The Tudor Black Bay Chrono has long been one of the most compelling chronograph bargains on the market. Beneath the dial is the Breitling B01-derived movement, one of the most competent modern automatic chronograph movements in serial production, paired with Tudor’s own free-sprung balance with adjustable inertia weights and a silicon hairspring. As far as I’m aware, no other chronograph at this price offers quite the same combination of movement quality, technical specification and everyday reliability. There was, however, always a catch. At 41mm in diameter and 14.2mm thick, it was also a watch that asked for a fair amount of wrist.

Tudor has finally addressed that. The new Black Bay Chrono shrinks the case to 39mm while trimming its height to 13.1mm. But more than that, it has chosen to introduce the smaller chronograph in perhaps the most eye-popping guise imaginable. The new model arrives with a bright yellow dial and contrasting black registers. The familiar Snowflake hour hand remains but has been subtly shortened so it interferes less with the chronograph registers. The hands and applied dot markers are coloured black to match the watch’s accents and are filled with Grade A Super-LumiNova for maximum legibility.

The case is stainless steel with an anodised aluminium bezel insert. Screw-down crown and pushers along with a 200 metres of water resistance remain part of the package, giving the Black Bay Chrono a level of ruggedness uncommon among chronographs in this class. One detail enthusiasts may appreciate is the revised knurling on the pushers, a subtle nod to Tudor’s Mk II Series 7100 chronographs of the 1970s.

Just as importantly, Tudor has left the movement alone. Inside remains the MT5813, with its column wheel, vertical clutch, 70-hour power reserve, free-sprung balance and silicon hairspring. Those specifications have become familiar enough, but what is easy to miss is how thoughtfully engineered the calibre is.

Unlike many vertical clutch chronographs, the fourth wheel drives the running seconds display directly at 9 o’clock, while the vertical clutch sits at the centre of the movement. Bridging the two is an intermediate pinion that transmits power to the central chronograph seconds wheel. Rather than using a conventional gear, the pinion features split teeth whereby two elastic halves can deflect slightly relative to one another. This eliminates backlash and helps ensure that the chronograph seconds hand starts cleanly and remains stable in operation.

The reset system is equally clever. It uses a patented articulated assembly in which the hammer is connected to the reset lever through a pivot and an elongated guide slot. This allows the hammer a small degree of freedom relative to the lever during reset and ensures its faces settle naturally against heart cams while maintaining sufficient force to return both counters cleanly to zero.

COSC certification guarantees a daily rate variation of -4/+6 seconds, but Tudor applies a more stringent standard to the completed watch. The Black Bay Chrono is adjusted to run within -2/+4 seconds. It may not be a Master Chronometer, but the part most susceptible to magnetic fields in the regulating organ, the hairspring, is made from silicon. Being diamagnetic, it is effectively unaffected by the magnetic fields that have become an unavoidable feature in life.

Lastly, the bracelet is equipped with the practical T-fit clasp with a ratcheting micro-adjustment feature. In five positions, the bracelet can be extended or shortened by 8mm.

Tudor Black Bay Chrono 39 “Bumblebee”

Movement Automatic Caliber MT5813; 70-hour power reserve; 4Hz or 28,800vph
Functions Hours, minutes, small seconds, date and chronograph
Case 339mm x 13.1mm; stainless steel with anodised aluminium bezel insert; sapphire crystal; screw-down crown and pushers; water-resistant to 200m
Dial Yellow with black registers; black hands filled with Grade A Swiss Super-LumiNova
Bracelet Stainless steel bracelet with T-fit clasp
Availability Regular production; available now at Tudor boutiques and authorised retailers
Price CHF 5,500