“My Tudor Is Running Fast” — What's Actually Wrong (Usually Nothing)

This is the most common Tudor complaint on the internet, and most of the time the watch is fine.

That's not dismissiveness. It's what the evidence says. There is no systematic "MT calibres drift fast over time" defect — and the tell is that when owners report drift, it runs in both directions. Some watches gain, some lose. A common mechanical cause would push everything the same way. Two different things are happening: a small number of genuinely faulty watches, and a large number of measurements that don't mean what the owner thinks they mean.

Let's separate them.

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First: know your actual spec

Half the arguments about Tudor accuracy come from people comparing against the wrong number.

What it is	The standard	Tested on
COSC chronometer	−4 to +6 s/day	The bare movement, before casing
Tudor's own spec	−2 to +4 s/day	The fully assembled watch
METAS Master Chronometer ("-U" calibres)	0 to +5 s/day	Cased watch, 6 positions, 2 temperatures, at 100% and 33% power reserve
Pre-2016 ETA-based Tudor	No published Tudor figure	—

Note the direction of that comparison, because people get it backwards constantly: Tudor's standard is tighter than COSC, not looser. COSC tests a naked movement. Tudor holds the finished watch to a narrower band.

And for pre-2016 ETA-based Tudors, there simply is no published figure. Tudor bought high-grade ETA movements and regulated them to chronometer standards without paying for certification, so there was never an official number to hold them to. Assume roughly ±10–15 s/day unless you have evidence otherwise, and don't be alarmed by a figure that would be out of spec on a modern watch.

This matters for a specific reason: many of the most-cited "Black Bay running fast" forum threads predate the in-house movements entirely. They're about ETA-powered watches for which Tudor made no chronometer claim at all. Don't read those as evidence about your MT5602.

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How to self-test properly

The rate test

Nearly everyone does this wrong, in the same three ways: too few days, sloppy readings, and no record of position.

Set up:

1. Open time.is — it corrects for your device's clock offset and network latency, which a plain clock app doesn't.
2. Fully wind the watch. Pull the crown to hack, align the seconds hand to 12, and push the crown in exactly as the reference rolls to a new minute.
3. Then never reset it again for the duration of the test.

Each day:

Put your phone or a screen showing time.is next to the watch and take a photo from directly overhead, with both the dial and the reference display in frame. Phone parallel to the dial. Parallax — shooting at an angle — is the single biggest source of nonsense readings.

If you want real precision, shoot a five-second video at 60 fps and step through to the frame where the seconds hand crosses 12. That gets you to about ±0.02 seconds, and eliminates human reaction time entirely.

Log the cumulative offset, not a daily reset. Day 1: +3.2 s. Day 2: +7.1 s. Day 3: +9.8 s. Tracking a running total means small reading errors don't accumulate.

Run it for 14 days. Seven is the absolute minimum.

Also log: how many hours you wore it, and what position it spent the night in.

Why one day tells you nothing

• Temperature alone. COSC permits a thermal coefficient up to ±0.6 s/day per °C. Your wrist is about 33 °C; a cold nightstand is maybe 18 °C. At the COSC limit that's up to 9 s/day of entirely legitimate difference between a worn day and a desk-drawer day. Real movements are usually better than that, but it's a genuine confounder.
• Power reserve state. Rate at full wind isn't rate at hour 60 of a 70-hour reserve.
• Position. Your watch's spec is a mean across positions. If you leave it crown-up every night, you'll never see the mean.
• Reading error. Tapping a stopwatch adds ±0.2–0.5 s per reading. Over a single day, that's the whole signal.

Reading your results

This is the part that matters, and it's not the number most people focus on.

What you see	What it means
Mean out of spec, but stable and repeatable	Just needs regulation. Cheap. Not a health problem. This is the single most over-diagnosed "fault" in watch ownership.
Mean fine, but individual days swinging ±10 s or worse	This is the red flag. Dried or migrated lubricant, dirt in the escapement, a damaged pivot, or a hairspring intermittently touching something.
Sudden large gain (+20 s/day or more) that appeared abruptly	Magnetism — see below.
Rate progressively degrading over months	Lubricant breakdown. Book a service.
Losing 30+ s/day	Low amplitude — dirt, dry oils, weak mainspring, excessive friction.

Consistency beats accuracy. A watch that runs a steady +8 seconds a day is mechanically healthy and needs a five-minute adjustment. A watch that averages +2 but swings from −12 to +16 is sick. Most people would be delighted with the second one and worried about the first. That's backwards.

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Magnetism: the free thing to check first

The Tudor-specific nuance

Every Tudor Manufacture calibre uses a silicon balance spring, which is non-magnetic. That removes the classic magnetism failure mode — magnetized hairspring coils clinging to each other, effectively shortening the spring and making the watch gain minutes a day.

