Originally Posted by
Bianchigirll
I think the plastics in that SunRace are lightyears better than the plastics in those old Simplex derailleurs.
Good luck with that. Plastics don't age well, in my opinion. I'm in a discipline that uses lots of them. I expect that when today's plastics are 40, they'll look and perform way worse than their manufacturers and mfgr's flacks want us to believe; sorta like Keith Richards or Steven Tyler.
In addition to aging badly, plastics have pretty bad strength-to-weight ratio, and coefficient of thermal expansion that's crazy -- way higher than metals (even aluminum) -- which makes them poor partners for metals IMO.