Body mount bolts

[Monastero]

Hello, I have a 2024 2dr JL. I’m currently installing step sides that bolt to my body mounts. The factory bolts are high strength galvanized (10.9) metric bolts that are comparable to a grade 8 bolt. The new Rock Hard side step bolts are just zinc coated grade 5. I’d like to use new bolts as used ones get weaker (with all the torque I put on them). Why did Rock Hard send me grade 5? Thought these guys were on top of it. It’s really no problem for me to get some grade 8 from the hardware store but if there’s a reason grade 5 would be better than a grade 8 I’d like to know.

I do have experience working with bolts but not in the auto industry. I know about sheering etc. However, these factory bolts are closer to a grade 8. Seems like Rock Hard skimped out and cut some corners here. Otherwise let me know

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[AcesandEights]

Seems grade 5 may be less expensive, but you'd have to verify that. Follow the money.

 

[Monastero]

Yes they are more money.

 

[jac04]

...
The factory bolts are high strength galvanized (10.9) metric bolts that are comparable to a grade 8 bolt. The new Rock Hard side step bolts are just zinc coated grade 5.
...

If the factory bolts are metric, then how do they expect you to use Grade 5 SAE bolts (since there is no such thing as a metric Grade 5 bolt).

 

[Monastero]

My bad, They are actually 8.8 the equivalent of sae grade 5

 

[jac04]

My bad, They are actually 8.8 the equivalent of sae grade 5

Ah, that makes more sense.

 

[Philly_]

I know some people have swapped out grade 5 hardware that comes with aftermarket bumpers and other items with grade 8, but back when I was researching for my JK, some members of those forums chimed in saying that grade 5 was actually better for the abuse because it would flex more, rather than breaking in high impact situations.

Whether this is desirable for rock rails or even accurate, I couldn't tell you, but thought I would relay their opinions.

 

[Monastero]

Appreciate it. Makes sense. Based on these factory bolts (thread locker and torque)and taking them out carefully I’ll go with grade 8.
If one of these bolts was grade 5 or 8.8 and was bent from hard impact I can almost guarantee it will break anyway if I had to take it out. So I’ll take my chances with a grade 8.
Again, thanks for the insight.

 

[jac04]

I’ll go with grade 8.
...
So I’ll take my chances with a grade 8.

By "grade 8" you actually mean metric Class 10.9, correct?

 

[Yawnie'sPapa]

I know some people have swapped out grade 5 hardware that comes with aftermarket bumpers and other items with grade 8, but back when I was researching for my JK, some members of those forums chimed in saying that grade 5 was actually better for the abuse because it would flex more, rather than breaking in high impact situations.

Whether this is desirable for rock rails or even accurate, I couldn't tell you, but thought I would relay their opinions.

They'd better not flex. The bolted joint strength is in the clamping force and should not move at all.
I can't think of any Jeep bolted connections that I want to flex. Flexing loosens bolts. They'll stretch and lose their elastic properties and fail.

Bet that weren't getting their info from the Machinists Handbook.........

 

[Philly_]

They'd better not flex. The bolted joint strength is in the clamping force and should not move at all.
I can't think of any Jeep bolted connections that I want to flex. Flexing loosens bolts. They'll stretch and lose their elastic properties and fail.

Bet that weren't getting their info from the Machinists Handbook.........

Great points! I guess those JK forum members were circulating bad info a while back.

 

[Monastero]

By "grade 8" you actually mean metric Class 10.9, correct?

 

[Monastero]

Yes

 

[Monastero]

Great points! I guess those JK forum members were circulating bad info a while back.

 

[Monastero]

You are absolutely correct. They better not flex. People come up with ideas and want it to make sense. But common sense says otherwise. If a bolt flexes it becomes weaker and weaker. As I stated I understand sheering however, I wanted a damn good reason to use a 8.8. As I thought, there is none.
To be honest I’m sure a 8.8/grd 5 will be just fine. But why use it when you can have better. It’s not that much more money. And taking these bolts out is another story. I never reuse bolts on structural areas and I’m not about to reuse a bolt on my vehicle that has been torqued to the max. Not to mention it will snap the next time I take it out.

Take care Y’all. This helped confirm.

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