What thickness of thresholds should I choose for welding into a car: 1, 2, 3, 4, 5 or 6 mm?

Why the thickness of the threshold is critical for the safety and durability of a car

Question, what thickness of thresholds is better to weld into a car, occurs in anyone who has encountered corrosion or mechanical damage to the body. Not only the appearance of the car, but also its torsional rigidity, impact resistance, as well as passenger safety in case of an accident. Metal that is too thin will quickly rust or deform, while metal that is too thick will complicate welding and increase the weight of the car.

Original aftermarket manufacturers (OEMs) use thresholds ranging from 0.8 mm up to 2.5 mm depending on the model. However, on the secondary market there are options from 1 mm up to 6 mm. So which choice will be optimal? The answer depends on the type of car, operating conditions and even the region of residence (for example, in coastal areas with salty air, corrosion develops faster).

In this article we will look at:

• 🔍 Standard threshold thicknesses for passenger cars, SUVs and classics;
• ⚖️ Pros and cons thin (1–2 mm) and thick (4–6 mm) options;
• 🔧 Technological nuances welding metal of different thicknesses;
• 🚗 Recommendations for selection for specific brands (VAZ, Toyota, BMW etc.).

Standard threshold thicknesses: what the market offers

Thresholds of the following thicknesses (in millimeters) are available on the auto parts market:

Thickness, mm	Vehicle type	Material	Application
0.8–1.2	Passenger cars (economy class)	Galvanized steel	Original spare parts (Renault, Hyundai)
1.5–2.0	Passenger cars (middle class), crossovers	Zinc coated steel	Universal repair inserts
2.5–3.0	SUVs, pickups, commercial vehicles	Carbon steel	Enhanced off-road options
4.0–6.0	Special equipment, rally cars, tuning	High strength steel or aluminum	Extreme loads, impact protection

Original thresholds for mass models (VAZ 2107, Ford Focus, Kia Rio) usually have a thickness 1.2–1.8 mm. It's a trade-off between weight, cost and strength. However, after 5–7 years of operation in the Russian climate, even galvanized parts begin to rust. Therefore, many car owners choose repair inserts 2–3 mm thick, which resist corrosion longer.

For SUVs (Toyota Land Cruiser, Nissan Patrol) and pickups (Ford Ranger) thresholds are relevant 2.5–3 mm, since they experience increased loads when driving off-road. Thickness 4 mm or more used in rally cars or when preparing a car for serious tuning (for example, to protect against stones when driving at high speed on gravel).

Thin thresholds (1–2 mm): when they are justified

Thresholds thickness 1–2 mm Most often installed on economy and middle class passenger cars. Their main advantages:

• ✅ Lightness: minimal increase in body weight;
• ✅ Easy to weld: do not require powerful equipment (a semi-automatic device with 130–160 A is sufficient);
• ✅ Low price: cheaper than thick-walled analogues by 30–50%;
• ✅ Compatible with original mounts: no need to modify the joints.

However, thin thresholds also have serious disadvantages:

• ❌ Prone to corrosion: even galvanized parts will rust in 3–5 years when driving on salty roads;
• ❌ Low impact resistance: may be deformed in a side impact;
• ❌ Difficulty of straightening: Dents often require replacement rather than repair.

Thin thresholds are suitable if:

• 🚘 Your car is a city sedan (Skoda Octavia, Honda Civic), which is not used in aggressive conditions;
• 💰 Budget is limited and you need temporary repairs before selling;
• 🔧 You are planning additional anti-corrosion treatment (for example, ML-mastic or liquid plastic).

Thick thresholds (3–6 mm): when you can’t do without them

Thresholds thickness 3 mm or more used in cases where the car is subjected to extreme loads. Their key advantages:

• 🛡️ High strength: withstands impacts from stones, branches and minor accidents;
• 🔩 Durability: even without additional treatment they last 7–10 years;
• 🚙 Improved body geometry: increase torsional rigidity, which is important for SUVs;
• 🔥 High temperature resistance: do not deform when in contact with the exhaust system.

