What bolts to use for tow hooks?

[Glen4X4]

I want to put these tow hooks on my explorer, they're rated for 10,000 pounds they have 3 holes in each one, so I want to make sure it can live up to or close to 10k pounds what fer kinda bolts should I use in these to ensure they're strength to the frame?

 

[MountaineerGreen]

Me personally, I'd use grade 5 bolts minimum, as big as will fit. Grade 8 would be even better. Use washers on the frame to spread the load out.

 

[Glen4X4]

Ok, they're the ones 4wheel parts sells. And as far as I know they just sell that one model. I guess i'll have to take one with me to the hardware store to ensure they fit right, just didn't know a grade to go with.

 

[manaen]

also as important as the grade, is the proper torque specs for a given bolt size. If you overtighten a bolt it will greatly reduce it's strength

 

[unclemeat]

Use a grade 8.

 

[Glen4X4]

Ok, well I'll try and get that info at the hardware store unless any of yenz know once I get the bolts, I figured the package would have came with a paper recommending the right bolts but it didn't.

 

[manaen]

here is a good page on torque specs, and I also recommend grade 8 or better


http://www.angelfire.com/fl4/pontiacdude428/Bolt.html

 

[aldive]

I would only use Grade 8 hardware.

 

[Travis91]

i work at a local hardware and go grade 8. they will look almost a goldish color

 

[Glen4X4]

Welcome To The Forum! thanks for the heads up, I been pissin around with the weather we been havin but I soon gotta do'em since one of the legal trails rules is to have some.

 

[joecrna]

Grade 8 and use the biggest washers that will fit. You need to spread the load over as large an area as possible on the frame.

 

[IZwack]

Grade 5 or greater .

When looking at bolts for tow hooks, they are typically in shear stress so make sure you look at that and not tensile strength.

http://www.rockcrawler.com/techreports/fasteners/index.asp
Shear strength of a 1/2" bolt grade 5 is over 14k ponds. But you typically rate it for the next bolt down because chances are, the bolt you're going to use is threaded at the shear axis so its not a full 1/2" bolt and you have to subtract twice the height of the teeth. So instead of 1/2", its actually 1/2"-2*[teeth depth]. So rate a 1/2" bolt to 7/16" -- its a good enough estimate.

 

[unclemeat]

I dont have the table in front of me but isn't the yeild strength on grade 5 38,000-psi, and grade 8 60,000-psi.