The Rolex Caliber 3255 -

The Rolex Caliber 3255

It’s a very rare occurrence when Rolex gives in to peer pressure. Over the years, critics have poked fun at their overriding design ethos of slow and gradual evolution, rather than launching radically revamped versions of their trademark pieces or entirely new models altogether.

But their steady progression in developing their central core of watches into the very best they can be, while keeping their outward appearances tightly uniform, is what has made them so identifiable as a brand to such a wide cross section; everyone from horology fanatics to those with only the most passing interest can identify a Rolex at a glance.

However, they did not become the world’s most successful watchmaker by completely ignoring the winds of change when they blow hard enough. They managed to resist the trend for larger watches for longer than most, but eventually, even they had to concede it was one fad that showed no sign of going away.

Many of the old guard in the sports range, including such icons as the Submariner and the Daytona, were considered, at 40mm, just about big enough for a modern audience. The Yacht-Master II, launched in 2007, ushered in the new wave of bigger is better with a 44mm case, the largest in the fleet. And the latest release, the Sky-Dweller, weighs in with almost the same dimensions.

That was all well and good for the tough guy professional models, those pieces sold on their reputation for strength and robust reliability as much as their looks. But what about the dress watches? The elegant wrist adornments that have traditionally maxed out at 36mm?

Whereas a generation ago, 36mm was the ideal size for a man’s watch, these days it is considered very much a midsize, with more and more being bought by women.

So, Rolex finally embraced the shift and set about bringing their entire catalog into the 21st century. First up for the non-sports models was a reworking of the legendary Day-Date, the President’s watch. Making the leap from the age-old 36mm to 41mm in 2008, the newly christened Day-Date II represented more than just a bigger case. Its relative dimensions had changed too, with a thicker bezel and more muscular lugs taking away much of the graceful profile that had been its former calling card.

Its short-lived and only moderately successful production run was halted in 2015, when Rolex took another stab at bringing out a version of their flagship with a little more presence.

The Day-Date 40 and the Cal. 3255

The new President, known as the Rolex Day-Date 40, gives up a single millimeter to its predecessor, and is a fascinating blend of the traditional and the contemporary. Outwardly, it shares the styling and comparative proportions of the smaller watches in the range, all simply enlarged for a new era.

Inside however, and the engine that drives the brand’s most prestigious offering is out far beyond the cutting edge. Where the Day-Date II used a mechanism based very much on the venerable Cal. 3155, called the Cal. 3156, Rolex decided for this version, they might as well go all the way.

The Day-Date 40’s new movement, the Cal. 3255, was designed from the ground up to be better, lighter, more reliable and more efficient than its predecessor. Every element of the outgoing Cal. 3156 was analyzed for improvements, and more than 90% of them replaced.

The self-winding module was completely reworked, with new reversing wheels and a monobloc rotor mounted on ball bearings allowing for faster winding of the high capacity mainspring, giving a much increased 70-hour power reserve. The spring itself is housed inside a barrel with walls half the thickness as before, to accommodate its larger size.

The oscillator is now fitted with the Parachrom Bleu hairspring with an optimized Breguet overcoil. Made from a niobium and zirconium alloy that is impervious to temperature variations and magnetic interference, two of the biggest killers of mechanical watch accuracy, the Rolex patented component also offers up to 10 times more shock resistance than previous hairsprings.

Using the latest precision, microstructure manufacturing techniques such as LiGA, the geometry of the large balance wheel has been redesigned, leading to a threefold enhancement in poise, regulated by four gold Microstella screws.

Rolex even developed and synthesized its own lubricants to keep the new gear train running smoothly and reduce wear and tear. Unlike any other mechanical watchmaker, modern Rolexes can now go 10 years between services.

The Chronergy

But the most significant improvement came in the shape of an entirely revised and upgraded escapement. Although still based, very loosely, on the traditional Swiss Lever Escapement used by the vast majority of manufacturers, the Cal. 3255 has gone a long way to addressing the system’s inherent flaws.

With the conventional escapement mechanism, which has been around in one form or another for over 250 years, about two thirds of the energy it receives from the mainspring is lost.

The Chronergy Escapement, Rolex’s redesign of the antiquated arrangement, has an improved efficiency of 15%—achieved with the brand’s usual innovative approach and obsessive attention to detail.

The Chronergy’s two main components, the escape wheel and the pallet fork, have both been heavily reengineered. The escape wheel has been skeletonized, cutting out as much of the structure as possible to reduce its weight and, consequently, its inertia. To preserve its former strength, it has been constructed from a nickel-phosphorous compound, also making the component paramagnetic.

The synthetic ruby stones on the pallet fork have been halved in thickness and now measure just 125 microns but, through a shift in the escapement’s alignment and a reworking of the teeth on the escape wheel, the contact surfaces between the two have doubled.

Superlative Chronometer

As well as rewriting the rulebook for mechanical calibers with the Cal. 3255, Rolex also rewrote the parameters for their accuracy.

The brand’s watches have carried the Superlative Chronometer mark for decades, identifying them as having passed the stringent tests set down by the COSC, the Official Swiss Chronometer Testing Institute. To do so, they must prove themselves accurate to within +4/-6 seconds a day, over a 15 day period in a number of different temperatures and positions.

Deciding that wasn’t challenge enough, Rolex tightened up the regulations for themselves, taking the allowable variance down to +2/-2 seconds a day, and testing each movement twice; once as a separate unit and again after it was fitted inside its case.

The Cal. 3255 was the first of the breed to endure these particularly severe tests, and the traditional red tag signifying the previous certification has been replaced with a new green one.


By updating the venerable President and embracing the fashion for bigger watches, Rolex has brought a fresher, younger following to the all time classic.

The Day-Date 40 is a very special version of a very special watch, one that is perfectly in keeping with the trends of a new century. So it is only fitting that it is powered by the most advanced mechanical movement of its type. The culmination of everything the most progressive manufacturer in the world has learned in more than a century at the top, it stands as a true masterpiece of the watchmaker’s art.

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