[M2_MEDUSA]

Originally Posted by 2020m2c

Sorry this happened to you but that's not quite how odds work. Tuning may or may not increase the odds (unfortunately only BMW has any real robust data set on this). Even IF tuning increases the odds of it happening we don't know by how much and to what extent the preventative upgrades prevent slipping.

I take issue with saying "it's a matter of time". You simply don't know that with any certainty and what little data is available contradicts this. Truth is these motors don't seem to be failing by the thousands despite how many copies of BM3, JB4, etc are being used in the open market. Your statements about this issue are colored by your recent experience. In simplest terms it's what is known as reverse survivorship bias.

A true pro forma to evaluate the cost / benefit of a clutch hub upgrade would need to evaluate how often they spin, how often each clutch hub upgrade still fails, what the average and range of the cost of repair of a spin is (timing, hub replace, full motor, etc), and the cost of the upgrade. Of course you'd need to evaluate the various options available to figure out if some or any of them were really worth it based on how much they prevented (or exacerbated) the damage. And yes, there is some thought that the damage is more catastrophic when an "upgrade" fails violently rather than a slight slip of the stock hub.

Most of that data is unavailable to us so really this is a case study. Purely anecdotal and not actionable to the S55 motor writ large. Again, sucks that it happened to you but for me it's a small risk to begin with and a lot of marketing hype based on what *appears* to be a marginal amount of failures of the S55. The problem is that if you are one of the unlucky few it hurts bad. I just don't know that the expensive "fix" is really good insurance per dollar or not. I guess if it happens to mine it will be 100% a problem, and if it doesn't then it's 100% a win. Roll the dice…

I believed exactly what you said, and you sound like my responses the past few months on the forums to crankhub posts. Your response has been no different than mine and now I understand. If you tune the car your outside of tolerance dude. Plain and simple. It is a matter of time once you start going outside of tolerance and putting extra load on the crankhub. Simple engineering. Vehicle components are rated for specific loads and when you go outside of that things happen. Yes it is a matter of time. We've seen it time and time again from crankhub deniers all over the forum. I payed $1,800 parts and labor. Not worth rolling the dice.

You can deny it and use all the analogies you want. You are outside of tolerance at the end of the day and let's hope the hub stays intact before you face the music yourself

[Oliv]

Issue is that CS/ M4 GTS uses the same exact crank hub, and are estimated by BMW to be still in tolerance...
What is safe/what is not ? CS map with same torque/460hp ? If that is safe, GTS/500hp one still OK ?

We can only guess...logically it seems that:
-increased torque remap (stage 1 and above) is a factor of increased probability of failure
-DCT too in extreme map (due to aggressive clutch engagement)
-harsh driving too (engine brake at high revs)

But again, some people break those 3 rules and still seem OK...
Personally I intend to remap one day, but will stay at CS levels - if mine ends up with a spun crankhub I’ll report there

[Bass_Masterson]

OP, sad to hear, I had a similar experience a few months ago. Ended up installing a one piece hub myself.

But I will pose this question as I have before, how does increased torque (or horsepower) output put more load on the crank hub? You're absolutely correct, tuning subjects parts to forces they weren't necessarily designed for, but I don't see how it causes the hub to spin. Additional output from the crankshaft doesn't impart any extra force to the hub, assuming your valvetrain is all stock.

Outside of some other part of the valvetrain failing, only over-revving or very fast changes in RPM could impart more stress on the timing sprocket. I also don't buy that reverse load causes this.

As far as the bolt loosening/backing out, that's more plausible, I guess. But that sounds more like a factory installation error/metallurgy problem. With how tight the bolt is/gets stretched, I don't see how it could back out if tightened properly, but I won't die on that hill. For the record, my bolt was still fairly tight. Took a lot more to tighten the new one than remove the old one, but that's a characteristic of torque-to-yield/stretch bolts, as far as I know.

I'm not trying to antagonize, I'll accept any credible evidence, but I've yet to see anyone explain how increased power output puts more stress on the hub. I'm also not asking for numbers of failures, because we don't have complete data, and without complete data on all failures, it's hard to come to a sound conclusion.

Anyways, glad to hear you got it back on the road!

