All MGBs used semi-elliptic leaf springs at the rear, with hydraulic lever arm Armstrong shock absorbers. The rear suspension specification changed at several points across the production run, with differing spring rates, leaf counts, and hardware between model years and body styles.
Rear Spring History
The original Roadster springs had six leaves without any interleaving, but from car number 11313 in May 1963 interleaving was added, and at the same time the springs were made slightly softer to lower the rear end of the car. The GT model in 1965 was given seven-leaf springs to offset the car’s increased weight at the rear. On the MGB GT V8, the only difference to the rear springs compared with a four-cylinder GT was that the load rating was slightly higher. Important modifications to the rear suspension occurred in September 1974 from the start of rubber bumper production.
As it became necessary to increase the ride height of the four-cylinder cars to meet US bumper height legislation, the rear spring hangers were slightly lowered and the rear springs were stiffened, while the rear shock absorbers were also revised and given longer links. The ride height of the V8 was not altered.
From the start of rubber bumper production, the Roadster was equipped with the GT-type seven-leaf springs, although the Roadster reverted to six-leaf springs in September 1975. The adverse comments incurred by the inferior handling of the early rubber bumper cars undoubtedly influenced the decision to fit, belatedly, a rear anti-roll bar, which was introduced from the start of the 1977 model year in June 1976. It is not possible to fit the rear anti-roll bar to earlier cars without extensive welding and fabrication of suitable brackets. Rear spring condition is one of the most common causes of vague, wallowing handling on an older MGB, a car that leans noticeably to one side is frequently suffering from nothing more than tired springs.
Springs should always be replaced in pairs, as replacing one alone results in uneven ride height and a handling imbalance.
Rear Suspension Components
Parabolic leaf springs are available for chrome bumper Roadster, chrome bumper GT, rubber bumper Roadster, and rubber bumper GT, with a Special Tuning uprated spring also available. Parabolic springs use a tapered profile that allows each section to flex proportionally, absorbing small road imperfections while retaining load-bearing capacity, providing a significant improvement in both ride quality and tyre contact over the standard multi-leaf items. Small bumps that do not generate sufficient force to flex a conventional multi-leaf spring are transmitted as shock through the still-rigid springs to the occupants; the parabolic design addresses this directly. Parabolic spring kits must be fitted in conjunction with telescopic rear shock absorbers.
Spring kits supply matched pairs for all variants with standard or uprated polyurethane bushes, covering banjo and tube axle chrome bumper Roadster, chrome bumper GT, rubber bumper Roadster, and rubber bumper GT applications. Spring fitting kits supply all hardware for complete installation on banjo and tube axle cars, in standard and polyurethane bush versions. The spring hanger arrangement differs between chrome and rubber bumper cars, an important detail when ordering hangers and associated hardware. Front spring eye bushes are available in standard rubber and polyurethane.
Rear spring shackle kits supply the shackle with all hardware, with bushes available individually in rubber and as a polyurethane car set. Spring locating plates for banjo and tube axle, spring pads in rubber and polyurethane, U-bolts for both axle types, bump rubbers and bump rubber pedestals for both axle types, and axle check straps for chrome and rubber bumper cars are all available. Rear shock absorber mounting brackets for right and left hand sides are available for early and later cars.
Shock Absorbers & Rear Anti-Roll Bar
Rear shock absorbers are available as reconditioned exchange units in standard and uprated specifications, the uprated units providing improved damping for more responsive handling. The adjustable Armstrong damper valve allows owners to tune the damping rate of existing units without full replacement. Rear damper gaskets and shock absorber link assemblies are available separately for chrome bumper MGB, rubber bumper MGB, and V8 applications, as the link arm specification differs between these variants, chrome bumper and rubber bumper link arms are distinct items and not interchangeable. The rear anti-roll bar for rubber bumper cars from September 1976 and the MG RV8 specification bar are available alongside all associated mounting hardware, end joint and eye bush, locator end stop kit, centre bushes in standard rubber and polyurethane, bearing straps, and all fixings.
Anti-roll bar centre bushes in 11/16-inch specification are available in rubber and as a polyurethane pair.