Anti-Sieze on Hitch Bolts

[Rhymingmechanic]

I'm going to install a receiver hitch on my 2010 Vibe, so I can use a bike rack.

If I use anti-sieze on the bolts, should the torque be reduced and by what percent?

The torque spec is 86 ft. lb. There are 4 bolts that screw into nuts factory-welded into the frame.

When I was building an engine years ago, someone from a fastener company (ARP) gave reduced torque figures for anti-sieze vs. oil. I wasn't sure if overtorquing would be as critical here as on rod and main bolts.

Thanks All.

 

[63Marauder]

Not nearly important as rod and mains.

 

[The_Jeff]

To me this doesn't sound like the place for anti seize. I understand the disappointment that will happen if those nuts break loose ten years from now and spin freely, but counter that with the bike bouncing up and down constantly and leveraging/ rocking that receiver and shaking it loose.

 

[Corvette Owner]

It is about 20% reduction, BUT I agree, I would not use antiseize on these. In fact I would consider locktite unless nuts have a nylock or you use lock washers on them.

Heck, this is a location where you WANT the nuts to seize !

 

[doitmyself]

I agree with Corvette Owner. If I were to use anything, it would probably be blue thread locker, which claims " It protects threads from rust and corrosion and prevents loosening from shock and vibration".

Use proper grade bolts and inspect them regularly. After a few years, if they appear to be rusting, remove and replace before it becomes a problem.

 

[Donald]

I would use it. The only time I heard of an issue was screwing a nipple into a cast iron exhaust manifold. They said no teflon tape.

 

[SOHCman]

Blue loctite. Wouldn't necessarily have to reduce torque spec.

 

[Rhymingmechanic]

Thanks Guys. Good point about wanting the bolts to stay put. I think I have some blue Loctite, so I'll try that.

There's a new wrinkle. I just opened the hardware packet. The instructions list a torque value of 65 ft.lb. The .pdf sheet on the manufacturer's website has a more recent date, and says 86 ft. lb. Of course they're closed today, so I sent an e-mail.

These are M12-1.25 bolts with no lockwashers. They have 1/2" conical washers with "teeth" on one side that will bite into the frame rail.

 

[JZiggy]

If you know the bolt grade you can find a table that gives torque to proof stress, which is what you want to torque to. For instance:

http://www.swtc.edu/ag_power/diesel_engines/lecture/metric torque values.pdf

 

[morris]

i have ALLWAYS used anti-seize on ALL bolts on bottom of a car/truck, with NO trouble. break system mostly. after 70,000 miles you will be glad you did.

 

[The_Jeff]

Originally Posted By: JZiggy
If you know the bolt grade you can find a table that gives torque to proof stress, which is what you want to torque to. For instance:

http://www.swtc.edu/ag_power/diesel_engines/lecture/metric torque values.pdf


True, but the manufacturer may also be motivated by crushing those grippy washer things. My car has 12mm x 1.5mm lug studs and demands 100 ft lbs, FWIW.

 

[Mr_Incredible]

If it were me, I simply use a reduced amount of anti-seize if there are any concerns.

In addition, I would suspect the bolts are large enough to hold a good amount of torque and that it isn't quite rocket surgery.

 

[supton]

Originally Posted By: eljefino
To me this doesn't sound like the place for anti seize. I understand the disappointment that will happen if those nuts break loose ten years from now and spin freely, but counter that with the bike bouncing up and down constantly and leveraging/ rocking that receiver and shaking it loose.


What is worse: a 40lb rack + 30lb bike on a bumpy road (more than 70lb shock load); or a 100lb trailer tongue weight (static case) when one slams on the brakes (and is then a lot higher)? All sorts of leverage and high shock loads.

I'm guessing the bike rack: on my car, I put my rack on a hitch extender, mostly because the rack was for a 2" receiver and my car is 1.25". So it's long, and hangs low. Whacked the setup more than a few times, either backing into sloping driveways, dragging on uneven ground, or slamming into a speedbump that I've taken too fast.

That said, I wouldn't think 100ft-lb of torque onto the bolts is that high, after all the ones on my car are like a half-inch diameter at the threads.

OP, does the instructions for the hitch require you to drill through sheet metal to install? Am curious, I had to, and have always kicked myself for not doing a better job at the time of rust proofing.

 

[Rhymingmechanic]

Originally Posted By: supton

OP, does the instructions for the hitch require you to drill through sheet metal to install? Am curious, I had to, and have always kicked myself for not doing a better job at the time of rust proofing.


The car already has three holes on each side with nuts welded in at the factory. The hitch uses two of those. It is class II, rated at 250 lbs. tongue weight. Strangely, the other hitches available use all three holes but are class I. The main tube on this one looks beefier, as far as I can tell by photos online.

I heard back from the manufacturer (Curt) today. They said use the lower torque if the bolts are silver (as mine are) and the higher one if they are gold. I asked back what the advantage of the newer fasteners would be, but haven't heard back.

I don't guess this is rocket science. I just want to make sure I get the bolts tight enough without overtightening. I'll go ahead and use the 65 lb figure and blue Loctite.

 

[doitmyself]

Before you start, you might want to figure out a way to clean out any dirt that may have built up on the female threads. A blast of air, tiny bristle brush, pipe cleaner, whatever.

Run a correct sized bolt into each hole beforehand to make sure they are good to go. Get all bolts started before you start tightening up. I've ignored this rule enough times....tighten one up only, then the holes don't align to install the rest (sometimes).

I wonder if the bolt colors relate to grade (5 vs. 8)?

Best of luck with your project.

 

[Rhymingmechanic]

Thanks for that suggestion. I'll chase the threads with a bolt before installing. I did hold the hitch up in place, and it looks like it should fit perfectly.

The bolts are marked 8.8. That's the second of four grades on the chart JZiggy posted above. I guess metrics are graded differently from the SAE bolts I'm more familiar with? (Curt wrote back and said there's no advantage to the different bolts.)

 

[JZiggy]

Equivalent to SAE grade 5.