[akkando]

Originally Posted by SpecialEdition_F87

I believed exactly what you said, and you sound like my responses the past few months on the forums to crankhub posts. Your response has been no different than mine and now I understand. If you tune the car your outside of tolerance dude. Plain and simple. It is a matter of time once you start going outside of tolerance and putting extra load on the crankhub. Simple engineering. Vehicle components are rated for specific loads and when you go outside of that things happen. Yes it is a matter of time. We've seen it time and time again from crankhub deniers all over the forum. I payed $1,800 parts and labor. Not worth rolling the dice.

You can deny it and use all the analogies you want. You are outside of tolerance at the end of the day and let's hope the hub stays intact before you face the music yourself

That's just not true. For one the m2c comes detuned from BMW, so depending on the tune, you might just be tuning it to perform as originally designed by bmw. For example if you ran the stock m3 tune on an m2c the motor would been running within the tolerances its be designed around.

Also stock m3 motors still fail sometimes.

Stock m2c motors still fail sometimes.

Tuned m2c and m3 motors sometimes do not fail.

M3cs motors run at a higher state of tune. I'm sure sometimes they fail, sometimes they don't.


You're taking your situation and applying it to everyone else and every s55, but the world is bigger than just you.

[M2_MEDUSA]

Originally Posted by akkando

That's just not true. For one the m2c comes detuned from BMW, so depending on the tune, you might just be tuning it to perform as originally designed by bmw. For example if you ran the stock m3 tune on an m2c the motor would been running within the tolerances its be designed around.

Also stock m3 motors still fail sometimes.

Stock m2c motors still fail sometimes.

Tuned m2c and m3 motors sometimes do not fail.

M3cs motors run at a higher state of tune. I'm sure sometimes they fail, sometimes they don't.


You're taking your situation and applying it to everyone else and every s55, but the world is bigger than just you.

Keep denying it all you want. When your outside of tolerance things happen. Once again everything is rated for a specific load. When you start tuning outside of that tolerance you are playing with fire. Stock ones spin also, yes because it's a shit design flaw. When you go outside of tolerance that design flaw says HELLO. I was just like you man. Continued to fight everyone who claimed a stock crankhub issue. Now look at me. Spun hub.

Your putting extra load on the hub whether you like it or not when your tuned and that's a fact. The further you travel away from tolerance the higher chance it is.

To everyone else, the purpose of this post is to let everyone know the year doesn't matter. Nothing has been fixed.

Basically there's no 100% clear answer. I'm not saying this is the answer. Stock ones do go bye bye also. It's a poor design flaw and when you create additional load it really makes that poor design flaw work less effectively.

I'm here to share my story and everyone wants to attack me. It's okay, I attacked everyone else too when my hub wasn't spun.

Now here I am.

[M2_MEDUSA]

Originally Posted by Bass_Masterson

OP, sad to hear, I had a similar experience a few months ago. Ended up installing a one piece hub myself.

But I will pose this question as I have before, how does increased torque (or horsepower) output put more load on the crank hub? You're absolutely correct, tuning subjects parts to forces they weren't necessarily designed for, but I don't see how it causes the hub to spin. Additional output from the crankshaft doesn't impart any extra force to the hub, assuming your valvetrain is all stock.

Outside of some other part of the valvetrain failing, only over-revving or very fast changes in RPM could impart more stress on the timing sprocket. I also don't buy that reverse load causes this.

As far as the bolt loosening/backing out, that's more plausible, I guess. But that sounds more like a factory installation error/metallurgy problem. With how tight the bolt is/gets stretched, I don't see how it could back out if tightened properly, but I won't die on that hill. For the record, my bolt was still fairly tight. Took a lot more to tighten the new one than remove the old one, but that's a characteristic of torque-to-yield/stretch bolts, as far as I know.

I'm not trying to antagonize, I'll accept any credible evidence, but I've yet to see anyone explain how increased power output puts more stress on the hub. I'm also not asking for numbers of failures, because we don't have complete data, and without complete data on all failures, it's hard to come to a sound conclusion.

Anyways, glad to hear you got it back on the road!

