good thread. I have a BT090 front that was made in 09 (so coming on 5 years old). It has some marks in the centre of the tread that look like someone has sliced it lightly with a razor blade. Call me crazy, but I did a track day on it and had no issues and got it cranked right over. I'm replacing the tyre soon!

Well. If it was cranked over you weren't in that bit ... Just kidding. Check if it's slices or if some rubber has just been rolled across the tyre surface from working hard on the track and it looks like slices. .. You shouldn't really confuse the two but maybe?

actually I have slits along the sides too!

Whats really odd is that the scratches are superficial (look carefully and you'll see that they don't run through the groove of the tread), but at the same time you will see they continue perfectly from one side of a tread groove to the other (ie it looks like something was dragged across the tyre surface to cause this - sort of cheese grater style). Do you let your cat use it as a scratching post ?

It's exposure to UV light.

The sun is much stronger in many Asian countries than in the UK. UV kills plastics and rubbers very quick

Thanks Neophist (you too Tigerclaw!). It does get a bit of sun here in NZ. I'll be the S20F test dummy soon..... hoping for similar grip and probably a shorter life to the BT090