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528e Control arm torque specs
Posted: May 12, 2024 2:54 AM
by Notelect
I am replacing both lower control arms, I know i have to preload, have to borrow sandbags but going to have to wait a few days due to mothers day.
I need the torque specs for the bolt that goes through the bushing in the control arm. Ive searched around and just find people talk about the preloading, not the actual torque specs
Ps. Does anyone know how long I will be ok going without a proper pre load? May have to druve around my city between when I can get the sandbags 🫣
Re: 528e Control arm torque specs
Posted: May 12, 2024 1:30 PM
by Blue Shadow
the bushing gets trapped by the install torque. Preload is to put the bushing in a location where it won't be stressed until the car is moving and the stress on the bushing is what makes it work. So without proper preload, just tighten it in place with the car on the ground and someone in the driver's seat, good enough until you go through the procedure.
You don't want to tighten the bushing in place with the wheel hanging by the suspension...too much out of place to be good.
These are Newtonmeters need to be converted from the Haynes manual.
lower control arm ball joint 85
lower control arm pivot bolt 77
thrust arm to steering arm ball joint stud nut 77
thrust arm through bolt 130
Re: 528e Control arm torque specs
Posted: May 13, 2024 12:22 PM
by turbodan
I don't believe ballast is necessary for tightening the control arm bushing bolt. Just put the car up on ramps with the suspension loaded and tighten them.
I've also never used a torque wrench here. This is a big bolt with beefy threads, you don't really have to worry about overtightening. Get them as tight as you can with whatever big-ass wrench you have the fits in there and don't worry about it.
Re: 528e Control arm torque specs
Posted: May 13, 2024 11:36 PM
by gwb72tii
With all due respect, a good torque wrench is a small investment and will insure you get it correct.
My tii front suspension has specific torque specs I pretty much ignored, grabbed a big ass wrench and reefed on it. Car had snap oversteer until I torqued to down correctly, with a torque wrench and a pipe "come along"
Do it correctly
Re: 528e Control arm torque specs
Posted: May 14, 2024 1:49 PM
by turbodan
gwb72tii wrote: May 13, 2024 11:36 PM
With all due respect, a good torque wrench is a small investment and will insure you get it correct.
My tii front suspension has specific torque specs I pretty much ignored, grabbed a big ass wrench and reefed on it. Car had snap oversteer until I torqued to down correctly, with a torque wrench and a pipe "come along"
Do it correctly
Always a safe position to take. However if the suspension is loaded before tightening and there is sufficient torque applied to prevent the core of the bushing from moving in any way within the ears of the subframe, the torque value is not particularly important. If you undershoot, the bushing core will be able to wiggle fore and aft and rotate within the ears of the subframe. It would make noise but have no real effect on handling until the bolt holes and bushing core get worn away from the movement. I'm not at all familiar with the tii front suspension but my experience with the e28 has been as I have described. A fairly wide range of torque values would suffice, and most guys will have trouble generating anything excessive with an ordinary big-ass wrench.
Re: 528e Control arm torque specs
Posted: May 15, 2024 10:47 AM
by Ju@n
Last time I did the job I found that there wasn't an easy way to put a torque wrench on that bolt, so I just used a big spanner and gave it a goodntight
Re: 528e Control arm torque specs
Posted: May 15, 2024 10:51 AM
by gwb72tii
turbodan wrote: May 14, 2024 1:49 PM
gwb72tii wrote: May 13, 2024 11:36 PM
With all due respect, a good torque wrench is a small investment and will insure you get it correct.
My tii front suspension has specific torque specs I pretty much ignored, grabbed a big ass wrench and reefed on it. Car had snap oversteer until I torqued to down correctly, with a torque wrench and a pipe "come along"
Do it correctly
Always a safe position to take. However if the suspension is loaded before tightening and there is sufficient torque applied to prevent the core of the bushing from moving in any way within the ears of the subframe, the torque value is not particularly important. If you undershoot, the bushing core will be able to wiggle fore and aft and rotate within the ears of the subframe. It would make noise but have no real effect on handling until the bolt holes and bushing core get worn away from the movement. I'm not at all familiar with the tii front suspension but my experience with the e28 has been as I have described. A fairly wide range of torque values would suffice, and most guys will have trouble generating anything excessive with an ordinary big-ass wrench.
And I don't understand the e28 as much as the tii. And my comment was meant to be a "general" comment about following the manual when reassembling parts of the car.
Your explanation of why the suspension is loaded prior to tightening makes sense, something I've been wondering about as I left my front suspension "loose" knowing it needed to be loaded first. Thanks for the explanation.