OVERVIEW The right size tire for any truck is the one that fits at FULL COMPRESSION. This principle might sound foreign, but simply lifting a truck to clear larger tires is a flawed concept. Full compression is full compression, regardless of where the truck sits at ride-height (providing the suspension pivot-points and bump-stops are in the stock location). This means that in order to REALLY clear oversized tires, you need to make room for them. That’s what this article is all about. We want to encourage enthusiasts to cycle their suspension and see what’s really going on under their vehicles. Almost any truck will benefit from a little additional clearance in the right places and while you’re down there, take a look at the suspension linkage and steering components. There’s a good chance that you’ll find a few other things to fix or improve at the same time. With that said, make sure that you are comfortable with the level of fabrication required before you rip into a project like this. Results are entirely dependant on the execution; so don’t start cutting unless you know what you’re doing.
Tools we used to complete this job included some basic hand-tools, a hand-held reciprocating saw with metal blade, 4-inch angle-grinder with cut-off wheel and a small 110-volt MIG welder. This is a time-consuming project that took us an entire day to complete from start-to-finish. Tip: make sure to have some sheetmetal to use for patch-panels on-hand. MODIFICATION The Total Chaos long-travel kit that we run on the Trails Less Traveled Tacoma is designed to run 33x10.5-inch tires, because that tire diameter and width clears the factory sheetmetal on full compression and lock-to-lock steering (flared fiberglass fenders are required to cover the additional track-width). We ran 33x10.5x15” BFGoodrich Mud Terrain and All Terrain tires on this truck for over two years and loved them both. But ultimately we wanted to clear 35x12.5” BFG MT’s at full compression AND lock-to-lock steering, for the more aggressive and tight 4WD trails this truck is built to run. Of course there are both upsides and downsides to larger tires. We decided that the additional ground clearance, larger circumference/diameter (larger tires = smaller holes) and larger contact-patch (traction) was worth the additional unsprung weight (negatively affects acceleration, braking, handling & fuel economy) and additional stress on drivetrain components (such as axles, wheel-bearings, etc.).
In order to determine exactly where material needed to be removed, first we confirmed that the truck’s alignment was in check. If the alignment is out of spec the suspension will cycle differently and cause the tires to contact different areas of the firewall and inner fenders. Then we removed the front shocks so that we could cycle the suspension. Then we mounted a 35-inch tire and turned the steering wheel so that the tires were straight. We used a floor-jack to raise the suspension until the tire came into contact with something. BUMPER
In our case the bumper was the first thing to interfere. We have a custom Hanson Enterprise winch-bumper but the stock Tacoma front bumper would also require similar modification. The bumper needed to be trimmed forward a good amount to allow full range of steering with such large tires. We made a preliminary line with a felt-tip pen, made the first cut and continued to trim the bumper forward in stages, rather than cut too much at once. FIREWALL
The major area of interference is at the firewall. We removed the fender to better gain access to the area that we would be cutting into. We had to be very mindful of things on the inside of the firewall, being careful not to cut any more wires. We also lifted the carpet and pulled it back to keep it away from heat and sparks created by cutting, grinding and welding. We marked cut lines that followed the tire and began to remove material with a reciprocating saw. We also had to trim our custom-made rocker-panel guards back a little bit. When we installed them at WFO Concepts, we intentionally left them long so that we could match the fender lines exactly.
This is how we checked the clearance between cuts, marking areas that needed additional trimming until we were satisfied with the clearance. This was a tricky area to cut for clearance because of the compound curves and layered sheetmetal at the firewall. We kept the shape of the patch-panel we’d need to make in mind as we went. We didn’t want to have to make a patch-panel with compound curves because it would have been very difficult to form.
This is what the final cuts at the firewall looked like. In order to eliminate all of the rubbing between the inner tread of the tire and the firewall at full compression and absolute lock-to-lock steering, we would have had to remove our interior plastic kick-panels, so we just trimmed-away all of the material right up to the kick-panel mounting tabs. In the extremely unlikely event that we do hit full compression at full lock steering, we’ve created a smooth surface for the tire to rub against without causing any damage. The interior shot shows the tire position at full compression and the kick-panel tab that we had to work around.
The next area to interfere was this bump in the front of the inner wheel-well. With the tire cycled to full-compression, we turned the wheel to full-lock steering. The tread block rubbing against the sheetmetal made a smudge that we used to determine exactly where material needed to be removed. We then drew a perimeter around the outside of the smudge. Although it’s a relatively smooth surface, the bulge is too pronounced to hammer flat without causing the sheetmetal to ripple or crease. We chose to remove the material completely using an angle-grinder instead.
This is the finished cut. Notice the exposed copper wires that show where we grazed the headlight wiring harness. We had to patch those wires because we didn’t take the time to move them out of the way like we should have. Lesson learned. PATCH-PANELS
Prep the holes for welding by cleaning/de-burring the cut edges and removing the paint/primer/undercoating.
After we were satisfied with the fit and everything was tack-welded into place, we finish-welded the patch-panel. Then we covered it with a coat of primer and a few coats of textured rubberized undercarriage spray.
FIBERGLASS FENDERS
We had to trim the flared fenders a little bit to completely clear the larger tires. This was the last thing we did because with the inner fenders, we could cycle the suspension with the wheel/tire mounted to full compression and through lock-to-lock steering without hitting anything else. The Glassworks Unlimited fenders were already cut higher than we needed, but we did have to re-shape the front and back edges of the wheel opening. We just used a marker-pen and a 4” angle grinder with a flap-disc to create a new contour that gives us the clearance that we needed.
With everything finish-welded, painted and reinstalled, we mounted the wheel/tire and cycled the suspension again to check the clearances one last time. We replaced the interior (carpet and kick-panels) and from the inside, you can’t tell that anything has changed.
Immediately following this work, we mounted-up our 35x12.5” BFG Mud Terrain tires on a set of OMF bead-locked Alcoa wheels and took our Tacoma on a 1,500-mile road trip down to Mexico for the San Felipe 250 Baja race, where we pushed the truck to/past it’s limits and bottomed-out the suspension several times with no tire interference. Anyone trying to create similar clearance on a Tacoma is welcome to download and print-out copies of our templates, but there really is no short-cut to save time through this process. Let us know how these work out by sending an email to
toyota@off-road.com.
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