But "silicon hairspring" does not mean "antimagnetic watch." Only the METAS -U calibres are certified to 15,000 gauss. On every other MT calibre, the escape wheel, pallet fork, balance staff, pivots and gear train are all steel, and steel magnetizes.

So:

• Modern in-house Tudor running suddenly fast → magnetism is possible but less likely than on other watches. Look also at shock damage or dirt.
• Pre-2016 ETA-based Tudor → conventional Nivarox steel hairspring, fully vulnerable. Magnetism is a leading suspect.

Why the compass test is mostly useless

Every consumer watch blog recommends holding your watch near a compass. Watchmakers largely reject it, and they're right about the physics.

A compass needle is itself a magnet. It's attracted to any lump of ferrous material — a steel case, steel movement plates, a steel bracelet — whether or not that object is magnetized at all. As one watchmaker put it: "any iron object could move the compass needle when held close enough." False positives are the default result.

The reverse also happens. A mildly magnetized hairspring is a tiny amount of metal deep inside a steel case that partially shields it. It can be magnetized enough to gain minutes a day and never visibly move a needle.

If you're going to do it anyway, here's a refinement that helps: a merely ferromagnetic object always attracts the needle, whichever way you hold it. A permanently magnetized object is a dipole — it has polarity. So bring the watch in, note which way the needle swings, then rotate the watch 180° and repeat from the same distance.

• Needle deflects the same way regardless of orientation → probably just steel attraction. False positive.
• Deflection reverses when you flip it → there's a real magnetic moment.

(That's physically sound reasoning rather than a published protocol — treat it as a sanity check, not a verdict.)

Phone magnetometer apps are worse than a compass, because the phone contains its own magnets: speaker, vibration motor, camera stabilisation, and on iPhones a MagSafe array. A magnetic case or ring holder ruins the test outright.

Just demagnetize it

Here's the practical answer. Don't test — treat.

A demagnetizer costs $15–25. Plenty of professional watchmakers demagnetize every watch that crosses the bench as a matter of routine rather than bothering to test first.

The procedure, and the one step everyone gets wrong:

1. Move phones, credit cards, hotel keycards and hard drives well away.
2. Place the watch dial-down on the pad.
3. Press and hold the button — the field is now on.
4. Slowly withdraw the watch to about 30 cm while still holding the button.
5. Only then release the button.
6. Repeat two or three times, rotating the watch 90° each time, plus one pass dial-up.

The withdrawal-while-energized is the entire mechanism. You're exposing the watch to a decaying alternating field. Releasing the button while the watch is still sitting on the pad can leave it more magnetized than when you started.

Cheap units are mains-powered with unimpressive insulation and no fuse. Inspect the cable, don't use them with wet hands, and don't hold the button down for more than a few seconds at a time — they get hot. Never try to "cancel out" magnetism with permanent magnets.

The real value is diagnostic: if the fast rate persists after two proper demagnetizing cycles, it was never magnetism. That's a free, definitive elimination test that saves you guessing.

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The solution, in order

1. Demagnetize. Free after the one-off cost, takes two minutes, and rules out the most common cause of a sudden gain.

2. Re-measure properly. Fourteen days, photo method, cumulative offset, positions logged. A large proportion of "my watch is running fast" resolves here, when the owner discovers their real mean is +2.

3. Check your wear pattern. If the mean looks bad but the watch is healthy, try a different overnight position. Dial-up and dial-down usually run differently from crown-up. You may be able to fix your own accuracy for free by changing where the watch sleeps.

4. Ask for regulation. If the mean is genuinely out of spec but stable, this is a short bench job, not a service. Inside the guarantee period it should be free — a watch outside its certified tolerance within the guarantee is a warranty claim, and Tudor service centres have regulated watches at no charge on exactly that basis.

5. Book a service — but only if the scatter is wide, or the rate has progressively degraded over months. Wide scatter is the symptom that actually indicates something mechanical is wrong.

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What the data actually shows

For balance, since this post is mostly caveats: the majority of MT-calibre owners report performance better than spec. A documented MT5612 ran −0.2 s/day over 109 days. WatchTime's instrumented test of the MT5813 chronograph averaged +2.9 to +3.5 s/day with a positional spread of only 2.3–2.9 seconds. Multiple BB54 owners report "+2/day at max."

There is a real minority tail — including some watches that genuinely failed and were replaced under warranty. But it's a tail, not a trend. If your watch is misbehaving, the odds strongly favour it being either fixable in five minutes or not actually misbehaving at all.

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Sources: Tudor — Manufacture Calibre certified by the COSC · Tudor — METAS certification · WatchTime — Reviewing the Tudor Black Bay Chrono · Caliber Corner — Tudor MT5612 (and comments) · Watch Repair Talk — Magnetism detection with a compass, was I wrong? · Craft + Tailored — Demystifying magnetism · Teddy Baldassarre — How to demagnetize a watch · Xavier Noria — Measuring mechanical watch accuracy · WatchGecko — The complete guide to COSC