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A View From The Driver's Seat: Car Wars - Episode 3: Revenge of The Regulators

By John Thorne / MJP Media | 6 April 2012

In this episode John Thorne tells us how the regulations affect the design of BTCC cars and explains how the rules ensure the cars on the track look as close as possible to the cars on the road.

The car set on flat bed at correct ride height

The whole concept of British Touring Cars is that the cars we race represent the road cars that you or I might drive on the street. Where other race series have adopted a silhouette concept, where all the cars have an identical chassis to which different bodywork is attached, the British Touring Car Championship has continued with the central idea that the cars we race must be the same chassis as those we buy. This concept extends throughout the regulations we must adhere to in the design of the cars. First off we must only use the road car doors, boot, wing mirrors, bonnet and roof so if we put out a tannoy announcement at a race that we need a door we really can just use one from a fans car - not that we would do that of course!

NGTC regulations are all about standardisation but of course when it comes to how a car looks, standardisation is a bit mad. We all want to see Vauxhall vs BMW vs Honda so regulations are limited to keeping a level playing field amongst the cars where possible. All the cars must be a maximum width and length which is the reason why some cars are 'stretched' for the race track a little with varying levels of success.

There are also rules about what we can change from the standard cars. Bumpers can be deepened and adjusted to allow for extra cooling but we must retain the original cars design features such as the grill position and design details such as the VXR 'fang' on the front bumper. Front wings should be extended to cover the wider track the cars all have but must not be radically altered from the original.

Of course some teams do seem to have a little more poetic licence with this than we do, but there you go. We originally went with a flattened front wing for better aerodynamics (the flat top adds to front corner downforce) but weren't allowed under the rules.

Fitting standard doors for fitment check

All the NGTC cars must run identical front splitters; these are the flat panels under the front bumper which extend under the front sub frame. The size is dictated by the bumper design of the base model but can only extend by a maximum amount. The bigger teams use all kinds of flash materials for these but most smaller teams use good old fashioned wood. Splitters have a habit of getting wrecked in races so are pretty much treated as a sacrificial item.

Aerodynamics was one of the main reasons we decided to use the Insignia as the base model as the standard road car has one of the best drag co-efficient ratings on the road. Its saloon shape is much more efficient than a hatch design in terms of cutting through the air but also its wider width meant that our bodywork design could concentrate on maximising this advantage rather than simply trying to extend the bodywork over the wheels. Arch extensions may look aggressive but they act as air brakes at speed. The net result is that the Insignia should always be pretty high up in the speed trap times - we simply cut though the air better than the other cars.

This quest for aerodynamics extends throughout the car design. The rear arches are extended into the rear doors to smooth airflow over the rear bumper which is a standard item so they are cheaper to replace in the event of damage.

Body shell with standard Insignia VXR bumper fitted

All the other panels are made from fibreglass which is light and cheaper than carbon fibre which is banned. Standard wing mirrors must be used but internals can be removed to lighten them - you'd be amazed how much a wing mirror weighs these days. The same applies to the doors which are standard but all the crash protection bars are removed from inside to again save weight. We must run standard front and rear lights. The bonnet must be a standard item but we are allowed to add vents to aid cooling from the turbo charger.

All the NGTC cars must run a wide box section side sill. The idea here is that replacing doors is more expensive than replacing side sills. The actual process of making the bodywork is straight out of a Blue Peter episode. Whilst some teams spend millions on computer aided design, we do it the old fashioned way with tape, cardboard and filler being used to design the overall shape which is then moulded into a plug. This plug is used to create a panel mould from which we get the final panel. It's an expensive process to design and set up but relatively cost effective to replace panels as they're damaged.

NGTC regulations also extend to the rear wing which is identical for all the cars. The angle of this wing is dictated by the organisers based on wind tunnel testing of the base model car. All the teams must attend a wind tunnel with a standard road version with the rear wing attached and testing is done to set the angle for each car.

Teams are allowed to adjust this angle for different circuits but only by a prescribed amount, the scrutinisers even have a little wooden tool to check wing angle after each race.

Next time we will get into the power part of the cars.

John #66

Touring Car content supplied by MJP Media

Additional gallery:

We originally went for a flat top edge on the wings for enhanced aerodynamics but TOCA banned it

This is the design we originally wanted

The revised front arch

Rear arch showing the smoothing into the rear door for enhanced aerodynamics

The finished front bumper and front wing design

Box section side sills designed to protect the doors

Standard car at MIRA for wind tunnel testing

Adjusting the TOCA rear wing height on a standard car