It was an era focussed on making Mercedes affordable to the masses. This design approach utilized an economy of design in commonality of the design features and parts spanning different strata of models. The same fundamental suspension design would span from the basic W114/115 sedans to the SL's. This enabled the building of the same quality into the cars regardless of the particular strata of the vehicle. Granted, there were certainly different comfort and performance differences between a 115 sedan and a R107 SL, but you had the same level of quality in these cars to enable them to last a very long time.

Now, longevity and quality was certainly present in the earlier W111's & W108's, but there was a more mass-oriented balance of quality and performance in the /8 era. The trailing arm rear suspension design of the /8's was far superior to the earlier swing-axle design. Better comfort and far improved nimble and agile handling. The front axle design also had improved comfort and handling over the earlier king-pin design, was cheaper to manufacture, and is easier to work on.

I think of this era as the pinnacle of 'balance in design'. As we move further beyond the /8 era to the W123's and on, the various strata in the Mercedes line no longer have the same level of functional quality built into the cars. We see more and more troublesome plastic interior components sprinkled all over. Stuff that cracks, develops rattles and breaks. Another problem compounding this era is that of contradictory markets. There were quite a number of W114's sold in the US market, but not so many W115's. The 4-cyl cars were viewed as underpowered in the US, so the vast majority of the US cars were 6-cyls evn though the 4-cyl makes much better fit and weight balance for maneuverability. This aspect of the US market complicated the Mercedes for the masses idea somewhat. The 6-cyl is a bit of tight fit in a 114. By the time you've added A/C & P/S, you've got a bit of a problem with air flow and cooling in hot climates. That setup isn't so easy to work on either. In a way, the US market pushed aside the functionalism of an affordable Mercedes quality for cars with more amenities. Amenities that would make proper maintenance more expensive especially over the long term in years.

I've owned a W111 220Sb, a W108 250S and a W115 220, and I think the W115 represents the best balance in functional quality, utility and comfort. I can drive that car quite nimbly over the nastiest bumpy, ragged winding mountain roads and it is quite happy. I couldn't do that with my 108 despite both having all the suspension bushings, king-pins/ball joints, Bilsteins all re-done. The 108 had a bit more comfort on the open freeway at 80 mph, but not a lot. I take a late model R129 on these same ragged mountain roads, and I've got lots of power, but the car is just not that happy with that terrain. It needs decent roads, but feels great and quite assured at 100 on a good road. There is still an element of balance in this later high end design, but it's no longer a realm acessible to the masses, nor will this $100k level car be around at 30-40 years of age.

There have certainly been a number of advances since the 1970's, but these have been implemented in more complex cars. These cars come with extra baggage that will be their death knell. The 70's was the end on the simple car era. In those cars, you still had the same level of functional quality as in the 60's & 50's cars and had the technical advances in the suspension design which was different from the earlier cars.

I'll say one thing about all the Mercedes I've ever owned or driven. This is that in the balance of their design, you get a vehicle that handles predictably in ALL circumstances, no matter what, as much as possible within the design technology of the time. They will not put a 350+ bhp motor in a car that does not have a suspension that is up to the task of maneuvering the car. There have been numerous nonsensical violations of this principle in US made cars over the decades. That is truly a design embarrassment that I think the US mfrs are STILL trying to work out of. Man that's embarrassing.