Originally Posted by
rccardr
50/36-34/28-30 is an unusual combination; I would not expect to find more than one or two of those on a complete crankset.
Gotta be patient and keep looking on eBay. Pounce when you find the right tooth count and BCD.
Over the last two months I’ve sold off maybe 20 hardly used chainrings, including a 50 big and a couple of 36 tooth middles & 28 inners, mostly for $12-18 including shipping.
It's an unusual combination because it probably won't work well. For the chain to upshift from the granny to the middle reliably, the chain has to get caught by the middle without coming into contact with the outer ring. The 50-36-28 might work... the 50-34-30 probably won't. With the latter combination the chain will shift from the inner to outer chainring, bypassing the middle.
IMO, it would be better to install a larger middle chainring, something appropriate for the majority of your riding. I've been pretty happy using a 38 or 40 tooth middle chainring with a 11-34 or 12-34 9-speed cassette. With a 48 tooth outer I'm able to to do most of my riding on the middle and outer rings. I have a 24 tooth inner ring for when stuff gets super-steep.
110mm bolt pattern rings are available from Origin8:
https://www.amazon.com/Origin8-Alloy...dp/B002G363XM/
I haven't tried them so I don't know how well they work. Like RCCARDR, I have a box full of used chainrings in various states of wear.