Most evidence in the field has pointed to kickdown fast rpm changes reverse torque etc etc. This is what we have to work with. When you increase the power output you are effectively changing the speed in which rpm's move. This increased force puts more and more load onto the hub. There's no 100% for sure answer because no one knows however we can only use what we hear and see in the field and that's what I've been attempting to do here.

All I know is I was running close to 600/600 and in 14K miles the crankhub kaboomed. There was no way I was inside of tolerance.

However, there have been stock crankhubs that kaboomed. Shit design flaw that gets exaggerated when you start throwing power at it.

design flaw. That's what it comes down too. Take the e9x M3 and their rod bearing issues which is 100x more failures then the crankhub. It's just a poor design and sadly this design is on the s55.

No one here can say the crankhub was designed well. Everyone agrees it was designed poorly. So by changing the speed of rpm movement because of power. What can occur there? What are the possibilities of increasing load on a poor design??

A spun hub.

[captain slowly]

Aren't you the same guy who claimed your "special" edition made more power stock than all other M2C? And the same guy who claimed to be beating FBO GTR's? Lol!.

[M2_MEDUSA]

Originally Posted by captain slowly

Aren't you the same guy who claimed your "special" edition made more power stock than all other M2C? And the same guy who claimed to be beating FBO GTR's? Lol!.

Yep. Some dynos read low some read high. Some people can't race some people can. Your point??

GTR weigh almost 4k pounds. Tons of tuned s55's beating them on on YouTube and IG. Nothing new. It's no surprise 600/600 S55 shouldn't do good against a gtr??

You look like a fool

[captain slowly]

Originally Posted by SpecialEdition_F87

Yep. Some dynos read low some read high. Some people can't race some people can. Your point??

GTR weigh almost 4k pounds. Tons of tuned s55's beating them on on YouTube and IG. Nothing new. It's no surprise 600/600 S55 shouldn't do good against a gtr??

You look like a fool

My point is, you have no idea what you're talking about, and this thread is no different.

[M2_MEDUSA]

Originally Posted by captain slowly

My point is, you have no idea what you're talking about, and this thread is no different.

You look like a fool. Always have. And your last attempt of a thread Jack proves it. Let's dissect what I said and let's talk about it. I have all day.

Instead of pointless posts to a thread use your brain and let's have a conversation. Let's start going over every piece I've said in this post.

Or is your only argument insults? Typical from you.

You'll always be slow. In your head and your car. I'd blow your doors off. This is the captain slowly argument technique. Did I do it right!??

[Bass_Masterson]

Originally Posted by SpecialEdition_F87

Most evidence in the field has pointed to kickdown fast rpm changes reverse torque etc etc. This is what we have to work with. When you increase the power output you are effectively changing the speed in which rpm's move. This increased force puts more and more load onto the hub. There's no 100% for sure answer because no one knows however we can only use what we hear and see in the field and that's what I've been attempting to do here.

All I know is I was running close to 600/600 and in 14K miles the crankhub kaboomed. There was no way I was inside of tolerance.

However, there have been stock crankhubs that kaboomed. Shit design flaw that gets exaggerated when you start throwing power at it.

design flaw. That's what it comes down too. Take the e9x M3 and their rod bearing issues which is 100x more failures then the crankhub. It's just a poor design and sadly this design is on the s55.

No one here can say the crankhub was designed well. Everyone agrees it was designed poorly. So by changing the speed of rpm movement because of power. What can occur there? What are the possibilities of increasing load on a poor design??

A spun hub.

Aggressive shift tuning for DCTs could contribute, that makes total sense.

I considered that point. Unless you DRASTICALLY reduce gear ratio or rotating mass (in the case of free-revving in neutral), the engine's RPM will not increase/decrease much faster than stock with 500 - 600 WHP, whether you're in neutral or in gear. Just blipping the throttle to rev it up in neutral is way faster of a RPM change than doing a pull, and that's safe to do with the engine/tune stock, right? (exception being shifts, but that's independent of engine power output).

Yes, can certainly agree it's a crap design. I cringed realizing any older engine I've ever worked on has a keyed timing chain gear. Sad example of BMW trying to cut corners. But for the S65 example, increasing power directly applies more force to any engine's rod bearings, whereas it doesn't to the S55 crank hub.

I won't get involved with the crap slinging, but I just wanted to state a point that I see a lot of people not full grasping.

