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Jeep Grand Cherokee Fender Trimming Done Right

Posted in How To: Body Chassis on February 10, 2014 Comment (0)
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Trimming sheetmetal to free up more room for bigger tires is easy, but frightening. Making that first cut is psychologically tough when you are not positive that the outcome will be good. It’s also very easy to quickly cause more damage than you would ever want to deal with if you are not careful. We here at Jp have been cutting up Jeeps for years. That means that we have screwed up enough times to know what you should and shouldn’t do. The truth is that trimming your Jeep without ruining it is easy, but there are several things that can make the end result look better and leave you with a solid rig. Here are a few tips, tricks, and tools that should make trimming your Jeep easier, retain structural strength of the body, and leave you with a Jeep that is still appealing to the eye. Follow along as we show you what we’ve learned.

You can trim the sheetmetal or plastic on just about any Jeep. The key to doing it properly involves learning a little Jeep body anatomy, namely identifying welds. This helps identify what part of the Jeep is attached to what. Jeep used screws, bolts, glue, and spot welds to attach panels to each other. This is a spot weld, usually located on a flat seam between two pieces of metal called a pinch seam. If you cut a spot weld off your Jeep, you’ve made the connection between the two panels weaker. Cut off several, and your Jeep could come apart now or in the future. You can trim the sheetmetal or plastic on just about any Jeep. The key to doing it properly involves learning a little Jeep body anatomy, namely identifying welds. This helps identify what part of the Jeep is attached to what. Jeep used screws, bolts, glue, and spot welds to attach panels to each other. This is a spot weld, usually located on a flat seam between two pieces of metal called a pinch seam. If you cut a spot weld off your Jeep, you’ve made the connection between the two panels weaker. Cut off several, and your Jeep could come apart now or in the future.
We like to try to keep as many factory spot welds intact by trimming between them and or folding pinch seams with spot-welds over. The best way we found to do this is trim below the spot welds and then make relief cuts up to the base of the pinch seam. Then use pliers (we love these wide jawed locking pliers) to bend the pinch seam over. Once you’ve got the bend started, you can use a hammer to fold the pinch seam flat. Retaining as many factory spot welds or rewelding panels is especially critical for Unitbody Jeeps such as XJs, MJs, ZJs, WJs, KJs, and WKs. We like to try to keep as many factory spot welds intact by trimming between them and or folding pinch seams with spot-welds over. The best way we found to do this is trim below the spot welds and then make relief cuts up to the base of the pinch seam. Then use pliers (we love these wide jawed locking pliers) to bend the pinch seam over. Once you’ve got the bend started, you can use a hammer to fold the pinch seam flat. Retaining as many factory spot welds or rewelding panels is especially critical for Unitbody Jeeps such as XJs, MJs, ZJs, WJs, KJs, and WKs.
Trimming sheetmetal properly requires some tools, and you probably have at least a few of them in the garage. You will need some kind of cutting device, a hammer, pliers, and a grinder of sorts. We’ve used everything from tin snips to grinders to cut sheetmetal. You can use a saber saw, jigsaw with a metal cutting blade, die grinder, rotary tool, or angle grinder with a cut-off wheel (although cutting radiuses is nearly impossible with these), tin snips, hole saws for lights, and so on. The best tool we have found so far is a high-quality air saw. Also, taping off where you are going to cut can help protect the paint near the cut. Trimming sheetmetal properly requires some tools, and you probably have at least a few of them in the garage. You will need some kind of cutting device, a hammer, pliers, and a grinder of sorts. We’ve used everything from tin snips to grinders to cut sheetmetal. You can use a saber saw, jigsaw with a metal cutting blade, die grinder, rotary tool, or angle grinder with a cut-off wheel (although cutting radiuses is nearly impossible with these), tin snips, hole saws for lights, and so on. The best tool we have found so far is a high-quality air saw. Also, taping off where you are going to cut can help protect the paint near the cut.
Another key tool is a grinder with a flap-wheel in a finer grit. This allows you to clean up metal, remove paint or undercoating, and do general grinding, but it’s also a great way to clean up burs, meat hooks, and round out rough radiuses that are bound to occur while cutting sheetmetal—even with a good air saw. A grinder with a flap wheel is also a great way to clean up the edges of any plastic bits you may have trimmed, such as flares, bumper covers, and so forth. Another key tool is a grinder with a flap-wheel in a finer grit. This allows you to clean up metal, remove paint or undercoating, and do general grinding, but it’s also a great way to clean up burs, meat hooks, and round out rough radiuses that are bound to occur while cutting sheetmetal—even with a good air saw. A grinder with a flap wheel is also a great way to clean up the edges of any plastic bits you may have trimmed, such as flares, bumper covers, and so forth.
If you’ve made the decision to cut off several spot welds you are going to need to make up for this weakening of the Jeep. This could be adding rivets, screws, or welding. We usually try to weld in this case, but welding thin sheetmetal isn’t easy, and newer Jeeps have zinc-plated sheetmetal that further complicates welding. In this case, we try to remove the zinc with a grinder with a flap-wheel as best as we can. Then using a low setting on the welder, we make small tack welds to hold the sheetmetal together. You can then clean up the tack welds with the grinder if you feel it’s necessary. If you’ve made the decision to cut off several spot welds you are going to need to make up for this weakening of the Jeep. This could be adding rivets, screws, or welding. We usually try to weld in this case, but welding thin sheetmetal isn’t easy, and newer Jeeps have zinc-plated sheetmetal that further complicates welding. In this case, we try to remove the zinc with a grinder with a flap-wheel as best as we can. Then using a low setting on the welder, we make small tack welds to hold the sheetmetal together. You can then clean up the tack welds with the grinder if you feel it’s necessary.
The last step should seem obvious. Once you’ve completed trimming, you need to add paint and seal up any gaps. We like hammered-texture paints because they are durable, and the textured finish helps obscure any imperfections in our trim job. We also have used automotive seam sealer, as well as grey caulking from the local hardware store. If you do need to use body filler, use a quality brand that contains only hydrophobic fillers—and use it sparingly. The last step should seem obvious. Once you’ve completed trimming, you need to add paint and seal up any gaps. We like hammered-texture paints because they are durable, and the textured finish helps obscure any imperfections in our trim job. We also have used automotive seam sealer, as well as grey caulking from the local hardware store. If you do need to use body filler, use a quality brand that contains only hydrophobic fillers—and use it sparingly.

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