Have you ever wondered what the correct name is for that lower part of the body that is often accidentally scratched when parking? Many drivers mistakenly call it a “step” or “step”, but in fact it is car threshold - a key element of the supporting structure. In this article we will examine not only the terminology, but also why thresholds are so important for safety, how to protect them from corrosion, and how they differ from decorative trims.
Disputes about the names of car parts are a common occurrence among new and experienced car owners. Some people say “threshold”, others “lower arch”, but the services may use professional jargon. We have collected all the relevant information: from official terms to GOST and factory catalogs to advice on repairs and tuning. If you are planning to buy a used car or just want to understand the structure of the body, this material is for you.
The official name of the threshold in a car: terminology and standards
In technical documentation and GOST 33997-2016 (which regulates terms for passenger cars) this part is called body threshold (English) rocker panel or sill). In colloquial speech, abbreviations are often used: “threshold”, “lower beam” or even “step” - the latter is incorrect, since the step (running board) is an optional accessory.
Interestingly, the terminology differs in different countries:
- 🇷🇺 Russia/CIS: body threshold (officially), "threshold" (colloquially)
- 🇺🇸 USA/Canada: rocker panel (main term), sill (in British English)
- 🇩🇪 Germany: Schweller (literally "amplifier")
- 🇯🇵 Japan: (sai-do shiru"side threshold")
In factory spare parts catalogs (for example, for Volkswagen or Toyota) thresholds are designated as Side Member Outer (outer element) and Side Member Inner (internal amplifier). This is important to consider when ordering parts for repairs after an accident or corrosion.
Threshold design: what it consists of and how it is designed
The threshold is not just a flat metal plate, but a complex multi-layer structure that performs several functions. In modern cars (for example, Skoda Octavia or Hyundai Tucson) it consists of:
- External panel - the visible part, which often suffers from chips and scratches.
- Internal amplifier — a load-bearing element made of high-strength steel, welded to the side members.
- Anti-corrosion coating — factory treatment (zinc plating, primer) or additional protection type ML or Dinitrol.
- Decorative overlays (optional) - plastic or aluminum “skirts” that are attached to clips.
In vehicles with a frame structure (for example, Nissan Patrol or Toyota Land Cruiser 70) thresholds can be part of the load-bearing frame and withstand loads when tipping over. And in city hatchbacks (like Kia Rio) they often perform a decorative role, hiding welding seams.
Why do thresholds rust first?
This part is at risk due to constant exposure to moisture, salt and sand from the road. Even in new cars, the drain holes can become clogged, causing water to accumulate inside the sill cavity. And if the factory galvanization is damaged (for example, due to careless parking), corrosion spreads 2-3 times faster than on other body elements.
| Threshold type | Material | Examples of cars | Features |
|---|---|---|---|
| Welded steel | Low-carbon steel (0.8–1.2 mm) | Lada Vesta, Renault Duster | Budget option, susceptible to corrosion without protection |
| Aluminum | Aluminum alloys (6xxx series) | Audi A8, Jaguar XE | Lightweight but expensive to repair |
| Composite | Carbon fiber + fiberglass | BMW i3, McLaren 570S | Does not rust, but cannot be repaired if damaged |
| Reinforced (off-road) | High strength steel (1.5–2.5 mm) + protection | Jeep Wrangler, UAZ Patriot | Withstands impacts from off-road driving |
Functions of the threshold: why it is not just a “step”
Many people mistakenly think that a threshold is needed only for the convenience of getting into a car. In fact he has three critical functions on which the safety and durability of the machine depend:
- Bearing role: sills connect the front and rear of the body, distributing the load during an impact. For example, in crash tests Euro NCAP Cars with damaged side sills perform 30–40% worse in side impact collisions.
- Corrosion protection: properly treated sills prevent rust from spreading to the side members and the interior floor. In cars older than 10 years (for example, Volkswagen Passat B6) corrosion of thresholds often becomes the reason for refusal to pass technical inspection.
- Aerodynamics: at speeds above 100 km/h, the sills affect the air flow under the bottom, reducing the drag coefficient (
Cx) by 2–5%.
