[TripleU]

Now that my warranty just expired this month, I'm curious about whether or not it is necessary to change the crank hub on the OG N55 M2. Since the N55 uses the same crank hub as the S55, has anyone on here changed the crank hub? I know the N55 is much less likely to suffer crank hub failure, but is it a precaution some of you that's worth it, especially since I'm getting into more track days.

[AWC-F87]

I'm curious as well

[detroitm2]

Not needed. The N55 crank hub doesn't suffer from the same issues as it does on the S55.

[SC435i]

My understanding is even though it has the potential to fail at stock S55 hp levels the crank hub is most prevalent to failing above ~600whp. So I'd say unless you were going with a bigboost or speedtech turbo then it would be overkill and wouldn't be worth the price to install it.

[F87source]

The n55 crank hub can and has failed before, however it is not as common as on the S55 for a few reasons:

1) Much less power than an S55
2) alot less mass on the crank hub and thus less inertia that the friction disc must over come when rpms increase due to WOT or down shifts. This is because the s55 has a mechanical water pump driven off of the crank hub wheras the n55 has an electric water pump, also the s55 has 2 HPFPs driven off the vaccum pump which is driven off of the cam which is again tied to the crank hub.


Most of the time when you see an N55 fail is because of a money shift, otherwise a failure due to the hub straight up slipping is less common (to the point of being extremely rare) than on an S55.


If you are really worried get a CBC, it is literally proven to work as high horse power (700 whp+) s55 guys who have had multiple crank hub slips literally stopped having any issues after this was installed. This has been observed on numerous cars that it has become known in the s55 community that a CBC will indeed help prevent spun crank hubs.

I had one last year but sold it to my friend with an m4 because he really needed it at the time as his car was in the shop and it was cheaper to get it installed at the same time. But I still am unsure if I should purchased another one and install it. But keep in mind if you have an n55 m2 and want to install this, it will be a huge pain in the butt as there is so much crap in the way and it is so hard to see the bolts on the harmonic damper, so torquing it properly will be a pain.

[boldy1]

Yes changed mine. It does happen on the n55 how much remains to be seen as not everyone posts theirs failures.

For me I had the engine out building it so just made sense to do it at that point. But a few of my friends running hybrids have also done it

[detroitm2]

Horsepower has very little to do with stress on the crank hub. It's more of an issue with RPM.

So unless you're money-shifting, there's little to worry about here.

The reason I said this isn't really an issue on the N55 is because a big percentage of those who had this failure were in M3/M4 DCT cars which has a much more aggressive shifting map.

There's a hell of a lot more N55s out there than S55s. If this was truly an issue with the N55, we'd be hearing about it a lot more than we do.

I'm not saying it doesn't happen, but it's exceedingly rare, and probably even more so once you filter out those who caused it by a money shift.


EDIT: Additionally, some of the keyed crankhubs have been known to break. So rather than spinning a crankhub a couple of degrees and causing a drive train malfunction, it spins freely and certainly grenades your engine.

[M Fifty]

Originally Posted by F87source

The n55 crank hub can and has failed before, however it is not as common as on the S55 for a few reasons:

1) Much less power than an S55
2) alot less mass on the crank hub and thus less inertia that the friction disc must over come when rpms increase due to WOT or down shifts. This is because the s55 has a mechanical water pump driven off of the crank hub wheras the n55 has an electric water pump, also the s55 has 2 HPFPs driven off the vaccum pump which is driven off of the cam which is again tied to the crank hub.
.

1) Torque. Power is an estimate of how much you could do with same based on how fast the engine is spinning and the use of gearing. Just saying.
2) Interesting point. The alternator will drag, but the belt - should - slip before the crank pulley moves...