Disadvantages of thick thresholds:

• ⚠️ Welding difficulty: requires a 180–220 A device and experience working with thick-walled metal;
• ⚠️ Weight gain: thresholds 4–6 mm can add up to 15–20 kg to the body weight;
• ⚠️ High price: the cost is 2–3 times higher than that of thin analogues;
• ⚠️ Fit issues: May not fit standard mounts.

Thick thresholds are necessary if:

• 🏔️ You are driving off-road (UAZ Patriot, Land Rover Defender);
• 🏁 Prepare your car for rally or drag racing;
• 🛠️ You are restoring a car after a serious accident with deformation of the side members;
• 🌊 You live in a region with an aggressive environment (seaside cities, chemical plants).

How to weld 4–6 mm thresholds without burns?

For thick metal use multilayer welding with reduced current (20–30% lower than the maximum for a given wire diameter). Optimal mode: current 140–160 A, wire 0.8–1.0 mm, gas Ar/CO₂ (80/20). First, boil the root of the seam, then fill the groove in 2-3 layers.

How to choose the threshold thickness for a specific car model

There are no universal recommendations - the choice depends on body type, operating conditions and budget. Let's consider the best options for popular categories:

1. Passenger cars (sedans, hatchbacks)

For most mass models (VAZ 2110, Toyota Corolla, Volkswagen Golf) ideal thickness - 1.5–2.0 mm. These are:

• 🔹 Corresponds to original parts;
• 🔹 Doesn’t weigh down the body;
• 🔹 Easily welded semi-automatically.

Exception - premium brands (Mercedes, Audi), where they are often used 2.0–2.5 mm for increased rigidity.

2. Crossovers and SUVs

For Toyota RAV4, Mitsubishi Outlander or Nissan X-Trail recommended thickness - 2.0–2.5 mm. If the vehicle is used off-road (UAZ Hunter, Land Rover Discovery), it's better to take 3 mm.

3. Classic cars (VAZ 2101–2107, Moskvich)

For retro cars with thin metal body (0.8–1.0 mm) thresholds are optimal 1.2–1.5 mm. Thicker parts may look unsightly and will require modifications to the fasteners.

4. Commercial vehicles and pickups

For Gazelle, Ford Transit or Toyota Hilux minimum thickness - 2.5 mm. For intensive use (cargo transportation, towing) it is better 3–4 mm.

Check the thickness of the original thresholds for your model|Check for the presence of zinc coating|Assess the operating conditions (city/off-road)|Make sure that the welder has experience working with the selected thickness|Compare the weight of the new thresholds with the original ones (the difference should not exceed 10-15%)

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Welding technology for thresholds of different thicknesses: nuances and errors

Not only its strength depends on the thickness of the threshold, but also welding technology. An incorrect approach can lead to burns, body deformation or cold seams. Let's look at the key points:

1. Welding thin thresholds (1–2 mm)

Basic rules:

• 🔥 Use semi-automatic (MIG/MAG) with current 80–120 A;
• 🔧 Wire diameter — 0.6–0.8 mm;
• 💨 Gas: Ar/CO₂ (90/10) to minimize splashes;
• ⚡ Weld pointwise in increments of 2–3 cm to avoid overheating.

Typical mistakes:

• ❌ Too high current → burn-through;
• ❌ Long seams without breaks → metal warping;
• ❌ No reverse hammer → internal stresses in the seam.

2. Welding thick thresholds (3–6 mm)

A different approach is required here:

• 🔥 Current: 140–200 A (depending on thickness);
• 🔧 Wire: 0.8–1.2 mm;
• 💨 Gas: Ar/CO₂ (80/20) or clean CO₂ for deep penetration;
• ⚡ Apply multilayer welding with cleaning between passes.

