Trailer Axles: Trailer Axles

A trailer axles primary purpose in life is to support and align the spindles, which in turn keeps the hubs and wheels (and your trailer) running straight and true.

Trailer axles come in all manner of shapes and designs and unless the trailer is mass produced or using independent or torsion style suspension/axles, then they are almost always custom built to suit the trailer and its end use.

From the basic straight beam axle, which accounts for the majority of utility trailers, stepped/overlay axles, dropped and gull wing axles, through to torsion style suspension/axles, there is a type of axle to suit every trailer.

Depending on design and setup, axles can dramatically affect the tow height, the deck height, the trailer stability when fully loaded and the way the trailer tracks behind the tow vehicle.

Unless the axle is professionally designed & manufactured, getting the axle design right for your trailer, can, in most cases be a bit of hit and miss, with either a poorly under built axle or a heavy, overbuilt axle that is much stronger and heavier than required being fitted.

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Straight beam axles are commonly machined from a single piece of solid square or round bar and although heavier than hollow section axles, they are inherently stronger and less likely to suffer from stress fatigue. One piece machined axles are normally beyond the realm of the home trailer fabricator and need to be professionally sourced or machined.

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Welded axles, on the other hand, can be made in the home workshop as long as you are a competent and experienced welder and can take the time to setup and align the stub axles with care and precision. If you have minimal or limited welding experience, it is recommended getting an experienced welder or trailer/axle manufacturer to manufacture your axle for you.

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One of the drawbacks of welded axles is their strength can be easily undone by poor, under or over welding and the introduction of stresses through both how the axle is designed, setup, and how it is welded.

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Wherever a weld is used to join metal, inherent stresses are introduced, particularly where the weld has not penetrated the base metals sufficiently. If the weld is undercut along its edges, the chance of stress fractures are greatly increased and together with the lack of weld material, axle failure is imminent. Too much heat can also cause the steels crystalline makeup to become weak and brittle, again promoting early axle failure.

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Getting the axle design and the welding just right will greatly improve the axles chance of fulfilling a long life under your trailer and prevent any unfortunate incident or accident. If you are in any doubt of your welding capabilities, leave the axle building to the professionals.

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The axles shown on this page are intended to be used with leaf spring suspension but can be used in conjunction with coil springs, air bags and shock absorbers or dampeners.

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Click here for axle building information

Axle Flex

A common fault with  homemade axle building is having too large an overhang between the spring mounting and the hub face. As this length increases, more loaded stress is placed on the axle and the effective load rating of the axle is reduced.

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This repeated flexing of the axle under load (cycling) can create microscopic cracks within the grain structure of the axle material.

Over time microscopic cracks can get larger and eventually reach a critical size, where the axle may suddenly fracture and ultimately fail potentially causing all manner of mayhem.

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The shorter the axle overhang the stronger the axle will be - an added advantage is there will be less wear and tear on tires and bearings, and reduced stress on the suspension and chassis.

If you have an existing trailer with tires wearing rapidly on the inner tread (closest to the chassis) or are regularly replacing wheel bearings, you may have axles with excessive overhang or are underrated for the loads you are transporting.