05-18-2018, 01:39 AM | #1 |
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Stiffening Plate (Belly Pan) Bolts
Last weekend I fitted my Fabspeed Sport Cat, which required removal of the front chassis stiffening plate. I know a few people have done this before, and in the DIY threads, no-one has ever posted about replacing the bolts that hold this on, even though ISTA+ gives torque settings of 56Nm + 90 degree rotation, and states that the bolts must be replaced.
This evening I had to remove the stiffening plate again to fit an upgraded Charge Pipe, and as I was putting the plate back on, I started to get concerned that these bolts might sheer if I don't replace them. I know the torque + angle tightening sequence is designed to stretch the bolts, and that doing this is only possible a few times. I have an upgraded FMIC on its way, and will likely need to remove the stiffening plate again... I'm thinking of getting some new bolts this time, but wanted to hear feedback from others on the forum... is this really necessary? Thanks in advance!
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Current Performance Mods: CSF FMIC, ER CP, Fabspeed Cat, Aquamist WMI, GFB DV+, NGK 97506, BM3 (Stage 2 93 OTS), CDV delete, UCP, M2C/M3/M4 Strut Brace, M3/M4 Reinforcement Rings |
05-18-2018, 12:02 PM | #2 |
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Just got a quote for these bolts from my local dealer... $8.65 each!
They offered to give me a discount to bring it down to ~$5.20 each... still very very expensive for an M10 x 33 bolt.
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Current Performance Mods: CSF FMIC, ER CP, Fabspeed Cat, Aquamist WMI, GFB DV+, NGK 97506, BM3 (Stage 2 93 OTS), CDV delete, UCP, M2C/M3/M4 Strut Brace, M3/M4 Reinforcement Rings |
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05-18-2018, 01:07 PM | #3 |
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I didn't replace my bolts but I did manage to damage the threads on one of the bolts. I am currently missing one bolt securing the belly pan lol. Need to visit the dealership and get a quote. Cheap online but shipping ruins it.
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06-01-2018, 05:28 AM | #4 |
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I've done this twice already without replacing them. I'm probably going to replace them soon.. these are definitely torque to yield bolts and the belly pan acts as a lower chassis brace.
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06-03-2018, 11:08 AM | #6 |
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07-06-2021, 11:22 AM | #7 |
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I’m sorry but these bolts are ONE time use—Seriously?!! So I installed my CP, change. FMIC, change. Down pipe, changed?!! Isn’t that a bit extreme?
Last edited by vrooooom; 07-06-2021 at 06:48 PM.. |
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07-07-2021, 12:39 AM | #8 | |
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Also water pump bolts are single use torque to yield as well. So are strut tower bolts, differential drain bolts etc.
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07-14-2021, 02:46 AM | #9 |
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I was just watching brake servicing on M2 Competition. It says 30 Nm + 90 deg.... but if re-use 110 Nm. Made me think about these one-time-use bolts. Why can't we re-use these bolts on stiffener plates but for (IMO) even more critical areas like what's holding our brake calipers or wheels are just torque to 110 or 140 and not need replacing w/ a new one.
Just throwing it out here. Time: 17:13
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07-14-2021, 03:22 AM | #10 | |
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1) didn't know they must be replaced because they don't have ISTA. 2) Don't want to spend the kind of crazy price for bmw bolts. 3) Don't care. But either way bmw says the bolts are single use so if you want to do it right the bolts must be replaced. Well I just looked at ISTA and they do specify that both front and rear bolts must be replaced whenever removing them. Real oem says they are also the exact same bolt so despite bmw not specifying that the front bolt must be yielded as they only give a torque spec, since they are the same as the rear caliper bolts which do need to be yielded and thus stretched we know these bolts will stretch when subjected to torques past 30 nm. This means they MUST be replaced and you really shouldn't reuse a previously stretched bolt. Because a previously stretch bolt is now weaker and is susceptible to snapping. It will also not be able to apply the same clamping load after the material is stretched (a bolt is stretched to enable it to provide a more equal clamping load along its whole thread length and prevent it from vibrating loose, once stretched its elastic properties change and clamping loads won't be the same anymore) so that bolt really shouldn't be reused. So imo FaRKle! shouldn't have put a used bolt torque spec, he should have said new bolts are required...
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07-14-2021, 06:49 AM | #11 |
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Interestingly, BMW also recommend replacing some bolts that aren't obviously being torqued to the point of being stretched - but are being screwed into aluminium.
Made me wonder about the plating on them being some kind of passivating layer designed to prevent electrolytic corrosion, and hence the need to replace them with new each time they are removed. |
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07-14-2021, 01:12 PM | #12 | |
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07-14-2021, 09:28 PM | #14 |
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Bmws dealership software which allows for full diagnostics of the car, programming, software updates, and full repair guides with step by step instructions + pictures and toque specs. Some parts of ista can brick your car if you don't know what you're doing so be careful.
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07-14-2021, 10:03 PM | #15 | |
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