For a few years now, teams have been extending the inner face of their brake ducts to reach forward towards the tyres forward edge. Up until recently teams placed the protruding vane as close to the tyre as possible, but latest solution offsets the vane from the tyres sidewall to allow airflow to pass in-between the tyre and vane. An inlet formed in the brake drum duct catches some of this air and redirects it towards the brakes for cooling. This year Williams went even further and removed the usual brake cooling scoop and have the brakes entirely cooled by an inlet between the tyre and vane.
Brakes need to be cooled to keep the carbon discs from overheating and oxidising, so brake ducts are a necessary evil, but they add drag. The larger the protruding inlet scoop, the more drag the duct creates. So teams always try to run as smaller duct as possible.
Ever since the front wing was raised back in 2001, the airflow in-between the chassis and the inside face of the front wheel has been critical. Ferrari were the first to recognise this and created the brake drum duct (or cake tin as many teams call them). This is the round duct that’s attached to the front upright and fits neatly inside the front wheel. This drum has several functions, firstly the inner face of the drum smoothes the path for air passing inside the front tyre, but the drum also seals the wheel off from through-flow. Previously flow could pass through the wheel from its open inside face, teams want the flow the between the chassis and wheel to retain its energy to drive the rear aerodynamics. Airflow passing through the wheel loses some of this energy. Even with the drum duct, brake cooling was via one or more inlet scoops, sized to suit the braking requirement of each track.
As mentioned at the top of this article, the inner face of the drum has increasingly been extended forwards (rules allow it to reach as far forward as the perimeter of the front tyre). This has further improved the flow off the front wing passing inside the front tyre, as the rotating tyre would interrupt the airflow, but is separated from it by the vane.
Last year Renault, Williams and eventually many other teams opened up the drum in-between the tyre and the vane for additional cooling. Then for this year Williams took the idea a stage further and did way with the protruding inlet scoop entirely. So far this set up has cooled the brakes at some of the most demanding tracks, so we can expect the scoop-less design to be raced at all tracks this year.
Having this smooth surface inside the front wheel allows airflow to pass inside the tyre without any losses, this also frees up more space for the flicks and vanes teams fit to the brake ducts to further augment the cars aero performance. These additional aero parts being legal ,despite moving with the front wheel, as the rules simply regard these as brake cooling ducts, even if the part in question have no cooling purpose whatsoever.
Ferrari were quick to follow this idea, with their Canadian GP update. Now Caterham have followed the same path, so we can expect most teams to find their own version of this design between now and the start of next season.