Fiat 125

In the mid-1960s, Fiat's mid-size models, the 1500 and 1800, were becoming outdated, while their intended replacement, the Project 132, was still at an early stage of development.

As an interim solution, engineer Dante Giacosa proposed combining existing components to create a new model. The design used the platform of the Fiat 1500, the central body structure of the Fiat 124, and newly designed front and rear sections. It also incorporated an updated version of the twin-cam engine from the Fiat 124 Sport. Eighteen months later the resulting model was the Fiat 125, introduced at the 1967 Geneva Motor Show.

The Fiat 125 was powered by a 1,608 cc inline-four engine with a square configuration, derived by increasing the stroke from 71.5 mm to 80 mm. In its initial version, the engine produced approximately 90 horsepower but achieved at 5600 rpm instead of the 6500 rpm of the 1,438 cc version. This improved torque distribution and smoothness of delivery. The technical package was completed by the four disc brakes, vacuum brake servo, and the four-speed, all-synchronized gearbox equipped with Porsche-type synchronizers, which gave excellent results in terms of handling. The gear ratios were designed with intensive use in mind, even on the highway. The top speed in third gear was 125 km/h compared to around 100 km/h for the 1500 C.

The car, using existing components, was rapidly developed and the first prototypes began to be tested as early as the winter of 1966. The suspension layout followed that of its predecessor, with slightly wider tracks. The rear suspension, derived from the Fiat Dino and later used for the 131, 132, and Argenta models, consists of a rigid axle that remained essentially the same as the 1500 C, but the anti-roll bar present on its predecessor was removed, replaced by a pair of longitudinal rods connecting the axle to the floorpan, used to improve steering precision. Fiat emphasized this detail in the brochures for the various versions of the car, referring to a so-called "wishbone layout."

The Fiat 125 was officially shown in May 1967, three months ahead of schedule. The car was immediately well received by both the public and critics. The interior, spacious and fitted with high-quality materials, and the bodywork, which had been expertly retouched to enhance its "prominence", were a hit with the public. It was one of the few cars in its class with a passenger compartment free of exposed sheet metal. After many years of "absence," the 125 marked the return of the circular instrumentation. Customers also appreciated the model's brilliant performance and overall robustness, although they lamented the lack of a fifth gear unlike its "rival," the Giulia Super. The 125 was one of the very first cars to feature intermittent windshield wipers as standard. From late 1967, an electronic rev counter was available as an option only. Other options available on request for the new Turin sedan are the anti-theft "steering lock", the white sidewall tires, the car radio and the semi-automatic "Idroconvert" transmission (which works in a similar way to the one already offered on the "850").

The chassis used was the same as that of the longer variant of the outgoing model, the 1300/1500, and the floor pan was virtually unchanged from it. The body was a slightly lengthened development of the Fiat 124: the two models had the same passenger compartment and doors, but the 125's rear seat was set slightly further back, reflecting the longer wheelbase, 85 mm (3.3 in) longer than that of the 124, inherited from the Fiat 1500 C.^[3]

The new car's engine was based on the one fitted in the Fiat 124 Sport:^[3] a 1608 cc DOHC unit with 90 PS (66 kW; 89 bhp) driving the rear wheels. The 125 was equipped with a Weber 34 DCHE 20 or Solex 34 PIA carburetor. The car was fitted with an alternator,^[3] reflecting the twin headlights and the increasing number of energy intensive electrical components appearing on cars at this time. Other noteworthy features included the electromagnetic cooling fan clutch which was prone to failure and was replaced with a normal cooling fan system.^[3]

A four-speed manual was standard for all 125 models built from '67 through '72, while the S and Special versions had the five-speed manual as standard. The Special could be optioned with a three-speed GM TH300 (Trimatic) transmission.