Fun fact: in racing cars (eg. Porsche 911 GT3) the sills are made of carbon fiber not only to make them lighter, but also to improve downforce at high speeds. And in armored vehicles (such as Mercedes-Benz Guard) they are reinforced with Kevlar to protect them from bullets.
If, when inspecting a used car, you see blistered paint or bubbles on the sills, this is a sure sign of incipient corrosion. Test with a magnet: if it doesn't stick, the metal has already worn thin or has been replaced with fiberglass.
Threshold vs step: how not to confuse and why both elements are needed
One of the most common misconceptions is to confuse the threshold with the step. Let's look at the key differences:
| Characteristics | Body threshold | Kick (running board) |
|---|---|---|
| Purpose | Load-bearing body element, corrosion protection | Additional step for easy boarding |
| Material | Steel, aluminum, carbon fiber | Aluminum, plastic, rubber |
| Fastening | Welding or riveting (at the factory) | Bolts or clamps (removable) |
| Repair cost | From 5,000 ₽ (partial replacement) to 30,000 ₽ (full welding) | From 1,500 ₽ (plastic) to 10,000 ₽ (aluminum with backlight) |
Footrests are installed in three cases:
- 🚙 On SUVs (Toyota Hilux, Ford Ranger) for ease of boarding in a high salon.
- 👨👩👧👦 On family minivans (Volkswagen Multivan) for children and elderly passengers.
- 💎 On premium cars (Range Rover, Bentley Bentayga) as a design element (often with lighting and logo).
Important: footrests do not strengthen the body and can even worsen aerodynamics at high speeds. Their installation requires drilling holes, which can become a source of corrosion if the edges are not treated ML- composition.
If you are offered to “strengthen the thresholds” by installing running boards, this is a marketing ploy. Real reinforcement requires welding and installation of internal bracing rather than external bracing.
Frequent problems with thresholds: corrosion, dents, cracks
According to car service statistics, 60% of damage to thresholds is associated with corrosion, 25% with mechanical impacts (parking lots, curbs), and 15% with the consequences of an accident. Let's look at typical problems and their causes:
- 🔥 Through corrosion: occurs due to lack of anti-corrosion treatment or damage to the paintwork. Cars over 7 years old are especially vulnerable (Renault Logan, Chevrolet Aveo).
- 🚗 Dents and scratches: most often appear when opening doors carelessly in a parking lot or running into a high curb.
- 💥 Weld cracks: typical for cars after an accident, where the thresholds were homemade (without argon welding).
- 🌧️ Blistering paint: a sign of internal corrosion, often found on Opel Astra H and Peugeot 308 first generation.
The most dangerous problem is rotting threshold from the inside. It is not visible from the outside, but can be diagnosed by the following signs:
- Creaking or knocking noise when driving over uneven surfaces.
- Uneven gaps between the door and the threshold.
- Smell of dampness in the cabin (especially after rain).
Remove rust by brushing or sandblasting|Treat with a converter (e.g. Tsinkar)|Apply primer and paint in 2-3 layers|Check the drainage holes|In case of severe corrosion, weld a patch-->
Warning: if the threshold is rusted through, simply filling it with putty will not help. Such details are subject to complete replacement welding, otherwise the body will lose rigidity and the car will not pass inspection.
How to protect thresholds from damage: 5 working methods
Prevention is cheaper than repair. Here are proven methods for protecting thresholds:
- Anti-gravel film (for example, 3M Scotchgard): a transparent coating 0.1–0.2 mm thick that protects against chipping. The cost of application is from RUB 3,000 for both thresholds. Suitable for new cars (Kia Sportage, Hyundai Creta).
- Liquid locker (Body 930, Tectyl): anti-corrosion compound that is applied to the inner surface. Effective for cars older than 3 years.
- Plastic linings: cheap solution (from 1,500 ₽), but requires regular cleaning underneath. Popular for Lada Granta and Datsun on-DO.
- Galvanizing: factory (for example, Volkswagen Polo) or additional (by cold galvanizing method). Extends service life by 5–7 years.
