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Do Polyurethane Leveling Kits Wear Out?

Posted in How To: Suspension Brakes on March 12, 2016
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Leveling kits are a popular and affordable way to fit larger tires on a truck or SUV equipped with coil springs or coilover struts. They basically come in three flavors: steel, aluminum, or molded polyurethane. Searching on web forums yields information like, “My truck weighs 5,000 pounds, so I went with steel spacers,” and, “Poly will compress and wear out faster.”

To test these theories, we borrowed a 2008 Super Duty that has been equipped with a polyurethane leveling kit for the past 200,000 miles. We pulled off one of the old polyurethane spacers and compared it to a brand-new unit to determine what, if any, wear there was on the part. As they say on the internet, you won’t believe what happened next.

This 2 1/2-inch spacer has been installed on this F-250 for the last eight years and 200,000 miles. Some have accused polyurethane leveling kits of being noisy on half-ton trucks equipped with struts, but noisy struts are typically the result of improperly sized hardware where the metal sleeve extends past the bushing and makes contact with the metal strut bucket, not the polyurethane itself.

Removing the spacer only took 20 minutes, about the same time you would need to install the spacer. We put a ratchet strap on the coil spring and unbolted the Scorpion shock. Next we put a jackstand under the frame of the truck and lowered the axle until the leveling spacer could be removed by hand.

In addition to regular duty pulling a trailer, this truck gets used in the dirt more than your average Super Duty. With a twin turbodiesel engine and 37-inch Falken tires, this F-250 goes pretty much anywhere it can fit.

Unlike a shock shaft or a control arm bushing that is subject to constant movement, a strut spacer is in a fixed position relative to the components around it (the top of the strut and the strut mount on the frame) and therefore experiences very little movement, regardless of the material it is made from. Where polyurethane offers an advantage is by providing less noise, vibration, and harshness (NVH) by acting as a cushion between steel components.

Just as steel and aluminum are both metal but different material, rubber and polyurethane are very different. Polyurethane can be made to various durometers (hardnesses) and is far more resistant to heat, oil, and ultraviolet light than rubber is. High-quality kits use Teflon-infused polyurethane for their leveling parts and spacers.

Measurements of the new spacer and the 8-year-old spacer revealed that there was no difference in height, whether due to compression of the material or wear. That puts this controversy to rest. Now if we can just figure out how a dog would wear pants, there will be complete harmony on the internet.

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