Tyre wear, cracks in sidewall

drumon

This tyre has a crack round the entire sidewall on both sides, (the shaky white line under the tread).

What causes this and Is it due for replacement? is it dangerous?
Could the innertube be damaged also? :?:

supersonic

Rubber tends to harden over time, and UV light degrades it. It would be best to replace it. Tube should be fine.