GT
GT (Grand Touring) cars are production sports cars that have been modified to race on road circuits. The Grand Touring car evolved from the earliest makes of road cars from early 1900s. They were built with luxury, style and horsepower for their era, all three of which were highly desireable to the rich clientele who bought them.
These exclusive cars were raced through the 1920s and 1930s, especially in longer endurance events such as the Mille Miglia (1000 miles) that lent themselves to a "Grand touring" car. As mass production of sports cars became widespread post WWII, the availability of high powered racing cars around the world spurred an explosion of GT racing.
GT race cars differentiate themselves from Touring cars by being sports cars first, whereas touring race cars generally begin life as a family-type sedan.
Racing is run on road racing circuits throughout the Americas, Europe, Asia and Australia.
| Power and Weight Stats | |
| Horsepower (Typical Range) | 400-650 |
| Race Weight (Typical Range) | 1225-1725 kg 2700-3800 lb |
Design and Construction
Race Car Models of This Type
Classes are specified for GT cars depending on power and level of modification. Sports cars from manufacturers such as Aston Martin, Audi, BMW, Chevrolet, Ferrari, Ford, Ginetta, Jaguar, Lamborghini, Lotus, Maserati, McLaren, Mercedes, Nissan and Porsche participate in series.
Build Your Own GT Car
Knowledge Level
Building a GT race car requires an advanced knowledge of all aspects of the vehicle (Handling/operation, suspension, chassis, powertrain, aerodynamics, and safety). The initial cost of the base car is serious and any modifications being made should be approached with equally serious understanding.
To make the learning curve more manageable, it is recommended that would-be GT racers select an "economical" (relatively speaking) base vehicle and work their way up through competitive classes locally using that vehicle as their "development platform". Many of the available books provide basic to reasonably advanced knowledge in the aspects mentioned above, so they can provide a good reference alongside your experience.
Autocross may also provide a good initial starting point, as there is less likelihood of damage to your vehicle when running by yourself on a circuit.
Design Challenges
Suspension: Within the regulations of the sanctioning body class you wish to run in, you will want to design your car with:
- Maximum track width
- Minimum unsprung weight
- Maximum tire contact patch and grip through the largest, widest and stickiest tires permitted.
- Maximum brake stopping power
- Low ride height (with any required changes to the suspension geometry to ensure maximum tire contact patch on the road).
- Appropriate springs, anti-roll bars and damping to manage weight transfer and help the tires follow the surface of the road better.
Chassis: In GT racing, depending on the class, the production chassis may be modified to increase torsional rigidity, lighten the vehicle and increase safety. Changes to the placement of components (i.e. Battery) in order to redistribute weight balance can often go hand-in-hand with lightening.
Powertrain: Powertrain modifications can include extensive changes to the engine components and driveline components. The goals of changes to the powertrain should be to increase horsepower and engine efficiency. This can be accomplished through replacing stock components for increased internal flow (Intake/exhaust), improved combustion, reducing friction and removing/replacing power robbing accessories. In terms of final drive, any modifications such as limited slip differentials that increase power delivery to the road should be considered.
Aerodynamic: Depending on the class, aero devices and bodywork changes to enhance aerodynamics may be permitted. Reduction of drag should be a priority as frontal area of a production car is not changeable. Aero devices such as an underbody floor, air dam, wing (or spoiler) and diffuser are all possible depending on what is permitted by the regulations.
Designing the aero devices to work together and to balance front/rear downforce will provide optimal downforce and stability. Designing in adjustability to generate a wide range of downforce will give flexibility in setup.
Safety: Any circuit racing with other cars will require a safety cell structure, with a racing seat/harness. Other safety items such as a fuel safety cell and fire extinguisher may also be required. If a driver safety cell structure is not available off-the-shelf, it will need to be designed and fabricated.
If you intend to race under a sanctioning body, always read and understand the regulations of your chosen racing class before designing or building any race vehicle.
Design Resources
Learn the basics about race cars and race car design from our free online knowledge series
Download our free race car design aids to assist you designing your race vehicle.
In-depth books and learning resources we recommend for GT car design.
Join our forum to ask and find answers to your GT car design/construction questions.
Construction Challenges
Having sufficient space is important, as a cramped workshop will be difficult to work in.
The tools to modify the engine, chassis and bodywork can add considerably to the cost of your project if you don't already have a workshop, but borrowing or renting items is also an option.
Many components permitted for GT racing can be bolt-on type components and therefore are within the mechanical skills of most people. Challenges include the number of components which are changeable, and the difficulty in changing them (i.e. Things like engine removal), which may require specialized workshop tools.
For driver safety cell structures that must be custom fabricated, there is the additional requirement of fitting it into the vehicle and of locating mounting points that do not compromise the uni-body chassis.
Build Costs
The base vehicle cost can be fairly high when dealing with sports cars, but used sports cars will offer a lower cost entry point, especially as the car will be a "development platform" for both the builder and driver.
Racing parts will likewise be lower in cost if the base vehicle is not exotic. If you have adequate knowledge, it is possible to select areas of modification that provide maximum value and keep costs to a minimum.
Build Effort
The effort depends on the number of areas that are modified, which is another good reason to start in a GT class that is entry-level or in Autocrossing. If your modifications are performed a little at a time, the effort will also be manageable and your experience will grow along side your knowledge.
Racing Cost
GT racing, by nature of its more expensive base vehicles, can consume a larger budget through racing tires, engine rebuilds, and damage repairs. If using Autocross as your "school", the costs can be kept much lower initially.
Transportation and Support Equipment
The vehicle will likely be trailered to the track unless kept in a street-legal configuration. Support equipment is usually carried in the trailer/towing vehicle.