Reinforcing the Roof of our '98 4Runner (1 Viewer)

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Living Overland's 3rd Gen 4Runner Build

Reinforcing the Roof of our '98 4Runner

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With the additional weight of our roof basket and the camping gear we carry in it, we began to notice some weakness in the roof. The roof didn't seem to be able to support a load in the front third of the factory load-bar track. Applying weight caused the track and roof to deflect downward, and the rack's inertia would cause the roof to vibrate while driving over rough terrain. During our recent trip to the Four-Corners area the vibrations went from occasion vibrations to non-stop vibrations even when we were driving on smooth roads and the interstate. It had become severe enough that it was time to investigate and see if I could stiffen things up.

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What We Found:
To gain access to the roof I began by removing the headliner from the 4Runner. This required pulling all the interior plastic side panels out; from the rear all the way to the front A-pillar. This process is fairly straight forward and can be accomplished in very little time. Once the panels were removed, I began removing the grab-handles, dome lights, rear-view mirror, sun visors, and the four plastic push fasteners holding the headliner in place.

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With the headliner removed, the structure supporting the weight of the load-bar track became visible. Each track is supported by a stamped sheet metal channel which runs directly below and sandwiches the roof between the two. Two braces run between the load-bar track supports to add overall rigidity to the roof structure. To allow room for the sunroof to be retracted, the front one-third of the roof is left unbraced. I believe this lack of bracing is the cause of our vibration issues.

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You can read about the rest of our project on our blog by clicking here.
 
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Pretty neat idea. I just added a safari rack to our 99 and will keep an eye out for any strain on the roof/rails.
 
Just wondering how much weight? On my 98 runner I completely removed the factory rack and fab bed my own. My rack had 1.25" x 1/8" thick flat bar used for the 2 runners that spanned the mounting holes. I've had some pretty heavy weight up there. I wonder if the base strips help distribute the load more evenly across the roof. Just food for thought.
 
Just wondering how much weight? On my 98 runner I completely removed the factory rack and fab bed my own. My rack had 1.25" x 1/8" thick flat bar used for the 2 runners that spanned the mounting holes. I've had some pretty heavy weight up there. I wonder if the base strips help distribute the load more evenly across the roof. Just food for thought.

I started noticing the deflection (and subsequent vibration noise) with two fuel cans, half the rack filled with firewood, and lawn chairs. Any weight on the forward portion of the rack would cause problems. Now our 4Runner is equipped with a sunroof, so I don't know if there is a structural difference between those with and without. For ours, there is no roof bracing for the forward 24in of the track. By adding the flatbar, I was able to transfer a portion of the forward load to the rest of the roof.

To give you an idea of how much this improved the load capacity, on our Idaho Expedition I carried the following items for about 300 backcountry miles without any vibration noise or noticeable deflection: 1ea 33in mounted spare, 3ea 20l filled fuel cans, 2ea 20l filled water cans, and 1ea chainsaw.
 

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