[F87source]

Originally Posted by E90convert

I agree. Please use 10.9.

If you use 12.9 there is a risk of hydrogen embrittlement that is further sensitive to certain fastener coatings and hardness of the fastener. With the right conditions, your bolt will fracture within a few hours up to a few weeks after tightening.

You're making it out to be way more of a risk than it actually is. With high quality and properly manufactured studs (baked to removed hydrogen during the manufacturering process, and coated to prevent hydrogen ion damage during use) the risk of embrittlement is low. If the issue was as bad as you make it out to be, then grade 12.9 hardware simply wouldn't exist. Bolt manufacturers clearly know there is a potential risk, and they work to ensure their bolts will be ok.

Take a look at the crank bolt capture guys, they use grade 12.9 hardware and there hasn't been a single reported case of a bolt snapping due to embrittlement. Most of the hex bolts vtt sell with their parts are grade 12.9, and again no reported issue of embrittlement.


So for track use where parts are frequently replaced, and strength is everything, if you use quality grade 12.9 hardware it's not going to be an issue.

[Track/S]

Originally Posted by E90convert

I agree. Please use 10.9.

If you use 12.9 there is a risk of hydrogen embrittlement that is further sensitive to certain fastener coatings and hardness of the fastener. With the right conditions, your bolt will fracture within a few hours up to a few weeks after tightening.

Hydrogen embrittlement can happen to 10.9 too, if they don't have the proper treatment & coating.

[F87source]

Originally Posted by Track/S

Hydrogen embrittlement can happen to 10.9 too, if they don't have the proper treatment & coating.

Not as common as in grade 12.9, but it can occur in grade 10.9. It can affect titanium too.

[E90convert]

Originally Posted by F87source

You're making it out to be way more of a risk than it actually is. With high quality and properly manufactured studs (baked to removed hydrogen during the manufacturering process, and coated to prevent hydrogen ion damage during use) the risk of embrittlement is low. If the issue was as bad as you make it out to be, then grade 12.9 hardware simply wouldn't exist. Bolt manufacturers clearly know there is a potential risk, and they work to ensure their bolts will be ok.

Take a look at the crank bolt capture guys, they use grade 12.9 hardware and there hasn't been a single reported case of a bolt snapping due to embrittlement. Most of the hex bolts vtt sell with their parts are grade 12.9, and again no reported issue of embrittlement.


So for track use where parts are frequently replaced, and strength is everything, if you use quality grade 12.9 hardware it's not going to be an issue.

That’s great news to hear there hasnt been any problems. Still wouldn’t use 12.9 when there are 10.9 available. If it really became an issue where 12.9 was the only option, I’d be emailing the company asking how their suppliers are controlling bolt hardness through batch material checks. The biggest contributor I know of is silver zinc plating. And fortunately these are at least black, not sure of the coating. I’ve had to deal with hydrogen embrittlement issues at an OEM level in engineering. In engineering usually have the luxury of upsizing a bolt in a design if the 10.9 is not big enough. If we can’t upsize the bolt, or get the 10.9 to work, then we better have a darn good reason to use a 12.9 bolt with a custom heat treat and hardness spec to reduce HE risk. The off the shelf 12.9 spec still has too much risk for automotive OEMs and requires further modification. And your right suppliers should know better, engineering should know better, quality should know better… yet it still happens.

[Track/S]

Originally Posted by E90convert

That’s great news to hear there hasnt been any problems. Still wouldn’t use 12.9 when there are 10.9 available. If it really became an issue where 12.9 was the only option, I’d be emailing the company asking how their suppliers are controlling bolt hardness through batch material checks. The biggest contributor I know of is silver zinc plating. And fortunately these are at least black, not sure of the coating. I’ve had to deal with hydrogen embrittlement issues at an OEM level in engineering. In engineering usually have the luxury of upsizing a bolt in a design if the 10.9 is not big enough. If we can’t upsize the bolt, or get the 10.9 to work, then we better have a darn good reason to use a 12.9 bolt with a custom heat treat and hardness spec to reduce HE risk. The off the shelf 12.9 spec still has too much risk for automotive OEMs and requires further modification. And your right suppliers should know better, engineering should know better, quality should know better… yet it still happens.

If 12.9 had a problem, no manufacturer would make them.

[E90convert]

Originally Posted by Track/S

If 12.9 had a problem, no manufacturer would make them.

It’s such a problem that OEMs avoid them, it rarely gets brought up in engineering to use a 12.9 because it’s so frowned upon as a design solution. At a minimum do not use in anything safety or structural. Having worked on powertrain OEM projects, there is design checklists that ask if 12.9 or modified spec is being used and the team has to justify how every other option was explored and why it is acceptable. If 12.9 is implemented correctly with the right coatings and heat treat specs and quality control, it is effective.

