Hi Baz,
Yes, I reckon sometimes those knocks are bites.
(I've said this before, so if anyone is bored of reading it - I'm sorry!)
One one occasion this year I had been getting loads of taps on pellet, but kept waiting for the so called inevitable wrap around.
After 3 hours of this I changed my position and almost pointed the rod and the lead and hooked my finger around the line. I also scaled down from large pellets on a large hook to 8mm pellets on a size 14.
In the following hour and a half (or so) I caught 6 Barbel and a Chub by striking at the tiniest plucks. I don't reckon any of these plucks would have moved the tip more than an inch, had it been set at a decent angle. I missed a few too.
I'm not saying that some of the knocks I missed weren't liners or Chub, but at least 6 of them were Barbel taking the bait in their mouth.
When I do get plagued with knocks I wish I had the quiver tops attached. We all know that Roach, Chub and most other species will drop a bait when they feel resistance, so why are Barbel any different?
This has only happened a couple of times this season and normally, like everyone else, I wait for the rod to go properly.
I'm never felt the hacksawing that Graham talks about.