Because of the way Concorde's delta-wing generated lift, the undercarriage had to be unusually strong and tall to allow for the angle of attack at low speed.
At rotation, Concorde would rise to a high angle of attack, about 18 degrees.
Prior to rotation the wing generated almost no lift, unlike typical aircraft wings.
Combined with the high airspeed at rotation (199 knots or 369 kilometres per hour or 229 miles per hour indicated airspeed), this increased the stresses on the main undercarriage in a way that was initially unexpected during the development and required a major redesign.
Due to the high angle needed at rotation, a small set of wheels was added aft to prevent tailstrikes.
The main undercarriage units swing towards each other to be stowed but due to their great height also need to contract in length telescopically before swinging to clear each other when stowed.

The four main wheel tyres on each bogie unit are inflated to 232 psi (1,600 kPa).
The twin-wheel nose undercarriage retracts forwards and its tyres are inflated to a pressure of 191 psi (1,320 kPa), and the wheel assembly carries a spray deflector to prevent standing water being thrown up into the engine intakes.
The tyres are rated to a maximum speed on the runway of 250 mph (400 km/h).
The starboard nose wheel carries a single disc brake to halt wheel rotation during retraction of the undercarriage.
The port nose wheel carries speed generators for the anti-skid braking system which prevents brake activation until nose and main wheels rotate at the same rate.

Additionally, due to the high average take-off speed of 250 miles per hour (400 km/h), Concorde needed upgraded brakes.
Like most airliners, Concorde has anti-skid braking – a system which prevents the tyres from losing traction when the brakes are applied for greater control during roll-out.
The brakes, developed by Dunlop, were the first carbon-based brakes used on an airliner.
The use of carbon over equivalent steel brakes provided a weight-saving of 1,200 lb (540 kg).
Each wheel has multiple discs which are cooled by electric fans.
Wheel sensors include brake overload, brake temperature, and tyre deflation.
After a typical landing at Heathrow, brake temperatures were around 300–400 °C (570–750 °F).
Landing Concorde required a minimum of 6,000 feet (1,800 m) runway length, this in fact being considerably less than the shortest runway Concorde ever actually landed on, that of Cardiff Airport.
Because of the way Concorde's delta-wing generated lift, the undercarriage had to be unusually strong and tall to allow for the angle of attack at low speed. At rotation, Concorde would rise to a high angle of attack, about 18 degrees. Prior to rotation the wing generated almost no lift, unlike typical aircraft wings. Combined with the high airspeed at rotation (199 knots or 369 kilometres per hour or 229 miles per hour indicated airspeed), this increased the stresses on the main undercarriage in a way that was initially unexpected during the development and required a major redesign. Due to the high angle needed at rotation, a small set of wheels was added aft to prevent tailstrikes. The main undercarriage units swing towards each other to be stowed but due to their great height also need to contract in length telescopically before swinging to clear each other when stowed. 
The four main wheel tyres on each bogie unit are inflated to 232 psi (1,600 kPa). The twin-wheel nose undercarriage retracts forwards and its tyres are inflated to a pressure of 191 psi (1,320 kPa), and the wheel assembly carries a spray deflector to prevent standing water being thrown up into the engine intakes. The tyres are rated to a maximum speed on the runway of 250 mph (400 km/h). The starboard nose wheel carries a single disc brake to halt wheel rotation during retraction of the undercarriage. The port nose wheel carries speed generators for the anti-skid braking system which prevents brake activation until nose and main wheels rotate at the same rate.
Additionally, due to the high average take-off speed of 250 miles per hour (400 km/h), Concorde needed upgraded brakes. Like most airliners, Concorde has anti-skid braking – a system which prevents the tyres from losing traction when the brakes are applied for greater control during roll-out. The brakes, developed by Dunlop, were the first carbon-based brakes used on an airliner. The use of carbon over equivalent steel brakes provided a weight-saving of 1,200 lb (540 kg). Each wheel has multiple discs which are cooled by electric fans. Wheel sensors include brake overload, brake temperature, and tyre deflation. After a typical landing at Heathrow, brake temperatures were around 300–400 °C (570–750 °F). Landing Concorde required a minimum of 6,000 feet (1,800 m) runway length, this in fact being considerably less than the shortest runway Concorde ever actually landed on, that of Cardiff Airport.
Concorde