most MTB’s (‘vintage’ steel MTB is the frame market I’m thinking of) are made for ~2" tyres so going to a to 650b even though it is a larger diameter will be generally be narrower ~42c and end up with about the same OD

i.e. (borrowed from VeloOranage blog)

edit: I see I really just re-inforced your point Blakey, carry on.

Be careful though, Tris bought a “vintage MTB”, and it can’t even take a 26x2.0" tyre!

If you want to fit some 650x32 / 650x38 / 650x42 into your MTB, holla. Hetres are where it’s at though for road/gravel, no other tyre comes close. Mud/snow/singletrack will unstick them.

Plus, with 700C conversions, you’re often going from a short/medium reach caliper/cpull to a medium/long reach caliper/cpull, whereas vintage mtbs have cantis that may or may not reach.

Disc frames open up all sorts of beardo conversion wet dreams though.

Recently I had dreams of converting my Cannondale Flash to 650b. Frame works however Fatty fork doesn’t.

What are some good 650b wheels?
I know nothing about this topic but I’m interested.

If you were going tubeless stans rims would be pretty hard to beat?

Wheels? Or rims?

Disc or canti?

Balleur or non?

Pacenti PL23 is the newest and hottest rim. The SL23 might be rolled in 650B if demand is there. Both tubeless friendly.

Velocity Synergy’s have a bad rep for the OC model cracking and other QC issues, swarf etc. US production might be different. Mine are all Oz made.

Velocity Dyad is stout, if heavy.

Velocity Aerohead is rare as rockinghorse poop, and mine was riddled with cracks.

Velocity A23 is recent US production and pretty good. Tubeless friendly. Narrow brake track

Sun CR18 is super cheap and high polish, possibly mis sized though, beware.

Grand Bois rims are ok, but very expensive.

Velo Orange rims are a bit soft.

Vintage Mavic are awesome, but $$$

New Stans (with extra material at the spoke bed) are good by all reports. Plus tubeless.

Note: Tubeless Hetres are not a plug and play option. It can work, but the carcass and bead aren’t designed for it.