How many wheels does a subway car have: a detailed analysis of the design

When it comes to the metro, most passengers think about schedules, transfers or station design. But there are questions that concern the curious - for example, how many wheels does a subway car have? and why their number varies depending on the model. At first glance, the answer seems simple, but in reality everything is more complicated: the design of the cars depends on the type of rolling stock, year of manufacture and even the country of origin.

In this article we will look not only at the number of wheels, but also at their location, functionality and how this affects the comfort of the trip. You will learn the differences between carriage wheels series "E" from modern "Moscow", why some models have “extra” wheels, and how this relates to safety. We’ll also reveal the myths about “spare” wheels and explain why they don’t exist in the traditional sense.

If you've ever wondered how the inside of a carriage works or why a train moves so smoothly on the rails, this material is for you. We've collected technical data, diagrams and expert commentary to provide a comprehensive answer.

Basic subway car design: how many wheels and why

A standard metro car is not just a “box on wheels”, but a complex engineering system. It is based trolley (or two trolleys) on which the body rests. It is the carts that determine the number of wheels. The classic scheme implies 4 wheelsets per car — 2 pairs for each cart. But this rule does not always work.

The fact is that the wheels in the subway are combined into wheelsets - two wheels rigidly fixed on one axle. This design ensures stability and uniform load distribution. For example, in carriages series 81-717/714 (familiar to many from line 1 of the Moscow metro) this particular scheme is used: 8 wheels per car (4 pairs), distributed between two bogies.

However, modern models such as "Moscow-2020", may have a different device. The weight of the car, maximum speed and maneuverability requirements play a role here. For example, to reduce noise and vibration, additional support elements are sometimes added - but these are not always full-fledged wheels.

Types of cars and their wheel formulas

The number of wheels directly depends on car type and its purpose. Let's look at the main categories:

• 🚇 Classic carriages (series “E”, “D”, 81-717): 2 trolleys × 2 wheelsets = 8 wheels. The most common scheme in post-Soviet metropolitan areas.
• 🚝 Modern carriages (“Moscow”, “NeVa”, “Oka”): may have 8 or 12 wheels due to additional support rollers or modified trolleys.
• 🛠️ Service cars (trailcars, track machines): the number of wheels varies from 4 to 20 depending on the purpose.
• 🚆 Articulated cars (rarely used): may have common trolleys between sections, which increases the total number of wheels.

Interestingly, some subways around the world (for example, Hong Kong or Singapore) use cars with independent wheel suspension. This reduces weight and improves dynamic performance, but requires more complex maintenance.

Comparison table: wheels in cars of different series

Please note: the table indicates total number of wheels, but not all of them are leading. For example, in cars with asynchronous motors (as in "Rusiche") part of the wheels can be driven, which reduces wear and energy consumption.

⚠️ Attention: Do not confuse wheel sets with individual wheels! One pair = two wheels on a common axle. The documentation often indicates exactly the number of pairs, not pieces.

Why do subway cars have so many wheels?

It may seem that 8–12 wheels per carriage is too many. However, each of them performs its own function:

1. Load distribution. A metro car weighs from 30 to 50 tons (depending on the model). The wheels distribute this weight evenly along the rails, preventing track deformation.
2. Cornering stability. The metro passes through curved sections with a radius of up to 100 meters. Multi-wheel design reduces the risk of derailment.
3. Braking and acceleration. In modern cars, some of the wheels are equipped with brake discs or magnetic systems, which ensures rapid deceleration.
4. Reservation. If one wheel pair fails, the car can continue moving on the rest (albeit with speed restrictions).

In addition, subway wheels have conical profile - they are not cylindrical, but slightly tapering towards the inside. This allows the car to automatically center on the rails as it moves, reducing vibration and wear.

Myths about “spare” wheels and other misconceptions

One of the most common myths is that subway cars have “spare wheels” that automatically start working if they break down. Actually this is not true. Here's what you need to know:

• 🚫 There are no “spare” wheels in the traditional sense. All wheels are constantly in contact with the rails. However, some models have additional support rollers for emergency situations.
• 🔧 The wheels do not “deflate” like car tires. They are made from solid steel and have no chambers. Wear is compensated by regular turning on special machines.
• ⚡ Electricity is not transmitted through the wheels. The supply current flows along the third rail or contact network, and the wheels are used only for movement.
• 🔄 The wheels do not rotate “idle”. Even when parked, the car is held in place by braking systems and the wheels are blocked.

Another misconception is that the number of wheels depends on the length of the car. In fact it is determined weight and design of trolleys. For example, short carriages "Oka" have as many wheels as long ones "Moscow", because their carts are identical in design.

⚠️ Attention: If you see a subway car with “flat” spots on the wheels, this is not a defect, but a consequence of emergency braking. Such wheels must be replaced or sharpened.

How to count wheels on metro trains: practical examples

To clearly understand how many wheels are in the composition, let’s take real examples:

1. Single carriage 81-717:
   • Trolleys: 2
   • Wheelsets per trolley: 2
   • Total wheels: 2 × 2 × 2 = 8
2. Train of 5 cars "Moscow-2020" (modification with 6 wheel pairs):
   • Cars: 5
   • Wheelsets per car: 6
   • Total wheels: 5 × 6 × 2 = 60

Total number of wheels = Number of cars × Wheel pairs per car × 2