You are going to have to clarify what you mean by collimator - this torch has appears to have a simple O/P reflector and as the LED is recessed maybe 20mm inside the front of the torch removing the REFLECTOR will have little beneficial effect.

I do have similar size ultrafire torches here and removing the reflector while wasting a lot of light allows a wider angle cone of light to be emitted - however it isn't anywhere near wide angle as a cycle rear light.

I'm hoping it will be possible to harness all the light output and direct it where required.

I'll experiment more when the torch arrives.

It may well be that better results can be achieved if the assault crown didn't block so much light.



EDIT: Interestingly, I just realised that the red Luxeon LED is a Lambertian so most of the emitted light is going to go straight out the lens without touching the reflector anyway, so removing the reflector will have much less effect than it does on my white LED Ultrafire torches.