If you've finally pulled the trigger on a set of 285s or bigger, you're probably realizing pretty quickly that a 4th gen 4runner body mount chop is in your near future. It's that classic scenario: you get the lift installed, the new wheels look aggressive, and the stance is perfect—until you try to pull out of your driveway. As soon as you hit half-lock on the steering wheel, you hear that dreaded "crunch" of rubber meeting metal. It's the rite of passage for almost every 4th gen owner who wants to actually use their rig off-road or even just park at the grocery store without sounding like their truck is falling apart.
Why the body mount is such a pain
The 2003–2009 4Runner is a fantastic platform, but Toyota's engineers didn't exactly design the front wheel wells with 33-inch or 35-inch tires in mind. If you look behind your front tires toward the rear of the wheel well, you'll see a massive steel bracket sticking out from the frame. This is the body mount. Its job is important—it's one of the points where the cabin attaches to the frame—but the way it's shaped makes it a total clearance killer.
Even with a 3-inch lift, the suspension geometry on these trucks means the wheel moves backward and inward as it turns. When you add a tire with a wider footprint or a wheel with a lower offset (which pushes the tire out), that corner of the tire wants to occupy the same physical space as that steel mount. No amount of "trimming the plastic" is going to fix this. If you want to keep your tires from getting chewed up, you have to move the metal.
Is a body mount chop actually safe?
One of the first things people worry about is whether cutting into the frame is going to make the truck unsafe. It's a valid question. You're literally sawing off a piece of the structure that holds the body to the chassis. However, if you do a 4th gen 4runner body mount chop correctly, it's perfectly safe.
The trick is that you aren't removing the entire mount. You're just "clearancing" the outer corner that sticks out into the wheel well. As long as you weld a new steel plate over the hole you've created, you're maintaining the structural integrity of the mount. In fact, most people find that with a thick enough filler plate and a solid weld, the mount is just as strong as it was from the factory, just with a much lower profile.
Getting your tools together
Before you go hacking away at your frame, you need to have the right gear ready. This isn't a job you want to start and then realize you're missing something halfway through, especially since your truck will be immobile with the wheels off.
- An angle grinder: This is your best friend for this job.
- Cutoff wheels: Get a few extras; frame steel is surprisingly thick.
- Flap discs: These are for cleaning up the edges and prepping the metal for welding.
- A welder: If you don't know how to weld, this is the part where you call a buddy or find a local fab shop.
- Replacement plates: You can buy pre-cut "BMC plates" online for cheap, or just cut some out of 3/16-inch steel scrap.
- Safety gear: Eyes, ears, and lungs. Metal shavings in the eye are a quick way to ruin a Saturday.
The process: how it actually goes down
First things first, you've got to get the truck up on jack stands and get those front wheels out of the way. Once you're in there, you'll see the body mount covered by a bit of the plastic wheel well liner. Pull that liner back or just trim it away—you're going to be doing a lot of trimming anyway.
Marking your cut
Don't just start swinging the grinder. You want to mark a line that angles back toward the frame. The goal is to remove enough material so the tire can clear it at full lock while the suspension is compressed, but you want to leave enough of the "perch" so the rubber bushing still has plenty of support. Usually, you're cutting off about an inch to an inch and a half of the leading edge.
The scary part (the cutting)
Take your time here. Cut through the top, the side, and the bottom of the mount. Once that chunk of steel drops off, you'll likely feel a mix of relief and "oh man, I just cut my truck." Don't sweat it. Use your flap disc to grind down the burrs and get the metal nice and shiny. Welding to rusty or painted metal is a recipe for a bad time.
Welding the plate
Position your filler plate over the new opening. This plate is what seals the mount back up so it doesn't become a bucket for mud and salt, which would eventually rot your frame from the inside out. Tack it in place, check your clearances one last time, and then run a solid bead all the way around. If you aren't a confident welder, please let someone else do this part. This is a structural component, and you want that weld to penetrate deep.
Don't forget the finishing touches
Once the metal has cooled down, you can't just leave it bare. Exposed steel on a frame will start rusting before you even get the wheels back on. Hit it with some high-quality primer and a few coats of semi-gloss black spray paint. It doesn't have to be a show-quality finish, but it needs to be sealed up well.
While you have the tools out, you might as well check your pinch welds. Often, if you're rubbing on the body mount, you're also going to rub on the metal pinch weld located just behind the plastic liner. Most guys take a big hammer (the "BFH" method) and flatten that pinch weld against the firewall to gain another half-inch of room. It's not pretty, but it's effective.
DIY vs. Professional Shop
Should you do your own 4th gen 4runner body mount chop? It really depends on your comfort level. If you have a grinder and a welder, it's a two-hour job that costs basically $10 in materials. If you have to take it to a shop, expect to pay anywhere from $150 to $300.
Honestly, for a lot of people, paying a shop is worth the peace of mind. A professional fabricator can make the cut look factory-clean, and they'll ensure the weld is strong enough to handle off-road abuse. Plus, they usually have a lift, which makes the whole process a lot less of a literal headache.
Life after the chop
The first time you drive your 4Runner after the chop, the silence is golden. Being able to pull a U-turn or flex out the suspension on a trail without that vibrating "rub" is a game changer. It makes the truck feel more capable and, frankly, more expensive. There's nothing that kills the vibe of a built rig like the sound of tires hitting the frame.
Keep in mind that if you eventually decide to go up to 35s, you might need to go even further with a "body mount relocation," which involves moving the entire mount further back on the frame. But for the vast majority of 4th gen builds running 33s (285/70/17 or 285/75/16), a standard 4th gen 4runner body mount chop is all you'll ever need. It's a simple, effective mod that clears the way for the tires your truck was meant to have. Just remember: measure twice, cut once, and always paint your welds.