Last time I always change my $300 helmet every few years. Now more than 3 years already, but only use once a week n ride slow slow. Dunno whether to change liao or not.
Not much different if not exposed to much UVA / UVB, ie if dont ride much later than 10am or before 5pm where UV Index is low, no issue. ie That is where you'd get your suntan.
PC, like most car headlamp covers, suseceptible to this yellow discolouration / structural breakdown.
(but i think sunrimoon not using PC, some other polyamide stuff). There are processes to slow this down but wont totally prevent it. Same thing with kevlar fibres and UV, that one for kite flying esp susceptible even with different types of coating protection employed hoping to mitigate breakdown, but ultimately still would degrade after prolonged exposure...something like your SPF sunscreen in practice.......that's why we also use Dyneema / UHMWPE but that one in field practice also got other issues).
Its gonna be the same with kevlar fibre spokes.
If wanna know and dont wanna change and you have extra helmets to use, just do it like i do to test. Whack with hammer / stand on it 2 pax. Or 1 pax wear shoe and stomp on it. etc etc
Bo bian, that's the best that we personally can do.
Anyway this is today's UVI. 12 noon came the sumatra squall.
When the sun is near the horizon and the light needs to pass thru quite a bit of our atmosphere, our atmosphere really cuts the UVA/UVB significantly, relative to visible.
Of coz not to say that 9am totally no issue even after decades, but wrt Feb's possible UVI 13-15 at 1pm, relatively no issue lah.
