I have run over something that cut a Marathon plus almost right across,except the bead.SO now i have a Marathon 368 Kevlar 26x1.75,with the bead cut off inside a continental town and country 26 x 1.9.Rolls OK,no flats for a year.We also have sharp flints that go straight through conti touring plus rubber belts.Works out about 1.4kg for front tyre