[SchnellerM2C]

So what hasn't come up on this thread and what I alluded to in my previous post, was the topic of harmonics which run through an engine's crankshaft & is of particular concern in straight 6 cyl. engines due to crankshaft length. Tunes and driving style all weave their variables into this vulnerability of BMW's 6 cylinder engine family.

Steve Dinan goes into some detail in the following link about this topic & specifically talks about the s50/52 failures due to the elimination of the engine's front crank vibration dampener in favor of an under driven crank pulley.

http://www.atiracing.com/products/da...mper_dinan.htm

The point I'm making here is that BMW designs & employs specific vibration dampeners to handle the harmonics of their different engines. The dampener used on the s55 engine is specific to it, and is tailored to the harmonics generated by that engine & the factory's s55 tune. When we add mods and power, we change the harmonics (in unpredictable ways) that travel to, and are most pronounced at, the end of the crank where the dampener & "failing" crank hub reside. It's quite possible that certain tunes amplify critical RPM harmonics, and if we often drive in that RPM range we eventually experience a failure.

"If the RPM remains at or near one of the major criticals for any length of time, fatigue failure of the crankshaft is probable."..."The oscillation of the crankshaft at a major critical (engine) speed will commonly sheer the front crank pulley and the flywheel from the crankshaft."

I wanted to also add,

"Every time a cylinder fires, the force twists the crankshaft. When the cylinder stops firing the force ceases to act and the crankshaft starts to return to the untwisted position. However, the crankshaft will overshoot and begin to twist in the opposite direction, and then back again." This is happening all along the crank as each piston fires. Can you envision all the wobbling that's going on all along the crank at 7000 RPM?!

Now imagine the driver, in either a high rpm sudden lift (think autocross?), kick down (ooh this Sti wants to race!), or money shift situation (oh shit!!!)...

Under full throttle load (acceleration) the crank is twisted in one direction, then suddenly, the driver delivers a reverse load & major change in harmonics running to the nose of the crank. Do that habitually over time (first its loaded one way, then suddenly snapped back in another direction) & that 300 lb-ft crank hub bolt starts to work its way loose, and may actually fail in the driveway upon start up, vs during that hair on the chest beat run. That's just how the universe handles us?

In my opinion, I think there are several factors at play here that under the right constellation of circumstances give rise to spun crank hubs.

1) First, the hub itself is an N55/S55 part, the sprocket is widely used in euro only engines and also the n51-N55 family and the s55 motors. The bolt itself is currently used in the N20/26, N55 & s55 engines. --- It may be possible that under certain operating conditions (Tune, engine RPM, driving style) that the design parameters of this hub are exceeded in the s55 engine, as it is the most powerful engine using this design.

2) Tunes and other mods themselves are introducing unknown harmonics into the s55 crank that the harmonic dampener cannot adequately control. Additionally, relative to harmonics, a 500HP BMW Motorsport tune isn't likely the same as a 500HP JB4 tune or whatever. Finally, maybe all that power on a 6 cyl inline crank is too much to dampen? Notice how the newer B58 engine has the crank hub & timing chain at the back of the crank near the flywheel, as far away from the uber vibrating front tip of that 6 cylinder crankshaft? Maybe high horsepower inline sixes are more reliable with the hub back there? (BTW, heaven forbid there's any B58 VANOS work to be done back there against the firewall!)

3) Lastly, and the one most will take offense to, is driving style...

We are, after all, perfect F1 level drivers that have just chosen a different career path
As a club racer, driving school instructor, shop owner & technician I am simply floored by how people drive their cars fast . It doesn't matter if it's a newbie w/ all the horsepower mods, a driving school instructor or fellow(team) racer. Some people mechanically do things to their cars from the driver's seat that I, understanding what's going on inside the engine and drivetrain, could never envision doing myself.
Let's be clear, cars can be driven fast and still be quite reliable. Witness the turds running a LeMons race... it's not the fastest cars that win, but the ones that are driven respectfully with the drivers listening to the feedback of the car and understanding what they are asking it to do. It's the repetitive rough driving style, abrupt transitions and a general beating that impart inertia loads vs constant tension on mechanical parts that will cause mechanical failures. (Remember the high school physics experiment with the weight on a string? You could pile a bunch of weight on that string & it wouldn't break, but take away a bunch of weight, lift the weight & let it drop and the string would break - that's an inertia load.)

