i will correctly measure them, but i have used them with and without the o-ring. i always used tubes so far, but i think i would try to run them without them if i have to mount them again as i always check pressure before going out. besides less air in the tyres means more grip
![Roll Eyes](http://cal-look.no/lounge/Smileys/default/rolleyes.gif)
as for using them, it is unavoidable to hit a pothole or something like a raised part on the road, debris,.. when you drive, so far i haven't got any cracks or dangs. being carefull helps.
like Ron said, be careful with the ring, if it isn't in the groove you can damage your wheels.
i do have another issue, that are the valvestems as i can only inflate the tyres with an angled one or i need to take the wheel off…
exept from this little problem they are the best wheel out there
![Grin](http://cal-look.no/lounge/Smileys/default/grin.gif)
i know i am biased
![Cool](http://cal-look.no/lounge/Smileys/default/cool.gif)