Davechopoptions was right. Lap 3 of 10 at kirroughtree on the fast downhill i blew a 1cm gash in the rear tyre and lost pressure so fast i nearly flew off the trail. After a protracted amount of time getting the tyre back on the rim (10 hours of rain and copious mud will do that) I slammed a tube in there, musing on the fact that the tyre in question had been ridden something around 7 times in total.
So ended my first ride on a tubeless rear wheel. The crossmark is a great tyre. It hooks up surprisingly well for a low profile tread, it is light and has quite a large volume. But even on wide (stans flow) rims, the sidewall bulges laterally beyond the tread, leaving it susceptible to rock gashes and wear. For the record, i have only worn out 1 crossmark tread, but i cant tell you how many sidewall splits i have had.
It was interesting racing on the Vertigo: it allowed me to ride so much faster over the rocks at kirroughtree. I regularly gained places per lap by out gunning other soloists on the rougher trail.
(pic is shiggy's)
This speed comes at a price though, and the tyres paid it. I need to accept that i need to use thicker tubes, or a meatier tyre to take advantage of the speed this bike will produce on the downs. Continental are bringing out a 29er version of the Rubber Queen tread (to be renamed the Trail King) and also another tyre called X King which will sit somewhere between the Mountain King currently available (my favourite winter and mud tyre) and the low profile Race king tyre.
(photo is jeff kerkoves)
This should give a good range of choices. For the record, i have always got on extremely well with conti tyres. Excellent durability and rubber compound with dependable sidewalls.
But what to do until then? At the moment i'm considering running an ignitor rear and a panaracer rampage front...the Vertigo needs more meat...but i dont want to hamstring it with super heavy/slow rolling tyres. I might look at the race king for the rear of the vertigo, but i suspect it will be a bit of a gamble. Its a huge volume tyre (see shiggy's mtbtire site) and at that weight, there cant be much sidewall material. The jones will stick with tubed crossmark or aspen rear and a mountain king front.
Interestingly, it looks like maxxis are producing some sidewall protection similar to the conti 'ProTection' system....might work well on some of the established treads.