So to conclude, you likely can drive a tuned car fast, but smoothly, and probably not have an issue, or you can beat the piss out of your stock s55 and spin the hub. If you've got a tune and beat the piss out of it, well there's only so much you can ask of that n20 crank hub bolt. If you're rough with things, you can opt for a different hub design and maybe it'll work. These cars are all pretty young and only time will tell if that's a solution, or if other failures will develop instead.

One thing is for sure, if you add power, you do it at the expense of reliability. If you constantly run at the upper end of the engine's operating range you'll greatly reduce engine life. Moreover, if you're rough with your expensive ride, she'll definitely ask you to open your wallet. Such is love!

[Ratcher]

Originally Posted by SpecialEdition_F87

Your completely incorrect. The one piece hub doesn't address the bolt. If the bolt backs out your one piece hub ain't doing anything.

$100 and 45 min of work is far from a scam. But keep believing that

By the way all the data in the market proved your claim completely false! Not a single spun hub has ever beeen reported outside of a moneyshift when crank bolt capture has been installed under 600/600. Data proves you completely incorrect.

You're funny. "All data". Data as in every decent or known shop that used to offer it now offers the one piece solution?

Do you know how the crank hub slips? And what the issue is? Basically two rings for oil (?) pump and valve timing moving together by friction. Making it one piece removes slippage from the equation.

But you can ask Kotte Performance, who builds the fastest M2's around the world how his experience was with the 100$ solution. Slipped anyway.

Also, if you were here for a bit longer you'd know that the one piece solution is only growing as of late. You know since people with the cheap solution noticed over time it actually doesn't help.

For someone this clueless you'd be better off by thanking people trying to help you rather than acting like a special edition know it all.

[warrenw]

Originally Posted by SchnellerM2C

So what hasn't come up on this thread and what I alluded to in my previous post, was the topic of harmonics which run through an engine's crankshaft & is of particular concern in straight 6 cyl. engines due to crankshaft length. Tunes and driving style all weave their variables into this vulnerability of BMW's 6 cylinder engine family.

Under full throttle load (acceleration) the crank is twisted in one direction, then suddenly, the driver delivers a reverse load & major change in harmonics running to the nose of the crank. Do that habitually over time (first its loaded one way, then suddenly snapped back in another direction) & that 300 lb-ft crank hub bolt starts to work its way loose, and may actually fail in the driveway upon start up, vs during that hair on the chest beat run. That's just how the universe handles us?

We are, after all, perfect F1 level drivers that have just chosen a different career path
As a club racer, driving school instructor, shop owner & technician I am simply floored by how people drive their cars fast . It doesn't matter if it's a newbie w/ all the horsepower mods, a driving school instructor or fellow(team) racer. Some people mechanically do things to their cars from the driver's seat that I, understanding what's going on inside the engine and drivetrain, could never envision doing myself.

This is why I'm conservative with downshifting my 6MT at the track. I've never downshifted to a lower gear where RPM's would jump above ~5500-6k. Leaves me plenty of room and is less shock than at redline.

[Cycle Pilot]

I have a 2019 DCT. Bought the car new. I've been running Stage 1 Bootmod for 30000 miles with no issues. Car sees about 4-6 track days a year. Never launched. I almost never use kick down. When I'm on the track or driving aggressively, I always shift with the paddles. I know I've been playing with fire but I also drive the car with respect about what's going on under the hood when I'm behind the wheel.

[SchnellerM2C]

You're selecting the correct lower gear appropriate for the given road speed if your revs increase by around a 1000 RPMs. If you're seeing 2000 RPMs or more you haven't slowed down enough to select that lower gear. Ideally, with proper heel/toe rev matching there actually is (should be) no change in RPM when down shifting and hence no reverse load on the drivetrain & crank.

Additionally, if you're not properly rev matching your down shifts on the track, not only are you stressing the drivetrain, but all that engine braking through the rear wheels will negatively affect your handling and car's behavior in the braking zone - it's akin to pulling up on the parking brake.

