2009.02.09 - Installed Hidden Hitch
- Removed exhaust (so that I could get leverage on hitch)
- Installed hidden hitch
- Used Class 12.9 M8x1.25-90mm socket cap screws, spacers, washers, and class 10.9 flanged nuts to secure hitch
- Cleaned up exhaust tip by wet sanding and polishing
- Reinstalled exhaust
Installing the hitch was kind of a pain in the ass, most likely due to the passenger side tie-down tower being tweaked. The directions said to drill out (despite the fact that it was advertised as a NO CUTTING + NO DRILLING install application) the 8mm captive nuts and install the supplied 7/16" grade 5 hardware. I wasn't really wild about this idea, so I found some specs and did some math. I determined that I could use some 8mm (OEM size) class 12.9 bolts and they would be 76%-90% as strong (depending on which spec you are comparing) as the supplied hardware. Since the Miata probably can't safely tow anything more than half the maximum rated weight of the Class 1 hitch, I felt that 76% is still strong enough for my needs. I retained the OEM tie-down loops by swapping the left and right sides and mounting them to the outside of the towers. I had to use some spacers on the lower socket cap bolts because the tower is narrower at the base and the bolt would bottom out on the captive nut before snugging up against the tie down loop. I also used some spacers to center and secure the smaller diameter bolts inside the mounting holes on the hitch. I torqued the bolts/nuts down to 48 ft-lbs.
Before reinstalling the exhaust, I decided that I should clean the tip up a little bit. There wer some very rusty patches on the top and bottom and the only way to remove them was to file/sand/brush/whatever, so I went ahead and sanded the entire thing. It had a decent brushed look when finished, but I opted to wetsand heavily and polish it slightly in order to get it closer to it's original appearance and also make it easier to keep clean.
$21.93 - Hardware for mounting hidden hitch (I got a bit more than needed just to be on the safe side)
- Installed hidden hitch
- Used Class 12.9 M8x1.25-90mm socket cap screws, spacers, washers, and class 10.9 flanged nuts to secure hitch
- Cleaned up exhaust tip by wet sanding and polishing
- Reinstalled exhaust
Installing the hitch was kind of a pain in the ass, most likely due to the passenger side tie-down tower being tweaked. The directions said to drill out (despite the fact that it was advertised as a NO CUTTING + NO DRILLING install application) the 8mm captive nuts and install the supplied 7/16" grade 5 hardware. I wasn't really wild about this idea, so I found some specs and did some math. I determined that I could use some 8mm (OEM size) class 12.9 bolts and they would be 76%-90% as strong (depending on which spec you are comparing) as the supplied hardware. Since the Miata probably can't safely tow anything more than half the maximum rated weight of the Class 1 hitch, I felt that 76% is still strong enough for my needs. I retained the OEM tie-down loops by swapping the left and right sides and mounting them to the outside of the towers. I had to use some spacers on the lower socket cap bolts because the tower is narrower at the base and the bolt would bottom out on the captive nut before snugging up against the tie down loop. I also used some spacers to center and secure the smaller diameter bolts inside the mounting holes on the hitch. I torqued the bolts/nuts down to 48 ft-lbs.
Before reinstalling the exhaust, I decided that I should clean the tip up a little bit. There wer some very rusty patches on the top and bottom and the only way to remove them was to file/sand/brush/whatever, so I went ahead and sanded the entire thing. It had a decent brushed look when finished, but I opted to wetsand heavily and polish it slightly in order to get it closer to it's original appearance and also make it easier to keep clean.
$21.93 - Hardware for mounting hidden hitch (I got a bit more than needed just to be on the safe side)