Under a classic Chevy, big rear meats are as American as apple pie and superchargers. It’s also more than just an aesthetic deal done to look cool. More tire width equates to more grip, and with engines getting more and more potent it’s challenging to get that power mated to the asphalt, especially when the road becomes curvy.
Adding bigger rear wheeltubs has been going on in drag world for decades. But for cars of the Pro Touring variety that want bigger rear street tires, mini-tubs are the way to go. Chris Alston's Chassisworks has recently released its own mini-tub kit for ’67-’69 Camaros, and one nice perk is that included are precut closeout panels that makes trimming down the frame a bit easier. Our ’68 Camaro project car already has stretched quarter-panels, but we figured this was the time to mini-tub the car just in case we want to stuff really big tires under it at some point. So, to see what’s involved we ordered up a kit and headed over to Best of Show Coach Works for a little cuttin’ and stitchin’.
01. Here are the driver-side components in the Chris Alston’s Chassisworks mini-tub kit (PN 5913-F10, $411). The 18-gauge steel tub gives an additional 2.5 inches of clearance and will accommodate up to 315- or 335-mm section width tires. A unique aspect of the Chassisworks kit is that it includes pre-cut and laser-etched closeout panels to save fabrication time when notching the frame.
02. If your car is together you’ll need to at least pull most of the interior and remove the fuel tank. We didn’t have that issue, so we started marking and cutting.
03. With the line marked, about 2.5 inches out, we broke out the cutoff wheel and got to work. As you can see, the upper shock mount will be removed so mini-tubs are only for cars with aftermarket coilover- type suspensions or ones where the upper shock mount has been relocated.
04. An air chisel was also used for less precise cuts and to get the inner tub out of the car faster.
05. We then drilled out the spot welds holding the trunk hinge to the inner tub bracket.
06. With the tub out of the way we could finish trimming away the metal. The best way to make sure you don’t make the hole too big is to cut, test-fit the tub, then cut more if needed.
07. And here are the main pieces that we removed from the driver side. With these out we went back and cleaned up all of the rough edges.
08. To maximize tire fitment, the frame also needs to be thinned down a bit. Following the instructions we marked the frame and started cutting.
09. This is where the pre-cut closeout panels start to come in handy.
10. Where needed, the closeout panels have laser etched guide marks to help make bending them easier.
11. In our case, the closeout panel was a bit short for the hole we needed to fill, so we split it in half and then made a small rectangular panel to bridge the gap.
12. And here’s how our closeout panels looked prior to welding. Notice how the pre-drilled holes in the panels line up with the framerail edges. This made doing the small rosettes even easier.
13. We then broke out our Miller 211 MIG welder and stitched everything in place.
14. The driver-side tub was put in place and fully welded to the Camaro. Again, the process is test-fit, trim, test-fit, trim, until everything lines up right. As we say, it’s something you have to “sneak up” on.
15. We then moved over to the passenger side and repeated the procedure to remove the old inner wheeltub and frame section.
16. Like the driver side, part of the frame is cut away and we used the supplied closeout panel to fill in the gap.
17. Here’s the passenger-side wheeltub installed prior to welding.
18. And here it is after welding. We also ran a bead of Fusor 123 seam sealer along the gap between the inner and outer wheeltubs.
19. Here’s the inside after welding and application of more Fusor seam sealer. When it comes to the brace that attaches the trunk hinge to the new mini-tub, you can either trim and re-use the original one or make a new one like we did.
20. Behold the driver side after welding, seam sealer, and a coat of black Eastwood paint.
21. As mentioned earlier, our Track Rat project has stretched quarter-panels. Combined with the mini-tub, and rolled fender lips, we now have over 16-inches of tire clearance, which is enough for just about any tire we might like to run.
22. Here’s the area coated with some Wurth SKS Stoneguard undercoating. The end product looks nearly factory.
23. After putting our Chassisworks suspension back under the car, we noticed that the lower link bar hit the corner of the new mini-tub. The easy fix was to notch the corner so the bar had clearance through its entire range of motion.