Grinding noise from front wheel

Hi Guys

I have a '99 R1 and have noticed a grinding noise coming from my front wheel. It is not as noticeable when at speed, but becomes really clear as I am slowing down. It also seems to be louder when riding for a while and the tyre is warm. I have taken the wheel off to investigate what is going on, but not sure what to look for.

Any help will be greatly appreciated, thanks.