Installation of new thresholds or fixation of decorative linings is a procedure that allows not only to improve the appearance of the car, but also to protect its body from mechanical damage, corrosion and impacts with small stones. Many car owners are faced with the need to replace the broken elements or install new ones to give the car a more aggressive and sporty style. It is important to understand that the quality of the result directly depends on the choice of consumables and the thoroughness of surface preparation.
The installation process may seem simple only at first glance, but ignoring technological nuances often leads to the fact that after a few months of operation, parts begin to move away, rattle or lose their presentable appearance. In this article, we will take a detailed look at all the steps of the job, from choosing the right adhesive to the final polishing so that you can get the job done in a quality and long-lasting manner. The right approach will save you money on re-repairs in the future.
Selection of the appropriate adhesive composition
The first and most critical stage is the choice. gluewhich will keep the slack throughout its lifetime. The automotive chemicals market offers many options, but not all of them are suitable for operating conditions in the lower part of the body, where there is a high probability of moisture, reagents and temperature changes.
The most popular and time-tested solution is polyurethane glue sealant. It has high elasticity after drying, which allows you to compensate for body vibrations and thermal expansion of the plastic. Unlike hard epoxy resins, polyurethane does not crack over time, providing a reliable grip on metal and plastic.
The second important component is often two-component tape, which serves for initial fixation until the glue is completely polymerized. The combination of these two materials gives the best result, ensuring that threshold It won't shift during the drying process.
⚠️ Note: Do not use regular "Superglue" (cyanacrylate) or mounting foam to fix thresholds. The first is too fragile and afraid of moisture, and the second will not provide the necessary strength and accuracy of the seam.
When buying glue, pay attention to the labeling "for external work" and resistance to ultraviolet light. There are also special activators and primers that are applied to the surface before the main glue to improve adhesion, and you should not neglect them if you want to get factory quality.
Buy adhesive and primer from one manufacturer – chemical formulations in the same brand’s lineups are often designed to interact perfectly with each other.
Required tools and materials
For high-quality work you will need to prepare not only the glue itself, but also a number of auxiliary tools. Lack of the right inventory can delay the process or make it impossible at a certain stage. Get everything you need in one place in advance so you don’t get distracted while working.
You will need a degrease (antisilicone) that will remove all fat spots and bitumen residues. Also, an abrasive material is needed - sandpaper of different grains or scotch-bright to create rice on metal. For applying glue, it is convenient to use a special gun if the tube requires it, or a spatula.
Do not forget about paint tape, which will help fix the detail in the desired position, and rags to remove excess glue. If you plan to paint or paint the edges, you will need the appropriate materials, but for a simple sticker, a basic set is enough.
- 🛠️ Degreasing and clean rags
- 🛠️ Sandpaper (P400-P600 grain) or Scotch Bright
- 🛠️ Glue gun (if necessary)
- 🛠️ Paint tape and fixtures
- 🛠️ Primer for plastic and metal
It is important that all tools are clean and dry. The entry of dust or moisture into the adhesive seam can be the point of beginning corrosion or detachment of the part in the future.
Preparation of body surfaces and thresholds
The quality of surface preparation determines 90% of the success of the entire operation. Even the most expensive polyurethane It will not stay on a dirty, greasy or smooth surface. Therefore, the cleaning and matting stage is mandatory and does not tolerate rush.
First, you need to thoroughly wash the threshold installation area, removing all dirt, sand and salt. After washing, the surface is dried and treated with a degreasing agent. Rub the metal and plastic with a clean wipe, constantly changing its side so as not to smear the fat on the surface.
Then comes the matting phase. Glossy paint on the body and smooth plastic threshold should be made rough. For this purpose, small sandpaper or scotch bright is used. Your goal is to create a uniform matte risk that will increase the area of contact of the glue with the surface.
Why do you have to retrieve the surface?
The microscopic scratches created by the abrasive work as anchors for the glue. On a smooth surface, the glue lies with a film that is easy to tear off, and in the pores of the matte surface it polymerizes, creating a mechanical adhesion comparable to welding in strength.
After machining, rub the surfaces again with a degreasing agent to remove dust from grinding. Then apply the primer (adhesion activator) to both glued planes. Let the primer dry according to the instructions on the package - this usually takes a few minutes.
☑️ Installation readiness check
Technology of applying glue and installation
The most important moment is the application of adhesive composition. If you use a tube with a gun, squeeze the glue with a flat strip ("sausage") with a diameter of about 5-7 mm. Apply the composition to the end of the threshold, and the return part of the body, if the design allows, or only on one of the surfaces, following the instructions of the glue manufacturer.
