Just thought I'd let you know of a brilliant tyre I've found for the FX and SLR (don't think they do a 21" for the Dommie).
They are Sava Invader MC30.
I had a set fitted to the Vigor and found them to be excellent in wet and dry and amazingly good off-road, even in the thick mud.
They look quite road biased, but what you can't see from photos is that the tread on the back tyre is 10mm deep!
I've just replaced a set of only partially worn Avon death-wings with a set of MC30 on the SLR, the Avons were sh*te.
They're cheap too