F23 Strut Tower Brace bolts confusion

AbnormallyAspirated · 12-10-2021, 02:33 PM

Hi!

Changed my spark plugs today on my 2016 M235i convertible, and very confused about strut tower brace bolts.

My car had the inverted Torx-head bolts at all four locations, but when I look at realoem it says that they are hex at the firewall but torx at the strut tower. The dealer parts department seems to think they are also all torx *they did not have stock)

Can anyone clear up what the deal is here?

Also, there seems to be no consensus on replace or not replace. installation sounds like stretch bolt, but dealer says they are not.

Thanks!

Dave

cooolone2 · 12-10-2021, 07:12 PM

Not a chance they're stretch bolts, so rest easy! If you're concerned, replace them, but it's not necessary.

And quite frankly, just match the thread pitch and length and use any bolt you like. Order some nice and fancy SS bolts to dress things up. It's a strut tower brace, the force is lateral and at an obtuse angle. It's not pulling on the threads, the bolt just needs to be properly torqued.

Good Luck

ggggbmw · 12-10-2021, 07:31 PM

The original cowl bolts on my strut brace were hex head. But the replacements I got were E-Torx. Same part#, same M10x25 size. I think the E-Torx has superceded the hex.

Based on the torque specs, 56Nm + 90 degrees, these are definitely torque to yield, aka 'stretch' bolts. My final torque was between 100-110Nm at the 90 degree mark. Now, whether you actually replace them is up to you. These are beefy bolts, and a lot of people don't replace them. However, if you re-use, I would aim for a final torque in the 90-100Nm range. Once they've stretched you don't do the +90 anymore.

aerobod · 12-10-2021, 09:29 PM

The proof load for a 10.9 M10 zinc plated bolt will be reached at around 95Nm, so 100-110Nm is definitely in plastic deformation territory.

12-10-2021, 02:33 PM	#1
AbnormallyAspirated Private First Class 16 Rep 122 Posts Drives: 2016 M235i 6-Speed Convertible Join Date: Oct 2021 Location: Rochester, NY iTrader: (0) Garage List 2016 BMW M235i F23 6MT [0.00] 2019 Audi Q7 55 [0.00]	F23 Strut Tower Brace bolts confusion Hi! Changed my spark plugs today on my 2016 M235i convertible, and very confused about strut tower brace bolts. My car had the inverted Torx-head bolts at all four locations, but when I look at realoem it says that they are hex at the firewall but torx at the strut tower. The dealer parts department seems to think they are also all torx *they did not have stock) Can anyone clear up what the deal is here? Also, there seems to be no consensus on replace or not replace. installation sounds like stretch bolt, but dealer says they are not. Thanks! Dave Attached Images
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12-10-2021, 07:12 PM	#2
cooolone2 Captain 624 Rep 706 Posts Drives: 20' M240iX B58, 01' 330XI E46 Join Date: Jul 2019 Location: NY, USA iTrader: (0)	Not a chance they're stretch bolts, so rest easy! If you're concerned, replace them, but it's not necessary. And quite frankly, just match the thread pitch and length and use any bolt you like. Order some nice and fancy SS bolts to dress things up. It's a strut tower brace, the force is lateral and at an obtuse angle. It's not pulling on the threads, the bolt just needs to be properly torqued. Good Luck
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12-10-2021, 07:31 PM	#3
ggggbmw Lieutenant 433 Rep 442 Posts Drives: 2017 M2 Manual Join Date: Jan 2017 Location: Minnesota iTrader: (0)	The original cowl bolts on my strut brace were hex head. But the replacements I got were E-Torx. Same part#, same M10x25 size. I think the E-Torx has superceded the hex. Based on the torque specs, 56Nm + 90 degrees, these are definitely torque to yield, aka 'stretch' bolts. My final torque was between 100-110Nm at the 90 degree mark. Now, whether you actually replace them is up to you. These are beefy bolts, and a lot of people don't replace them. However, if you re-use, I would aim for a final torque in the 90-100Nm range. Once they've stretched you don't do the +90 anymore.
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12-10-2021, 09:29 PM	#4
aerobod Car Geek 3612 Rep 3,578 Posts Drives: Caterham R500, M2-G87, Macan S Join Date: Mar 2008 Location: Calgary iTrader: (0)	The proof load for a 10.9 M10 zinc plated bolt will be reached at around 95Nm, so 100-110Nm is definitely in plastic deformation territory.
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