Audemars Piguet (AP) updates the Royal Oak Selfwinding Chronograph 38 mm with a new manufacture calibre, sapphire display back, while slightly tweaking the iconic design – and retaining the price of its predecessor.

The new cal. 6401 comes with welcome quality-of-life improvements such as a longer power reserve and instantaneous date without tradeoffs in wearability, beat rate, or even cost, making this compact chronograph one of the most sensible and compelling offerings in the Royal Oak line.

Initial Thoughts

AP debuted the first Royal Oak chronograph in 1997 and it was powered by the Frederic Piguet cal. 1185, a landmark movement for automatic chronograph design. Now, nearly three decades later, AP is a true industrialised manufacture, and the cal. 1185 has been replaced with the new cal. 6401, a modern movement that with meaningful upgrades under the hood.

This also comes with some minute tweaks to the dial and a crowd pleasing display case back, while the case and bracelet remain as excellent as always. Laudably, this comes without a significant price increase, with the new Royal Oak Chronograph 38 mm in steel costing only 3.6% more than its predecessor.

New Engine

AP’s new cal. 6401 is a solidly-spec’ed movement despite being small and thin for a modern chronograph. It’s wide and taller than the Frederic Piguet cal. 1185 but only slightly. It is 27 mm in diameter (up from 26.2 mm) and 5.7 mm tall (up from 5.5 mm) though even with the addition of a sapphire case back the watch is only 0.1 mm taller.

The cal. 1185 (left) and the new cal. 6401

Despite the negligible change in dimensions, the new Royal Oak Chronograph will run for 15 hours longer than its predecessor (for 45 hours total), at a higher beat rate, and with an instantaneous date change.

The cal. 6401 is also equipped with a free sprung balance that looks to have a greater mass than the previous calibre, though AP hasn’t disclosed exact figures. It also features a balance endshake adjustment system, and more tenacious ball bearing support for the rotor.

It is worth mentioning that the calendar can be quickly corrected using the crown, unlike Patek Philippe’s automatic chronograph movement with a date.

For now the new movement is only available in three models: steel with the Royal Oak’s signature “Bleu Nuit, Nuage 50” hue dial, in 18k pink gold with grey dial, or the same with a brilliant cut diamond bezel (40 stones, 0.92 carats) and a sand gold dial.

However, according to AP, the cal. 6401 will also come to the Royal Oak Offshore line later this year.

New Dial

The dial has been redesigned to accommodate the cal. 6401, and the chronograph operating buttons are slightly further apart.

All three sub-dials are slightly further from the centre, while the sub-dials for the hour and minutes totalisers are swapped and sit slightly higher on the dial, leaving them no longer aligned with the six and nine 0’clock markers – giving the dial a layout similar to the Rolex Daytona with the cal. 4130.

AP also recalibrated the seconds scale hash marks to suit the 4 Hz beat rate of the new movement. Also, date window is now halfway between the four and five o’clock markers – it previously abutted the latter.

The outgoing model on the left and incoming on the right. Images – Audemars Piguet, composite by the author

Key facts and price

Audemars Piguet Royal Oak Selfwinding Chronograph 38 mm
Ref. 26450ST.OO.1356ST.01-B (steel)
Ref. 26450OR.OO.1356OR.01-B (pink gold)
Ref. 26450OR.ZZ.1356OR.01-B (pink gold with diamonds)

Diameter: 38 mm
Height: 11.1 mm
Material: Stainless steel or 18k pink gold
Crystal: Sapphire
Water-resistance: 50 m

Movement: Cal. 6401
Functions: Hours, minutes, running seconds, chronograph with minute and hour totalisers
Winding: Automatic
Frequency: 28,800 beats per hour (4 Hz)
Power reserve: 72 hours

Strap: Metal bracelet in same material as case.

Limited edition: No.
Availability: At AP boutiques, AP houses, and Authorised Retailers
Price: US$43,000 in steel, US$84,500 in 18k pink gold, and US$91,600 in 18k pink gold with diamonds, before taxes

For more information, visit Audemarspiguet.com.