Was just wondering how exactly do you calculate gear ratio. I don't think I'm doing it rite, I was told you divide bottom to top, But what I'm looking for is how do you calculate for different size 8 tooth, or 9 tooth drivers. For example: I'm using a 43 bottom and 25 top with an 8 tooth driver on one sled and on another sled I'm working on has a 9 tooth with exact same bottom and top gear, 43/25 . How much difference would there be in gear ratio. Both sleds are 136s with 1.5 tracks.