On my 400F, the Spitfires are doing very well on the streets of New York City, with all their goo, oil residue, barf, dead rats, trash truck juice, sand, steel plate street covers, potholes, dog poo, garbage, wavy pavement, cobblestone, autumn leaves, big smooth painted letters, subway grates, bridges, etc.
No kidding - during the winter I found a whole stick of butter wedged in between my front fender and tire. Dunno if someone put it there or if it somehow came up off the road. I really should have put it on ebay under "Sandcast: Automatic Tire Butterer" Probably could have gotten $1000 for it.
