How much difference does an inch make? If we're talking about the Michelin Pilot Sport 4S NAO tyres that come on the Porsche 911, then there's a big distinction between them. In this video, the UK's Tyre Reviews tests both sizes and digs into their characteristics.
Michelin makes the Pilot Sport 4S NAO specifically for the 992 generation of the Porsche 911 Carrera. The standard setup has 19-inch diameter rubber in front and a 20-inch size at the back. Buyers can upgrade to a pairing that's 20 inches at the nose and 21 inches at the tail.
Gallery: 2020 Porsche 911 Carrera and Cabriolet
The video explains that this isn't a situation where the larger-diameter choice is simply a slightly bigger version of the smaller ones. Michelin had different teams working on each setup.
For normal, everyday driving on the road, there's not much disparity between these tyres. Dry braking from 62 miles per hour to 3 mph (100 kilometres per hour to 5 kph) takes 33.18 metres (108.86 feet) for the smaller size and 33.03 meters (108.37 feet) for the bigger one. That's a difference of just 15 centimetres (5.9 inches).
On a wet road, stopping from 50 mph to 3 mph (80 kph to 5 kph) takes 33.63 metres (110.33 feet) for the smaller tyres. The larger ones need 33.67 metres (110.47 feet). That's a difference of only 4 cm (1.6 in).
The contrasts between the tyres are most evident on track. The video starts on a wet track. The driver notes that the smaller ones seem to have a bit more tendency toward oversteer. On the clock, the differences are harder to see. The 19/20-inch combo laps the Michelin test course in an average of 97.55 seconds. The 20/21-inch setup cuts this time to 96.83 seconds, making the gap between them just 0.72 seconds.
Around the same track in the dry, the larger tyres really show their advantages. The driver comments that the optional setup feels similar to Michelin's Cup 2 track rubber. The smaller setup does an average time of 71.53 seconds, and the bigger ones cut things to 70.43 seconds. The difference is 1.1 seconds.
Porsche is currently preparing a refresh for the 911 Carrera. It has active slats in the front, and the cabin has a fully digital instrument cluster.
Jonathan Benson from Tyre Reviews has been a guest on Motor1.com's Rambling About Cars podcast: