I was interested in trying out 650b, but put off by the cost.
I knew my frame and forks would accommodate them, and fancied having a lighter set of tubeless XC wheels that I could use for normal riding, and then keep the burlier/wider/heavier 26″ ones set up with heavier tyres and DH tubes.

So after a bit of googling and searching I found these:
Mavic Crossroc 650b Wheelset on Rose Bikes

£139 all in including 2.2″ tyres, tubes, & tubeless kit. Front wheel is 15mm axle, and rear is 12×135 or QR. Delivery was about £7.
Rims are 24mm wide (19.5mm internal measured with my verniers). So not fashionably wide, but not too skinny either.

Mine arrived yesterday, and they seem up to the normal quality that I’d expect from Mavic. I’ve just fitted the tubeless rim-strip to the back wheel, and the tyre went on easily and up with a track pump no sweat. Not added sealant yet, but it seems to be holding air anyway 🙂

Yet to ride them, but will set up the front wheel tonight, add sealant to them both and hopefully give them a shakedown at the weekend.

If the 650b wheels with smaller tyres fit in the same space as 26 inch wheels with bigger tyres what’s the advantage? Genuinely interested as I can see a benefit. I thought the whole point of 650b was that you got a bigger diameter than 26 wheels+tyres.

And also if 650b+ is just big 650b tyres in a 29er then why aren’t companies pushing 26+ as well? Or will that be the next big thing in a few years?

Tom KP

Ps not trolling,

It is bigger though, the diameter on my 26″ wheels with chunky 2.4 tyres is 685mm and the diameter of the 650b (notice I’m not saying 27.5″!) wheels with 2.2 tyres is 705mm.
So 20mm difference on the overall diameter. The back wheel, at full compression with the 650bs on my DMR Bolt, leaves about 5mm of clearance from the seat-tube. If I were to use the 650b dropouts you can buy for the bike I could easily put in a larger 2.4 tyre.

I was planning on getting some lighter wheels for it anyway for local XC/trail loops, so I could set up my wider rimmed 26″ wheels with DH tubes and heavier tyres. It was a good deal for a set of wheels and tyres anyway, the extra little bit of diameter might make a difference, or it might not!

Did you get a chance to weigh them at all? If so are the figures as they say on the site?

go demo a few 650b bikes, free and easy and you get to see what you a bike designed to run with 650b wheels is all about rather than a 26″ bike with some bigger wheels in

Did you get a chance to weigh them at all? If so are the figures as they say on the site?

Yes, because I’m sad! Mine were actually 30g under for the pair – 1795g.
The Mavic Roam tyres were also slightly under the listed 800g at 750g and 760g respectively.

Thinking about getting some of these.. does anyone have any idea what i’d need to convert to 142×12? Looks like the wheels come setup for 135×12 but can’t find too much detail on the mavic website.

HoratioHufnagel – Member

Thinking about getting some of these.. does anyone have any idea what i’d need to convert to 142×12? Looks like the wheels come setup for 135×12 but can’t find too much detail on the mavic website.
It’s worth double-checking as I’ve never had to put my money where my mouth is :), but I think they are exactly the same as far as the wheel is concerned. Difference is in the frame afair in that there is a lip on 142 to put the cones into.