SRO’s Motorsport Technical Director Claude Surmont explains the intricacies in gauging parity for GT3 racing to Speedcafe.com.

In GT3 racing paritising the field is critical with so many different makes and marques and all kinds of sizes and shapes and naturally aspirated and force-fed engines.

What is Balance of Performance?

Balance of Performance is simple. In GT3 all cars are different. There can be cars with engines in the front, back and centre. Weights can go from 1330kg to 1220kg so you have to balance all of these cars to make sure they can produce the same performance on track and do the same lap times.

You work around the strong points of the cars which are aero, weight, power and torque.

You analyse those points and you try to make an equation where in the end everybody is doing the same lap times with a 0.3s difference at a maximum.

How do you equate the figures for each car?

First you have the homologation files of the cars and you have the data from the testing of the cars. This can be in the form of track testing, engine testing and dyno testing.

We will test the cars with our own drivers to get certain feedback from configurations we put on the car.

The data then goes into simulation software.

At the start of every season I will make four sets of BoP figures because we have four track categories.

There are some differences we have to build in for some categories like Super GT in Japan because the tyres are completely deferent.

We have other customers that use different rules see we have to make allowances.

It is  a lot of work. It is not just the figures but you have to give interpretation to those figures and then you have to make a final decision on the BoP figure.

The other big moment is at the end of qualifying at an event because then you know what the score is.

What measures can be made to the cars to ensure the cars are balanced?

It depends car by car. In the past when we had a Ferrari 458 going up against a BMW Z4, the Z4 was the car with the highest downforce so to slow the car down we had to look at power and then the ride height.

The Ferrari on the other hand was the fastest car we had. When we went to a very fast track we would put on a restrictor and extra weight to slow down the car.

How challenging is it to work out the BoP for Bathurst?

The Bathurst circuit sits in the category of Monza and Macau. I have the right to change whatever I want but it something I have never done.

Can you make changes to BoP during events?

It is in the regulations that I can change something up until the start of the race.

Liqui-Moly Bathurst 12 Hour Balance of Performance charts