Errors:

• ❌ Insufficient penetration → fragile seam;
• ❌ Lack of cutting edges → lack of penetration;
• ❌ Rapid cooling → cracks in the metal.

General recommendations for any thickness:

• 🔹 Before welding strip the metal until shiny (rust and paint degrade the quality of the seam);
• 🔹 Use potholders for fixing the part before the main welding;
• 🔹 After welding, treat the seams primer for metal and anti-gravel.

What to do if the threshold starts to move after welding?

If the metal has become deformed due to heat, use gas burner for local heating (temperature 200–300°C) and copper hammer for straightening. For thick thresholds (4+ mm) it may be necessary thermal straightening with temperature control by pyrometer.

Common mistakes when choosing and setting thresholds

Even experienced car owners make mistakes that shorten the service life of thresholds or impair safety. Here are the most common:

⚠️ Attention: Setting threshold thickness 4 mm or more on passenger cars without reinforcement of the side members can lead to violation of body geometry in case of an accident. Thick metal does not deform, but transfers the impact energy to thinner elements, which increases the risk of injury.

Top 5 mistakes:

1. Ignoring anti-corrosion treatment. Even galvanized thresholds need to be coated ML-mastic or liquid plastic from the inside.
2. Saving on welding. Using cheap electrodes or low quality gas results in porous seams.
3. Thickness mismatch. If the new threshold is thinner than the original, it will “sink” into the body, which will spoil the appearance.
4. No drainage holes. Water getting inside the threshold accelerates corrosion by 3–5 times.
5. Do-it-yourself welding without experience. 70% of defects in threshold repairs are due to incorrect device settings.

How to avoid problems:

• 📏 Before purchasing measure the thickness of the original threshold with a caliper;
• 🔍 Check it out quality certificate for metal (especially for parts from China);
• 🛠️ Trust welding only to proven professionals with equipment for MIG/MAG or TIG.

FAQ: Answers to frequently asked questions about thresholds

Is it possible to install 3 mm thick thresholds on a VAZ 2114 instead of the original 1.2 mm?

Technically it is possible, but this will lead to:

• ⚠️ Increase in body weight by 5–8 kg (will worsen dynamics);
• ⚠️ The need to refine the attachment points;
• ⚠️ Risk of warping during welding (different thermal conductivity of metals).

The best option is 1.5–2.0 mm with additional anti-corrosion treatment.

Which gas is better to use for welding thresholds: argon or carbon dioxide?

Optimal mixture - Ar/CO₂ (80/20). Clean CO₂ Cheaper, but produces more splashes and does not cook thin metal well. Argon provides a stable arc, but is more expensive. For thresholds 1–2 mm will do Ar/CO₂ (90/10).

How long will 2 mm thick thresholds last without additional treatment?

In the Russian climate:

• 🌆Urban use (salt in winter, rain in summer): 3–4 years;
• 🏡 Garage storage, rare trips: 5–7 years;
• 🏔️ Off-road + aggressive environment: 1–2 years.

With anti-corrosion treatment (ML-mastic + wax) service life increases by 1.5–2 times.

Is it possible to cook 4 mm thresholds with a regular inverter?

Technically possible, but:

• ⚠️ Electrodes will be required ∅3–4 mm and current 160–200 A;
• ⚠️ The seam will be less neat than with MIG/MAG;
• ⚠️ High risk of lack of penetration (inverters do not provide a stable arc on thick metal).

For high-quality welding it is better to use semi-automatic or argon arc apparatus (TIG).

How to check the quality of a weld on a threshold?

Inspect the seam for:

• 🔹 Uniformity: no sharp transitions, pores;
• 🔹 Color: silvery tint (blue/black is a sign of overheating);
• 🔹 Strength: tap with a hammer - a high-quality seam will not crumble;
• 🔹 Tightness: Treat with kerosene - if it leaks, there are microcracks.

For 100% control use ultrasonic flaw detector (the service costs ~1000 rubles).