Spring Problems caused by Hanger Location
Spring problems are more likely caused by an incorrect rear hanger location than wrong size spring.
90% of Shackle Springs have hangers located so that the axle is the centre of the mudguards but the rear hanger can be incorrectly located by as much as 35mm.
35mm is a disaster and leads to broken eye springs. Incorrectly installed hangers cause the spring to smash into the dumjack under shock loading events or during normal transit.
I have no idea why or who coined the name “dumjack” but my guess is, it was not a complimentary term.
The image below is perfectly installed hanger for the spring at NO LOAD. Notice the shackle plates are pointing at 7 pm @ no load? When the load comes on the position changes to 5 pm @ full load.
Can you imagine a full load @ 3 pm? Clearly, 3 pm is the wrong position.
Are your springs squeaking as you travel down the highway?
This common problem has an easy fix that will surprise you.
A lot of DIY installation tighten spring bolt nuts and nylocks too tight. As a result of overtightening, the hanger rubs on the spring thereby causing metal on metal squeaking.
Loosen the nut 1/2 a turn to release the pressure and as a consequence, the springs will move more freely and stop squeaking.
Rocker Roller Conversions and Spring Hanger Locations
The towing equipment in the right-hand image is the result of tandem spring hangers in the wrong location on a 4.5t bobcat trailer.
The spring problems here were an incorrect centre of balance was selected to hang the centre hanger. We also found the front and back hangers welded in the wrong location.
Although it can be tempting to install rocker roller springs yourself, it is better to get an expert to do the installation. After all, the experts must provide a warranty on their work.
So how do I get my hangers right?
First of all, go out and measure your hanger measurement and then measure your spring width eye to eye.
If the brackets are the same length as you spring measurement then there is a problem.
For 710mm and shorter springs, your hangers must be 25mm longer than your springs. So move your rear dumjack or the front hanger.
To move this dumjack, you will need to grind it off and but buy 2 new dumjacks to replace the old ones. The old ones are damaged by the heat from the grinder.
Tack weld the newly installed dumjacks first, double-check measurement then weld both dumjacks into place.
This opportunity for vibration fatigue has been defeated.
The image on the right is an Outback Offroad spring. Springs lengths measured at 841mm should have hangers welded 35mm longer than the spring eye to eye measurement.
Shock absorbers are an excellent option to add to your rig to give it an even smoother ride.