Where can I find a replacement bolt for the one that goes through the trailing arms and knuckle in the rear of an '88? Its like 10 inches long or so. Mine is really bent and I can't find it locally.
I agree. This is not a place to use threaded rod. Get the proper bolts. If you have trouble finding them, I have several sets, fully traceable, ISO certified. They may take a few days to reach you and the shipping costs aren't cheap to the States, but you mustn't cheap out in this area.
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07:39 AM
Jun 22nd, 2011
Fieroking Member
Posts: 2144 From: Coeur D Alene Idaho USA Registered: Jun 2002
Aside from the threaded rod simply being wrong part of the purpose of that long bolt is to fit fairly tight inside the rear knuckle. There is already too much play from the factory, why Rodney is rebuilding the 88 rear knuckles. Imagine as that threaded rod moves around, that will speed up wear tremendously inside the bore as well as providing many great opportunities to shear at the joint between the cast knuckle and end link, which the bolt with the smooth bore would be less prone to do.
It might work for a while but its not an area I would use threaded rod at all.
B7 all thread has a tensile strength of about 125k psi. Shear strength is generally accepted to be .6 of what the tensile strength is
Seeing as how it is threaded rod lets assume as low as 40%
That is still 50,000 psi. There is no way you will break it. This is all assuming the load is landing all on this one bolt and we are ignoring the friction grip between the link and the knuckle
As for it cutting grooves into the bore of the links and knuckle, that isn't going to happen either. The pressure would be applied across MANY threads and would only rotate maybe 30*
I use threaded rod every single day building hydraulic aerial work platforms. I'm not talking out my butt
[This message has been edited by FriendOfYours (edited 06-23-2011).]
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04:42 AM
lateFormula Member
Posts: 1048 From: Detroit Rock City Registered: Jul 2002
Originally posted by FriendOfYours: That is still 50,000 psi. There is no way you will break it. This is all assuming the load is landing all on this one bolt and we are ignoring the friction grip between the link and the knuckle
Think again...
50,000 PSI is the shear strength as determined by a one time load application to failure. For this application where the suspension is being constantly subjected to cyclical loading, you want to know the fatigue strength rating. Even if B7 all thread has a high fatigue strength rating, I would never use it for this application.
Is that so? Don't you think specifying B7 in your first post would have been important? What thread pitch were you suggesting again? Did you analyze the clamping load from the threaded rod given the necessary torque applied? What torque value did you use again? Oh, and I suppose the GM engineers decided to go overboard on the bolt strength thinking that if a B7 threaded rod (yield = 105K psi, tensile = 125K psi) was good enough, then surely the bean counters would be OK with a more expensive higher grade M12 X 1.75 X 210 grade 10.9 bolt threaded 50mm (yield = 130K psi, tensile = 150K psi) just to buy peace of mind.
Once you show that you've calculated the loads exerted on the bolt, and proven that a lesser grade rod will do the job, then people won't second guess your ability to suggest using lesser grade fasteners in critical locations like the suspension.
B7 all thread has a tensile strength of about 125k psi. Shear strength is generally accepted to be .6 of what the tensile strength is
Seeing as how it is threaded rod lets assume as low as 40%
That is still 50,000 psi. There is no way you will break it. This is all assuming the load is landing all on this one bolt and we are ignoring the friction grip between the link and the knuckle
As for it cutting grooves into the bore of the links and knuckle, that isn't going to happen either. The pressure would be applied across MANY threads and would only rotate maybe 30*
I use threaded rod every single day building hydraulic aerial work platforms. I'm not talking out my butt
Lets assume it will hold (not break). 1) The bolt doesn't rotate in the bore. Having said that, even a SOLID bolt will wallow out the hole - what do you think a threaded rod will do? 2) Have you ever seen one of these rusted in the bore so bad you can't get it out? Happens all the time. What do you think a threaded rod will do with all the moisture & air it will hold? ~ Paul aka "Tha Driver"
I agree with the posted recomendations,you might allso try the link below,but you should get the same or greater bolt strength (look on the bolt end,something should be stamped there). http://www.boltdepot.com/ http://www.instockfasteners.com/
[This message has been edited by James Bond 007 (edited 06-23-2011).]
