Installing thresholds on a car: a complete guide from selection to installation

Thresholds are not just a decorative element of the body, but an important protective part that prevents corrosion, mechanical damage and gives the car a finished look. Their installation may be required after an accident, when replacing rusted original parts, or for tuning. However, improper installation of thresholds often leads to squeaks, peeling paint, or even accelerated corrosion. In this article we will look at all stages of threshold installation — from the selection of materials to finishing — and we’ll also tell you how to avoid common mistakes and save on car service costs.

Is it worth installing thresholds yourself? If you have experience with welding machine, putty and spray gun, then yes - this is a real task for the garage. For beginners, the process may seem complicated, but if you follow the technology, the result will be no worse than in the service. The main thing is to take your time and follow proven schemes. In the article you will find step-by-step instructions with photos, comparison of materials (steel vs aluminum vs plastic) and tips on anti-corrosion treatment.

Types of thresholds: which one to choose for your car?

Before purchasing thresholds, you need to decide on their type. They differ in material, design and purpose. A mistake at this stage can lead to the part not fitting in size, quickly rusting, or ruining the appearance of the car.

By material of manufacture thresholds are divided into:

• 🔹 Steel - the strongest and most durable, but heavy and susceptible to corrosion. Suitable for accident restoration or replacement of rusty original parts. Often used on domestic cars (VAZ, GAS) and budget foreign cars.
• 🔹 Aluminum - lightweight, rust-resistant, but more expensive than steel. Popular for tuning and premium cars (Audi, BMW). Requires care when welding due to low melting point.
• 🔹 Plastic (ABS, polyurethane) - cheap, light, do not rust, but fragile. Used as overlays for protection against chipping or decoration. Not suitable for replacing load-bearing body elements.
• 🔹 Composite (carbon fiber, fiberglass) - ultra-light and durable, but very expensive. Used in sports cars or for exclusive tuning.

By designs there are thresholds:

• 🔧 Bearers - part of the power structure of the body (for example, on Volkswagen Passat B3 or Ford Focus 2). Replacing them requires welding and precise fitting.
• 🔧 Non-load-bearing (decorative) — fastened with clips or bolts, protect from dirt and give a stylish look (for example, linings on Toyota RAV4 or Kia Sportage).
• 🔧 Universal — suitable for several car models, but may require modification.

Which option should I choose? If your goal is body restoration after rust or accident, take steel or aluminum thresholds with factory catalog numbers. For chip protection Enough plastic covers. And for tuning Aluminum or composite parts with chrome plating are suitable.

Tools and materials: what you need for work

Installing thresholds involves not only welding, but also surface preparation, metal cutting, puttying and painting. Without the right tools, the process will take twice as long and the results may be disappointing. Below - full checklist everything you need.

Basic tools:

• 🔧 Welding machine (semi-automatic MIG/MAG for steel, TIG for aluminum) with wire 0.8–1.0 mm.
• 🔧 Bulgarian with cutting and grinding wheels (125 mm).
• 🔧 Drill and metal drills (3–10 mm).
• 🔧 Set of screwdrivers and keys (including end ones).
• 🔧 Clamps for fixing parts.
• 🔧 Hammer and mallet (for customization).

Materials for preparation and processing:

• 🧴 Anti-corrosion primer (for example, Body 930 or Dinitrol).
• 🧴 Putty (two-component, for example, Novol or 3M).
• 🧴 Paint in cans or for a spray booth (selection by car color code).
• 🧴 Sealant (for example, Terostat or SikaFlex).
• 🧴 Degreaser (White spirit or Antisilicone).

Additional equipment (if necessary):

• 🛠️ Pneumatic riveter (if the thresholds are fastened with rivets).
• 🛠️ Blowtorch (to heat the metal during fitting).
• 🛠️ Compressor and spray gun (for professional painting).

If you plan to paint the thresholds yourself, pay attention to indoor conditions: the temperature should be 18–25°C, humidity - no higher 60%. Otherwise, the paint will lie unevenly or take a long time to dry. Also prepare in advance respirator, gloves and safety glasses — working with metal and chemicals requires compliance with safety precautions.

