For good reasons – like a stealth CX build over the next year or so – I might need to get some components pre-bought and fitted to the mtb frame that is currently spare. Then by magic, they'll move across onto the CX frame (when I can get it on Bike 2 Work) which will appear to cost less than would otherwise be the case.

So, the simple question is whether I can run 700c wheels on my 26" mtb, hence the question. 622mm isn't acceptable as that seems to be the default answer regardless of 700c or 29er tyre size, and I fail to see how a 29er 2.4 Racing Ralph can have the same radius as some 28mm roadie tyre or 35mm CX tyre.

Cheers.

Any help?

http://www.dimensionsguide.com/bicycle-tire-size-chart/

Not really – just tells me that 700c is 622mm, not what the radius is with a seated tyre. Or am I missing something?

Get the circumference from computer tables then work it out? 622mm is the bead.

Lots of folk run 700c wheels on 26" frames so ask them about clearance?

622 is the rim dia (bead seat)

as for dia & circumference for tyres..

tyres in section are roughly round.

so fro 622-28 tyre dia would be 622+56 giving approx a dia of 678 – would have to allow a bit for tread depth say of + 4mm so

682mm overall diameter.

for a mtb 559 for the rim say 52mm tyres so 559 + 104 = 663mm + 10mm for knobbles total dia of 673mm or so

as for fitting – road bike wheels with thinner tyres will fit on most mtb frames – lots of people have done this.

Note:- you'll only be able to run 700c wheels in a 26" frame if they are disk. The canti studs will be in the wrong place for the different size rims, though I think Mavic do some adaptors to make them fit.

Also CX wheels tend to be 130mm (road width) hubs and mtb are 135mm width, so again fitting to your new CX frame might be a problem.

Thanks all.

Plan is a disc-ready CX frame, so will not have any trouble with brakes or 135mm spacing.

Now, any recommendations on good road wheel builders?

there is no such thing as good 'road wheel builder' a good wheel builder is a good wheel builder, does not matter what type. But more fun to do it yourself, not that hard either. Si