My RR does exactly the same in hot or wet weather and periodically when it feels like it. Not evident when in lower or higher suspension but in normal mode it was driving me wild! It squeaked at the slightest undulation in the road's surface let alone over bumps i was being stared at by all whom i passed. Anyway, I wend bloody mad one day and took a kill or cure approach. I drove at high speed (40mph) over a series of about 40 speed bumps, accelerating before each one. Being that the insufferable squeaking was on driver's side, I ensured that this was the side which was doing most of the mounting. It was fun and bumpy. My wife nearly had a fit! It cured the irritating and constant squeaking instantly!