As you can see, these rear wheelwells barely have enough room for the 20-inch wheels on the truck. After some work, though, we won't have to worry about tearing up the new 23-inch combo.
One of the biggest problems with lowering just about anything is tire clearance. It never fails that once you get your rig low, the tires rub every time you hit a bump. There are many ways to keep this from happening. The most obvious one is ordering the right offset. But what if the style of rim you like doesn't offer the correct backspacing? You end up modifying the body. You can roll or trim the lip, but that will give you a small amount of clearance; if you need more, some bodywork will be needed.
In our case, we wanted to stuff a set of 23-inch Rozzi Vixen rims under a Supercrew. The truck has been dropped with a DJM kit and rolls 20s, but we want to go bigger. The problem is that the combo we have now already rubs, so upsizing the diameter of the rim and tire would just make matters worse.
The Supercrew's bedsides are constructed out of fiberglass. As a result, rolling the lip with a bat is out, so bulging the fenderwells was kind of a no-brainer. We hooked up with Rick at Primo customs in Chatsworth, California, to have him show us how it all goes down. Rick has been doing this sort of stuff for years, and he pointed out that this whole process can be done on a fiberglass or a steel-sided bed; the glass cloth will adhere to both materials. If you have a steel-bed truck and are not comfortable welding and forming sheetmetal, then this might be a realistic way for you to do it.
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01. To get started, Primo laid a tape line down for the cut. The cut line was put toward the top of the factory bulge. All that has to be done is to bridge the gap instead of also trying to recreate the transition. | 
02. A quick check was made to make sure any inner structures or wires will get cut. |
03. Out came the air saw, which made quick work of the fiberglass bedsides. |  | 
04. The surrounding area is ground down to give it some "tooth" for the new 'glass to bite and make a strong bond. |