The question of where exactly the bolts in the wheel are screwed in, at first glance, seems elementary, but it hides a lot of technical nuances, on which traffic safety depends. Many motorists confuse the design features of the hub and the disc itself, and do not know the difference between the mounting systems on bolts and studs. Understanding how these elements interact is critical when seasonally replacing rubber or emergencyly replacing a broken wheel on the track.
Hub. It is the central unit on which the wheel is put. It is in it that the seats for fastening elements are located. Depending on the design of the car, it can be threaded holes, where bolts are screwed, or protruding studs, on which nuts are screwed. The mistaken notion that bolts are attached directly to the disc itself can lead to spoilage of expensive cast discs or, worse, to spinning the wheel in motion.In this article, we will take a detailed look at the anatomy of the wheel assembly, explain the difference between the types of mounts, and provide clear instructions on how to properly install.
Wheel assembly anatomy: hub and disc
To understand where the bolts are screwed, it is necessary to consider the interaction of two main details: the hub and the wheel disc. The hub is the part of the suspension connecting the wheel to the rest of the car. In the center of the hub is a central hole, and around it in a circle (at a diameter called PCD) are fasteners.
Wheel drive, if it were. stamped Or, it has a sleeves, or a sleeves. It is important to understand that the disk itself does not have threads. The carving is always either in the body of the hub (for bolts), or on the studs pressed into the hub (for nuts). Thus, the bolt passes through the hole in the disk and is screwed into the thread of the hub, tightening the disc with the flange.
The conicality or sphericality of the bolt head (or nut) plays a key role. When tightening, the cone part enters the return hole of the disk, centering it relative to the hub. This ensures a uniform distribution of the load and the absence of wheel beat when driving. If you use bolts with the wrong shape of the head, the disk will not fall into place, which will lead to vibrations and destruction of holes.
Always check the shape of the bolt head (cone or sphere) to match the shape of the hole in your drive, especially when buying new cast discs, where the holes often have complex geometry.
Bolt connection against hairpin
There are two main types of wheel mounting, and the type of your car depends on what you will encounter. In the first case, which is often found on cars of French, Korean and some German brands, a system of cars with a high-speed system is used. bolt. Here, the carving is cut directly into the body of the hub. When installing the wheel, you take a bolt, insert it through the disk hole and screw it into the hub.
In the second case, typical for most domestic cars (for example, the LadaJapanese and American models are used stud. The studs are rigidly pressed into the hub and stick out. In this case, you put a disc on the studs, and then screw them up. Here the question "where the bolts are screwed" is transformed into "what the screws are screwed up on."
Each system has its advantages and disadvantages. The bolt connection allows you to remove the wheel completely without fear that it will fall, but it is more difficult to get into the holes when installing the wheel on weight. Stilettos make it easier to install, as the wheel can simply be put on, but when removed it can slip if you do not hold it with your hands.
- 🔩 Bolts: carving in the hub, it is easier to store the removed wheel, it is more difficult to get into the holes during installation.
- 🔩 Stilettos: thread on protruding elements, it is easier to put on the disk, caution is required when removing in order to avoid falling.
- 🔩 Secrets: It can be used in both types of mounts to protect against wheel theft.
Location scheme and parameters of the fastener
It is not enough to know that the bolts are screwed into the hub. It is critical to observe the location of these holes. The main parameter is PCD Pitch Circle Diameter is the diameter of the circle along which the centers of the fastening holes are located. Even if the number of bolts is the same (for example, 4 or 5), a discrepancy of the PCD even by 1-2 mm will make the installation impossible or dangerous.
Also important is the diameter of the thread and the pitch of the thread. For example, a designation M12x1.25 means that the bolt diameter is 12 mm and the thread pitch is 1.25 mm. If you try to screw a bolt with a large step into a small thread of the hub, you can tear the thread in the hub itself, which will require expensive repairs with drilling and installing repair bushings.
The length of the bolt also matters. Too short bolt will not provide the necessary strength of the connection, and too long can rest on the brake mechanism or suspension elements, not allowing to tighten the wheel to the end. When installing slots or disks with a large flight, elongated bolts are often required.
| Parameter | Designation | Example of meaning | Importance |
|---|---|---|---|
| Number of holes | Number of | 4, 5, 6 | Critically. |
| Diameter of a circle | PCD | 98, 100, 114.3 | Critically. |
| Diameter of thread | D | M12, M14 | Critically. |
| Length of thread | L | 25 mm, 30 mm | Tall. |
What is a 4x98 and 4x100 chat?
These values are very close, and some grief masters try to put 4x100 discs on the hubs of 4x98. This is NOT CATEGORIAL to do. The wheel will become skewed, the bolts will work at a break, and after a few hundred kilometers the wheel can come off, and the studs - to pull from the hub.
The correct order of tightening of bolts
When you have decided where the bolts are screwed, and have begun installation, it is extremely important to observe the sequence of their tightening. If you just twist the bolts in a circle (1-2-3-4-5), the disk can be skewed, and it will not lie tightly against the hub along the entire plane. This will lead to the fact that when moving the wheel will beat, and the fastener will begin to loosen spontaneously.
