Originally Posted by mander
Look here, according to Fraction the denominator doesn't have to be odd. Only the numerator matters. I just want to get clear on this because everyone's website says a different thing and Fraction's result is backed up by his proof (which looks OK to me, but ought to be checked by someone better at math) as well as Rabbit's brute force algorithm.
yep, a bit of careless cut and pasting. agreed that fraction is correct, and that only the numerator matters when deciding whether or not to double skid patches.
this is for the most part academic, though. anything more than about 8 skid patches is probably overkill. if you're worried but don't want to do the math just run a 17t cog (and not a 51t chainring) and rest easy.