TrailerTech: Aluminum vs. Solid Steel

Welcome back for our latest TrailerTech article!

Today, we’re taking a look at something that’s been brought to our attention before: why do we use 6061-T6 aluminum for our lift/lowering blocks as opposed to solid steel? This is not the first time alternative materials and composition methods for Trailer Blocks have been discussed (see our previous article here), but since we’ve had some questions regarding the use of solid steel for blocks, we’d like to reexamine the issue here.

A Trailer Block fabricated from solid steel such as billet steel, has a compressive strength capability as high and depending on the alloy, higher than a Trailer Block fabricated from 6061-T6 aluminum. We can see strength is certainly not the issue, but what about weight? A Trailer Block composed of solid steel will add a relatively large amount of unsprung mass to the axle. When a leaf spring breaks, this can often be caused by a sudden unloading of weight, such as when a wheel drops into a hole in the road. In a situation such as this, unsprung mass is often the biggest culprit. A large increase in unsprung mass caused by a solid steel block would require a custom spring designed to accommodate the extra mass. If the trailer is not equipped with proper shock absorbers, the effect can be even greater, causing more suspension oscillation over bumps. To reduce the amount of unsprung mass, aluminum remains the ideal alloy to fit the technical demands of the application due to its strength to weight ratio and corrosion resistance.

We also recommend that you consider the following points when lifting or lowering your trailer with our signature Trailer Blocks:

• Use only solid billet aluminum lift/lowering Trailer Blocks that will resist crushing forces
• Use only SAE Grade 8 U-bolts with rolled threads.
• Do NOT re-use U-bolts under any circumstances. When reused, U-bolt clamping force is reduced by over 55%, even though your torque wrench reading is identical. U-bolts should never be used with lock washers, as they will fatigue and eventually break.
• U-Bolts MUST be torqued to the manufacturer’s recommendation. If U-bolts are not torqued sufficiently, they may loosen and if they are over-torqued, they can exceed their maximum tensile strength and break.
• Carefully asses tie plate wear. It’s generally a good idea to replace tie plates every time you replace U-bolts. Ensure the tie plate is strong enough to support the required U-bolt.
• Always ensure that springs, spring clip, shackles, suspension bolts, bushings and mounting brackets are in good, lubricated condition (up-to-date in the case of a dry system) and are corrosion-free.

Thanks for reading.

Trailer Tech: Cambered Axles

Welcome to a new installment of Trailer Tech! This entry, we’re taking a look at the importance of cambered axles and how this can affect your lift/lowering endeavors.

Camber refers to the measurement of a vehicle’s wheels vertical alignment with the ground. The camber angle can have a profound impact on a vehicle’s handling, as well as the grip and overall lifespan of the tires. If the bottom of the wheel sticks out further then the top, this is called a “negative camber”. On the other hand, when the top of a wheel sticks out further than the bottom, this is a “positive camber”. Most trailer axles come with a slight arc in them by design, allowing them to compensate for any unwanted cambered angles while bearing the weight of the vehicle and keeping its wheels straight. These angled axles are also known as cambered axles (pictured below),

The axle pictured above is oriented correctly for both the lowering state (suspension pictured in front) and the lift state (suspension pictured in rear). With weight applied to the suspension, the arc in the axle straightens and the wheels stay straight.  Consider that if a cambered axle such as the one pictured is rotated 180 degrees while retaining the current suspension orientation, it would cause a positive camber angle when the weight of the vehicle is applied. Positive camber angles are particularly unsafe as this position reduces the tire’s contact with the ground, reducing overall grip and increasing wear and tear.

If an axle is being transitioned from a lowering state to a lift state or vice-versa, spring seats opposite of each other are required so that the axle can remain in the same orientation.

Thanks for reading.

TrailerTech: Reusing Tie Plates

Welcome back to TrailerTech!

We all know you shouldn’t re-use u-bolts when servicing or modifying your trailer’s leaf spring suspension. Tie plates though, aren’t as cut and dry. There are obvious qualitative observations that can be made, such as the presence of rust or total failure. Structural integrity is a much different story. At a casual glance, tie plates often appear unchanged after a use or two. In this TrailerTech article, we’ll take a closer look.

Lateral bending is one of the biggest concerns when assessing a tie plate’s structural integrity. The tie plate flexes across the leaf spring, bending towards the u-bolt’s clamping force. The photo below shows an unused tie plate on the left and a tie plate torqued down only once on the right. Notice the slight circular markings from the u-bolt washers.

A keen eye will also notice the slight arc in the tie plate on the right (a 1mm rise). This might not seem like much, but if we graph the result, the deflection is much more apparent.

Naturally, the proper care must be taken when re-using tie plates, as lateral bending is not always visibly obvious and a closer inspection is necessary. If you have any doubts about your existing tie plates, the safest thing to do is to replace them along with other one-time use parts, such as u-bolts.

We hope this TrailerTech article is helpful when making your assessment.