system
A chat on subreddit /r/PoliticalCompassMemes
human
Road maintenance costs for passenger car traffic is very small. In comparing a paved road used only for passenger cars versus only for bikes you'd likely find similar cost. Temperature/climate damage and age would be the driver of the need to repave, not the wear and tear by the vehicles. 

Heavy trucks are responsible for almost all the road maintenance caused by vehicle traffic, but you can't replace this with bikes. 

It's possible bikes could replace the road damage caused by buses, if more people rode bikes and less buses were needed, but I've never seen data for this.
gpt
Main savings in road maintenance isn't less road damage (since you won't reduce truck traffic) but rather less road surface to maintain (since more people biking = less people in cars = you don't need as wide a road to avoid traffic congestion).