Preparing the car: dismantling old thresholds and cleaning

This is the most labor-intensive stage, on which the quality of the entire installation depends. If rust is left on or the surface is poorly cleaned, new thresholds will quickly become unusable. Let's look at the process step by step.

1. Dismantling doors and interior elements

Before starting work, remove:

• 🚪 Doors (or at least disconnect them so as not to interfere).
• 🪑 Seats (if the thresholds pass under them).
• 🔌 Wiring and seals (carefully label the connectors!).
• 🚗 Rugs and floor covering (so as not to be damaged during welding).

2. Removing old thresholds

If the sills are rusted or damaged, they need to be cut out. To do this:

1. Mark cutting lines marker (back off 1–2 cm from the edge of rust).
2. Use a grinder to cut off the threshold, starting from the edges. Do not cut in one pass - this will overheat the metal and may deform the body.
3. Remove any remaining weld spots chisel or drill.

3. Cleaning and surface treatment

After dismantling:

• 🧹Remove rust metal brush or sandblaster (if you have access).
• 🧴 Treat bare metal rust converter (for example, Tsinkar).
• 🔥 Warm up problem areas blowtorch (if the metal is deformed).
• 🧴Apply primer for metal in 2–3 layers.

What to do if rust has eaten through the metal?

If corrosion has destroyed the metal into holes, you will need welding patches. To do this:

1. Cut out the damaged area with a grinder.

2. Select a piece of metal of the same thickness (usually 0.8–1.2 mm).

3. Weld the patch spot welding, then clean the seam.

4. Treat with anticorrosive and putty.

If the hole is large (more than 5 cm), it is better to use overlap welding with lining on the inside.

Please note: if the body is in the place where the thresholds are attached deformed, it needs to be straightened straightening or spotter before installing new parts. Otherwise, the thresholds will lie unevenly, and you will have to redo them.

Installation technology: welding, fastening and fitting

Now we move on to the most important stage - the installation of new thresholds. The important thing here is to be consistent and take your time, especially if you are working with welding for the first time.

1. Trying and fitting

Before welding:

• 📏 Attach the new threshold to the installation site and check the gaps (they should be the same along the entire length).
• 🔧 Customize the part if necessary hammer or bending machine.
• 🔩 Secure the threshold clamps or magnetic holders.

2. Welding thresholds

For steel use semi-automatic welding (MIG/MAG), for aluminum - argon-arc (TIG). Basic rules:

• 🔥 Weld pointwise (step 2–3 cm), rather than a continuous seam - this will reduce the risk of deformation.
• 🔥 Start with edges and move towards the center.
• 🔥 After each seam, let the metal cool (1-2 minutes).
• 🔥 Use filler wire diameter 0.8 mm for steel and 1.6 mm for aluminum.

3. Seam processing

After welding:

• 🔨 Clean the seams Bulgarian with a petal circle.
• 🧴Apply putty on unevenness (layer no thicker 2–3 mm).
• 🧴 After the putty has dried, sand the surface sandpaper P120→P400.
• 🧴 Cover with 2 layers of primer.

4. Fastening without welding (for pads)

If you install plastic or aluminum pads, they are attached to:

• 🔩 Self-tapping screws (with pre-drilled holes).
• 🧲 Double sided tape (for light pads).
• 🔩 Rivets (if the cover is metal).

Important: when fastening with self-tapping screws, use rubber gasketsto avoid corrosion at fastening points.

Anti-corrosion treatment and painting

Even perfectly installed thresholds will not last long if they are not protected from rust and external influences. This step is often overlooked, but it is no less important than welding.

1. Anti-corrosion treatment

Before painting:

• 🧴Apply acid soil (for example, Reoflex) on bare metal - it transforms microscopic rust.
• 🧴 Coat the inner surface of the thresholds anti-gravel (for example, Dinitrol 479 or Tectyl).
• 🧴 Treat welds sealant (for example, Terostat 922).

