It is also important to look at OPTIMAL RIM size. Very early on I did find a size chart on USA Metzler that put the optimal size for the 150/80 as a 3.75". But 3.5 "acceptable". This means the tyre is a pinched fit and as such reacts differently - will tend to run better upright and feel very lazy in bends. I measured the tyre fitted and it was actually 143mm wide and the aspect ratio came out at 90%. I had quite long talks with several tyre places about it and all confirmed this is a common error (usually fitting extra wide tyres)
I currently use a 150/70 - this rolls beautifully. Same as a 140/75 - not spec'd really for a 3.5 rim but holds its form better - it is 150 wide. Maybe tougher as it is a rear tyre.