Hi, Cynic,
thanks for replying.
I thought about the spokes and headstock, both appear to be good. The bike is 2000 reg, and only done 8.5k; so the tyres are good - although I must admit I hadn't thought of checking the date stamp. I know the front needs changing in the next thousand or so miles, and the rear has a bit more on it.
I'm trying to find out if this is a common issue with the K555s regardless of their age (before I fork out for another set), and whether there is a better alternative. I've spent hours trawling for information, but most of it seems to point to tubeless tyres (Michelin, Metzler, Pirelli, etc) for alloy wheels - although both the 1100 Custom, and Classic models come with spoked wheels.
Cheers
Red