THE CLASSES
SUPERBIKE/SENIOR:
These are the holy grail of all the bikes racing the TT; full blooded, superbike-spec machines, with a minimum weight of 165kg and a power output knocking on the door of 230hp. They’re allowed to run any brand of slick tyres and fairly modified engine internals (basically World Superbike specification) with a BSB spec Motec or KIT ECU, alongside the trickest brakes, suspension and swingarms money can buy – as long as they conform to the original homologation. Tanks can be altered both in position and to allow for more fuel, and although they look like a general showroom machine – they are not. It also states in the rules that non-homologated motorcycles may be accepted for the Superbike and Senior races “at the discretion of the Race Management Team. Machines will be considered if they provide a demonstrable and significant marketing opportunity for the event.” This is why you’ve seen bikes like the Norton SG7 and Honda’s RC213V razzing round the Island. There is one six-lap Superbike race, and the crown jewel of the TT is the six lap Senior – both consisting of two pitstops for each rider for refuelling and sometimes even a tyre change.
SUPERSPORT:
Coming in at a minimum weight of 161kg, the Supersport machines really have come of age, with Dunlop’s lap record sitting just shy of the magical 130mph mark at 129.197mph. Just like on the short circuits, treaded tyres must be used, although the choice is open as there is no control tyre. Internally, the engines are pretty trick as porting and polishing of the cylinder head is allowed, alongside modifying the valves, combustion chamber and compression ratio. A kit ECU/Motec system is allowed, although electronic aids are not (launch control, traction control, anti-wheelie, etc) and the fuel tanks can be modified. Add some trick brakes, suspension and fairings, and you’re good to go. There are two Supersport races throughout the week that are both four laps in duration with one pitstop during the race.
SUPERSTOCK:
As the name implies, these bikes are only allowed a very limited amount of modifications, making it the most cost-effective way to tackle the TT. Running on any brand of treaded tyre, the Superstock bikes weigh in at a minimum 174kg, and aren’t allowed any modifications to the internal aspects of the engine like on the Superbikes. Aftermarket quickshifters and slipper clutches are allowed, alongside a Kit ECU (or flashed ECU) and an aftermarket wiring harness. Handling-wise, the rear shock can be changed, as can the fork internals. The fuel tank can also be altered to fit more fuel (up to 24 litres), but the fitment and shape of the tank must be identical to the standard unit. A lot of the privateers will actually be running their stock bike in the Superbike and Senior races as well to save on costs, while some of the bigger names prefer running them to a full blooded superbike! The Superstock race is run over four laps, and riders have to make one pitstop for fuel.
LIGHTWEIGHT:
These bikes are almost like mini Superbikes. For the Lightweight TT, any four-stroke twin-cylinder water-cooled engine of up to 650cc capacity machine sold for road use can be entered, with no price limit. The engines are incredibly trick, although the bore and stroke must remain standard, the cylinder head, pistons, valves and cylinders can be modified polished or lightened, the compression ratio can be altered, cam timing changed and the conrods and pistons may be replaced. The standard ECU must be used but can be flashed, or can run alongside a Power Commander or Bazzaz system. Suspension can be altered, as can the brake calipers, which means the top bikes will be weighing in around 150kg and knocking on the door of about 100bhp. Although open to different manufacturers, treaded tyres must be used and with one four-lap race there is a pitstop for fuel.
TT ZERO:
The TT Zero runs as a race that emits absolutely no emissions, and it is growing in stature year on year. These bikes are incredibly experimental and the rules are very strict. The bikes must be two-wheeled and electronically propelled by stored electricity. The minimum weight is 100kg while the maximum is a whopping 300kg, and the machines must conform to a whole host of health and safety guidelines. Voltage is limited to 800v, the machines must be able to be charged via a 240v supply and there are incredibly tight rules regarding streamlining and aerodynamics. Any type of tyre is allowed and near enough every machine is a prototype. The race for these machines is one lap.
SIDECAR:
Unlike their two-wheeled counterparts, the sidecar regulations are slightly more open to allow for the construction of the mental three-wheeled machines. The 600cc engines are heavily modified to run and cope with the different stresses that are associated with sidecars, meaning that any fuel pump can be used, while all engine, gearbox and clutch modifications are allowed. The ECU is free, and the chassis must confirm to strict rules. The minimum weight for these machines is 136.5kg with fuel, and they run racing car slick tyres. There are two sidecar races, each consisting of three laps, with no pitstops.