Overweight Meets Baltimore City Streets

AG200 had those stupid wishbones. AG100 has the round bars like his does.

 

I'll say this also. Steel bolts into cast aluminum parts equals corrosion, seizure, and likely a broken bolt when trying to loosen if no anti-seize was applied. Dissimilar metals cause reactions and seizures.

 

Here is the service manual. 5/8" close to M16, 3/4" close to M20. Judging by bolt in year hand and old style hangers you have 5/8. Probably engineering reason they went to 3/4 / M20...

 

You have a "stress raiser" failure here. The start of the failure will be in the bottom of the thread you see that intersects the failure crack. You may see whats called a "shear lip" on the opposite side of the failure. This type of failure is actually fairly common on bolts with course threads and can be caused by misalignment which causes a bending force on the thread while being torqued. Sometimes the nut has a wobble face on it which causes this effect. The other cause can be simple over torqueing.

Using fine threads will increase the cross section area under the threads, and increase strength in the area of failure. Dropping to a grade 5 is not advised. Correctly manufactured grade 8's will never be brittle.

A lot of these foreign countries seem to have trouble understanding sound metallurgy, and pretty much all fasteners are imported. No telling what the steel really is in some hardware imported now days.

I use to do failure analysis quite a bit in my manufacturing business. NDT was a part of almost everything I made. Metallurgy is both an art and a science.

 

No I did not take offense.

My mind is narrow. Once i fasten onto something I cannot let go and think bigger.

One poster did state that Zinc on bolt is a deliberate process to give itself (Zinc layer) to corrosion or some other problem so that the bolt itself is not affected. I learned something from that post.

I have a very strong interest to see how this plays out and ultimately solved. However... when people (Not necessarily you...) begin to ask questions to which I know nothing, I feel that I reached the limits of what I think I know. Maybe and get reluctant to follow though.

There have been times on this forum related to trucking Ive talked to people back and forth and I think both parties learn from each other. We are better for it. I don't have a problem with you or anyone really. It's one thing about internet. You cannot sit there in person and evaluate the person's face, body language and so on while having a conversation about a trucking problem like that bolt. As a deaf man I need that visual evaluation.

The other part of my problem is no knowledge of the costs of these bolts. I can only fall back to whatever is a OEM bolt and use that. Now if Peters People are over enthusiastic about tightening way too much well... that needs to be checked with a torque wrench. But to suggest that would be like telling God his Ark is BS. Follow me?

Ive done a little bit of vehicle mechanical work in my time particularly the old time Push Rod engines, like the 460 in a ford two axle dump truck once and certain other big bolts on frame where necessary in the shop under supervision. I had taken some abuse in the dormitory from other deaf who were jealous of my .. position working on things that they were deemed too stupid to work on. Follow me?

Finally but not last. Frame to suspension brackets that you show in pictures, I have never had a bolt fail in that particular area. (They should have a couple of times...) but I do check em for excessive rust near the atlantic ocean for salt rust and other problems often) And blue beacon took care of the road salt back in the old days after a winter storm with plows were taken care of.

Anyway enough about me. Im beginning to think that someone on Peters crew is too heavy on the torquing. How else are the bolts built for that truck is breaking?

As much as I left baltimore, Baltimore has not left me unfortunately. Depending on how you look at it.

 

I didn't get a notification telling me bout this, just stumbled on it.... :/ sorry Tug.

Those appear to be the steel brackets that came on ag100 originally. As I recall they were bad for cracking.... the upgrade was the aluminum ones.

I can't speak to torque, or spec. I can say that if that set of bolts broke, 1 get better bolts, and 2 look at everything around that bracket n make sure nothing else is loose allowing movement.

 

That's based on the diameter and thread pitch of the bolt by grade. Easy to look up a torque chart on the internet.

 

Yes, there is a dissimilar metals chart and I believe the farther the metals are from each other on the chart the more reactive they are with each other. At least that's how I remember it from a chart I had many years ago.

 

If your concerned about the quality of the bolt, mil-spec is an option. I'm pretty sure mil-spec fasteners come with a bill of materials that is traceable. They are also more expensive.

I've been buying my hardware (grade 8) from Mcmaster-Carr for decades and never had an issue with quality. Metric 10.9 is equivalent to grade 8