Motorsport Hardware is not an OEM with a century of experience and millions of vehicles sold. Its an independent aftermarket supplier trying to sell you some race car parts lol. I don’t trust they are doing anything to ensure HE risk is minimized.

[Track/S]

Originally Posted by E90convert

It’s such a problem that OEMs avoid them, it rarely gets brought up in engineering to use a 12.9 because it’s so frowned upon as a design solution. At a minimum do not use in anything safety or structural. Having worked on powertrain OEM projects, there is design checklists that ask if 12.9 or modified spec is being used and the team has to justify how every other option was explored and why it is acceptable. If 12.9 is implemented correctly with the right coatings and heat treat specs and quality control, it is effective.

Motorsport Hardware is not an OEM with a century of experience and millions of vehicles sold. Its an independent aftermarket supplier trying to sell you some race car parts lol. I don’t trust they are doing anything to ensure HE risk is minimized.

Just one example that comes to mind, and if I start to investigate, I'm sure there are many more:

Vag 1.9tdi engines from 90hp to 130hp version use 10.9 head bolts, 150/160hp versions use 12.9 bolts.


Bmw Motorsport knows what it is doing, for this reason they have studs that cost more than a CSR rim.

[E90convert]

Just for fun, I googled “hydrogen embrittlement NHTSA recall.” Here is a good one. There are many. 12.9 is certainly possible and useful when done right. But the “off the shelf” spec still offers HE risk.

https://static.nhtsa.gov/odi/rcl/201...9V039-4268.PDF

https://static.nhtsa.gov/odi/rcl/201...5V347-4420.pdf

[F87source]

Originally Posted by Track/S

Just one example that comes to mind, and if I start to investigate, I'm sure there are many more:

Vag 1.9tdi engines from 90hp to 130hp version use 10.9 head bolts, 150/160hp versions use 12.9 bolts.


Bmw Motorsport knows what it is doing, for this reason they have studs that cost more than a CSR rim.

That's what I'm seeing too, head bolts and fly wheel bolts by oems tend to be grade 12.9.

[F87source]

Originally Posted by E90convert

Just for fun, I googled “hydrogen embrittlement NHTSA recall.” Here is a good one. There are many. 12.9 is certainly possible and useful when done right. But the “off the shelf” spec still offers HE risk.

https://static.nhtsa.gov/odi/rcl/201...9V039-4268.PDF

https://static.nhtsa.gov/odi/rcl/201...5V347-4420.pdf

I'm not saying HE isn't a possibility, I'm saying it's possible to have good quality after market, grade 12.9 fasteners that don't fail.

Btw you don't have to be an OEM with "centuries" of experience to make good products, you can have after market companies make parts that are even better than oem, and just because a product is made by an OEM doesn't guarantee quality. For instance verus engineering makes way better aero parts than even Porsche's factory OEM parts, why? Because they don't have any restrictions stopping them from doing so.

Then look at bmw, look how good their OEM charge pipes are.

[Track/S]

Originally Posted by E90convert

Just for fun, I googled “hydrogen embrittlement NHTSA recall.” Here is a good one. There are many. 12.9 is certainly possible and useful when done right. But the “off the shelf” spec still offers HE risk.

https://static.nhtsa.gov/odi/rcl/201...9V039-4268.PDF

https://static.nhtsa.gov/odi/rcl/201...5V347-4420.pdf

I'm about to buy a CSR stud and do a hardness test on it, I'm 99.99% sure it's 12.9.

Originally Posted by F87source

I'm not saying HE isn't a possibility, I'm saying it's possible to have good quality after market, grade 12.9 fasteners that don't fail.

Btw you don't have to be an OEM with "centuries" of experience to make good products, you can have after market companies make parts that are even better than oem, and just because a product is made by an OEM doesn't guarantee quality. For instance verus engineering makes way better aero parts than even Porsche's factory OEM parts, why? Because they don't have any restrictions stopping them from doing so.

Then look at bmw, look how good their OEM charge pipes are.

Totally agree,

[F87source]

Originally Posted by Track/S

I'm about to buy a CSR stud and do a hardness test on it, I'm 99.99% sure it's 12.9.

Keep us posted!

[E90convert]

interested to hear the results! Can you share the process for measuring the HRC as well? Sectioning the bolt, and were the measurement on the cross section is being taken. Do top and bottom cross section too. Are you able to check alloy element % as well?

[Track/S]

Originally Posted by E90convert

interested to hear the results! Can you share the process for measuring the HRC as well? Sectioning the bolt, and were the measurement on the cross section is being taken. Do top and bottom cross section too. Are you able to check alloy element % as well?

12.9 bolt





For alloy element % we send to an external laboratory.