As far as down shifting for acceleration is concerned, look at the torque curve of your car. For best acceleration you want to select a gear that's pulling you through the meat of the power band. On a Stock M2C that meat lies roughly between 3700-6000 RPM and acceleration continues but trails as torque drops after 6K. So a downshift at 4500 RPM that puts you at 6500 won't deliver much other than drivetrain stress.

[doughboy]

Originally Posted by Bass_Masterson

Aggressive shift tuning for DCTs could contribute, that makes total sense.

I considered that point. Unless you DRASTICALLY reduce gear ratio or rotating mass (in the case of free-revving in neutral), the engine's RPM will not increase/decrease much faster than stock with 500 - 600 WHP, whether you're in neutral or in gear. Just blipping the throttle to rev it up in neutral is way faster of a RPM change than doing a pull, and that's safe to do with the engine/tune stock, right? (exception being shifts, but that's independent of engine power output).

Yes, can certainly agree it's a crap design. I cringed realizing any older engine I've ever worked on has a keyed timing chain gear. Sad example of BMW trying to cut corners. But for the S65 example, increasing power directly applies more force to any engine's rod bearings, whereas it doesn't to the S55 crank hub.

I won't get involved with the crap slinging, but I just wanted to state a point that I see a lot of people not full grasping.

Reading this thread I was getting ready to post exactly what you just said...

Free revving in neutral is faster rotational acceleration than any tuned pull, 1000hp or whatever.

Starting from cold is probably the biggest instantaneous shock load on the hub and in the "unscrew" direction too.

Money shifts maybe, not tune related. Dct downshifts the same.

Maybe tunes add some sort of torsional flex / vibration in the crank that may worsen things?

I'm running stage 2 now 4k, stage 1 for 8k, no issues. It may happen but I'll deal with if it does.

In my experience it's likely to damage more things having a pre-emptive hub fix fitted than leaving it alone.

[Bass_Masterson]

Originally Posted by SchnellerM2C

So what hasn't come up on this thread and what I alluded to in my previous post, was the topic of harmonics which run through an engine's crankshaft & is of particular concern in straight 6 cyl. engines due to crankshaft length. Tunes and driving style all weave their variables into this vulnerability of BMW's 6 cylinder engine family.
!

Very well said, and that's a plausible explanation, in my opinion. Obviously there are a lot of S55 specific factors that could come into play, but is anyone aware of crank bolts loosening on other modified engines? It's not a problem I've come across, but I've mostly been involved in modifying American cars.

Also, as to driving style, mine failed at around 7,500 miles, and I did not drive it hard often, and when I did, I didn't abuse it. Never overrevved, launched, and always properly rev-matched, rarely exceeded 7k RPM. Not arguing your point, just adding some more data.

[chris719]

Originally Posted by Bass_Masterson

Very well said, and that's a plausible explanation, in my opinion. Obviously there are a lot of S55 specific factors that could come into play, but is anyone aware of crank bolts loosening on other modified engines? It's not a problem I've come across, but I've mostly been involved in modifying American cars.

Also, as to driving style, mine failed at around 7,500 miles, and I did not drive it hard often, and when I did, I didn't abuse it. Never overrevved, launched, and always properly rev-matched, rarely exceeded 7k RPM. Not arguing your point, just adding some more data.

I tend to think the bolt is not the root cause, but who knows. If I had to guess, the friction disc is just right at its limit in the original design. Why that is, only BMW knows. I can't believe there's no leaks on German forums or something, though.

[Ratcher]

Thought this could be of interest

[NathObeaN]

Originally Posted by Ratcher

Thought this could be of interest

Could you please elaborate and share source? I'm aware it's a sheered capture plate, but more context would be useful. Thanks

[F87source]

Originally Posted by Ratcher

Thought this could be of interest

1) IIRC this was from a money shift so it's not a case of the bolt getting loose.

2) The way the metal is sheared around the bolt holes it looks like the hub spun counter clock wise while the crank bolt did not move causing the sheering. So they were lucky the crank bolt capture did not loosen the crank bolt because the metal sheared before hand.


This is my prime concern with these bolt captures, because if the crank hub spun counter clock wise, and the bolt capture is strong enough to do its job, it will losen the crank bolt and make the entire scenario even worse than if it was not present.