Got an old 26″ frame with sliding dropouts that are currently all the way back. The rear 26″ tyre is 2.4″, adequate clearance – which has me wondering how tight it’d be if I tried to fit in a 650b wheel with, say, a 1.75″ tyre…anybody done/doing that? Chainstays no problem, seatstay bridge might be.

I don’t currently have either 650b wheels or tyres, so interested in others’ experiences before spending money.

According to this “The outer diameter of a 26×2.00, a 650×42 and a 700×23 tyre is about the same” it should be fine. A 1.75 is around 44 so should fit fine if a 2.4 on 26 fits.

What are you hoping to achieve by changing to a narrower 650b tyre with same outside diameter?

A mate did this with his old frame. He managed to get WTB 47mm tyres on 25mm rims in it with a bit of clearance

What are you hoping to achieve by changing to a narrower 650b tyre with same outside diameter?

Limited funds, old 26″ frame I like going spare. Seems obvious to me I might be able to repurpose it with faster rolling wheelset for minimal expense, but thanks for asking. I have the other components I need. See also WTD ad for 27.5″ wheels that’s just gone up in the Classifieds…

I’ve had 700×35 in the back of my voodoo Wanga 26″, dropouts almost all the way back so it should work. Every frame is different though obviously

A lot of old 26″ frames just happen to have appropriate geometry for gravel, although the top tube may be a bit on the long side.

I went even further than 650b with 2″ 29er tyres on wide rims in a 26″ sliding dropout Voodoo Bokor frame.

Purists won’t like the amount of spacers but it gets the handlebars where it’s comfortable for all day rides for me.
Handles well, and about the only snag is there is not the full range of adjustment available.

(Yes, I know there’s no bar tape. I rode it like that for a few days until I found the perfect angle for the bars and then position for the levers.)

Limited funds, old 26″ frame I like going spare. Seems obvious to me I might be able to repurpose it with faster rolling wheelset for minimal expense, but thanks for asking

Wasn’t sure whether you already had 26″ wheels as guessing you did as you have 2.4 tyres on them. I would just put faster rolling tyres on the 26″ wheels to make them faster and they would be just as fast as the 650b but with less cost…

I went even further than 650b with 2″ 29er tyres on wide rims in a 26″ sliding dropout Voodoo Bokor frame

That looks great! Totally works.

Planning to do something similar to my Surly Troll if/when 26″ rims and tyres become much harder (ie more expensive) to source

I had 700c wheels with 35mm gravel tyres in a slot dropout 26 inbred. Very close at the chainstay bridge even with the wheel all the way back. 26 back on again now as didn’t really see the point of it after a bit of tow path riding reminded me how boring it was!

I only have one set of (26″) wheels. Buying 27.5″ wheels for the spare frame would fill a different purpose and, at least in theory, be more forward-compatible with any frame I might buy in the future.

I’ve also tried 29er wheels in a 1990s frame.

Old narrow rim 29er wheels with 47mm tyres

I never took this any further because I had the Voodoo and other 26″ frames hanging around, but I did trial fit seat and bars, and can see no reason it wouldn’t be a good bike.

It’s a great way to re-use an old mtb frame which otherwise would end up on the tip, not to mention a nice cheap entry into gravel bikes. Those old Raleighs were quite well made steel frames.

About the only negatives are slightly long top tubes for drop bars*, and a small increase in BB height (not necessarily a negative especially if you want to ride fixed).

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*Try On-One ‘Brian’ bars and/or a shorter stem.

I am in the process of doing this. You need to think about how high your BB will end up as well, and what a-c fork to use (if you are using a rigid). You can go 650b or 700c in the front, it will affect the angles as well.

Fork’s no problem, it’s the frame that limits things. BB height is also a non issue given the wheels will be roughly the same diameter.

I run a 1998 Airborne with 26 x 2.3 tyres as my bikepacking hardtail. Numerous friends have bought modern gravel bikes with similar frame angles but shorter top tubes to suit drop bars. I could fit 650b wheels in there but is it really worth it if the 2.3s are a similar circumference? The other option is to mothball a perfectly good frame and splash a couple of grand on a Tempest, which seems wasteful. Do those of you who fitted bigger wheels feel there was a real benefit in rolling resistance or speed?

downshep
…Do those of you who fitted bigger wheels feel there was a real benefit in rolling resistance or speed?

It all depends on the tyre.

It’s important to get a tyre that’s supple, and that usually means a big tpi number. I’m happy with my setup.

Follow-up: I got a set of 650b wheels from sillyoldman of this parish, complete with 2.25″ knobblies still on. Took off the knobblies, put the bare rims in the frame to check clearance…

Bags of room. So much that I re-installed the knobblies – and they still fit, front and rear, without needing to adjust the mudguards.

Might rethink my intentions for this build.