[E90convert]

Isn’t a 12.9 bolt 39-44 HRC per ISO 898? Not sure exactly where ISO 898 specifies the measurement. Perhaps section just under the head of the bolt and measure half way between the center and OD on the transverse plane. Take 4 measurements, 90 degrees apart. Might as well do the center core too. You might be measuring the carburization (or decarb) layer on the OD.

[Track/S]

Originally Posted by E90convert

Isn’t a 12.9 bolt 39-44 HRC per ISO 898? Not sure exactly where ISO 898 specifies the measurement. Perhaps section just under the head of the bolt and measure half way between the center and OD on the transverse plane. Take 4 measurements, 90 degrees apart. Might as well do the center core too. You might be measuring the carburization (or decarb) layer on the OD.

To compare it is perfectly fine, those of the csr seem to be coated with DLC, to see if it leaves a mark after the test, if not I will have to remove the treatment on the head.

[E90convert]

Originally Posted by Track/S

To compare it is perfectly fine, those of the csr seem to be coated with DLC, to see if it leaves a mark after the test, if not I will have to remove the treatment on the head.

The OD leaves a lot of risk to being fooled by coatings, carbon layer from forming, ect. This is already evident because the 12.9 bolt you measured is below 39 HRC. I’d really like to learn why the CS-R studs would have a DLC. Seems strange to put a coating that specifically reduces contact wear on the threads… If you have the extra time, I’m sure the M2 community would really like to see the transverse section measurements

[to_riffic]

Originally Posted by medphysdave

Which of the online BMW retailers can sell the BMW motorsports products? Mine can order the CSR wheels, but can't get the sway bar. I didn't insist or get into a VIN conversation. Buying local saves on shipping.

https://www.apmotorsport.co.uk/m2csracing

[Track/S]

Originally Posted by E90convert

The OD leaves a lot of risk to being fooled by coatings, carbon layer from forming, ect. This is already evident because the 12.9 bolt you measured is below 39 HRC. I’d really like to learn why the CS-R studs would have a DLC. Seems strange to put a coating that specifically reduces contact wear on the threads… If you have the extra time, I’m sure the M2 community would really like to see the transverse section measurements

It is a Chinese bolt, we will not see more than 38.1HRC
When csr stud arrives I will test a 12.9 bolt from another brand.

Originally Posted by to_riffic

https://www.apmotorsport.co.uk/m2csracing

Do not buy anything on this page, the price they have is twice as expensive as any BMW dealer....

UK is outside the euro zone, they must pay customs on everything they import from the EU.

[Maynard]

Not to dampen the engineering debate, but all of this is somewhat missing the point - the screw in stud has inherent flaws, 10.9 or 12.9. The frequent use of these type of studs amazes me, given their failure rate - I know it makes for an easier wheel swap, but not worth the risk (I can take the extra 2 minutes to use screw-in guide studs for mounting wheels - I'm not timing my pit stops). If you are going to run these, please remember they are race parts, with a rather short duty cycle before replacement (ask the BMW.

It also sidesteps the fact that there are limitations to effective clamping force that are far more problematic than the ultimate fastener strength (a bolt tht isn't properly torqued is already half broken, and there are a host of issues that compromise the effectiveness of torquing lugs).

CORE motorsports has some good discussion, and they are good with Q&A for you techhies. If I get any more serious about tracking, I'm going to have them make me a set of hubs (about 650-700/hub, IIRC). I believe CORE sells 12.9 studs (ARP or MSI) with these kits, and matching nuts. https://www.core4motorsports.com/tech

Here is an excerpt from my communications with them:

From and engineering stand point, going to a grade 12.9 for a wheel bolt isn't justified. Need to keep in mind the material you're screwing into (hub), which is typically far from the strength of a grade 12.9 fastener. It's the equivalent of using mis-matched screws and nuts. If (and that's a big if) a grade 12.9 bolt is to be tightened to the level that they should theoretically be tightened to, there's an increased risk of deforming the threads in the hub, or worse, stripping them since the capacity of the bolt is much greater.

So in essence, the benefit of a grade 12.9 fastener is the ability to be able to clamp the parts more tightly. If that can't be done, what's the point? Answer: there is none. This is where there's another advantage of a press-in style stud since you don't rely on the hub material to generate clamping/tension if you want to move to a higher grade fastener. You just get the correct grade lug nuts.

My first recommendation would be to stick to the OEM wheel bolt or equivalent grade 10.9 and just make sure you keep track of the cone seat of the bolt to be sure that no galling is occurring from the aluminum wheel to the lug nut.

