Tudor · Tudor MT5402

Tudor Black Bay 58 and Ranger power reserve: inside the MT5402

The Tudor Black Bay Fifty-Eight (from 2018 until its 2025 to 2026 update) and the 39 mm Tudor Ranger run on the Manufacture Calibre MT5402, which lasts about 70 hours off the wrist. That's just under three days, enough to cover a weekend in a drawer.

Updated September 2026 · Based on manufacturer specs, published reviews and watchmaker/owner reports

Watches that use the MT5402

Tudor built the MT5402 for one job: getting the Black Bay's in-house movement into a smaller, thinner case. It made its debut in the Black Bay Fifty-Eight in 2018, and it's the reason the BB58 is about 12 mm thick instead of the 41 mm Black Bay's 14.8 mm. It later went into the 39 mm Ranger. If your Black Bay 58 has a sapphire caseback, a GMT hand or "Master Chronometer" on the dial, it has a different movement; see the notes below.

The last two rows use the MT5400. The 36 mm Ranger introduced in 2025 also uses the MT5400, while the 39 mm Ranger keeps the MT5402.

Specs at a glance

History and where it came from

Tudor's in-house movement arrived in the 41 mm Black Bay in 2016 as the MT5602: 70 hours, COSC, silicon spring. It was a big upgrade on the ETA it replaced, but at 31.8 mm wide and 6.5 mm tall it made the Black Bay thick, and that was the watch's most common complaint.

For the Black Bay Fifty-Eight in 2018, Tudor shrank the design. Monochrome's review gives the numbers: 26 mm across and 4.99 mm high, against 31.8 mm and 6.5 mm for the MT5602, with the same 70-hour reserve, COSC certification and silicon hairspring. The result was a 39 mm diver about 3 mm slimmer than the 41 mm Black Bay, sized like the 1958 Tudor ref. 7924 it's named after. It became one of the most popular dive watches of its era.

Like the rest of the family, the MT5402 is a Tudor "Manufacture" calibre produced with Kenissi, the movement maker Tudor part-owns. In 2022 it replaced the ETA in the new 39 mm Ranger.

From 2025 Tudor began moving the Black Bay 58 to the MT5400-U, a METAS-certified version of its slightly larger sibling. The burgundy BB58 got it first, followed by the black-gilt model in 2026. So the MT5402 is on its way out of the Black Bay 58, while the 39 mm Ranger still uses it.

Accuracy in the real world

Every MT5402 is COSC-certified, and Tudor adds its own check on the finished watch: -2/+4 seconds a day, tighter than COSC's -4/+6. Monochrome's spec sheet for the Black Bay Fifty-Eight Navy Blue lists that -2/+4 adjustment.

Owners on watch forums generally report Fifty-Eights running a few seconds a day fast, well inside that window, and holding a stable rate. The silicon hairspring helps it resist everyday magnetism from phones, laptops and bag clasps, which is one of the commonest reasons a watch suddenly starts gaining. As with any mechanical watch, individual examples vary, and one that runs well outside -2/+4 while under warranty is worth sending back.

Reliability and servicing

The MT5402 shares its architecture with the MT5602, which has been in service since 2016, and there's no known systemic fault. The full-width bridge over the balance is designed for shock resistance, which suits a watch many people wear every day.

• Warranty. Tudor's current guarantee runs for five years.
• Servicing. Tudor's own network is the realistic route. Parts for the manufacture calibres aren't sold as freely as ETA or Sellita parts, so fewer independents take them on.
• Old versus new. A 2018 BB58 is a COSC watch rather than a METAS one, so there's no Master Chronometer rating to "lose" if an independent services it, but check they can source parts first.

Quirks worth knowing

• Thin, but not the thinnest. At under 5 mm, the movement lets the BB58 sit at about 11.9 mm. The newer Master Chronometer BB58 is 11.7 mm.
• No date. It's a true no-date movement, so there's no "ghost" crown position.
• Hidden movement. Steel Black Bay 58s and Rangers have solid backs. When Tudor wanted a sapphire back, on the 925 and 18K BB58s, it used the larger MT5400 to fill the view better.
• Winding from empty. A 70-hour mainspring needs a proper wind. Give it a good number of crown turns rather than hoping a quiet desk day will fill it.
• Reserve differences within the "58" name. The MT5402 BB58 is rated 70 hours, the newer MT5400-U BB58 65 hours, and the BB58 GMT's MT5450-U also 65 hours.

