I have an excellent condition Trek Domane 6.9 disc bike and yet, in most cases, I use one of my single speeds for day rides even in the mountains (WNC) I have seen an amazing improvement in my fitness level by sticking with the SS program.
Last weekend an 80 miler spread over two days, yesterday a 73 miler in one day.
Most interesting to me is, at a stopping point, none (zero) of other riders never notice or say anything about it being a single speed. I can't help it but I always look at the other riders cluster, no wise cracks please
