The backbone chassis for the M-series cars was designed by automotive engineer and dealer Mike Bigland in 1971.
Bigland had been hired by Lilley after demonstrating a number of suspension and steering improvements he had made to a 1967 TVR Tuscan SE owned by one John Burton.
The chassis Bigland designed was of a central-backbone layout with perimeter tubes.
Both round- and square-section 14-gauge and 16-gauge steel tube was used in the construction, with the square sections used to allow easier joining of the frame to the body.
To facilitate production of the new chassis, Lilley upgraded TVR's workshop with fixtures that allowed two welders to produce five units per week.
During testing, Bigland drove the gold-painted prototype car between his own workshop in Halesowen and the TVR factory several times per week.

Unusual at the time, TVR offered a five-year guarantee against corrosion on the M-series chassis.
Corrosion was prevented by leaving a film of oil from the manufacturing process on the metal, capping the ends of the tubes, and fastening components without driving fasteners through the tube walls.

The radiator selected for the M series was shallow enough to allow locating the spare wheel in front of the engine; this improved luggage space behind the seats (where the spare wheel had been stored on pre-M-series models) and also offered some additional crash protection for occupants.
An M-series car was sent to the Motor Industry Research Association in 1971 for crash testing, and it was the only vehicle that remained steerable after a 30 mph (48 km/h) front-end collision with a concrete wall.
Indeed, the engine remained in position through the impact, the doors were still openable, and the steering column had actually moved forward (away from the driver.)
This last fact almost caused the MIRA officials to require that the car be re-tested, as they presumed that such as result was not possible and was a result of a fault with their measurement instruments.
Mike Bigland was able to demonstrate to the officials that the result was legitimate, and approval was granted.

The car's suspension was via double wishbones and coil springs front and rear.
Although the wishbones and aluminum hub carriers were an original TVR design, many components on the cars were sourced from other manufacturers.
The brakes, which were 11-inch discs at the front and 9-inch drums at the rear, came from the Triumph TR6.
Steering on all cars was via rack-and-pinion, with the rack manufactured by Alford & Alder.
The steering column was a British Leyland part.
Some components — such as the differential carrier and front suspension wishbones — were unique to TVR and manufactured in their own welding shop.

Because of production overlap between the M-series cars and earlier models, some earlier models were built with the pre-M bodywork over an M-series chassis.
This includes the last series of the TVR 2500 (comprising ninety-six cars; known in the US as the Vixen 2500 and not to be confused with the 2500M), all twenty-three Vixen S4s, and the final six examples of the TVR 1300 (which used the 1296 cc Standard SC engine from the Triumph Spitfire).
The very last 1300 was also built with M-series bodywork, although it was not officially given the "1300M" designation.
The backbone chassis for the M-series cars was designed by automotive engineer and dealer Mike Bigland in 1971. Bigland had been hired by Lilley after demonstrating a number of suspension and steering improvements he had made to a 1967 TVR Tuscan SE owned by one John Burton. The chassis Bigland designed was of a central-backbone layout with perimeter tubes. Both round- and square-section 14-gauge and 16-gauge steel tube was used in the construction, with the square sections used to allow easier joining of the frame to the body. To facilitate production of the new chassis, Lilley upgraded TVR's workshop with fixtures that allowed two welders to produce five units per week. During testing, Bigland drove the gold-painted prototype car between his own workshop in Halesowen and the TVR factory several times per week.
Unusual at the time, TVR offered a five-year guarantee against corrosion on the M-series chassis. Corrosion was prevented by leaving a film of oil from the manufacturing process on the metal, capping the ends of the tubes, and fastening components without driving fasteners through the tube walls.
The radiator selected for the M series was shallow enough to allow locating the spare wheel in front of the engine; this improved luggage space behind the seats (where the spare wheel had been stored on pre-M-series models) and also offered some additional crash protection for occupants. An M-series car was sent to the Motor Industry Research Association in 1971 for crash testing, and it was the only vehicle that remained steerable after a 30 mph (48 km/h) front-end collision with a concrete wall. Indeed, the engine remained in position through the impact, the doors were still openable, and the steering column had actually moved forward (away from the driver.) This last fact almost caused the MIRA officials to require that the car be re-tested, as they presumed that such as result was not possible and was a result of a fault with their measurement instruments. Mike Bigland was able to demonstrate to the officials that the result was legitimate, and approval was granted.
The car's suspension was via double wishbones and coil springs front and rear. Although the wishbones and aluminum hub carriers were an original TVR design, many components on the cars were sourced from other manufacturers. The brakes, which were 11-inch discs at the front and 9-inch drums at the rear, came from the Triumph TR6. Steering on all cars was via rack-and-pinion, with the rack manufactured by Alford & Alder. The steering column was a British Leyland part. Some components — such as the differential carrier and front suspension wishbones — were unique to TVR and manufactured in their own welding shop.
Because of production overlap between the M-series cars and earlier models, some earlier models were built with the pre-M bodywork over an M-series chassis. This includes the last series of the TVR 2500 (comprising ninety-six cars; known in the US as the Vixen 2500 and not to be confused with the 2500M), all twenty-three Vixen S4s, and the final six examples of the TVR 1300 (which used the 1296 cc Standard SC engine from the Triumph Spitfire). The very last 1300 was also built with M-series bodywork, although it was not officially given the "1300M" designation.
TVR M series