Mercedes-Simplex 40 hp racing car, 1902
Following the success of the Mercedes 35 hp, chief designer Wilhelm Maybach and his engine developer Josef Brauner immediately set about making further technical improvements to the successor model for the following year on the basis of the successful basic concept. To make these improvements clear at first glance alongside the now established Mercedes name, the brand name for the 1902 model year was given the addition "Simplex" - the Latin word for "simple", which emphasised ease of operation.
Development work initially centred on the four-cylinder engine. Its displacement was increased from just under 6 to a good 6.5 litres thanks to a slightly larger bore and significantly longer stroke. The two lower camshafts were encapsulated at the same time. The maximum output of the engine, which now only had one carburettor, increased by 5 hp/3.7 kW to 40 hp/29 kW at an unchanged rated speed of 1000 rpm.
To take account of the increased performance, an ingenious method was devised in Cannstatt to further improve engine cooling: the flywheel, which rotated at crankshaft speed, was designed as a fan wheel, encapsulating the engine compartment at the bottom and thus creating a strong suction effect on the air flowing through the radiator. The increased cooling air flow rate in turn resulted in more efficient cooling.
The brake system was also adapted to the higher performance of the Mercedes-Simplex 40 hp. Although the time had not yet come for a front brake, an additional foot brake improved the deceleration performance. In addition to the hand lever-operated inside shoe brakes on the rear wheels and the foot-operated outside band brake on the transmission output shaft, there were now two additional outside band brakes that acted on the drive shafts of the sprockets. These could be operated separately from each other, which gave a skilful driver who knew how to handle the complex system certain traction advantages when cornering. The brakes were even equipped with water cooling to increase their thermal load capacity. During the braking process, individual droplets fell from a reservoir onto the friction surfaces.
In order to further improve the handling characteristics of the Mercedes-Simplex 40 hp, Maybach extended its wheelbase by 205 mm to 2450 mm compared to the 35 hp model. In conjunction with a reduced vehicle weight of 942 kg, this measure resulted in handling that was as stable as it was light-footed.
Just how purposeful the development work of Maybach and Brauner had been was demonstrated by the first motorsport appearances of the Mercedes-Simplex 40 hp at Nice Race Week in April 1902. At the Nice-La Turbie hill climb on 7 April, which marked the start of that year's race week, the four 40 hp cars driven by the British driver E. T. Stead, Frenchman Albert Lemaître, the previous year's winner Wilhelm Werner and Frenchman Henri Degrais took 1st, 2nd, 3rd and 5th place. The same placings were also achieved in the mile and kilometre races on 13 April; here the order was Degrais - Werner - Lemaître - Stead. Degrais achieved a speed of 103.4 km/h with a flying start - an improvement of no less than 17 km/h compared to the performance of the previous year's Mercedes 35 hp model. The only competitions during the week in Nice in which the new Mercedes did not win were the sprint races for the Coupe Rothschild and the inaugural Coupe de Caters. Léon Serpollet, whose new steam car Oeuf de Pâques ("Easter egg") boasted a streamlined body and reached 120.82 km/h over the flying kilometre, won again. The same speed was recorded for Baron Pierre de Caters in a Mercedes-Simplex 40 hp at the kilometre race in Ostend, Belgium, in July.
The car was no less successful when it came to reliability as it was in terms of speed. In the Paris - Vienna long-distance race from 26 to 29 June 1902, which covered a total of 1429 kilometres (312 kilometres of which were neutralised through Switzerland), US-born Eliot Zborowski finished first in the heavy class in a Mercedes-Simplex 40 hp, shortly after Marcel Renault in a Renault in the light class. However, Zborowski, who was taking part in his first major race, was stripped of his class victory and second place overall, when an unscheduled 48-minute stop in the neutralised stage was added to his driving time, much to the amazement of the public and the trade press. Due to this incomprehensible measure, Zborowski slipped to 5th place in the overall classification and also lost his victory in the heavy class - but this should not detract from his remarkable performance in this race.
The Mercedes-Simplex 40 hp also made headlines at the Semmering Race in September 1902 - the popular hill climb over 10 kilometres and 400 metres in altitude from Schottwien to the Semmering, which was held for the fourth time. Driving the car of US millionaire and automobile enthusiast Clarence Gray Dinsmore, Wilhelm Werner set a new track record of 10 minutes and 37.2 seconds, or 56.5 km/h, to win the overall classification. Dinsmore won the challenge trophy donated by Theodor Dreher for the best time across all categories.
The 40 hp car also achieved another remarkable success in the Paris-Madrid race in May 1903, which was unusual in many respects and stopped by the French authorities in Bordeaux due to a series of fatal accidents: at the early finish after 552 kilometres, Eugen Max and his Mercedes-Simplex 40 hp were in 15th place among the 110 participants who had made it to the stage finish. The only faster Mercedes drivers were John B. Warden with 60 hp (5th place), Gastaud with 60 hp (8th place) and Camille Jenatzy with 90 hp (14th place). The trade press rated the performance of the 40 hp very favourably: "The performance of the 40 hp car should actually be the pride of the Daimler factories. This is because the 40 hp Mercedes car managed to work its way into a position that, on the basis of its engine power, it should not have claimed. Just look at how many remained behind this 40 hp, and how few there were in front of it! It's fair to say that the performance of the 40 hp Mercedes in this race is one of Daimler's greatest triumphs."
Much like its predecessor, the Mercedes-Simplex 40 hp only enjoyed a short-lived motorsport career, as two new high-performance cars, the 60 hp and the 90 hp, became available the following year.