Check tire inflation. They may be overinflated. When I put new Michelin MXV tires on my 2011 LEAF and inflated them to 40 lbs or above, they followed every groove in the freeway. It translated to a very nervous ride. I think it's called "tramlining", meaning following the lines in the pavement. Use an accurate tire inflation gauge, not the thing that's attached to the air pump at the gas station. Check Nisssan's recommended inflation pressures in your manual and the max pressure marked on your tire sidewall. For best fuel economy, many LEAFers prefer 40 lbs, though some go higher. Nissan recommends something like 36 pounds, IIRC. Try different pressures between Nissan's recommendation and 40 lbs and see if it improves.