The FIA has changed its procedures for measuring tyre temperatures and pressures on the grid in the wake of Felipe Massa’s exclusion in Brazil.

The move follows an internal investigation of Massa’s tyre issue by the team, the results of which were shared with the FIA by Pat Symonds.

One of the key issues for Williams was that no senior personnel were aware that Massa’s right rear tyre had been checked on the grid by FIA technical delegate Jo Bauer and his assistant Kris de Groot, and the team knew nothing of any discrepancy until an official message came from the FIA some way into the race.

Henceforth any FIA tyre check on the grid will have to be witnessed by the car’s race engineer, who will thus clearly be made aware of any issues. This is similar to the way car weight checks are carried out, when team members can observe and log any figures.

This will also resolve another key issue – the anomaly that allows the FIA to record that a car is “unsafe” before the start, given that the checks are in place at Pirelli’s request, and yet the car is allowed to start the race. This became a major talking point with Mercedes at Monza, as well as in the Massa case.

Now if the FIA records illegal numbers the team will still have the option to take the car off the grid, change its tyres, and start from the pitlane. The driver will thus head into the race with a legal car and thus won’t be wasting his time by running under the threat of an exclusion, although there could still be a penalty for the grid issue.

Meanwhile the Williams investigation indicated that the reading recorded by the FIA’s infra red gun was affected by heat reflected by the tyre blanket, and that the logged figure of 137C was not the true temperature of the tyre itself.

Although the FIA has not officially accepted that as an explanation it will adjust is tests in future by ensuring that when the temperature is checked the blankets are opened sufficiently, and the gun aimed into an are not shaded by the blanket, so that there is no risk of heat reflection having an impact.

The teams themselves also have the option to make sure that they are happy that the blankets are fully open when any test is conducted.

Williams explored the phenomenon of heat reflection by using a thermal imaging camera on a tyre in a blanket, which demonstrated what happened when the blanket was partially unwrapped. As the blanket was opened, the tyre temperature dropped dramatically.

“What we’re seeing is a heat reflection in exactly the same way that you get a light reflection,” said Symonds. “That reflection is occurring where the tyre is closest to the blanket, the reflection coming off the blanket. Where you are well away from that heat source you don’t see the reflection, so therefore the reading is good.”

Symonds also confirmed that had the team been informed on the grid in Brazil that a tyre had potentially been overheated – as happened on the Friday of the 2015 Russian GP weekend when a set was effectively ruined by a blanket issue – it would have reacted.

“Bear in mind this was a safety thing. If they really felt the car was unsafe, they should have told us straight away. If we had a tyre blanket controller failure, like we had in Russia, we would have taken the car off the grid, because we would not have felt safe to start the race.”