I have a SRAM Rival 10 sp. derailleur and cassette. The cassette has a 28t cog on it(lots of hills in Seattle). I noticed on several sites that sell SRAM derailleurs that they only support up to a 27t cog. I had a problem recently that is in another thread where my derailleur got hung up in the wheel and cassette and bent my hanger. I thought, and still do, that it was caused by when my bike previously fell over.
My question is....why would they sell a 28t cog on a cassette(Rival) when the matching derailleur(Rival) doesn't support it? Why does the box not mention it? Is there really that much of an issue? Could it have caused my problem?
'''96 Litespeed Catalyst, '05 Litespeed Firenze, '06 Litespeed Tuscany, '12 Surly Pacer, All are 3x8,9 or 10. It is hilly around here!
Most manufacturers have very conservative max tooth ratings for their rear derailleurs. Shimano states their road derailleurs have a 27T max but experience shows they will almost always work fine with a 30T cog and sometimes with a 32T. Unless SRAM is way different, a 28T cog should cause no problems.
I expect your problem was indeed caused by the bike's fall, particularly if it landed on the drive side.