There are plenty of pictures on here of people running 275 and 305 tyres on stock wheels and they look fine, they are also still within Michelin's recommendations, in fact 9.5" is their measured rim width for 275's
http://www.tirerack.com/tires/tires....omCompare1=yes
Click on the Specs tab.
As the rolling radius is still very similar the ABS and traction systems won't notice.