A similar low-tech approach is the king-pin arrangement (as used on MG's). It has all the technology of a door hinge. The suspension upright is align-bored vertically (actually at a slight incline or king-pin inclination angle) and a hinge pin slipped in place. At the bottom of the pin was a steel boss that was cross drilled fore and aft to accept a bolt for the outer control arm pivot... very much like a trunnion. At the top of the king-pin, another cross-drilled boss could be bolted on, or a trunnion, or go crazy and use a ball joint.

So why did a leading edge sportscar like Lotus use trunnions? Chapman was masterful at using found parts... Parts Bin Engineering. Way back when, the Standard-Triumph suspension bits were readily available to the English motor industry, they were relatively light, they had the "right" geometry and they were widely used in early racing cars and specials. Yes, they used trunnions, but they worked effectively, so why NOT use them.

Back in 1972, when the Elite/Eclat were penned, Triumph was still a current English car manufacturer and Lotus continued to rely on the same suspension bits. 25 years after the fact, you might question the wisdom of the decision to keep trunnions in a new design (the Elite), but that's what they did. Lotus was going through a very dangerous time for them. They were just barely keeping the wolves away from the door, regulations were forcing them to abandon production of all current designs, they had just taken on the design of their own proprietary engine concurrent with the design of a new, more complex up-market car, and they'd cut the work force by more than half. They were meeting themselves coming and going. I think that if something worked, they didn't bother to re-invent it. They had enough to do. And lord knows that Lotus's suspension had never come under too much criticism. Once the car was designed that way, it was not likely to be changed unless something was very wrong. Lotus at it's biggest was a small, low-volume company. Fixing what wasn't broke just wasn't in the budget.

Lotus' first attempt a getting away from trunnions was the S1/S2 Esprit where the front suspension bits all came from the Opel Ascona complete with ball joints. That suspension never really worked as well as was hoped, and the Turbo/S3 chassis was re-designed to a suspension based closely on the then current Elite/Eclat design. Complete with trunnions. It wasn't until the 1985 model year that the trunnion finally was designed out, replaced by a ball joint. This happen at the time of a redesign that eliminated the front anti-roll bar's function as part of the lower a-arm. A new proper a-arm with a ball joint was introduced along with a separate anti-roll bar.

The only significant disadvantage to trunnions is that you only have two degrees of freedom... two pivot axis. There is no back and forth freedom for changing castor. What ever is built in is what you must live with. But that was okay with Colin Chapman. He intentionally made the suspension non-adjustable so that un-informed shade tree mechanics couldn't screw it up. I don't remember the exact quote, but he said something to the effect of, "See how much damage an idiot armed with a screwdriver can do to a set of Webers in just a few minutes. Why turn him loose on the suspension."