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How Suspension Bolts Work

Types of Suspension Bolts
Shackle bolts lock shackle links into place between the suspension system and the vehicle or trailer.
Shackle bolts lock shackle links into place between the suspension system and the vehicle or trailer.
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Attaching wheels to a car body is easy when you're playing with those building blocks for kids. Connecting a real suspension system to a vehicle or trailer, however, isn't as simple. Different connections involve the use of different bolts. Below, we'll examine the main types of suspension bolts you'll find in a suspension system.

Shackle bolts: Shackle links are one way automakers connect the vehicle body to the wheels. As you can see in the adjacent image, one side of each shackle link hinges to the vehicle and the other to the suspension. Nuts screw down over the ends to prevent the bolts from sliding off, and grease keeps these parts moving freely.

U-bolts: These horseshoe-shaped bolts loop over or under a vehicle's axle, while the ends screw firmly into nuts on the other side of a metal plate. Carmakers use this arrangement to fix bow-shaped leaf springs snugly against the axle. To learn more, read How Leaf Springs Work.

Spring eyebolts: While U-bolts attach the center of a leaf spring to the axle, eyebolts attach the ends of the spring to the vehicle or trailer body. These simple bolts slip through round eyes at either end of the bow-shaped leaf spring, as well as through round hanger holes on the frame.

Spline bolts: When you want a bolt to fasten something without rotating, then this is the hardware for you. Spline teeth extend from the sides of the bolt, securing it. Frequently, they're used to lock shock absorbers in place.

Equalizer bolts: Equalizer hitches apply leverage across the trailer tongue and towing vehicle, distributing heavier loads more evenly. Equalizer bolts simply secure these hitches. Some models feature a cotter pin, which slides through the end of the bolt and the castle screw to keep the nut from sliding off the end.

On the next page, we'll explore how to use suspension bolts.