It is important to observe a step from the edge of the part (usually 5-10 mm), so that when pressed the glue does not get beyond the lining too much. Excess glue will be difficult to remove, and they can spoil the appearance of the car. Some masters recommend applying glue with dotted or zigzag for better distribution.
After applying the glue, carefully apply the threshold to the installation site. Do not press it hard at once - first combine all the holes and edges. After making sure that the positioning is correct, tightly press the detail along the entire length. For fixation, use paint tape, stretching it across the threshold to the roof or hood / luggage.
| Type of glue | Seizure time | Time of complete polymerization | Temperature regime |
|---|---|---|---|
| Polyurethane | 15.30 minutes. | 24 hours. | +5°C to +35°C |
| Epoxy (2K) | 5-10 minutes | 12:24 hours. | +10°C to +30°C |
| Modified silicone | 20-40 minutes. | 48 hours. | 0°C to +40°C |
If the kit is double-sided tape, first glue the thresholds on it for primary fixation, and then, if the design allows, run the glue through the technological holes or around the perimeter. However, the method of "scotch + glue" most often involves applying glue under the tape itself or in the center of the part.
⚠️ Attention: The work on bonding should be carried out at an air temperature not lower than +15 ° C. In cold rooms or in the cold, the glue may not polymerize correctly, which will lead to a loss of strength of the compound.
Fixation and drying time
After setting the threshold and stretching the fixing tapes, the waiting process begins. Primary grasp time It is 15 to 40 minutes, depending on the type of adhesive and ambient temperature. During this period, it is strictly impossible to touch, shift or check the part for strength.
Full polymerization (maximum strength set) takes 12 to 24 hours. During this time, it is better to leave the car in a warm garage. If this is not possible, try not to operate the car actively, avoid washing under high pressure and off-road driving in the first day.
Paint tape can be carefully removed after 2-4 hours, when the glue is a little "grabbed" and ceases to be liquid. However, remove the fixing stretch marks that keep the threshold pressed against the body, it is recommended not earlier than 12 hours, and ideally - leave for a day.
The rate of drying depends on the humidity and temperature. In hot dry weather, the process goes faster, in cold and humid - slower. Do not try to speed up the process with a hair dryer unless recommended by the chemical manufacturer, as uneven heating can lead to bubbles in the adhesive seam.
Removal of surpluses and finishing
If the excess glue is still outside when pressing the thresholds, they must be removed before complete polymerization. While the glue is fresh, it can be carefully removed with a spatula or a rag dipped in a solvent (if the type of glue and coating of the car allows it).
After drying, it will be very difficult to remove the glue mechanically, you can damage the paint coating. Therefore, carefully inspect the perimeter of the installation immediately after installation. If the glue is frozen in the form of "snot", they can be carefully cut with a sharp blade, but act extremely carefully.
The final stage will be the washing of the car and polishing the area around the rapids to remove fingerprints, tape and possible micro scratches obtained in the process. This will give the work a complete, professional look.
- 🧼 Check the perimeter for the presence of protruding glue
- 🧼 Carefully remove the residues before freezing
- 🧼 Wash the body from traces of primer and degreaser
- 🧼 Polish the transitions between the threshold and the body
Now your car is protected and the rapids will be pleasing to the eye and will perform their function for years to come. Properly glued elements withstand washings with kercher and gravel strikes on the track.
The main secret of success is not to save on drying time. Trying to start operating the machine ahead of time can negate all previous work.
Frequently Asked Questions (FAQ)
Can I put the doorsteps on the street in winter?
It's not recommended. Most adhesive formulations require temperatures above +10 ... +15°C for normal polymerization. In the cold, the glue will remain sticky or become brittle. Work should be carried out in a warm room.
Do I need to remove old thresholds before gluing new ones?
Yes, old elements need to be dismantled. It is impossible to glue new rapids on top of the old ones, since moisture and dirt will accumulate between them, which will lead to corrosion of the metal of the body, which you will not be able to see and process.
How to degrease the surface if there is no special antisilicone?
In extreme cases, isopropyl alcohol can be used. Gasoline, kerosene or solvent 646 is undesirable to use, as they can damage the paint coating or leave a greasy film that worsens adhesion.
How long does the glue for the thresholds dry?
The initial grasping time is 20-40 minutes, but the glue gains full strength after 24 hours. Before the expiration of this time, it is not recommended to wet the car or expose the thresholds to loads.
Can we use liquid nails?
Conventional construction liquid nails are not suitable for a car. They are afraid of constant moisture, vibration and temperature changes. Use only specialized automotive polyurethane sealant adhesives.