My next recommendation would be to use a wheel bolt that has a floating conical washer, like these: https://www.bimmerworld.com/Wheels-T...3-X5-19mm.html

In my torque/tension testing, I found this floating-washer style not only gets the clamping closer to the ideal value, it does so very consistently after many tightening/loosening cycles because it prevents aluminum from the wheel galling onto the cone set of the bolt/nut. You will see many OEM vehicles and trucks starting from early 2000's onward that have this floating style concept. There's a reason for it. If you haven't read our tech pages which goes more into galling, etc. see here: https://www.core4motorsports.com/tech

[E90convert]

Maynard these are really good points. Ironic you dampen our materials engineering debate and bring in fastener engineering 101! I 100% agree with the points you made. I suspect the hub is hardened steel given that the thread engagement looks to be about 1.0x the thread diameter. Moving to a stiffer 12.9 might make stud fatigue more problematic based on bolted joint stiffness diagrams. However a 10.9 tightened to factory spec with racing slicks end up slipping the joint and causing loosening. I’ve not heard of that happening so I suspect the clamp is adequate.

The collared fasteners were factory on my Cayman. I thought the design was unique, and in the manual you had to grease the threads and flange to collar face with a very specific grease type. I suspected this was to give a consistent friction coefficient for more consistent clamp.

Question: do you think the stud and nut eliminates a failure mode of the bolt fracturing at the ball to shank transition? Or would the transition be smooth enough that the notch factor is basically doesn’t matter.

Anyone know the tightening torque of a CS-R wheel nut?

[F87source]

Originally Posted by Maynard

Not to dampen the engineering debate, but all of this is somewhat missing the point - the screw in stud has inherent flaws, 10.9 or 12.9. The frequent use of these type of studs amazes me, given their failure rate - I know it makes for an easier wheel swap, but not worth the risk (I can take the extra 2 minutes to use screw-in guide studs for mounting wheels - I'm not timing my pit stops). If you are going to run these, please remember they are race parts, with a rather short duty cycle before replacement (ask the BMW.

It also sidesteps the fact that there are limitations to effective clamping force that are far more problematic than the ultimate fastener strength (a bolt tht isn't properly torqued is already half broken, and there are a host of issues that compromise the effectiveness of torquing lugs).

CORE motorsports has some good discussion, and they are good with Q&A for you techhies. If I get any more serious about tracking, I'm going to have them make me a set of hubs (about 650-700/hub, IIRC). I believe CORE sells 12.9 studs (ARP or MSI) with these kits, and matching nuts. https://www.core4motorsports.com/tech

Here is an excerpt from my communications with them:

From and engineering stand point, going to a grade 12.9 for a wheel bolt isn't justified. Need to keep in mind the material you're screwing into (hub), which is typically far from the strength of a grade 12.9 fastener. It's the equivalent of using mis-matched screws and nuts. If (and that's a big if) a grade 12.9 bolt is to be tightened to the level that they should theoretically be tightened to, there's an increased risk of deforming the threads in the hub, or worse, stripping them since the capacity of the bolt is much greater.

So in essence, the benefit of a grade 12.9 fastener is the ability to be able to clamp the parts more tightly. If that can't be done, what's the point? Answer: there is none. This is where there's another advantage of a press-in style stud since you don't rely on the hub material to generate clamping/tension if you want to move to a higher grade fastener. You just get the correct grade lug nuts.

My first recommendation would be to stick to the OEM wheel bolt or equivalent grade 10.9 and just make sure you keep track of the cone seat of the bolt to be sure that no galling is occurring from the aluminum wheel to the lug nut.

My next recommendation would be to use a wheel bolt that has a floating conical washer, like these: https://www.bimmerworld.com/Wheels-T...3-X5-19mm.html

In my torque/tension testing, I found this floating-washer style not only gets the clamping closer to the ideal value, it does so very consistently after many tightening/loosening cycles because it prevents aluminum from the wheel galling onto the cone set of the bolt/nut. You will see many OEM vehicles and trucks starting from early 2000's onward that have this floating style concept. There's a reason for it. If you haven't read our tech pages which goes more into galling, etc. see here: https://www.core4motorsports.com/tech

Great post!

But the goal of using stronger bolts such as grade 12.9 bolts was to try and prevent snapping (not due to the common reasons that studs fail on this platform, but compared to weaker/light weight bolts such as titanium - which has a very high strength to weight ratio, but for a fixed size object where the weight of titanium is going to be significantly lower than steel, the out right tensile strength ends up lower. For example: aluminium has a way higher tensile strength to weight ratio than steel at 99 vs 63. But when the object's size is fixed like alumium vs. steel bolts, the steel bolt will be way stronger. The only time the alumium bolt is stronger is when it is equal in weight, but that leads to a bolt that is way bigger and in the case of wheel bolts we are limited to a fixed size - M14 threads iirc.), not to try and increase clamping loads.