Yes it is the reduction ratio. I don't run foams so I don't know what roll out to run. We only run on rubbers down here. Gearing has been an issue for us too. Some guys are gearing in the low to mid 7's some are in the low 6's. A friend of mine that won the NORRCA Nats a few months back in 19turn was gearing @ 5.5 running a C2!