Tubless scary? you must shit your pants every time you get in a car then...

The reason tubelss tyres are heavy is that they don't have Stan's latex cum-gunk splashing around in them to seal up the holes... so they have to be thicker.

Managed to get mine to leak last night. i bashed the valve on a rock and it started leaking. oops. I think the problem is to do with me having schrader-size holes in my rims (the kit is designed for presta holes).

I have knocked together a solution using rubber grommets to reduce the hole sizes in my rims, maybe it'll work.