There shouldn't be any hard and fast rule about riding one size down. My road bike is listed as a 54 but has a 55 top tube. Both of my cross bikes have 54.5 top tubes which I find to be very comfy. Stem lengths are identical on all bikes.cjpavlov said:thanks jroden - that is exactly the sort of info for which I was looking. Are there any gereralities, such as, "typically people ride a cx bike one size smaller/larger than their road bike"?
As long as you have standover, that's enough. It is a fallacy that cross requires more room than road. Cross bikes often have higher bb's and the tires have a bit higher profile so that will reduce standover a bit so YMMV.hairscrambled said:I like a size smaller. 54cm road toptube. 52.5cm cross. If it is a traditional toptube (non-sloping) you may go a little smaller to get better standover.