Do you know that when fitting these collars you will need to allow the axle some end float?
This means that you remove all grub screws. Then bolt the collars to the inside face of both outside bearings. You leave about 1mm for the axle to move. Realise that when the axle gets warm through braking it expands. And if this expansion cannot be taken up by the end float between both collars then it will push onto the axle bearings.
This pushing sideways onto the axle bearings causing them to bind. Its like putting on the brake. Which in turn will rob your engine of power. Often it will overheat your engine. Then what happens is your lap time get slower.
Can you see that this end float put into your axle is very important? It really is. So go out and see that your Axle Collars are really fitted correctly. It will mean the difference in racing at the front or struggling to keep up with the pack.