Extremely over tightened pinch bolt, how to remedy?

Motor Vehicle Maintenance & Repair Asked on September 2, 2021

I was replacing my upper control arms today, however the manual I simply stated “tighten” the bolts (they’re meant to be self-locking). So after some googling my car model (Audi B8 A4/A5), I wrongly thought I should tighten them to 90nm (first tried 40nm as I saw, but it didn’t seem tight enough). The torque wrench never clicked, so I kept tightening them. I then reduced it to 70nm, and it finally clicked, and I stopped.

Now, thinking about what I did, I did more googling and it turns out the bolt should’ve been tightened to 40nm + 180 degrees stretch.

Here’s a picture I took of the original set up:

enter image description here

And after (note there’s no gap between the pinch weld)

enter image description here

So my questions are:

  1. Is it possible to fix what I have done?
  2. If so, how?
  3. How badly did I mess up my car?
  4. Should I use a new bolt and nut?


Update: Tried to take the thread out, got it about an inch out, then it just started spinning. Had to call a thread repair specialist to pull it out. The bolt was completely deformed. Slightly widened the pinch, and used a new nut and bolt and tightened to spec. All looks well (for now).

One Answer

Replace bolt and nut

Likely, there's no damage to the control arm. 70 to 40 is a big jump, but not likely extremely damaging, in my opinion. However, I would definitely replace the bolt: putting that much strain on it risks reducing the bolt strength such that it could break while you're driving.

Replace the bolt, and while your at it, replace the nut as well. How much does a bolt actually cost, after all? Another one of my famous mathematical equations:

cost of (future suspension damage + time getting fixed) > cost of bolt

Correct answer by anonymous2 on September 2, 2021

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