Available for the 125 between '68 and '69 was a Idroconvert four-speed gearbox which was a semi automatic gearbox along the same lines as a 'Sportomatic' Porsche. The clutch is electric and is actuated by a switch on the top of the shifter, which means that the car can start in first, second, third or fourth gear and when you stop on a red traffic light you can keep the car in gear with your foot on the brake and the engine will idle. When you want to go again you just press on the accelerator like in a "normal" automatic car. While you are in fourth gear, if you would like to pass a car, you can downshift in to third or even second gear, just using the shifter lever. A very rare option, with very few units having been built and an option that is not featured neither in the driver's manual or the shop manual of this model, with only a couple of period auto magazine articles attesting to its existence.^[4][5]

The 125 featured one of the world's first intermittent wipers and was praised when new for its handling and dynamics. British Autocar found the slight understeer tendencies were easily cured by adjusting the front camber.

In 1968 the 125S was added to the range, with 100 PS (74 kW; 99 bhp) (from a modified cylinder head, camshafts, inlet/outlet manifold and Weber/Solex carburetor) and, unusually at this time, a five-speed gearbox.^[6] It also had halogen lights, servo-assisted twin circuit brakes and optional superlight magnesium wheels. A variety of other improvements were made including improved cabin ventilation, trim and styling. The S had black leather dash trim instead of faux wood and a different style center console which was made to accommodate the new five-speed location. The S body differentiates from the standard version by being slightly shorter and slightly wider.

The Special received a facelift late 1970, using pretty much the same trim as the 125S, but the visual width of the car was enhanced by a wider grille (the indicators moved from the side to the bumper) and by replacing the square rear lights with larger, horizontal ones.^[7]: 24 The interior gained upgraded upholstery of the seats and a wood facia. A three-speed GM automatic transmission as well as air conditioning, sunroof and rear window defroster became available as an option.

A variant, the 125 T, was made by the Fiat importers in New Zealand, Torino Motors, for the annual 6 hour production car race, the Benson and Hedges 500.^[8] The 125T has larger valves, two twin Weber DCOH or Dell'Orto 40DHLA carburetors (depending on availability), modified camshafts and a higher compression ratio to produce around 125 bhp (93 kW), lowered and stiffer suspension.^[8] All featured Ward alloy wheels and were painted bright yellow.^[8] Sources for production figures quote that between 84 and 89 were modified.^{[citation needed]} Reasons for stopping production are sometimes given that Fiat headquarters found out and stopped this venture.^[8] However a more likely scenario is that selling the required 200 cars in a market that only sold 1,000 Fiats in total each year was a tall order.^{[citation needed]}

In South Africa he Fiat 125 OTS Scorpion was built by local tuner Alconi Scorpion of Pretoria, based on the chassis of the base Italian sedan. It had a 1608 cc engine with power increased to 125 DIN hp (at 6,300 rpm) thanks to new camshafts, two twin-choke Weber 40 DCOE carburetors, and new intake and exhaust manifolds. The top speed was claimed to be 172 km/h and it accelerated from a standing start to 400 m in 16.1 seconds. The transmission had only 4 gears. The steering column was also lowered for a sportier driving position. The company offered the option of further modifications to reach power outputs of up to 190 DIN hp for track use.

Other versions were built by Moretti, who made the 125GS 1.6 with styling similar to the Fiat Dino Spider. Zagato made the 125 GTZ; Savio, a 125 Coupé and 125 Station Wagon; Bertone, a 125 Executive to a Marcello Gandini design; and Vignale produced the Samantha, a two-door coupé with pop-up headlights, designed by Virginio Vairo. Another 125 Station Wagon was built by OSI to a Sergio Sartorelli design.

Production by Fiat in Italy ceased in 1972 when the Fiat 132 was introduced, a total of 603,877 cars having been built^[7]: 24, although it continued for many years in different markets.

The Fiat 125 also achieved success in rallying and endurance events, where its durability and reliability contributed to strong results, often with few mechanical retirements. In racing specification, the engine output reportedly reached approximately 145 horsepower. Its performance helped reinforce Fiat's renewed involvement in motorsport, including support for private entrants.

One notable result came in the 1969 24 Hours of Nürburgring, where a Fiat 125 driven by Ratazzi, Luca Montezemolo, and Ceccato finished ninth overall. The car was reportedly close to standard specification.