Steering Rack to Sub-Frame Torque

[Vanguard]

Good evening,


I replaced my front subframe about 6 years ago. I had some noise coming from the front and tracked it down to loose steering rack bolts. I found the old locknuts were no longer locking.


I picked up new nuts from the dealership and have both blue and red locktite on hand.


Looking for the torque spec for the two bolts that secure the rack to the subframe.


Thanks!

[Henn28]

E53 “steering gear to front axle carrier”:

TIS calls for an initial 50 nm, then another 90 degrees.

[andrewwynn]

Fifty N·m plus ninety degrees.

New bolts of course.

In destructive testing with stiffening plate, they put up with two additional cycles before they became so soft you can feel them stretching and not holding.

You mentioned new nuts but they prob got loose from not being torque to yield when you replaced the gear and didn't TTY.

You can likely get away with TTY with your existing bolts since i bet you didn't get to yield when replacing the gear.

[Vanguard]

Thank you both! No new bolts available for a week, but the nuts clearly weren't 'locking'. New nuts were available so those are going in.


The gear wasn't replaced last time, just the subframe due to rust.

[andrewwynn]

Bolt is just a normal M12-1.5x75 10.9 you can buy at a hardware store.

Snugging m12 gets you 6000 ± 2000-#

Proper dry torque gets you over 11,000 (the first time). (9,900 second and 9300 third fastening).

TTY gets you 13,700# every time.

When wet with oil you might get 10,000-14,000 it's crazy variable.

It's not hard to understand why BMW uses TTY to get "laws of physics" based precise clamping forces. 10.9 bolts with xx cross section will apply a very precise force when stretching to yield.

One XO member came up with joint then 45°. Not a terrible compromise. Not going to get to yield but better than attempting to guess with torque which doesn't work at all.

Unless you upgrade to 12.9 hardware and dry torque. Use nord-lock actual locking reusable washers. Then you get the clamping force of TTY 10.9 with an ∞ repeatable solution.

https://apps.apple.com/app/id369825047

That's the app i use for bolt reference.

[Themoog]

I just re used the bolts and tightened mine up as much as I could and haven't had any problems. That was 5 years ago.
The subframe bolts were a different matter - they worked loose so I had to re tighten them to get rid of a clunk I had..