This is an excerpt from a race i saw, i dont quite understand the statement 39-21? is this front chainrings they are talking about? becasue then it says 23? i dont get it. here is the excerpt.
In general, the course is safe, smooth, and challenging. We recommend a 39-21 or even 23 gearing due to the extended climb you'll face at the beginning of each lap. Lead and follow vehicles will be provided for each race. At a minimum, Men's A & B and Women's A will have wheel vans.