I've never used 2.6" or similarly large tyres before, but my (FS) bike has clearance for them.
What do people reckon is best for Calderdale / Yorkshire grit moorland style riding (and the odd trail center)?
Is the extra volume worth the extra weight / drag?
Any size is fine, more about the type and compound of the tyre rather than size.
I'd suggest thinner tyres at the moment to slice through the slop.
Don't think it really matters. It's simply a trade off between up vs down. I've ridden every tyre size from 2.0 to 2.75 in Calderdale. The thinner tyres are useful for cutting through the gloop (plenty of that at this time of year round here), thicker good for bulldozing down descents. 2.3/2.4 would seem to be a good compromise.
I wouldn't trust 2.6 in the slop round here at the minute. You spend as much time going sideways as forward...
