I think a lot of the fear of spacers comes from one or two horror stories that have made their way around every off-road forum. I believe the one I read the guy had them installed incorrectly. When you think about it, there are thousands and thousands of spacers installed on trucks all over the U.S. and there are very few stories of them failing. Good spacers aren't expensive so I really don't understand why people go cheap and order off eBay when it's something that important.
I wanted to purchase some spidertrax wheel spacers not too long ago, but after all the surgery that needs to be done to prevent rubbing (cutting the fender liner, removing mud guards). I decided to wait it out and purchase wheels with the proper offset and tires.
Be careful in replying on the jeep guys analysis.
What's important to remember is that the fasteners are only there to provide clamping force. Not resist rotation. And wheel failure from adding spacers is generally am issue of friction failure and wheel spinning against the hub. So the real issues are whether the spacer material has a lower coefficient of friction against either they wms or the wheel, whether the spacer is compressible under the force of the fastener, and whether adequate thread interface remains. All of these depend on the starting point and the spacer thickness and material.
For example aluminum spacer between steel wheel and wms likely makes it marginally safer. But steel spacer between aluminum wheel and steel wms is less safe. Anodized spacer is less safe than raw aluminum. And many other variables.
The FEM analysis seems misplaced to me. I don't think they really understand how fasteners work if they are looking at static failure. I wouldn't put much value in that analysis. In fact id put it in the category of engineering nonsense. Is analysis of the wrong problem and does nothing to indicate whether spacers are safe or not. That's simply not how they fail. Please don't rely on that for much. It's not wrong per se. It's simply not useful.
For me, I would buy a proper wheel for what I want. Unless there's a very small - 1/4 inch space needed for something like clearing a caliper or a remote resirvoir can then I might use a spacer. At some point your really stressing the hub, ball joints, and wheel bearings to much for long service life. On my trail rig with 12" wide wheels and 2" back spacing I know I'm dramatically shortening the life of the bearings but it's not a daily driver so I don't all that much care. And it weighs 3000lbs on big axles. On my 4 runner I wouldn't want to push the bearings that hard. They aren't very big compared to something like a land cruiser. And I've had a few failures on my last mini truck that used similar size bearings.
So I would suggest keep em small. Keep them uncoated. And check your torque a few times after installing.
Be careful in replying on the jeep guys analysis.
What's important to remember is that the fasteners are only there to provide clamping force. Not resist rotation. And wheel failure from adding spacers is generally am issue of friction failure and wheel spinning against the hub. So the real issues are whether the spacer material has a lower coefficient of friction against either they wms or the wheel, whether the spacer is compressible under the force of the fastener, and whether adequate thread interface remains. All of these depend on the starting point and the spacer thickness and material.
For example aluminum spacer between steel wheel and wms likely makes it marginally safer. But steel spacer between aluminum wheel and steel wms is less safe. Anodized spacer is less safe than raw aluminum. And many other variables.
The FEM analysis seems misplaced to me. I don't think they really understand how fasteners work if they are looking at static failure. I wouldn't put much value in that analysis. In fact id put it in the category of engineering nonsense. Is analysis of the wrong problem and does nothing to indicate whether spacers are safe or not. That's simply not how they fail. Please don't rely on that for much. It's not wrong per se. It's simply not useful.
For me, I would buy a proper wheel for what I want. Unless there's a very small - 1/4 inch space needed for something like clearing a caliper or a remote resirvoir can then I might use a spacer. At some point your really stressing the hub, ball joints, and wheel bearings to much for long service life. On my trail rig with 12" wide wheels and 2" back spacing I know I'm dramatically shortening the life of the bearings but it's not a daily driver so I don't all that much care. And it weighs 3000lbs on big axles. On my 4 runner I wouldn't want to push the bearings that hard. They aren't very big compared to something like a land cruiser. And I've had a few failures on my last mini truck that used similar size bearings.
So I would suggest keep em small. Keep them uncoated. And check your torque a few times after installing.
It seemed to me that the FEM analysis simply assumed a set of properly installed SpiderTraxx and tested them accordingly. Theoretically if they were installed correctly then the SpiderTraxx should not rotate at all and be a solid component of the hub and wheel; so load forces and stresses should translate into the wheel. Granted I imagine they didn't bother to mention shearing forces on the studs because the studs were equal to or greater than OEM units and thus would have similar failure points at a shearing level.
Now it would have been interesting to see some testing with loose, slightly loose, or improperly installed units to get an idea of how they fail.
I'm going to throw a curveball at you
DUALLY TRUCKS COME WITH A FACTORY 6" WHEEL SPACER IN THE FRONT
of course they're safe, just buy good ones.
It seemed to me that the FEM analysis simply assumed a set of properly installed SpiderTraxx and tested them accordingly. Theoretically if they were installed correctly then the SpiderTraxx should not rotate at all and be a solid component of the hub and wheel; so load forces and stresses should translate into the wheel. Granted I imagine they didn't bother to mention shearing forces on the studs because the studs were equal to or greater than OEM units and thus would have similar failure points at a shearing level.
Now it would have been interesting to see some testing with loose, slightly loose, or improperly installed units to get an idea of how they fail.
Untrained people mess stuff up. Read some of the build threads here. Would you want to buy a vehicle modded by them?
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I have had 1" spacers on my 2015 for a few years and have not been offroading in over a year. Last week my wife and I were heading out to go grocery shopping and I felt a weird sway in the back so I immediately pulled onto a side street and heard a loud bang.