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Donovan Spring Co., Inc.
Donovan Equipment Co., Inc.
6 Enterprise Drive
Londonderry, NH 03053
(603) 627-9800

1-800-458-3867
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U-BOLTS    

What is a U-bolt?

U-bolts are common bolts that are used for building construction and/or vehicle suspension like leaf springs. Considered one of the major parts of your leaf spring installation, u-bolts will provide a permanent tie between the spring leaves and your axle.

• Primarily, the truck u-bolts provide the force required to clamp the leaf spring and  related components firmly together. In addition to the leaf spring, these  components include the top plate, axle seat, axle and bottom plate.

• The properly installed u-bolt eliminates any flexing of the leaf spring in the area between the u bolts. This is particularly critical since the hole for the centerbolt  in each leaf acts as a stress concentration which would lead to rapid leaf  breakage if spring flexing was not totally eliminated by the U bolt clamping force.

• By firmly clamping the spring to the axle seat the horizontal forces acting on the centerbolt are greatly reduced which in turn prevents shearing of the centerbolt.

• Proper clamping of the spring by the truck u-bolts provides the desired spring stiffness  and contributes to maintaining the vehicle ride height and handling characteristics as originally specified for the vehicle.

When would I have to replace my existing u-bolts?

This is one of the most common questions we get concerning U-bolts. When you remove your existing u-bolts for maintenance, we highly recommend that you replace them with new bolts of the same size and shape

 • Used U-bolts will have rusted and damaged threads from the previous installation.

 • A previously torqued U-bolt will suffer from distorted threads from the engagement of the deep nut.  Deep nuts should be tightened once and re-torqued, never loosened and retightened.

 • A used u bolt may have suffered from fatigue as well excessive stress since achieving accurate torque with commonly used impact wrenches is very difficult.     

How do I measure a u-bolt?
So you are now ready to get your new or replacement u-bolt. We offer u-bolts bent to the manufacturers specifications  including Chevy/GMC, Dodge, Nissan, Ford and Toyota. But if you do not see your measurement here then we will custom bend the u-bolts for your specific vehicle. When ordering a custom bent u-bolt it is important to know the type of measurement you need. Regardless of the bend type, all u-bolts are measured in the same manner.  The u-bolt size is given as:

  • ( A ) x Rod diameter
  • ( B ) x Distance between the legs
  • ( C ) x Leg Length.
    Additionally the bend type must also be given; Round, Semi-Round, or Square. If the top is a Forged top u-bolt, these are best ordered by application and leg length.

How to install new U-bolts

Removing and replacing your existing u-bolts is rather easy. When doing so, make sure your vehicle is on a flat, level surface. You will jack one side up and place your vehicle onto jack stands(always work safe). Find the damaged u-bolt or u-bolts you want to replace. Remove the nuts to the small metal piece that is connecting each part of the u-bolt. Remove it then place the newer u-bolt around the leaf spring. Using two nuts, you will connect the two parts of the “U” with the small metal piece. Using a socket wrench, you will tighten the nuts. Lower your truck and you are finished. Please note, you must always keep the u-bolt nut tight at all times and re-torque the u-bolt within 500 miles after being replaced. This will help when your spring is settling.

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