TruckSpring Times

Truck & Trailer Parts - News & Information

Replacing Your U-Bolts

When installing your U-bolts, it is important to remember to keep your truck on a level surface that is as close to flat as possible. Jack up one side, put the truck on the jack stands and locate the damaged U-bolt that you would like to replace. Take off the nuts of the u-bolt and remove. Old, rusted u-bolts many need to be cut off. Place the new U-bolt around the leaf spring. Connect the two portions of the "U" with two nuts. Use a torque wrench for the installation. Tighten them in a cross pattern, gradually bumping up the torque.

Consult with the vehicle or suspension manufacturer for your particular truck model's advised torque level. The pressure of the U-bolt should be distributed in an even manner along the top plate's width. Make sure the proper fit is attained for a solid clamping force. Lower your truck back to the ground. Don't forget that the U-bolt should be kept tight throughout the year. Mark your calendar to re-torque the U-bolt after 500 miles worth of driving after the replacement. Your spring will settle much more nicely as a result. 

Proper Fit of your U-bolts

If your U-bolts are semi-round, proper fit is essential to maintain clamping forces. Unlike square or round bend U-bolts that do not vary much from one manufacture to another, semi-round bend shapes are usually unique to a particular vehicle or suspension manufacturer. A mismatch between the shape of the semi-round U-bolt and its mating parts can cause an inability to provide the proper clamping force.

In figure 1 the U-bolt has been formed with a shape that causes all the pressure to be concentrated at the center of the suspensions top plate. As the leaf spring flexes under normal operation, the U-bolt will work into the top plate which will lead to loose U-bolts and possibly premature leaf spring failure.

In figure 2 the shape mismatch is causing the pressure to be concentrated at the corners of the top plate. This will cause deformation of the top plate and as a result the clamping force will be diminished and premature leaf spring failure may be the result.

In figure 3 the proper U-bolt fit has been accomplished. The shape of the U-bolt matches the suspensions top plate resulting in even pressure distributed along the width of the top plate allowing for proper clamping forces.

U-bolts are a vital part of your suspension system and should never be reused. Failure to replace or properly fit your U-bolts when maintaining or servicing your suspension could cause premature failure of your leaf springs or other components with catastrophic results.

We have been custom bending and installing u-bolts in our service department for years. If you have any question about install you u-bolts or need new ones, call 1-800-358-4751 to talk to one of our leaf spring suspension experts.

Leaf Springs and common causes of failure.

Ever have a leaf spring crack, become fatigued or break and wonder what the cause is? We will take a look at a few common reasons why leaf springs fail.

Loose U-Bolts

The image below shows center bolt failure due to a truck spring not having tight enough u-bolts. U-bolts, especially on newly installed truck springs should be checked periodically to verify they are tight. Even if you have a professional installer install springs on your truck, you should stop by after 500 miles and have your u-bolts inspected to make sure they didn't come loose.

Leaf Spring Failure

Corrosion and Fatigue

Corrosion and fatigue are typically caused by a combination of time and the elements. Numerous variables will weigh on how long your leaf spring will last before it suffers from corrosion or fatigue. How much weight you haul, what part of the country you live in, etc. will play a role in the life of your springs. Making sure salt and other corrosive materials are washed off and not overloading your truck will help prevent corrosion and early spring fatigue.

Leaf Spring Failure

Overloading Your Truck Springs

Everyone says they never do it , but we see it all the time. Overloading is pretty self-explanatory. You have more weight in the back of your truck or you are towing a load heavier than what your truck is rated at. We all love to do it, but the negative effect on your truck springs is unavoidable. On the left image below you can see the radial shear marks from an overloaded spring. The image on the right shows distortion of the spring eye from overloading.

Leaf Spring Failure

How do you prevent overloading your truck springs? Obviously you could carry less weight or purchase a truck with a higher weight rating. If buying a new truck or hauling less weight is not an option, you could add an overload kit like a Firestone Air Spring kit, Hellwig Helper springs or a Air Lift Air Spring kit. Overload kits are designed to take some of the weight off the leaf springs and place it onto the overload kit.

Another option that is more popular with commercial vehicles it to add another piece of steel to the spring pack. This may cause the ride to be stiffer, but if you are always hauling heavier loads in a commercial setting this may be your best bet.

We do not recommend adding a new piece of steel to leaf springs that already suffer from fatigue. You are better off replacing both of your truck springs with new ones with a higher weight rating. It's very common that we will have someone only want to replace one busted leaf in a spring pack and a few months later a different leaf breaks. If one has cracked, the others are probably in the same condition and will not last much longer.

Weld Splatter

Weld splatter is more common in commercial trucks and vans that come from the factory without a bed or on motorhome leaf springs . This is caused by welding a body or accessories to your truck in the same area as your leaf springs. Just a small amount of weld spatter can be disastrous to the life of your spring. About the only way to prevent this is to inspect your springs after and make sure no one was careless with the welder.

Leaf Spring Failure

Above are a few common reasons why leaf springs fail. There are other manufacturing reasons such as quench cracks, tight eyes, notches, incorrect temperatures, etc. that can cause failure. With today's modern, high-tech manufacturing processes and quality control, they are not nearly as commons as they were in the past.

If you need have any questions about your leaf springs or need replacment leaf springs, call Michigan Truck Spring at 1-800-358-4751. They carry OEM replacment leaf springs for everything from old corvettes to semi trucks and trailers.