Angle tightening problems

johnnyfd · Post by **johnnyfd** » 10 Dec 2016, 22:10

I torqued and angle tightened my subframe bolts after replacing my sway bar. After torquing the bolts to 77 pounds I put a socket on my breaker bar because I knew it would be hard to turn the 120 degree angle tighten that was specified after the intial torquing . I put so much force on my 28 inch breaker bar that I had to let up for fear of it snapping as I watched it flex and I was only able to get an additional 40 degrees or so on the bolts . I don't think I was able to get to half of the 120 degrees on any of the four bolts and now I'm worried that I put so much force on them that I might have over tightened them . This same type of thing has happened to me with other bolts on the car that required angle tightening such as the lower strut assembly bolts . I must have been applying about two hundred pounds of torque with the breaker bar on the subframe bolts( enough to slightly drag my body across the pavement as I was laying down under the car) . I wanted to get the angle tightening correct but was afraid I put way too much force on the bolts in an attempt to get there. Why has this happened to me several times and how should I proceed. Thanks in advance for any responses.

Post by **theWIFES_S70** » 10 Dec 2016, 22:28

hey johnnyfd,
I don't think you should worry too much about getting the "perfect" torque on those bolts. (You should be happy you didn't snap the welded nuts that these bolts screw into! There's a thread here of quite possibly one of the scarriest things that can happen when doing subframe bushing jobs...)

When I replaced my subframe bushings (ehem, twice over the course of a few months...) the only way I was able to get "close" to the 120 degrees past 77 pounds was by laying on my back, a 4' cheater on my breaker bar, and pushing it with my legs, grabbing the frame of the car with my hands for leverage... I'm not sure If I got to exactly 120 degrees. But I know I torqued all four of them down evenly.

If I had to guess, being as close to 120 degrees as possible is important, but just as important is making sure they're all torqued down evenly. We've put in over 1500 miles since the last subframe bushing job and the car feels amazing...

johnnyfd · Post by **johnnyfd** » 10 Dec 2016, 22:44

It sounds like you put at least 300 pounds of torque on those bolts if not more with your procedure. Weren't you afraid of breaking or stretching the them ? This can't be the same amount of force applied to the bolts that was intended by the engineers . My bolts were virtually corrosion free. Do you know why these bolts are requiring so much force to get to the correct angle?

Post by **theWIFES_S70** » 10 Dec 2016, 22:56

Well, I'm a little guy!

I had to produce torque any way I could!

I wasn't afraid at all. I didn't know these bolts went into a little welded nut... I figured they screwed into the frame somewhere... Talk about ignorance! I figured with all that torque (more than an axle nut gets...) that they screwed into something similarly beefy.

I have no clue why they need that much torque, I imagine it has to do with keeping the engine/frame steady? My bolts were corrosion free, too!

As long as it's even torque all around, I think you'll be OK. I wouldn't really overthink it too much.

Post by **abscate** » 10 Dec 2016, 23:37

Are these bolts one time use? If so, you can't re-use them. They stretch when torqued and this you can't reach proper torque again.

I confirmed in Alldata they are one time use bolts.

johnnyfd · Post by **johnnyfd** » 11 Dec 2016, 00:53

The way we did it doesn't sound like the right thing to do and it now sounds like these bolts have been over stressed. If a person had to reuse the bolts for whatever reason what would be the best approach in other words how much force or how much of an angle should they be turned to? If I am going to replace the bolts what's a reliable source for getting quality bolts that won't be made from inferior quality steel which might be worse than using the original over stressed bolts?

Post by **abscate** » 11 Dec 2016, 05:03

ideally you want to match the grade and steel of the bolts of the Volvo ones.

What I would do here is put two punch marks on each bolt and on the frame next to each other , and examine them weekly for a month, then monthly for six months, then annually. If they don't move after a year, corrosion and rust will lock them in place.

johnnyfd · Post by **johnnyfd** » 11 Dec 2016, 07:33

If the bolts are going to be used again or have to be used again if they've already been stretched as it was mentioned , the specified amount of force can't be applied . What's a good guess as to the amount of force or angle to apply to get them appropriately tight since the specified about would be too much for the stretched bolt ?

Post by **abscate** » 11 Dec 2016, 07:53

Fastener tension is roughly equal parts thread friction, head friction, and fastener stretch. For a one use fastener, or torque to yield, the stretch component is much bigger

The right thing to do here is get new bolts from Volvo. They may not be crazy expensive, check out Tasca or Lisle Volvo for part numbers..maybe even IPD or FCP.

I would not hazard a guess at how to correctly re-use a one use fastener, way too many variables. If you aren't going to get new ones, mark and monitor what you did as above.

johnnyfd · Post by **johnnyfd** » 11 Dec 2016, 17:44

Thanks for all the knowledgeable information. Knowing this about single-use fasteners will be critical in future jobs and I really appreciate it. I will replace with Volvo bolts soon since there is no other way to be certain about these critical fasteners . I hope they don't break when I try to remove them since I put so much force on them .