I drilled my stock rollers. Don't know what they weigh, but I only went about 3/32 larger than the stock. At my local 1/8 mile drag strip I went from 11.35 seconds to 10.96. Top speed remains the same, actual 83-84 by GPS. Also, if anything, my gas mileage has improved slightly, as checked on a recent 800 mile 4 day ride. What's not to like!! This thing will outrun any stock single cylinder scooter in the 1/8th mile.