- Parking sensors with camera: help avoid bumps when parking. This is especially true for long vehicles (Skoda Kodiaq, Toyota Camry).
Advice from the experts: if you often drive on gravel or salt (in winter), treat the thresholds ML-composition every 2 years. This is cheaper than repairing through corrosion, which costs 15,000–40,000 rubles.
To check the quality of anti-corrosion treatment, use an endoscope (costs from 500 ₽ on AliExpress). Stick it into the drainage hole of the threshold - if the inside is dry and the layer of protection is visible, then the treatment has been done correctly.
Repair and replacement of thresholds: when is it required and how much does it cost?
The cost of door sill repair depends on the degree of damage and the make of the car. Here are the estimated prices for Moscow and the regions (2026):
| Type of work | Budget sedan (Lada, Renault) | Middle class (Toyota, Skoda) | Premium (Audi, BMW) |
|---|---|---|---|
| Local welding (hole up to 5 cm) | 3 000–5 000 ₽ | 6 000–9 000 ₽ | 10 000–15 000 ₽ |
| Partial replacement (segment 30–50 cm) | 8 000–12 000 ₽ | 15 000–20 000 ₽ | 25 000–35 000 ₽ |
| Complete replacement (both thresholds) | 20 000–30 000 ₽ | 40 000–60 000 ₽ | 80 000–120 000 ₽ |
| Anti-corrosion treatment (comprehensive) | 2 500–4 000 ₽ | 5 000–7 000 ₽ | 8 000–12 000 ₽ |
When is a complete threshold replacement required?
- 🚨 If rust has eaten through the metal over an area of more than 10 cm².
- 🚨 If the threshold is deformed after an accident and cannot be straightened.
- 🚨 If the welds are cracked (risk of body breaking upon impact).
Important: when replacing thresholds on vehicles with airbags (Airbag) it is necessary to turn off the power and use special ties to avoid damaging the shock sensors. Otherwise, the airbags may deploy spontaneously!
Is it possible to drive with rusty sills?
Technically yes, but it's dangerous. Corroded sills lose up to 70% of their strength, which increases the risk of body deformation in an accident. In addition, rust can spread to the side members, and then repairs will cost 2-3 times more. In some countries (for example, Germany), a car with through-corroded sills will not pass inspection and will be prohibited from operation.
FAQ: Frequently asked questions about car thresholds
❓ Why do thresholds rust even on new cars?
Reasons: poor-quality galvanization at the factory (typical for budget brands like Datsun), damage to the protective layer during transportation or storage in open areas. Also to blame are drainage holes that become clogged with dirt - water accumulates inside and triggers corrosion.
❓ Is it possible to paint the thresholds yourself?
Yes, but only if there is no through corrosion. You will need: a sander, primer, spray paint (select by color code), varnish. The main thing is to thoroughly clean the surface and heat it with a hair dryer for better adhesion. For beginners it is easier to use liquid rubber (Plasti Dip), which is applied without special equipment.
❓ What is the difference between the thresholds on a sedan and a hatchback?
On sedans (Toyota Corolla, Hyundai Solaris) the sills are longer and often have a curve at the rear for rigidity. In hatchbacks (Kia Ceed, Volkswagen Golf) they are shorter, but thicker, since the rear door creates additional load. SUVs (Mitsubishi Outlander) have sills with integrated running boards.
❓ How to check thresholds when buying a used car?
Use this checklist:
- Tap the threshold with a hard object - a dull sound means rust inside.
- Check with a magnet: if it does not stick, the metal has been replaced with putty.
- Inspect the gaps between the door and the threshold - they should be the same on both sides.
- Look under the car: traces of welding or fresh paint may indicate repairs.
❓ Is it possible to install thresholds from another car model?
Theoretically, yes, but in practice this requires modifications: adjusting the length, drilling new holes for fastening, welding. For example, thresholds from Volkswagen Passat B6 sometimes they put on Skoda Octavia A5, but at the same time the factory anti-corrosion protection is lost. It is better to buy original parts or high-quality analogues (Febi, Meyle).