LOL man look at this discussion, gotta love it. We use 12.9 bolts for just about everything. They are the highest grade, and we prefer overkill on strength. You do not have to go to the recommended TQ spec if you feel it's too tight. As for the bolts themselves. We get them from a very well-regarded bolt manufacture locally in California. They are made in the USA, and we pick them up directly from the warehouse. They are not plated they use a coating on them which is black oxide. This is not like Zinc if in a very damp or salty environment the head will indeed rust, but they are MUCH stronger than a SS bolt which may not, we will always lean towards function over fashion. People have this misunderstanding that SS bolts are best due to corrosion resistance, SS bolts are weaker than the lowest grade metric steel bolt. These are going into the TQ plate we would never use SS bolts there regardless of a little rust on the head if things stay wet or get salt on them. We have sold almost 700 of these since Jan 1st all with 25 ft/lbs instructions. You know how many emails from people we have gotten cussing us out for stripping their block with our elevated TQ spec. I'll let you guess, but it rhymes with Hero. Good to see nothing on the forums changes, it's no wonder I rarely come here. Your feedback is appreciated and noted.
That's not how you're supposed to engineer things properly... Overkill =/= quality.
When you choose a fastener you have to take a few things into account:
1) how much torque the application requires
2) the female thread material
3) pitch, and length
4) head width
this will determine what grade bolt you are supposed to use, because a bolt exerts alot of its clamping force through its preload aka the stretching of the bolt itself. If you choose a bolt that is too strong for the material to get the optimal clamping force your preload must be very high (hence why the recommended torque for a grade 12.9 bolt is so high), and that can exceed the pull out strength of the female threads which is not good. So rather than going over kill for no reason you can pick a bolt with a more suitable preload range for the application so it can exert the proper clamping force at a lower torque range. Hence why in this application bmw use an aluminium bolt which is the weakest of them all...... Since aluminium tty bolts of the appropiate length aren't the easiest to find to match what bmw specs for the bed plate, the next most appropriate bolt is stainless as that preload range is perfect for the torque specs bmw calls for.
An analogy for this is going forged internals designed for 1k whp power levels for stock power, its over kill and undoubtedly stronger than the stock internals, but is it better? No because forged motors have a shorter life than cast motors because more clearance is required for forged pistons as they expand and contract more than hyper eutectic pistons. This means more piston slap on cold starts and over time these engines wear much faster - none of my built ej257 sti's lasted more than 80k km before piston slap and oil burning was really bad. Another analogy is a stage 3+ clutch for stock power, is is stronger? Yes but what for the stock clutch can do the job at stock power just as well and drive ability is better. It is all about building to the required demands in some cases, and over building sometimes is not better. This is one of them times...
Great to know you get quality bolts... But in this case fashion and strength is irrelevant. Neither is needed just a bolt that meets the task it needs to do, and in this case stainless fits the job better than a grade 12.9 ss bolt.
Well thats good to hear no one has stripped out their bed plate yet... But as a manufacturer you have to take the responsibility to determine what torque specs bmw calls for and ensure your design suits it, otherwise you risk screwing over your customers who don't know better, don't have access to the TIS, and follow your instructions like they are the only truth. Because if they run into issues who ends up having to front the repair bill? Exactly the end user, so maybe instead of being upset try to understand the feedback and improve. You don't loose anything but you have the potential to gain more trust from the customer when they know you are paying attention to every detail like torque specs, and aren't assigning arbitrary numbers.
BTW I have nothing against VTT, I'm not one of those "haters" that bashes you on every post. I am a fair end user, I compliment you when you deserve it and correct you when I believe you are wrong. In the past I have purchased products from you guys and have had nothing but high praises to say regarding your immensely quick shipping speeds and product processing times. I also liked how nice your CBC quality was.
www.engineeringtoolbox.com
www.coastalfasteners.co.nz
.
