I've been having a similar slow leak for about a week now. Couldn't find anything puncture-wise and replaced the valve core. After the core swap it was still losing around 5lbs a day. With no real answer, I ordered a 240 and put it on today. Initial thoughts are that it looks big almost in a distracting way and I feel like I lost something in handling. Il. Probably get used to the look, but time will tell on the handling. I should mention that I've only put about 5 miles on it so far, so I may feel different. It's just that my immediate though was that I was having to push it into turns more instead of it falling in. About to put a few more miles on for comparison.