What's that noise

I hadn't taken my xc race wheels (tubeless Mavic Slr's) for a spin for about 2 months. As I roll off there is a noise inside my tire. Go a little faster, it's gone now. Slow down, back again.




After the ride I have a look inside the tire & here's what I found.

These amazing structures created from liguid latex. The one on the left was about 5cm across.

I must remember to check the latex in my tires more often ;o)