Said the company’s Managing Director John Yea: “It is clear that the classic spares industry is beset with poorly produced replacement parts, many of which are safety critical items. The manufacture of leaf springs has recently suffered from overseas suppliers simply being asked to replicate original British items. The resultant products may fit, but that is where their suitability for purpose frequently ends. The examples we have tested had completely different spring rates (hardly surprising when leaves of equal thickness had been used in place of ones that were deliberately of varying dimension), and distorted alarmingly when subjected to load on a test rig.

“GB Springs Ltd has the technical expertise to correctly specify our springs and ensure the production items fully adhere to that specification. Our joint commitment to supporting the market has even led to us having imperial spring steel rolled in the UK, shipped abroad for the manufacture of springs, and the finished products then returned to the UK. This was necessary for the MG TC, TD and TF, for which no equivalent metric spring steel is available. This has required a significant commitment in terms of both expertise and working capital.”

Most British classic cars of the ‘60s and ‘70s rely upon the tried and tested leaf spring for their rear suspension. Its success in period resulted from its relatively low cost and simple adjustability to differing vehicle configurations. For example, the MGB has different specifications for the Roadster and GT and for both chrome and rubber bumper variants. They were derived by the models’ original engineers and then validated through extensive testing in all conditions.

The increasing weight and sophistication of modern cars has meant the once thriving domestic leaf spring manufacturing base is long gone. A further complication is the move to metric sizing for volume production, which has given rise to the considerable engineering challenge of matching modern materials and dimensions with period springs specified in imperial ones.

Concluded John Yea: “From hereon we will use the British Motor Heritage label on all our springs. This is the customer assurance that the product is as close to the original manufacturer’s specification as possible, and that the quality of the spring has been validated and therefore justifiably carries the original part number. Without this sign of authenticity, it is really a case of buyer beware.”