Purchased a new DS4-style 1.6 5 weeks ago and love the car but have experienced this annoying vibration (lump lump)when driving at 60 to 85 k. Have taken it back twice and they don't know what it is. The dealer says he thinks it is a flat spot on the tire but not sure which one so they pumped the pressure up all 4 to 64 kpi and ask me to drive around for another 500 k's. Have done that but still experiencing issue. I also have an issue with the brakes which hiss and squeak when applying at low speeds and seem to grab when braking hard. Dealer says they are new and just need breaking in. Does anyone have any idea what this can be?