How to Measure the Length of a Tapered Lug Bolt

A tapered mag or shank lug bolt

Lug bolts, also known as lug nuts, fasten wheels onto a car. Selecting the proper size and type of lug bolts is crucial to the performance and safety of your vehicle. Lug bolts are classified by their shape: ball seat lug bolts use a spherical head, the body of mag or shank lug bolt is pointed, beginning with a fat head and tapering off to a narrow point, and conical or acorn lug bolts have a tapered head. Whether you're measuring a tapered mag bolt or a tapered-head conical bolt, the principles are the same.

Things You'll Need

• Measuring tape

Instructions

1. Align the metal end of a measuring tape with the base of the lug bolt's head, between the head of the bolt and its threads.

2. Open the measuring tape to the end of the lug bolt. Read the length on the tape. The distance from the base of the bolt's head to the end of the bolt is known as its usable length, and is the most common measurement found in lug bolt length descriptions

3. Place the end of the measuring tape at the end or top of the lug bolt's head.

4. Open the tape to the end of the lug bolt. Read the length on the tape. This is the bolt's total length.

Tips & Warnings

• Only use lug bolt types specified by the manufacturer of your car.

References

• UC Davis College of Engineering: To Determine the Size of a Bolt (PDF)
• Custom Wheels Market: Wheel Installation Instructions
• Bolt Depot: Measuring Fastener Length