Tudor · Tudor MT5652 GMT

Tudor Black Bay GMT and Black Bay Pro power reserve: inside the MT5652

The Tudor Black Bay GMT and Black Bay Pro run on the Manufacture Calibre MT5652, a true traveller's GMT that lasts about 70 hours off the wrist, just under three days. The METAS-certified MT5652-U in the Pelagos FXD GMT and 2026 Northflag GMT is rated at 65 hours.

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

Watches that use the MT5652

The MT5652 is Tudor's GMT movement: the MT5602 base with a date and an independently set 24-hour hand added. It arrived in the Pepsi-bezel Black Bay GMT in 2018 and has since powered most of Tudor's dual-time watches, with a Master Chronometer version, the MT5652-U, appearing from 2024.

The Black Bay 58 GMT is different: it uses the thinner MT5450-U, also rated at 65 hours. And a Black Bay that shows a date but no GMT hand uses a different member of the family.

Specs at a glance

History and where it came from

Tudor's in-house movement family started in 2015, and the time-only MT5602 went into the Black Bay in 2016. At Baselworld 2018 Tudor added a GMT: the Black Bay GMT with a burgundy-and-blue bezel that looked deliberately like Rolex's "Pepsi" GMT-Master II, at a fraction of the price. Inside was the new MT5652.

It was a "true" GMT from the start, which was unusual at the price. The hour hand, not the 24-hour hand, jumps in one-hour steps, forwards or backwards, without stopping the watch. That's what you want when you land somewhere new: pull the crown out one step, click the local hour hand round, and the date follows it.

The GMT module added about a millimetre compared with the MT5602: 7.52 mm, against 6.5 mm. That's why the Black Bay GMT is about 15 mm thick, and why the 39 mm Black Bay Pro in 2022, despite its smaller diameter, is still around 14.6 mm.

In 2024 the Pelagos FXD GMT introduced the MT5652-U, with METAS Master Chronometer certification and a quoted reserve of 65 hours. The 2026 Northflag GMT uses the same version.

Accuracy in the real world

All MT5652s are COSC-certified, and Tudor regulates the finished watch to between -2 and +4 seconds a day, as Monochrome notes in its Black Bay GMT S&G review. The MT5652-U adds METAS testing of the complete watch to 0/+5 seconds a day, plus a 15,000-gauss magnetism test.

Owners on watch forums generally report Black Bay GMTs and Black Bay Pros running a few seconds a day fast. The silicon hairspring keeps them steady around everyday magnets. As with any mechanical watch, a particular example can be off; if yours is well outside -2/+4 during the five-year guarantee, send it back.

Reliability and servicing

The base movement has a long track record, and the GMT works have now been in production since 2018. Reader comments on Monochrome's Black Bay Pro review mention a date-wheel issue on earlier GMTs, which commenters describe as resolved. We couldn't find an official statement on it, but if you're buying an early Black Bay GMT, check that the date changes cleanly at midnight local time.

• Warranty. Tudor's current guarantee is five years.
• Servicing. Tudor's network is the realistic option. Parts for the manufacture calibres, and particularly the GMT works, aren't as available to independents as ETA or Sellita parts.

Quirks worth knowing

• Thickness. At 7.52 mm this is a tall movement. The Black Bay GMT is about 15 mm thick and the Black Bay Pro about 14.6 mm. If thickness bothers you, the Black Bay 58 GMT's MT5450-U is the slimmer option.
• Setting it. On a true GMT you set home time with the 24-hour hand and the minutes first, then jump the local hour hand to where you are. The date moves with the local hour hand, including backwards across midnight.
• Hacking. The seconds hand stops when you set the time, but moving the local hour hand doesn't disturb the running time.
• Date changes. As with most date movements, avoid setting the date by hand in the hours around midnight. Here's why.
• Two reserves. A Black Bay GMT or Black Bay Pro is rated at 70 hours. A Pelagos FXD GMT or Northflag GMT with the MT5652-U is rated at 65.

How it compares

• Rolex 3285: the GMT-Master II's movement, also a true GMT with 70 hours, plus the Chronergy escapement and Rolex's -2/+2 standard, at a far higher price.
• ETA 2893-2 / Sellita SW330: the common Swiss GMTs. Easy to service, but around 42 to 56 hours, and they're "caller" GMTs where it's the 24-hour hand, not the local hour hand, that you set independently.
• Miyota 9075: an affordable Japanese true GMT, with about 42 hours and a much looser tolerance.
• Tudor MT5602: the time-only base, 1 mm thinner, same 70-hour reserve.

Living with the 70-hour reserve

For a travel watch, reserve matters. Take your Black Bay GMT off at 6pm on Friday and, from a full wind, it will still be showing both time zones correctly at about 4pm on Monday. You don't have to reset the second time zone after a quiet weekend.

Holidays are where it gets tight. Pack a Black Bay Pro and wear a diver on the beach, and the GMT will stop by the third afternoon. A Pelagos FXD GMT, at 65 hours, stops a few hours earlier. Resetting a GMT with a date is more work than resetting a three-hander, so it's worth winding it before you put it down. 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 MT5652 made the Black Bay GMT one of the most sensible routes to a true traveller's GMT: 70 hours, a silicon spring, COSC certification and a jumping local hour hand, at a small fraction of the price of a GMT-Master II. The costs are thickness, which the Black Bay Pro inherits, and servicing that mostly goes through Tudor. The newer MT5652-U gives up 5 hours of reserve for METAS certification, a trade most owners won't notice.

FAQ

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

About 70 hours from a full wind, just under three days. If it was only partly wound, it will stop sooner.

Is the Tudor Black Bay GMT a true GMT?

Yes. The local hour hand jumps in one-hour steps, forwards or backwards, without stopping the watch, and the date follows local time.

What is the power reserve of the Tudor Black Bay Pro?

The Black Bay Pro uses the COSC-certified MT5652 and is rated at 70 hours.

How accurate is the Tudor Black Bay GMT?

The movement is COSC-certified, and Tudor regulates the cased watch to within -2/+4 seconds a day.

Why is the Tudor Pelagos FXD GMT rated at 65 hours?

It uses the MT5652-U, the METAS Master Chronometer version of the movement, which Tudor rates at 65 hours rather than 70.

Why is the Tudor Black Bay GMT so thick?

The MT5652 is 7.52 mm tall, about 1 mm more than the time-only MT5602, because of the GMT and date mechanism. The case ends up around 15 mm.

Does the Tudor Black Bay Pro hack?

Yes. Pulling the crown to the time-setting position stops the seconds hand, and the movement can be wound by hand.

Sources

• Monochrome: Tudor Black Bay GMT 79830RB (Baselworld 2018)
• Monochrome: Tudor Black Bay Pro 79470 review
• Monochrome: Tudor Black Bay GMT S&G M79833MN review
• Monochrome: Tudor Pelagos FXD GMT Zulu Time
• Monochrome: 2026 Tudor Northflag GMT

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 MT5652 GMT. 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 MT5652 GMT: 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.