amc78cj7

Opened the packaging for the Curt 2" rear receiver and was disappointed to find it contained Grade 5 bolts. Since tow points require grade 8 bolts I was a little shocked to see they would sell it this way. Anyway, I dig through my 1/2" bolts then call all the local hardware shops only to find 4" and 5" when I need 4.5" to fit. A cutoff wheel and a die did the trick to shorten those Grade 8 5" bolts.

I just hope nobody installs a clevis and tries to recover someone with the grade 5 bolts. In fact, I'm a little worried now what DC used for factory rear 2" receivers. I've heard of too many deaths from tow points snapping and slingshoting the clevis into someones skull. Please use Grade 8 bolts if you intend to install the Curt receiver.

wayland1985

Just took a look at my mopar hitch in it's box at the end of my bed... I'm not sure what grade bolt they are, since they don't have the typical markings. all the head has is a symbol (an H inside of a C) and 10.9 printed on it.

I wasn't sure if it was a corrosion resistant bolt, so I was waiting to go to Lowes and get some stainless bolts.

stock jk

how in the hell do i know if i have grade 5 or grade 8 bolts? i bought an aftermarket receiver, and had to use the factory bolts that were used with the factory tow hook....

thanks for pointing this out. i guess a trip to the hardware store is in order possibly....

wayland1985

Most bolts have the SAE markings on their head. grade 8 bolts usually have 6 lines on the head. Grade 5 bolts have 3 lines on them (like a mercedes symbol, with the middle erased)

I'm not sure what standard my bolts are though. What's this 10.9 crap? Metric standards or something

amc78cj7

10.9 is metric and I think a Diamler Chrysler friend told me that they are equivalent of grade 8, but hopefully someone will confirm this for you.

bly109

10.9 is the metric grade. Its basically equal to a grade 8.

Wayland, Dont get stainless. They are weaker bolts. Grade 8 or 10.9 are usually zinc coated alloy steel. Corrosion resistant and much stronger then stainless.

bly109

beat me to it

wayland1985

Thanks for the info! I was actually thinking about this a little. I wasn't sure how stainless stacked up. The bolts look coated, I just wanted to make sure, in case I need to take it off down the road to repaint the hitch. (The road salt isn't very friendly).

Phishjeep

Where are the specs for hardware grade for towing hitches and recovery points. Does anyone have a link to a website with this information. I'm too lazy to pull out my ASME books tonight.

samc

Nothing wrong with grade 8, but 5 should be fine; grade 5 bolts have a shear strength of about 90,000 lb/sq in, grade 8 is about 130,000. For a half inch bolt, that's a shear of 17,600 lbs each for grade 5, vs 25,000 each for the grade 8. Even if you're planning to pick up the vehicle by the hitch, one grade 5 in shear is more than strong enough. Their tensile strength is slightly higher than the shear, so that'll work too, but now you're putting all the load on the threads.

Moreover, the bolts are only in shear from vertical loads on the hitch; the pulling load on the hitch goes right to the crossmember. I'd worry more about how the Curt hitch isn't welded all the way across at the front of the channel that goes around the crossmember. And anybody notice that the factory rear hook uses three bolts?

Hardware store stainless steel is not only softer and weaker than carbon steel, you can get funny corrosion problems as well; plus which, it'll round off and bugger no end. Bad idea.

Not to say don't use grade 8; just no need to get hysterical about it. Four grade 5's have about the same shear strength as three grade 8's.