My brother in law and I are going to Copper Triangle ride in August and I will start doing more during the upcoming years. I have a 53/39T SRAM RED crank (he has a FSA SL-K Lite Carbon Fiber crank, 53/39T). I have a full SRAM RED on mine and he has the Shimano 7900 component group. Neither of us want to buy a compact crank and literally just want to buy a cassette for the ride and future rides (will be used only for mountain rides once a year, the other 364 days a year we want to still with our original cassettes). Another SRAM RED cassette is expensive for its limited use and only goes up to 28T. The Rival is about a third of the price and goes up to 32T. Will this fit our bikes? We both would like some extra emergency gears when we get on the final 10+ mile climb. Any other suggestions? Thanks!