After getting side-swiped by a Tundra in late 2023, I decided to replace the 15x8 wheels that barely fit in the RX-7's stock wheelwells with a set of even wider 15x12's that required 1-3/8" mini-tubs. Wanted to lower the car a little as well, so I also radiused the outer wheelwell openings. Here's the end result...



Here's some pics of the process after removing the inner part of the original tub with a cut-off wheel and sawzall...



cut right down the middle of the car's original upper spring seats...



After removing the original tubs, I cut 1-3/8" off the inner flange and added a 1-1/2" wide strip of metal to the outer circumference. Here's a shot of a modified tub getting fitted back into place...



On the shop floor, you can see the modified Crown Vic 8.8 housing. It was narrowed and 9" ends installed, housing width is 46.5". With a 2.50" brake offset, axle flange / axle flange width is 51-1/2". The 15x12 wheels have a 5" backspace. You can also see the torque arm I fabricated, the nose anchors up in the trans tunnel with a shackle arrangement. The driveshaft passes between the shackles, they double as a forward driveline loop. The bracket on the right axle tube is the pivot for the watts linkage that centers the rear in the car. Same torque arm that was on the 8.5" 10 bolt that got bent in the crash, just modified it to fit the 8.8. Easy 1.30 60's with this setup...



Here's the bare 8.8 with brackets and mocked in-place, necessary to determine where and how tall the new bump-stop brackets needed to be....



Here you can see the new bump stop brackets welded to the underside of the frame rails You can also see where I notched the stock sheetmetal "frame rails" to make room for the coil-overs...



Here's a shot with the rear at full extension! Plenty of front and rear travel to hook-up on those un-prep'd Mexican backroads...



Here you can see that the car's original upper control arm brackets were completely removed, no longer needed when converting the car over to torque arm...



These are stock un-modified springs from the rear of a '86-'91 RX-7, rate is 98lbs/in. The inside dia is larger than the typical 2-1/2"id coil-over spring, so I machined some spring adapters from a 4-1/2" dia chunk of Delrin. With the larger dia springs, I shouldn't have to worry about the springs rubbing on the coil-over sleeves.

Here you can see that I made the spring base as wide as possible. I could have easily put the shocks on the inside of the frame rails, but that narrow spring base would have required a very stiff sway bar. Narrow spring base, a spool, and very stiff ARB's are the reason you see cars at the strip crash into the wall. With a wide spring base, a TruTrac diff, and some articulation available, this car is far easier to control when it gets out of shape...



Rear sway bar is an oem Crown Victoria unit that has it's ends modified...



Here's the left side of the car. As you can see, I fixed all the broken bones from the crash but left the scars...



Just a fun street toy that I use to develop my clutch control products. Doesn't have any chassis reinforcements or even a roll bar.

Grant