As I understand it is where the brake reservoir hits the bar not allowing the clamp to close. When I had the 1-1/4" bar there was a necked down part as shown on the BC bars...I was looking at my bars today at noon, I can see there is about 1/8" or so gap between my 1" bar and the reservoir...That is why I said the 1-1/2" bar may not work....
