I remember when I first got my Brompton S2L-X and went out for a ride. I was riding on the sidewalk in Japan going slow and all of a sudden my tires (Schwalbe Stelvios) went into a small groove along the side of the side walk and I couldn't get out so I ended up crashing onto the dirt. Those tires are not meant to be used on rough roads or sidewalks. I use the Marathon Racers now and they are ten times better in regards to speed (because my bum doesn't hurt I can keep going fast) and safety.