The correct method is a puff with a "star" or "cross-cross". For four-bolt wheels, the scheme looks like a cross: 1-3-2-4 (conditionally: upper, lower, left, right). For five-bolts, it is a continuous five-pointed star: 1-3-5-2-4. This scheme ensures a uniform adjoining of the disc to the hub.
The tightening process should take place in two stages. First, the bolts are twisted from hand to stop to make the disk stand in place. Then, lowering the car so that the wheels slightly touch the ground (or using a dynamometer key on the weight), a preliminary puff is made. The final puff is carried out strictly after the wheel is completely lowered to the ground, with the force indicated in the manual of the car.
☑️ Algorithm of wheel installation
⚠️ Attention: Never use a shock wagon for the final tightening of the wheels on alloy wheels. Excessive force can lead to cracks in the disk or a failure of the thread. Use the dynamometer key.
Common mistakes in wheel installation
One of the most common mistakes is to ignore the purity of landfill surfaces. There should be no dirt, sand or thick rust between the disc and the hub. If you screw the bolts into a dirty connection, the disk will sit with a skew. On the first trip, the dirt will thicken or swell, and the bolts will weaken, which will lead to the loss of the wheel.
Another mistake is the use of rusted or damaged bolts. If the thread of the bolt is "slime" or covered with corrosion, it will not create the necessary tightening force. Often drivers forget that bolts tend to stretch and get tired. Modern cars often use controlled tightening bolts, which are recommended to be changed every time the wheel is removed, although this is rarely observed in practice.
It is also dangerous to use adapters (eccentrics) to change the chatter without consulting an engineer. Such details change the shoulder of the application of force and can lead to breakage of the hub or the adapter itself at high speed.
- 🚫 Dirt: Lack of cleaning of the hub before installation.
- 🚫 Lubricant: lubrication of bolt thread with oil (the coefficient of friction changes, the risk of dragging and breaking the thread).
- 🚫 Order: It's a round-robin bolt, not a cross-root.
The purity of the landing plane of the hub and disc is more important than the force of the tightening. Mud between metals is the main reason for the wheels to unscrew themselves.
Pushing moment and safety control
After the bolts are screwed in, you need to make sure the work is done correctly. For each vehicle, the manufacturer regulates puff-up. For passenger cars, it is usually from 90 to 120 Nm, for SUVs and crossovers it can reach 140-150 Nm. Accurate data is always in the instructions for operation or on specialized sites.
After installing new wheels or seasonal replacement of rubber, it is recommended to check the tightening of the bolts through 50-100 km of run. The metal of the disc and hub may slightly "sit down", and the tightening force will decrease. A lift is mandatory at this point.
Check the condition of the bolts regularly. If you notice that the paint on them climbed, rust appeared or they look deformed - replace the kit. The cost of new bolts is incommensurable with the risk of losing a wheel on the track. Remember that the question of where the bolts are screwed in is not only a question of geometry, but also the reliability of the entire node.
⚠️ Attention: If you feel the rudder beating or body vibration when you are driving, stop immediately and check the tightening of the wheel bolts. The weakened fastener destroys the holes in the disk in a matter of kilometers.
Can I use the bolts from another car?
Use bolts from another car can only be if all the parameters are completely identical: length, diameter of the thread, pitch of the thread, shape of the head (cone / sphere) and the radius under the turnkey. Visual similarity does not guarantee compatibility. An inappropriate bolt may not reach the thread or, conversely, rest ahead of time.
What to do if you break the thread in the hub?
If the thread in the hub is torn, screw the bolt normally will not work. Solutions: drilling old thread and cutting new (greater diameter) with the selection of appropriate bolts, or installing a repair sleeve (throwers). In some cases, the entire hub assembly is required to be replaced.
Do I need to smear the bolts before installation?
Modern standards of most automakers prohibit lubricating the thread of wheel mount bolts with oil or graphite lubricant. The lubricant drastically reduces friction, and when tightened with a dynamometer key, you will create excessive tension, which will lead to the pulling of the bolt and eventual failure of the thread. The bolts should be clean and dry.
Why do the bolts rust and stick?
Bolts rust due to the ingress of moisture and reagents into the threaded connection. To avoid cramming, some craftsmen use copper lubricant (antiseptic) on the smooth part of the bolt and on the thread (with caution), but not on the cone part. However, the best protection is the regular removal and cleaning of the wheels, as well as the use of quality bolts with a good zinc coating.
How to identify PCD without tools?
It is difficult to accurately determine the PCD ruler, especially for 5-bolt disks. For 4-bolts, you can measure the distance between the centers of opposite holes - this will be PCD. For 5-bolts, the distance between the centers of neighboring holes is measured and multiplied by a special coefficient (for 5 holes x 1.701), but it is easier to use an online chatter calculator or a barbell taking into account the formula.