2. Painting

For quality results:

• 🎨 Use spray paint (if you are painting for the first time) or compressor with spray gun (for professional results).
• 🎨 Apply paint in 3–4 layers with intermediate drying 10–15 minutes.
• 🎨 Last layer - varnish (for shine and protection).
• 🎨 Dry in dustproof box or under a canopy (direct sunlight will damage the paint).

3. Protection after painting

To keep the thresholds looking longer:

• 🛡️Apply polish 2-3 days after painting.
• 🛡️ Install mud flaps or protective film (vinyl).
• 🛡️ Wash thresholds regularly contactless car washto avoid chipping.

Common mistakes and how to avoid them

Even experienced craftsmen sometimes make mistakes when setting thresholds. We have collected TOP-5 most common mistakes and ways to prevent them.

Error	Consequences	How to avoid
Incomplete removal of rust	Corrosion spreading under new threshold, rework required	Use sandblaster or rust converter
Continuous weld	Deformation of metal, cracks in paint	Cook in batches with breaks to cool
No anti-corrosion treatment	Rust appears after 1–2 years	Apply primer and anti-gravel to all surfaces
Incorrect selection of thresholds	Gaps, loose fit, creaks	Check catalog numbers or templates
Painting without degreasing	Paint is peeling and bubbling	Treat the surface with white spirit before priming

Another common problem is squeaks after installation. They arise due to:

• 🔊 Poor fit of the threshold to the body (needs to be digested or modified).
• 🔊 Lack of sound insulation (use bitumen mats or vibroplast).
• 🔊 Poor-quality fastening of the linings (check the tightness of the fit).

Cost of installing thresholds: comparison of self-installation and car service

The price of installing thresholds depends on the material, complexity of the work and region. Below are approximate prices for 2026.

Type of work	On your own (rubles)	Car service (rubles)
Steel thresholds (replacement by welding)	3,000–8,000 (materials + tools)	15 000–30 000
Aluminum thresholds (TIG welding)	5 000–12 000	25 000–45 000
Plastic linings (fastening with clips)	1 500–4 000	5 000–10 000
Painting thresholds	2,000–5,000 (cans)	8,000–15,000 (paint booth)

Is it profitable to do it yourself? Yes, if you have the tools and experience. For example, replacing steel thresholds in a service will cost 20,000–30,000 rubles, and independently - in 5,000–10,000 rubles (including the purchase of materials). However, if you have never held a welding machine in your hands, it is better to trust the professionals - redoing poor-quality welding will cost more than the original installation.

Where to buy thresholds? Optimal options:

• 🛒 Official dealers - original parts, but expensive.
• 🛒 Online stores (Exist.ru, Autodoc) - a wide selection of analogues.
• 🛒 Showdown — used thresholds in good condition (cheap, but risk of corrosion).

FAQ: Answers to frequently asked questions

Is it possible to install thresholds without welding?

Yes, if it is overhead thresholds made of plastic or aluminum. They are attached with self-tapping screws, rivets or double-sided tape. However, to replace load-bearing thresholds welding is required - other methods will not provide sufficient strength.

Which welding machine is best for thresholds?

Suitable for steel semi-automatic MIG/MAG (for example, Resanta SAIPA-160 or Svarog MIG 200). For aluminum you need TIG machine (for example, BlueWeld TIG200ACDC). Power - no less 160 A.

How long does it take to install thresholds?

Depending on complexity:

• 🕒 Plastic linings - 1–2 hours.
• 🕒 Steel thresholds (welding + painting) — 8–16 hours (extends over 2–3 days, taking into account drying).

Do I need to remove the doors when installing thresholds?

It is advisable, especially if the thresholds are adjacent to the racks. This simplifies access and reduces the risk of door damage during welding. If you don’t want to remove the doors, at least unscrew them and move them to the side, securing them with a rope.

How to avoid corrosion after installation?

Key measures:

• 🔹 Treat the inner surface anti-gravel.
• 🔹Apply sealant on welds.
• 🔹 Wash thresholds regularly and apply wax or polish.
• 🔹 Inspect the thresholds once every 3 months for chips.