How it compares

• Tudor MT5602: the 41 mm Black Bay's larger, thicker movement with the same 70-hour, 4 Hz, COSC spec.
• Tudor MT5400: the same design at about 30 mm, used in the Black Bay 54, Pelagos 39 and now the Master Chronometer BB58.
• Rolex 3230: the Submariner No Date and Explorer's 70-hour movement, tested to -2/+2 cased. A similar reserve at a much higher price.
• Sellita SW200-1 / ETA 2824-2: what most vintage-style divers in this price range use. Easy to service anywhere, but only about 38 to 41 hours.
• Longines L888: the Longines equivalent of an upgraded workhorse, with about 72 hours and a silicon spring in current versions, but at a lower 25,200 vph beat.

Living with the 70-hour reserve

Seventy hours means a Black Bay 58 survives an ordinary weekend. Take it off at 6pm on Friday after a full day's wear and it's still running at about 4pm on Monday, so you can wear something else on Saturday and Sunday and pick up where you left off.

It's not a whole week, though. Swap your BB58 for a Ranger on Monday and wear that all week, and the Fifty-Eight will have stopped by Wednesday or Thursday. If you're putting it away, wind it fully by the crown first so you get the whole 70 hours. Watch Winder counts down this 70-hour reserve for each watch you own and reminds you before it stops. To check a specific gap, try the "Will my watch stop?" calculator.

Verdict

The MT5402 is what makes the Black Bay Fifty-Eight feel right on the wrist: all the specs of Tudor's bigger movement in a package that allows a slim 39 mm case. Seventy hours, a silicon hairspring, COSC certification and Tudor's -2/+4 target add up to a very capable daily watch. The main compromise is servicing, which mostly means going through Tudor. With the BB58 now moving to the METAS MT5400-U, an MT5402 Fifty-Eight or Ranger remains a slightly longer-running and entirely competent choice.

FAQ

How long does a Tudor Black Bay 58 run off the wrist?

An original Black Bay Fifty-Eight with the MT5402 runs for about 70 hours from a full wind. The newer Master Chronometer BB58 with the MT5400-U is rated at 65 hours.

Does the Tudor Black Bay Fifty-Eight hack?

Yes. The MT5402 stops the seconds hand when you pull out the crown to set the time, and it can be wound by hand.

How accurate is the Tudor Black Bay 58?

The movement is COSC-certified, and Tudor adjusts the finished watch to run within -2/+4 seconds a day. Most owners report results inside that range.

What movement is in the Tudor Ranger 39mm?

The 39 mm Ranger 79950 uses the COSC-certified MT5402 with a 70-hour reserve. The 36 mm Ranger introduced in 2025 uses the closely related MT5400.

What is the difference between the MT5402 and MT5400?

They're the same design at different sizes. The MT5400 is about 30 mm across against 26 mm, chosen for watches with display backs or different cases, but it keeps the same 70-hour, 4 Hz, COSC spec.

Why did my Tudor Black Bay 58 stop over the weekend?

It most likely wasn't fully wound. The 70-hour figure assumes a full mainspring, and light wear can leave it well short. Wind it by the crown before you put it down.

Sources

• Monochrome: Tudor Black Bay Fifty-Eight 39mm 79030N review
• Monochrome: Tudor Black Bay Fifty-Eight Navy Blue review
• Monochrome: 2022 Tudor Ranger 39mm 79950
• Monochrome: 2026 Tudor Black Bay 58 Black-Gilt Master Chronometer
• Monochrome: The entire Tudor Black Bay lineage, 2012 to 2024

Keeping it running

• On an average day an automatic gains roughly 4 hours of reserve per hour on the wrist, so about 18 hours of wear fills the Tudor MT5402. Desk days charge more slowly.
• Most automatics can also be wound by the crown. If yours has stopped, a few dozen turns gets it going before you put it on.
• Off the wrist it stops about 70 hours after it was last full. Stopped sooner?
• On a watch winder, start at about 650 turns per day, both directions. Winder settings for every movement.
• If it does stop, don't set the date between 9pm and 3am. Check if it's safe.

All Tudor movements · Other 70-hour movements

Never let it stop

Watch Winder counts down the reserve of every watch you own and reminds you before one stops. It already knows the Tudor MT5402: type your watch's name and the reserve fills itself in.

Manufacturer's published figure. Real reserve varies with the watch's age and service; check your manual.