my wheel seems to flex and rub the brake when pushing a big gear, for example when doing like 40 km/hr which is like 25 mi/hr and when i downshift so going from a cadence of say 90ish to 80 it seems like its rubbing all the time and not smooth and very annoying. is this because the rim is weak? i'm like 185 pounds and ride mavic kyrsium rims. thanks for the help