I often have guys at the track ask me why I run the Bridgestone Ultra Heavy Duty tubes at all times on my SXF. Yes, they do really increase the weight of the tire/wheel combo. But I am not a factory rider and figure that the slight loss in acceleration won't really hurt me in my quest to finish top ten in my local Vet pro class. I figure that no factory scouts are out looking for me and if I really cared I'd quit drinking so much beer and actually train. Well I was able to provide proof as to why I run the heavy tubes last weekend. I have no idea what I hit. I do know that the bike ran this way for at least the last two hours of the day when four other guys were test riding it between my own practice motos. The tire did not go flat and still had 13psi of air in it when I pulled it all down to fix the wheel.