do you think 2nd curtain sync would have eliminated the halo effect (helmet,rearview mirrors,indicators)? - great shot anyway! In my experience with this process, cleaner editing (sides of bike + front struts)would have been achieved by cutting and pasting the bike to a new layer and radial blurring the layer below, then defringe or feather bike layer as needed. (but you knew all that didn't you)
Not only do I know it but I did it Still there was some amount of blur inherent in the original picture and also just cutting and pasting the bike rider over the top of a blurred layer doesn't stop the fact that the layer underneath still contains some rider that gets blurred.
RE 2nd curtain shutter snyc, In a word - nope. Even if I could use 2nd curtain sync (which I couldn't as I was using studio lights powered by a genny rather than canon speedlights) it wouldn't make a difference as there was no absolute direction. 2nd curtain sync is used when you have an object moving across the frame and you want the movement trail to extend behind it rather than in front of it. In this case the bike rider was 'relatively' stationary in terms of subject vrs camera positioning. Any blur is merely the case of involuntary movement of the camera by me or the bike rider not staying exactly constant, rather than an intention sideways movement.
not necessarily...the tyre was frozen by the flash, in reality the ground was too (which is why I added some radial blur in post) but I COULD have had the flash appropriately snooted to illuminate the tyre but not the ground.
As it is though I've decided to add some motion blur to the tyre also, just to add to the realism