Other than the slight tire rubbing they cause, my Spidertrax spacers have been trouble free for the last 8000 miles since I installed them. Here is an interesting write up I found from a guy on a Jeep forum.
"I recently installed a set of 1.5" Spidertrax spacers. However, prior to doing so, I took one of them, along with my spare wheel, into our engineering lab.
We modeled both in 3D using the latest NX CAD software. We did this by reverse engineering. That means taking all dimensions and determining the materials.
We identified the wheel material as alloy 356-T6. The spacers are made from 6061-T6 alloy. 356-T6 has tensile strength of 30,000 PSI. 6061-T6 has a tensile strength of 45,000 PSI. This means that in reference to the basic materials, the spacer is 50% stronger than the wheel for a given thickness, and the spacer is much thicker in section.
We ran an extremely complex finite element analysis of both to determine where peak stresses are and where each component is most likely to fail. The result is what I expected. In short, spacers are not the weak link. The wheel itself is 2x more likely to fail under severe loading than the well designed spacer.
Now, let me qualify our findings. Our corporate engineering team has designed significant portions of the Airbus A350 landing gear system. We engineered the latest landing gear system for the Boeing CH-47. Our hardware is on the F-35, F/A-18, F-16 and a number of other aircraft.
This same engineering team has analyzed the Spirdertrax spacers and concluded that they are extremely strong, stronger than they need to be. Over engineered. These spacers are utterly safe if installed properly. Like an offset wheel, they may accelerate bearing wear, but the offset is so little as to be of no great significance.
I installed the spacers very carefully. Not knowing specifically what brand and type of threadlocker compound was provided with the spacers, I tossed it and used Loctite 271 Red. Each spacer was torqued to recommended specs in a star pattern. The wheel was then installed and torqued to 95 lb/ft.
After about 150 miles, I pulled off the rear wheels and checked the spacer lug nut torque. No change... I'll re-check torque at each tire rotation.
Installed correctly, Spidertrax wheel spacers are not only safe, they're stronger than the wheels you bolt to them."
I didn't mention that we found areas of stress concentration in the factory wheels. We were able to pinpoint the most likely location of failure. I'll explain where that is...
The Factory Moabs have spotfaces milled into the wheel hub to provide clearance for assembly washers used during manufacture to secure the brake rotors on the hub prior to final assembly. Using an endmill, each lug hole is spotfaced on the inside (think of a spotface as a shallow counterbore). The edges and corners of these spotfaces are quite sharp. This is where the FEA predicted the greatest concentration of stress. Unfortunately, this is also adjacent to the where the studs transmit all rotational torque into the wheel. The failure to radius edges and corners is what leads to stress concentration. If your Moab is going to fail at the hub, it will crack at a spotface.
In short, Tom and Eddie at Spidertrax have designed and engineered a very high quality spacer, that if properly installed, will provide you with many years of problem free and safe use.
