Wheels

SB2237 has had a number of different sets of wheels during its lifetime.

In 1968 it had Elan wheels, suggesting that it may very well have been delivered with these. As can be seen from the picture, no hubcaps were fitted, and the tires were quite narrow.

Later, likely when used for racing, it was fitted with American Racing Libre magnesium wheels and wider tires. These were on the car when it was brought back to the UK, but they were unfortunately lost (as was the  steering wheel) previous to the restoration.

When restored in 1993, the car was fitted with a set of new Minilite style wheels.

Although the Minilites were nice period wheels, we have since sourced a set of Elan wheels and use these both with and without Lotus hubcaps.

Finally, we have fitted 145/80 tires. Although these are probably close to the tires that were on the car when it was delivered back in the 1967, they do look a bit narrow, and we are thinking of increasing the tire width slightly next time. On the other hand, wider tires might not fit inside the narrow rear wings – and the Standard 10 axle is probably better off with as little grip as possible.

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.

Engine

We have learned from an early owner that SB2237 was originally delivered with a pre-crossflow engine with one Weber 40DCOE 2. During its life, the car has been equipped with a number of different engines, including Holbay and Cosworth racing trims.

Today, it is again equipped as when it was delivered, with a 1500 cc pre-crossflow engine and the single Weber mounted on the original Lotus alloy inlet manifold. The  manifold was kindly provided by a previous owner.

The performance of the basic engine is moderate, 66 HP at 4600 rev/min. Therefore, the ports of our engine have been enlarged and the combustion chamber has been flowed moderately. Also, humps and edges in the inlet manifold have been smoothed out and the exhaust is 4-2-1. Most importantly, the engine is equipped with a GT cam.

With the 0.06″ overbore our data show a power output of some 80 HP at 5200 rpm. Not a high revving engine but an engine with good midrange torque.

With this setup up the car is lively and has no hesitation during acceleration.