Standard 10 axle

The Standard 10 rear axle of the Lotus 7 Series 2 is probably the most controversial component of the car. Colin Chapman’s concept of a lightweight, live axle with a simple A-frame to provide longitudinal and lateral guidance gives a performance that is close to an independent suspension. The concept is brilliant, but its implementation is doubtful. Had the axle been suspended the way it was designed for, no doubt it would be capable of handling the most powerful Series 2 Sevens. However, Colin Chapman’s concept supports the axle in a manner it was never designed for, leading to frequent failures, also on the not so powerful cars. One problem is that the suspension introduces large torsional loads on the axle casing leading to cracks and oil spillage, and subsequently seizure of the differential. The addition of the Thesaurus plate helped that problem to some extent.

To make things worse, the concept introduced large local loads where the A-frame is attached to the lower part of the differential casing. This led to a crack in SB2237’s casing as far back as in 1968, according to a previous owner. The crack was braze welded and doesn’t seem to cause any problems.

We treasure our Standard 10 rear axle which has caused no trouble since we bought the car. We inherited a minor problem caused by bad shimming  of the half-axle making it difficult to fixate the left rear hub. This problem was solved by our Lotus mechanic.

With our engine and tire selection we do think that our Standard 10 rear axle will survive. However, if we should ever think of reinforcing the axle, we are much impressed by the Standard 10 axles that Chris Beebe builds. Due to the requirements of the racing rules in the US it has been mandatory to use the original axle. Chris Beebe’s approach to support the torsional loads and relieving the loads of the A-frame attachment is very appealing and, most importantly, has proved its worth in practice.

Some critics may question the originality of the reinforced axle, though.

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