Front Axle , broken bolt

[Doehring]

Need help:

At my '72 240Z I found a broken M8 bolt, the one that connects the ball joint to the track control arm. It took me some time to get the remaining bolt out of the ball joint. In between I ordered new bolts, part no. 08130-82062.

First question: Is this the right bolt or what is the right part no ?

I put that new bolt in and tried to torque 45 lb-ft. The bolt broke already at a bit over 36 lb-ft. So I had to drill that one out, too. My second question now is: What could I have done wrong?

My dealer also ordered another M8 bolt for me, Part No. 081A0-8201A, named Bolt-Flange.

Question3: What is this bolt for, where does it belong to?

On the head of bolt 08130-82062 there is a "9", on bolt 081A0-8201A there is a "7".

Question 4: What do the numbers 7 or 9 on the head of the bolts mean?

Thank you for your help

Rolf

[ktm]

I managed to shear a brand new metric grade 10.9 M8 bolt in the same location torquing to the same specs.

[hd240z]

I understand some replacement ball joints dont line up precisely with the mounting holes in the control arms. If that were the case it might be putting a bind on the bolts. I havnt personally seen that, but its one possible explanation.

Sorry, I cant answer your questions on the metric bolt markings, but someone here on the forum likely knows the answers.

[beandip]

The numbers indicate the hardness of the bolt. The higher the number the harder the steel. Be sure all the threads are clean before assembly for anything that you are going to torque down. Any dirt or rust will cause a false reading. What was mentioned about misalignment is a possibility , have you run a tap into the threads. I haven't heard of a misalignment problem before. If your Z is a '70 or '71 I know the ball joints are different from what is available now. I don't know if this is what you are finding. Arne and recently went through this I believe. Gary

[JimmyZ]

Silly question but don't torque wrenches in Europe use the metric system? Just grasping at straws here. (ftlbs& kg are very diff of course)

Try using a beam style torque wrench. If you have a "click" type it may be defective if you are snapping bolts at 3/4 yield. Beam types are very cheap and are fine for the type work you are doing. IMHO

My 2c

Jim

[JimmyZ]

Another thought,

Did the bolts you were using have shoulders which may have come into interference with the threads? This area is the worst place to have stress on a bolt. (Notch) Missing washers could cause said interference if the bolt did have a special shoulder.

Are the bolts hand screwing in alright? If the threads were not the same pitch etc then things would bind and possibly break. Try running a tap in the hole and compare to the threads on the bolt. The female threads could also be galled. (Fancy term for boogared/messed up)

Just throwing another possibility out.

Jim

[Doehring]

Thank you all for your replies.

So I tried it again with the bolt with the 9 (harder bolt) I hope it isn't a 6!

As the original bolts are too long and touch the ball protecting rubber, I shortened them first and also hit a point on the top to make drilling out easier - in case .... . I also loosened the bolts of the push rod 'cause this might bring some torque on the outer M8 bolts.I could turn in the bolts by hand. No problem, so the holes are in line. The idea with the metric 10.9 bolt is okay. They have even a brider head (13 mm instead of 12). I will try to get some, they are specialities even in a metal ware shop (right word ?) here. The hint with the "click" wrench was good. I also have that other one here and you really have more feeling when torqueing 'cause you can see the how strong you are just pulling.. The toque in lb-ft was mentioned by me 'cause I thought that was more suitable for you in the US than our metric 6 kilopond or Newton meter. The bolt was broken in the middle, not where the washer is, material's problem? By the way, maybe the washer caused the problem. It "eated" itself into the metal of the axle where it sticks and than "eats" itself into the head of the bolt. Let's hope it works fine now. What might happen when the bolts break again while cornering?

Rolf

[cafebaltimore]

In the link below BMW has published a torque spec chart by bolt size and grade. For an M8x1.00 grade 10.9, they recommend a torque of 34 Newton Meters (25 pound feet).

I believe the Nissan factory service manual was incorrect, and the aftermarket manuals repeated the error.

http://www.scribd.com/doc/7691662/BMW-Torque-Specifications