Have a horrible noise coming from somewhere on my fixed wheel work bike which I am struggling to locate the source. It is random and not in time with the wheels turning or pedals turning, sometimes quite loud other times not. I suspect the chain as I know that to be maybe a couple of years old. Can somebody tell me if this could be a typical of an old/worn chain on a fixed wheel bike? The bike was rebuilt last year, has a sealed B/Brkt which is not too old but does have an old rear wheel which could do with replacing. If I lift the rear wheel and turn the cranks then there is no noise so only happens when ridden and a load is being transmitted through the transmission. I know that really you have to listen to know what I am on about but would appreciate your ideas. I have never had a sound like this on any of my other bikes so I feel that it could be typical of a fixed wheel.