MM Torque Specs Snapping Bolts!? - Ford Mustang Forums : Corral.net Mustang Forum
 
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post #1 of 19 Old 06-02-2011, 11:04 PM Thread Starter
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MM Torque Specs Snapping Bolts!?

I'm in the process of installing a MM Panhard Bar on my 89' LX. I drilled the holes, cut the frame bracket things to length, ect. I went to torque the G8 3/8" bolts to what MM said (47lb ft), and snapped the first one at 30lb ft. What do you guys torque these bolts (mounting the chassis mount to the frame) to? 30 lb ft was enough to snap the bolt.
Thanks,
Bob


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post #2 of 19 Old 06-02-2011, 11:11 PM
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That's really odd... 30ft lb is not a lot of torque at all, are you sure about that? 30lbs is like one hand tight with a 3/8s rachet, I can't imagine how that would snap a decent sized grade 8 bolt.

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post #3 of 19 Old 06-02-2011, 11:39 PM
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Quote:
Originally Posted by Blue91LX View Post
I'm in the process of installing a MM Panhard Bar on my 89' LX. I drilled the holes, cut the frame bracket things to length, ect. I went to torque the G8 3/8" bolts to what MM said (47lb ft), and snapped the first one at 30lb ft. What do you guys torque these bolts (mounting the chassis mount to the frame) to? 30 lb ft was enough to snap the bolt.
Thanks,
Bob
Did you use all the spacers between the bracket and the frame to take up the empty space? I know when I put mine on I had to use both of them on each side and it still squeezed the bracket a bit to get the correct torque. I remember thinking that if it had to compress it much more it might snap a bolt head off because of the angle between the underside of the head and the bracket.

Just out of curiosity did you snap the head off?

Steve
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post #4 of 19 Old 06-03-2011, 12:09 AM Thread Starter
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I'm starting to think my torque wrench may need some recalibration help.. Steve, I could only fit one spacer on the outer frame rail side. However, it still pulled the bracket in a bit because the second bracket just didn't fit. And actually, the bolt snapped at the nut, which seemed odd.

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post #5 of 19 Old 06-03-2011, 12:26 AM
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Yeah, that is really strange. Snapping at the nut with that low a torque is crazy. Is it a straight shot through the holes more or less. Unless the bolt is being stressed with a side load it would take quit a bit to break that thing.
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post #6 of 19 Old 06-03-2011, 12:30 AM Thread Starter
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Yep. I am thoroughly confused. I guess I'll grab another bolt tomorrow, borrow a torque wrench that I KNOW is calibrated correctly, and see if that solves my problem. I just want to get this dang car done!

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post #7 of 19 Old 06-03-2011, 12:33 AM Thread Starter
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And yes, it's a straight shot through. The holes/measurements came out really nice, so everything is flush.

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post #8 of 19 Old 06-03-2011, 12:36 AM
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Did you possibly damage the threads on the bolt? Reason I ask is if the threads on the bolt get jacked up material will gather between the threads on the nut and bolt and stop it from threading on. There is also the possibility of getting a bad bolt that already had a crack in it for whatever reason.
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post #9 of 19 Old 06-03-2011, 12:40 AM Thread Starter
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After I drilled, I took the assembly apart and deburred everything to prevent that from happening. It just seemed odd, because I really wasn't applying much pressure on the wrench. I guess I should stop lifting

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post #10 of 19 Old 06-03-2011, 01:37 AM
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Weld that bad boy in


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post #11 of 19 Old 06-04-2011, 12:27 PM
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I'm wondering if you're putting the bolt in some sort of bind situation?
Put some oil on the threads of the fasteners, see if the outcome is better?

Justin
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post #12 of 19 Old 06-05-2011, 06:22 AM
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Is that torque value for dry or lubricated threads? Makes a big difference.

I just googled torque specs real quick and lubricated 3/8 G8 is 22lbs. while dry is 44. That's double for all you math whizzes out there.

But still, twisting a bolt off shouldn't be very easy to do

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post #13 of 19 Old 06-05-2011, 11:15 AM
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I did the same thing with one of my rear sway bar bracket bolts. I just picked up a grade-8 replacement and didn't have anymore issues. I guess a bad bolt just got through the QC inspection.
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post #14 of 19 Old 06-05-2011, 05:09 PM
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Quote:
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Weld that bad boy in
Then he'll have to cut it back out if he ever wants to remove or replace the tailpipes.
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post #15 of 19 Old 06-06-2011, 06:00 AM
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Then he'll have to cut it back out if he ever wants to remove or replace the tailpipes.
Nope. Installed my PHB when the car had tailpipes. Then went to dumps. Now it has tailpipes again. PHB wasn't removed.

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post #16 of 19 Old 06-06-2011, 12:40 PM
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What brand of tailpipes? There was no amount of magic that was going to get my Dynomax pipes out with the PHB in place unless I cut them somewhere along their length or dropped the entire axle, but if you have those ones that are sectioned over the axle, sure.
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post #17 of 19 Old 06-06-2011, 03:07 PM
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Dynomax as well. Yes they were cut and then re-welded. But that's so much easier than messing w/ the PHB. Also, if you have extra hands, you can really line up the tailpipes and have an extra set of eyes to make sure the pipes clear everything.

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post #18 of 19 Old 06-09-2011, 09:58 PM Thread Starter
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Hey guys, I got the bolts in; thanks for all the help. I ended up getting thinner washers to fit in where the MM spacers were too thick.

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post #19 of 19 Old 06-11-2011, 12:41 PM
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Originally Posted by Blue91LX View Post
Hey guys, I got the bolts in; thanks for all the help. I ended up getting thinner washers to fit in where the MM spacers were too thick.
Good deal. Glad you got it figured out.
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