At BAER, we never tire of highlighting the **versatility of threads** – one such special product is the thread on wheel bolts. They literally hold your entire vehicle together, transmit movements, and help keep machines running smoothly, even moving fluids. However, there are applications where threads are **life-saving** in the truest sense, providing a firm grip and special properties for your safety. A perfect example is the thread on wheel bolts or wheel nuts.
Traveling at 90 mph on the highway and suddenly having a wheel come off? That would be an **absolute disaster**. Wheel bolt threads help prevent such scenarios and are exposed to **extreme conditions**. They have to withstand not only shocks and vibrations but also constantly changing **weather conditions**, **moisture, and temperature fluctuations**.
Whether due to a breakdown or during seasonal tire changes, you’ve likely changed a wheel yourself at some point. If so, you're already familiar with the **threads on wheel bolts or wheel nut threads** firsthand. Perhaps you've even wondered about their significance. But we still have a few **interesting facts** up our sleeve that you might not know. Let's dive in!
### Thread on Wheel Bolt or Wheel Nut? Here’s the Difference
The wheel hub acts as the **connecting piece between the wheel and the axle**. Modern cars use two different models for attaching wheels to the wheel hub. The location of the threads on a car wheel depends on which of the two **methods is used in a vehicle**.
Especially in Europe, **wheels are mostly attached to the wheel hub using wheel bolts**. This means the wheel hub has several holes with an internal thread. For mounting, you need **wheel bolts with the corresponding thread**. So, when attaching such a wheel, you must ensure that the **holes with the wheel hub threads and the openings in the rim align perfectly**. Only then can the wheel bolt threads properly engage.
In contrast, the wheel nut model uses **studs with an external thread** directly attached to the wheel hub. During mounting, the wheel is aligned so that the **bolts fit exactly through the openings in the rim**. Now, the wheel nuts come into play. The thread on wheel nuts is an **internal thread**, matching the external thread of the bolts. They can easily be screwed on to **hold the wheel in place**. Vehicles with this system are more common in the USA or Asia. However, some German manufacturers, like Opel, still use **wheel nut threads for many models**.
### A Special Case: Racing Cars
A **special case is racing cars**, where wheels need to be changed very quickly during pit stops. This is achieved using a **central lock system**. Here, a single wheel bolt thread is enough to mount the wheel. Manufacturers like Porsche use this technique in regular road traffic. Due to the **rotational movement in the central thread**, there's a risk that the wheel bolt threads on the right side of the vehicle might come loose during driving. Hence, a **left-hand thread** is used for wheel bolt threads on this side.
### Car Threads – These Threads Are Found on Car Wheels
Threads on wheel bolts and wheel nuts must be able to **withstand vibrations on various terrains** without coming loose. It's no surprise that many wheel bolt threads are **fine threads**. Fine threads have a smaller pitch compared to coarse threads. Wheel bolts with fine threads, therefore, have a **particularly high self-locking feature** and don't require **additional securing**.
Depending on the manufacturer, the most common **thread standards** for wheel bolt threads are the **metric fine thread MF** or its **American counterpart**, the inch-based Unified National Fine Thread (UNF). The sizes of wheel bolt threads vary depending on the model. Popular sizes include MF 12 and MF 14, each with a pitch of 1.25 mm or 1.5 mm. For American wheel bolt threads, UNF ½†– 20 is a common choice.
### Tap for Car Tire Threads
You might wonder why you should care about the size of the wheel bolt threads on your vehicle. If you do, you're among the lucky ones who've never encountered any problems while changing a wheel.
Unfortunately, the reality often proves different. After all, wheel bolt threads face a lot: mud, rain, snow — a fine thread can fail under these conditions. If rust sets in on the wheel bolt thread, the annual struggle begins: a wheel bolt simply refuses to come off. And it's always the last wheel that poses problems. Sometimes, with some force and/or persuasion, you might succeed, only to realize the wheel bolt thread got damaged in the process. To find a replacement, you could certainly pay a professional. Or you could **solve the problem yourself** if you know the **thread size of the wheel bolt**.
With the right **screw tap**, you can easily recut and clean the wheel bolt thread, wheel nut thread, and wheel hub thread from dirt and corrosion. And if you do this regularly, you'll less often encounter the problem of **stuck wheel bolts**. But be warned, in severe cases, you should still take your vehicle to a workshop and have the threads recut by a professional.
If you're looking to tackle the wheel bolt thread yourself, BAER, the **tap manufacturer**, has the right tool for you. In our online shop, we offer hand taps for metric or UNF fine threads, allowing you to gently repair your wheel bolt thread. If you have any questions, feel free to **contact us**. Our customer service is always here to assist you.
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