so, background. tomos motor on a puch frame project. i got 2 in mind that this effects.

lets start with the first one. now lets assume i am putting an a35 on my monza which has 17 inch rims and very large tires. i think 3.00 or 3.25 rear. optimally i would like a 31 tooth front sprocket but lets assume i only have a 27 front. i think the smallest rear i can go with is a 25 and that would have to be custom made. now tomos SPEED GEARING is 31x20. and like moderate speed gearing would be 27x22 right? and the gearing i am expecting to be able to reach is 27x25 or maybe 31x25 so...

31x20 = 1.55

27x22 = 1.23

31x25 = 1.24

27x25 = 1.08

so keeping in mind the much larger wheel diameter how do i find out if a 25 rear will be small enough? what is the dext step in the formula?

i also have another project that will be an a55 on a magnum with mbx wheels (18 inches). now i know i can get a 32 rear, would have to have anything smaller custom made. i can use whatever formula to figure out if that extra 2+ inches helps enough.

i assume that wheel diameter has to have a fairly significant role in speed so i am hoping it will make a large difference.