Suspension fastneeres - What grade bolts do you guys use?

[ruralandalone]

As I work to replace my rear suspension on my 86 Comanche, I have to replace at least some of the spring mounting bolts.

 

My obvious choices are "real" grade 8 or grade 5 bolts. 

 

My initial choice is grade 8.  The salesman insisted that that is overkill, as the 8's are not as good in applications that have shear loads.

 

My first thought is that he is wrong, and I should be using 8's for the spring bolts.  

My second thought is that this is going on a truck that has seen more than a few winters of Canadian salt, and the weakest link in the chain is likely the steel in the brackets, not the steel in the bolt.  I recon the steel will distort and fail before the bolt will shear.

 

Any thoughts from the group?

 

A related question:  Should I reuse ANY of the bolts?

 

(and I apologize for the typo in the title...)

[Pete M]

always grade 8s (when possible)  

 

common misconception about 8 vs 5.  

 

are you talking about the giant bolts for the leaf springs?  they are metric and identical to front control arm bolts.  any cherokee in the junkyard will have them.  :thumbsup:

[ruralandalone]

Yes, at this point I am referring to the 9/16 x 5 in  bolts that are used at both ends of hte leaf spring and where the shackle fastens to the frame.

 

I won't go to a junkyard.  Any 1986 vehicle that has been exposed to Ontario winters is going to be in exactly the same shape as mine.  And it was a pain to get some of these ones off.

[gogmorgo]

http://tinelok.com/grade-5-vs-grade-8-fasteners/

Grade 8 bolts will always be stronger.

 

You can use the bolts out of any XJ up to 2001, they don't need to come out a 30-year-old vehicle. But I lived in Ontario for a couple years and will confirm that you'll see way more rust on a 10-year-old vehicle than you would on a 30-year-old truck back home in MB (You know they build cars out there when...) so do whatever makes you happy.

[Pete M]

 ask in the classifieds.  I bet someone from a less rust-prone area has some extras around.   :thumbsup:

[Minuit]

NEVER trust anyone who says "use grade 5 bolts because they are more flexible". If someone you know says that, treat anything else they ever say or have said as being BS too. That little piece of bull$#!& just will not go away and probably has gotten people killed. A grade 5 bolt will have snapped before a grade 8 even begins to deform.  Your salesman knows nothing and uses says things like "grade 8 is not good for loads in shear" to make himself sound smart.

[ruralandalone]

OK, so grade 8's are a better choice.  But should I reuse the existing bolts?  Always? Never?  Only if they show signs of wear?

[DirtyComanche]

People reuse the existing bolts all the time.  They're a metric 10.8 or 12.9.  A 12.9 is superior to a grade 8 and is more or less on par with bling-blang F911 hardware.  That said, if they're rusty and the threads are all beat up, I would throw a grade 8 in without hesitation.

 

Please buy good locking nuts and hardened washers.  I prefer stovers, but nylocks are okay since they will not be exposed to enough heat to matter.

 

Yes, you will probably tear the bolt through the bracket before the bolt fails IF it's a single massive overload.  Fatigue cycles will kill the bolt before the bracket though, and some coarse thread grade 5 crap will probably fail before the bracket in either situation.

 

FWIW, generally inspections will fail any suspension component with a grade 5 or lower bolt.

 

Don't (never) reuse your u-bolts if you're going to take them off.

[Eagle]

Yes, at this point I am referring to the 9/16 x 5 in  bolts that are used at both ends of hte leaf spring and where the shackle fastens to the frame.

 

I won't go to a junkyard.  Any 1986 vehicle that has been exposed to Ontario winters is going to be in exactly the same shape as mine.  And it was a pain to get some of these ones off.

 

But they aren't 9/16" bolts -- they're 14mm.

[DirtyComanche]

 

Yes, at this point I am referring to the 9/16 x 5 in  bolts that are used at both ends of hte leaf spring and where the shackle fastens to the frame.

 

I won't go to a junkyard.  Any 1986 vehicle that has been exposed to Ontario winters is going to be in exactly the same shape as mine.  And it was a pain to get some of these ones off.

 

But they aren't 9/16" bolts -- they're 14mm.

 

 

True.  9/16" is very close and works fine though.

 

That said, the dealer still sells the bolts, or at least the XJ versions, if you want to keep things original.  Or a decent hardware supplier will have M14xwhatever in a 10.8, but it will be $$$.

[DesertRat1991]

You can reuse them, but after overhauling the rear suspension it really seemed like half-assing it to reuse the old fasteners. I bought new ones from Mopar Parts Giant:

 

https://www.moparpartsgiant.com/parts/mopar-bolt-hex-flange-head~34202118.html

[ruralandalone]

Since I am not restoring this to pristine OEM condition.  I am making a custom work truck. I have no problem is substituting 9/16 for an M14 bolt. Given that the difference is about .01 of an inch..

I did not know about inspections failing it for having gr 5 bolts on suspension components. Thanks for that

 

And is there any cure for "Obsessive Comanche Disorder"?

[Jeep Driver]

It's not the shear but the clamping force............grade 8. 

 

 

 

I wonder how many guys used a grade 5 on the axle end of the TB........then wondered why the hole is wallowed out???

 

 

 

9/16 and 14mm share the same pitch?. I can't imagine that. 

[DirtyComanche]

9/16 and 14mm share the same pitch?. I can't imagine that. 

 

No, but they're basically the same diameter.

 

14mm = 0.551"

9/16" = 0.562" (on a normal bolt)

 

Typically the holes will be slightly oversized and the 9/16" bolt will go in snugly.

 

If you're in a situation where there is a captive nut (there isn't on a MJ), you would need to use the correct M14xwhatever bolt.  This is the case on the XJ with the infamous front leaf pockets that have a captive nut inside the frame rail.

[Jeep Driver]

 

9/16 and 14mm share the same pitch?. I can't imagine that. 

 

No, but they're basically the same diameter.

 

14mm = 0.551"

9/16" = 0.562" (on a normal bolt)

 

Typically the holes will be slightly oversized and the 9/16" bolt will go in snugly.

 

If you're in a situation where there is a captive nut (there isn't on a MJ), you would need to use the correct M14xwhatever bolt.  This is the case on the XJ with the infamous front leaf pockets that have a captive nut inside the frame rail.

 

Never mind...........

 

 

I'm thinking of XJ with the weld-nuts........worked on my wife's yesterday.