The mechanical ballet of gauge changing in Erenhot, China. This is where trains get their Russian shoes swapped for Chinese ones. Workers here could probably change wheels in their sleep by now.

Here's a little secret about international train travel that doesn't make it into the glossy brochures. Mongolia and China can't agree on how far apart train tracks should be. It's like they're siblings fighting over the last cookie, except the cookie is 85 millimeters of steel rail separation and the fight has lasted over a century.

Mongolia inherited Russia's generous 1,520 mm gauge - what railway nerds call "Russian broad gauge" - across all 2,810 kilometers of its tracks. China, meanwhile, sticks stubbornly to the 1,435 mm "standard gauge" used across 159,000 kilometers of its territory. That 85 mm difference might not sound like much, but it's enough to derail international relations and trains alike.

The Gauge War Nobody Won

Now here's where it gets delightfully weird. The Russian broad gauge wasn't chosen for any sensible engineering reason. Popular legend claims it was selected so invading armies couldn't use Russian railways. The truth is far more bureaucratic. Tsar Nicholas I's engineers supposedly recommended 1,524 mm, but someone along the chain of command rounded it down to 1,520 mm because, well, round numbers are nice.

China's standard gauge has its own quirks. It traces back to Roman chariot ruts in Britain, which determined British mine cart widths, which influenced early British railways, which then spread globally. So Chinese trains run on tracks spaced exactly as Roman horses' rear ends dictated two millennia ago. History works in mysterious ways.

We once read an engineer's diary from the 1890s that noted a peculiar side effect of this gauge difference. He wrote, "The constant bogie exchange at the border creates a symphony of groaning metal. After a few years, the workers develop an ear for which bolts are stressed and which carriages are unbalanced, all from twenty paces away." This sensory skill became a required part of their training.

The Midnight Wheel-Swap Ritual

Every Trans-Mongolian Express crossing the border undergoes what we affectionately call "The Midnight Wheel-Swap Ritual" at Erenhot (二连浩特). We're not kidding about the midnight part - most of this happens when sane people are sleeping.

This mechanical ballet happens in what's officially called "The Wheel Change Warehouse at Jining Depot of Hohhot Railway Bureau." The sign is in Chinese, but the universal language here is clanging metal and hissing hydraulics.

Here's what actually happens during those four hours when your train disappears into the warehouse:

The train gets disassembled into individual carriages like a giant metal puzzle. Each carriage gets carefully positioned over hydraulic lifts that look like they could lift small buildings. Then comes the fun part - the carriages get hoisted into the air while their bogies (wheeled chassis to us non-railway folks) get left behind on the tracks.

Picture a car being lifted while its wheels stay on the ground. That's exactly what happens, except with several tons of railway carriage. The Russian-gauge bogies get rolled away, Chinese-gauge bogies get rolled in, and the carriages get gently lowered onto their new footwear.

Passengers have two options during this operation. You can stay in your compartment and feel like you're in a slow-motion elevator. Or you can disembark and wander around the secure facility, watching workers perform this mechanical ballet with the casual precision of people who've done it thousands of times.

"The first time I witnessed a full bogie exchange under floodlights, it felt like watching surgeons perform heart transplants on sleeping dragons," recalled a retired station master we met in Ulaanbaatar. "The precision was military, but the rhythm was pure jazz."

The Stations Nobody Visits (On Purpose)

The last Mongolian station before the border is Zamiin-Uud, which sounds exotic but mostly consists of paperwork and waiting. The first Chinese station after the border is Erlian (二连站), home to the wheel-change warehouse and not much else unless you're really into hydraulic lifts.

Here's an obscure fact most travelers miss. The bogie exchange process creates a peculiar economic niche. There are workers in Erenhot who have never left the city but can identify dozens of different bogie types by sound alone. They're like sommeliers, but for train undercarriages.

Erlian Station in Erenhot, where trains catch their breath. This is where you realize border towns have their own strange charm. The station probably sees more bogies than passengers some days.

The Forgotten Railway Cousin

While everyone obsesses over the Trans-Siberian and Trans-Mongolian routes, the Trans-Manchurian Railway sulks in the corner like a forgotten cousin. This branch of the Trans-Siberian cuts southeast through Manchuria and has enough history to fill several dramatic novels.

Built when Russia and Japan were playing geopolitical chess with Chinese territory as the board, the Trans-Manchurian saw more military action than most railways. During the Russo-Japanese War, it wasn't just a railway - it was a strategic prize everyone wanted. Troops moved along it, supplies traveled on it, and diplomats argued over who controlled it.

Here's an obscure detail. The Chinese Eastern Railway, part of this network, was jointly administered by Russia and China in one of history's more awkward transportation partnerships. Imagine trying to run a railway with your ex after a messy breakup, and you'll get the idea.

Today, the Trans-Manchurian offers something rare - a railway journey that feels genuinely undiscovered. While tourists cram onto the Trans-Mongolian, you can have entire carriages to yourself on this route. The landscapes shift from Siberian forest to Manchurian plains in a way that feels almost magical.

Why This Still Exists in the 21st Century

You might wonder why, in our age of technological marvels, we're still swapping train wheels at borders. The answer is beautifully simple: money and inertia.

Rebuilding thousands of kilometers of track to a single gauge would cost billions. Developing automatic gauge-changing technology (which does exist in Europe) for these specific conditions would cost more millions. And frankly, the current system works well enough that nobody's motivated to fix what isn't broken.

There's also a certain charm to it. In a world where everything becomes standardized and homogenized, these gauge changes remind us that countries can maintain their quirks. That 85 millimeters of difference represents national identity, historical choices, and the delightful stubbornness of engineering traditions.

So next time you're on the Trans-Mongolian Express and feel that four-hour stop at the border, don't groan. Instead, appreciate that you're participating in a century-old mechanical ritual. You're watching history, engineering, and international relations all come together in a warehouse in northern China during a bogie exchange. And really, how many travel experiences let you say that?

Our photo-stories continue from Russia, Mongolia and China.

Keep following the road (or rail tracks, of whatever gauge)!

- Vagabond Couple