I have found (through my own experience on the road) that the smaller section width give a better turning bike, and have found no difference in how long they last (this is more to do with compounds). Both my FT500 and NX650 came with 130 section rears, and when they wore out I replaced them with the standard 120 section (fronts not changed) and found that they steered into corners better. I believe this was because the wider rear tyre was being pulled around on the smaller rim and shifting the contact patch when leaned over. I could be wrong here, but my thoughts. In McLaren's case on the track, the wider 150 is an advantage. The wider section may not be noticeable in racing as most riders throw the bike into corners with a bit of slippage, and the extra 10mm of tyre could mean the difference between first and second place. As for the weight difference, has anybody weighed the tyres?
140 /70 works best for me, taller, keeping more heat in the rear, more predictable edge. suits my style. 150 blew chunks on cold days with long sessions, but to be fair that was on a 3,5" rim. 140 is working well for 4 yrs on both 3.5 and 4.0 rims. also 100-200 grams less unsprung weight. Just need some of the new 140 Supercorsas to try next or i'll stay with 140 DR2/110 SC1 front combo.
old thread here but I am up for tyres soon. I would have thought the lower profile of the 150/60 would make it very similar width to the 140/70 when fitted to the narrower rim? Any comment?
Any way you look at it pinching the radial carcass past the stock recommended amount will have some kind of impact on handling. It really depends on if you are aiming for grip or handling, personally I think 140/70 on a 4 inch rim is the best overall choice.