Aye xbally,
Pleased to read that you are reasonably OK and that the bike is just a wee bit roughed up and nothing more.
Man on FZR1000 going past my place just over a month back at no more than 40mph, had the front end tuck and fold on a straight road for no immediate apparent reason!

The road was damp from salt/brine solution and he was riding in between the car/lorry wheel tracks, where rubber, lorry chassis lubricant and other rubbish (fine dust/mud) accumulates and when rubbing the sole of the boot over it, the road was definitely slicker in the middle, than either side in the wheel tracks. The police also commented on this at the time. Incidentally, he wrote the FZR off, fairing, forks, frame after it slid over 50m on its side up the road pirouetting off the curb/verge. Whilst, he suffered a broken collar bone, that once investigated, required old war wounds to be rectified, followed by screwing and plating!

Without the flushing action of a good drop of rain, your summary "A month long largely dry spell,at the end of winter with salt deposits still apparent,followed by not particularly heavy drizzle." sums up the situation the best for me. "Et cave ne equitem!"

My regards, Bill
P.S. Now, about water/soil chemistry from road surface run-off?
