The lug nuts hold the wheel firmly to the mounting plate, but it is the wheel-to-axle connection that actually holds the weight of the car. This is a hub-centric connection, as the wheel is centered by its connection to the axle hub. The center bore of the wheel is sized to fit perfectly onto the axle of that car. The auto maker designs an OEM wheel to fit on a certain car or range of cars. Nearly all OEM Wheels are designed to be hub-centric. Many would be very familiar with these terms. Therefore it is imperative, that the lug bolts/nuts are tightened to the manufacturer's specified torque settings. As long as the clamp force is greater than the shear force applied by the hub trying to turn and the wheel resisting the turn due to inertia, all is well. In simple terms - the rotating hub also rotates the wheel, mainly due to the friction between the mating surfaces of the hub and the wheel, which are clamped together with lug bolts or lug nuts. If the bolt torque specified for a joint is applied, then the resultant Clamp Load should also be within specification. The amount of friction and Clamp Load determines the level of resistance the joint has to movement.Ĭlamp Load is created by tightening the bolts against the mated surfaces and is normally measured in foot pounds of torque with a torque wrench. The friction of the two mated surfaces and the force created from clamping them together with bolts (Clamp Load) allows the surfaces to resist movement. Let us have a brief look at bolted joints.Ī bolted joint, such as a wheel mounting system, works by tightly clamping two surfaces together. The wheels are attached to the hub by a bolted joint. The rest is beyond the scope of this discussion. Let us stick only to the hub - wheel power transfer. When we engage a gear and release the clutch, the engine starts to turn the transmission, which then turns the hubs and finally turns the wheels. I will be referring to them as "PCD Variation Bolts" only, if that makes people feel better. Many people feel that these are unsafe, just because they are called "Wobble Bolts". Wobble Bolt is just the shop floor name and is kind of scary.
![emotion aluminum racing red wheel lug nuts emotion aluminum racing red wheel lug nuts](https://cdn.shopify.com/s/files/1/1162/7278/products/IMG_5337.jpg)
This is an attempt to share my findings and the answers to these questions to the best of my knowledge and dispel some myths and present some realities.įor starters, the correct technical name is PCD Variation Bolt.
![emotion aluminum racing red wheel lug nuts emotion aluminum racing red wheel lug nuts](https://ae01.alicdn.com/kf/HTB1QuTIXVOWBuNjy0Fiq6xFxVXaS/Blox-Forged-7075-Aluminum-Racing-WheelLug-Nuts-P-1-25-L-50mm-20Pcs-Set-EP-BLOX.jpg)
What are these? When to use them? Are they safe? These were the questions that haunted me, when I considered putting 100 PCD alloys on my 98 PCD Linea T-Jet.