N Rated tyres, are they needed?

[geoff]

My mechanic at the dealer said the N-rated tires have to go through more QA processes than the same non-N-rated tires from the manufacturer. I've also read that the N-rated tires may have stiffer sidewalls than their non-N-rated counterparts.

Not all N-rated tires are high speed. The N-rated tires that came on my Cayenne only have a "V" speed rating (only good up to 150 MPH); they are rated for mud and snow. The summer rated tires that are N-rated are good for higher speeds ("Z" rating)