The more the front tyres wear at a different rate from the rears, the more the four wheel drive system will ‘think’ there is slippage and will engage drive to the front wheels. The other part of the problem is the width and the profile of the tyres. You can opt for 17-inch, 18-inch, 19-inch or 20-inch wheels on the 2005 - 2012 ML. 17s are the deepest profile, longest lasting and least expensive tyres. 20s are the lowest profile, shortest lasting, most vulnerable to damage and most expensive tyres.