Vintage tyres here in the UK have just returned a tyre to Avon for investigation as it is not normal according to Avon. My first tyre cracked at the crown when it was near the wear markers, so thought nothing of it. The second tyre was from one of the new 'improved' tyres from late summer last year and not even completed a 1000 miles. The first tyre was used with pressures from the Commando maintenance instructions, the second with the pressures from the Avon website for the Commando, there is a difference and I believe that the Avon pressures are too high.
I am now on my third tyre, but have only completed 45 miles on it so too early to tell if it going to be OK or not, if it fails then it back to the road runners for me.
Avon and Vintage tyres have been brilliant with their customer service.