I ride a 2006 Bianchi San Jose with the stock Fixed/Free flip flop hub. I picked up an English threaded FW today to increase my gear ratio (going from 17 to 16 tooth), and went to install it except I could not get it to go on the hub without crossing threads. I know for a fact that the FW is not metric and I don't know of any commonly used threading schemes beside English/Metric for modern single speed FWs so some input would be appreciated. The current FW (which threads on and off like butter so the threads are not damaged) is an ACS Claws the only other marking on it is (C2), the Freewheel I was trying to replace it with is also an ACS Claws but was marked (C7) if that makes a difference. Also, I threaded the new FW on a BMX wheel no problem, so I know its threads were also intact, the old FW would not thread on the BMX hub however; and a metric FW was too small to even begin to thread on either hub.