Jeep JK Wrangler Grade 8 Replacement Bolts - Do I Really Need Them?

[maxcustody]

Thanks for some great info.

[Linebacker]

Informative writeups like this are the reason I became and have stayed a member. Besides, I don't want a shot to the group by Greg.

[CrunchyPeanutbutter]

If its not broke dont fix it.

[wayoflife]

If its not broke dont fix it.

Depending on who you're talking to, some will tell you that the factory bolts are broke. Or, at least, they are the wrong size

[CrunchyPeanutbutter]

Depending on who you're talking to, some will tell you that the factory bolts are broke. Or, at least, they are the wrong size

I hear you.

I compiled a list and put together my own kit instead of buying one of the ones marketed and as it turned out, one of the supposedly undersized bolts and the self proclaimed experts said I had wasn't undersized at all. In other words, I went and got bolts I really didn't need because I believed what I read online.

[Silver Surfer]

I hear you.

I compiled a list and put together my own kit instead of buying one of the ones marketed and as it turned out, one of the supposedly undersized bolts and the self proclaimed experts said I had wasn't undersized at all. In other words, I went and got bolts I really didn't need because I believed what I read online.

^ This is the same for me. I had no clue what 10.9 meant on a bolt I know grade ratings but not the standard ratings. So i drank the cool aid on this one. I still have not installed them. But I will keep for a rainy day for the unlikely event I may need one on the trail. I did happen to run into a guy who broke a motor mount so I handed him a couple bolts and nuts and he was fixed. So my money was not totally wasted.

[catahoula]

Thanks for the post! As mentioned I was contemplating this too. Torgue wrench a plus. I do not have a high quality one....HF, but I have followed Eddie's torque specs and have had absolutely no problems at all. My rig is not highly modified. I always read about owners installing suspension kits that have problems. The first thing I always think about is did they torque correctly.

[MTG]

Thank you Big b,

Along with Eddie's earlier post, this is by far the best detailed explanation of "using a proper fastener" ever to grace the forum. If anyone disputes this well written, factual logic you should be kick in the genital region repeatedly for continuing to argue your ridiculous shade tree mechanic rhetoric.

Please lock this thread Admin.

Thank you Big b for your most insightful follow up to my post. It was so insightful that I felt that this whole discussion needed to be it's own thread so that others can benefit from it and save their money.

Wait a minute….

Wasn't there some guy or "man with a plan" that had this all figured out? Pretty sure he trailered his jeep to wherever he "wheeled hard" and then posted about it?

Seriously though, I want to hear from the AEV fans who have replaced their factory bolts in light of their research…

On the one hand they taught the advantage of having an AEV lift as being designed by "former" jeep engineers, yet would replace their factory bolts (also designed by jeep engineers) for some after market bolts promulgated by a few "for profit companies" and the aforementioned expert?

[jedg]

I don't normally post because I feel like I have a hard time putting my thoughts down. I also do not have near the offroad experience as a lot of people on here. What I do have is a background in automotive mechanics and engineering and now work in the natural gas industry which puts a lot of emphasis on fastener safety (I have been to week long courses about proper nut and bolt usage). With what little knowledge I have on the subject I can assure you that Jeep engineers put more thought into using non shouldered bolts into these bushings locations than any home mechanic ever will. A bolt is a "spring" and once torqued to it's design point or stretched it wants to relax back to it's original length, fastening the joint. To get the proper spring tension a lot of engineering goes into bolt design, I'm not sure but believe this is why full threaded bolts are used in these situations. When you use very high grade bots in shorter lengths it's actually harder to get the needed stretch or tension applied. For this reason in the Natural gas industry when fastening down high pressure pipe, vessels, or machinery we don't use the largest diameter, shortest, and highest grade bolt, but instead use several smaller diameter, longer, and the correct grade to give us the most clamping tension. Eddie is 100% right in the fact that the bolt is not designed for sheer, they are not axles and are not the parts that were engineered to accept the side load. The side load is handled by the sleeve and bushing, and is only fastened in place by a properly torqued bolt. When you decide to use shoulder bolts (especially high grade) you are bringing in some unknowns that weren't engineered into the system. These may in fact require a lot more torque to hold tension and not loosen, This could damage the crush sleeve, bushing, heim joint, or whatever else was not designed to be crushed as hard. I'm not saying that these grade 8 "upgrade" bolt kits do not work and solve some peoples issues. More than likely you are just masking the fact of improper torque. I just believe those issues could be solved with the factory bolts, proper torque, and maintenance. A better purchase would be a quality torque wrench.

Eh... I posted this in another thread.. it's more appropriate here.

Not sure it's been brought up before... the difference between the two bolts (14mm and 9/16") is just 11/1000ths of an inch.

FWIW, I have 78,000 on my stock bolts and no issues and won't switch as I see no reason to. BUT, I thought I would educate myself on the real differences between the two bolts.

As for the difference between Grade 8 and Metric 10.9; I looked at SAE J429 and ISO 898.1 (2013 version). I think it's a wash and so I don't think the argument that the 9/16th bolt is 'better' holds water. If anything, if you're not careful and use the course thread 9/16 (12 threads per inch), you might exceed the torque capacity of the bolt you're using.

I know one argument will be the shoulder present on the 9/16" bolt will make it stronger. Mechanically this is a wash as the threaded area portion will still be the weak point on the bolt. (per http://www.fastenal.com/content/docu...renceGuide.pdf).

The next argument for the shouldered bolt is that the shoulder works as a pivot point for rotation. I will argue that if the bolt is properly torqued, this isn't rotated upon. Rather the bushing (that surrounds the bolt) is held in place and the joint rotates around that. This would especially be true with aftermarket joints??

ISO 10.9
Med Carbon Alloy Steel, quenched and tempered
Tensile Strength - minimum 1040 mPa (150,000 psi)
14mm (M14 x 2.00) has a torque load up to 160 ft lbs dry

SAE Grade 8
Med Carbon Alloy Steel, quenched and tempered
Tensile Strength - 150,000 psi (1040 mPa)
9/16" (with 12 threads per inch) has a torque load up to 135 ft lbs dry
9/16" (with 18 threads per inch) has a torque load up to 150 ft lbs dry

Also, both have the same proof load (working tensile strength) of 130,000 psi (900 mPa)

[wayoflife]

Great follow up and great info but I can guarantee you that there will still be plenty of people out there who will still feel the need to buy replacement bolts and just because there are morons on the internet that sound like they know what they're talking about and say that they are needed.