# Do trailer couplers require hardened bolts ?



## Andy Taylor (Jun 28, 2012)

I recently replaced my coupler with a larger one, 2.5" wide, 2,000 lb. maximum. I used two 3/8" galvanized bolts to mount to tongue. Are those strong enough, or should I use hardened bolts instead? Thanks.


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## Gramps50 (Jun 28, 2012)

Hardened Grade 5 or better


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## Andy Taylor (Jun 29, 2012)

Any idea what grade a normal galvanized bolt is? The hardened bolts I just used for something else on the trailer were grade 8.


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## sawmill (Jun 29, 2012)

I don't think the ones the trailer companies use are hard but take one to a hareware and have them look at the bolt head and they can tell you. If you feel safer with hardned ones use them cannot hurt. Just use grade 5 or grade 8 whatever you want.


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## Gramps50 (Jun 29, 2012)

Andy Taylor said:


> Any idea what grade a normal galvanized bolt is? The hardened bolts I just used for something else on the trailer were grade 8.





No Markings Grade 2 Low or medium carbon steel


3 Radial Lines Grade 5 Medium Carbon Steel, Quenched and Tempered

6 Radial Lines Grade 8 Medium Carbon Alloy Steel, Quenched and Tempered


https://www.boltdepot.com/fastener-information/Materials-and-Grades/Bolt-Grade-Chart.aspx/


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## crazymanme2 (Jun 29, 2012)

I would not run grade 8.Grade 6 is plenty good.

Grade 8 is too hard & will break not bend.I want my tongue bolts to bend if they're going too not break.


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## Andy Taylor (Jun 29, 2012)

crazymanme2 said:


> I would not run grade 8.Grade 6 is plenty good.
> 
> Grade 8 is too hard & will break not bend.I want my tongue bolts to bend if they're going too not break.



Oops. I just bolted on a sleeve to extend my tongue, and used grade 8 hardened bolts. Was that a mistake?


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## bcbouy (Jun 30, 2012)

you really have to abuse your trailer in the worst possible ways to snap a bolt on your coupler.if you bust a grade 8 bolt,your trailer and boat are already toast :lol:


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## GYPSY400 (Jul 4, 2012)

bcbouy said:


> you really have to abuse your trailer in the worst possible ways to snap a bolt on your coupler.if you bust a grade 8 bolt,your trailer and boat are already toast :lol:



Yup... I use Grade 8 for everything.. Mostly because I get them for free!! At work, it's all we use. 

I never had a bolt break, or bend etc if it was properly ( read: not over-torqued) installed.


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## gotmuddy (Jul 4, 2012)

a 3/8" bolt requires thousands of pounds of force to shear. I wouldn't use a grade 8 bolt on one, but definetly a grade 5. I also wouldnt want a hardened bolt, because it will be more brittle than a normal bolt.


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## Andy Taylor (Jul 4, 2012)

Thanks everyone. I'm just going to leave the galvanized bolts in. I have no idea what grade they are, I bought them at Menards.


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## Andy Taylor (Jul 7, 2012)

GYPSY400 said:


> bcbouy said:
> 
> 
> > you really have to abuse your trailer in the worst possible ways to snap a bolt on your coupler.if you bust a grade 8 bolt,your trailer and boat are already toast :lol:
> ...



I recently extended my trailer tongue with a sleeve, and used grade 8 hardened bolts. What would the proper torque be? I snugged them down good, but I didn't go nuts with them. Thanks.


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## GYPSY400 (Jul 7, 2012)

Andy Taylor said:


> GYPSY400 said:
> 
> 
> > bcbouy said:
> ...



It depends on the diameter of the bolt.. You can google a torque chart to find out what they should be torqued to.


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## Hanr3 (Jul 8, 2012)

Whoa, I think we need to back up a bit here. 
Lower grade bolts will bend and snap before the grade 8 will bend. 

Grade 2 will snap at 74,000 psi, while grade 8 is 150,000 psi. Grade 2 will deform at 55,000psi while grade 8 will deform at 120,000psi.
Grade 2 bolts will bend and snap before grade 8 will deform.

https://www.boltdepot.com/fastener-information/Materials-and-Grades/Bolt-Grade-Chart.aspx/

Stick to the grade 8 hardware.


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