Problem with speeder

http://img387.imageshack.us/img387/5787/08062009001h.th.jpg
A few weeks after I got this speeder, the rims became black and ugly(see picture). Does anyone has an explanation for this? Is it because I put it in my pocket?

lol that is not a problem.your speeder rims are just getting tarnish and i bet everybodies yyj yoyos that is half plastic and metal gets tarnish.to clean it just use a metal polisher and a tarnished rim doesnt affect play and putting it in your pocket doesnt do affect it