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      12-24-2019, 10:56 AM   #1
hansomatic
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The CrankHub Counterpoint

I will be installing a keyed CrankHub when my warranty expires. This seems like a pretty simple fix for BMW to implement in current production. I'm thinking there must be a reason they haven't done so. ///M Engineers must have a counterpoint (to locking the crank hub) that goes beyond 'because the don't wanna spend the money'.

Anyone know what that reason may be?

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      12-24-2019, 12:01 PM   #2
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Quote:
Originally Posted by hansomatic View Post
I will be installing a keyed CrankHub when my warranty expires. This seems like a pretty simple fix for BMW to implement in current production. I'm thinking there must be a reason they haven't done so. ///M Engineers must have a counterpoint (to locking the crank hub) that goes beyond 'because the don't wanna spend the money'.

Anyone know what that reason may be?

It's not that simple, you have to rebalance the rotating assembly would be my guess.
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      12-24-2019, 01:59 PM   #3
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Likely the cost of slipped "warranty" crankhubs is less than it would cost to do a recall. Can't blame them for not offering a fix on what is likely less than 1% of cars which are affected. Obviously higher mileage and higher output power potentially increases the likelihood of the issue...but like all the vanols bolts/vanos exhaust hub tabs breaking/subframe/rodbearings/etc... of the past generations...the crank hub being the only achilles heel to the S55 is a relatively easy fix. I'm glad I did it preventatively since I plan to keep the car for a very long time.
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      12-24-2019, 09:22 PM   #4
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Quote:
Originally Posted by Commanderwiggin View Post
Likely the cost of slipped "warranty" crankhubs is less than it would cost to do a recall. Can't blame them for not offering a fix on what is likely less than 1% of cars which are affected. Obviously higher mileage and higher output power potentially increases the likelihood of the issue...but like all the vanols bolts/vanos exhaust hub tabs breaking/subframe/rodbearings/etc... of the past generations...the crank hub being the only achilles heel to the S55 is a relatively easy fix. I'm glad I did it preventatively since I plan to keep the car for a very long time.
Recalling vehicles already in the field may be very expensive, but making a change to the production of engines going forward would likely have very little cost impact to BMW unless the “fix” somehow wrecked havoc to their production line. If simply revising a part or tweaking a process could avoid replacing engines, why wouldn’t BMW do it? I’ll offer three possibilities:

1. They may have determined this problem is very unlikely at stock power level and the minimal cost to address the issue actually exceeds the cost of expected failures for stock cars.
2. Perhaps it’s very expensive for BMW to incorporate a fix to this issue (seems unlikely). Even though failures may be common, the cost of fixing again exceeds the expected warranty cost.
3. Maybe the design serves another purpose such as safeguarding another part of the powertrain.

I don’t think anyone, other than a BMW engineer, can say for sure what the reason is for not fixing it is. I’m of the opinion this is all a bit overblown for folks running near stock power levels and I think scenario 1 and/or 3 are the most likely. Unless you are tuning the engine well beyond CS power, I would be very hesitant to make a “fix” without completely understanding whether there is a reason for the design to begin with. Unfortunately, OP, I don’t believe anyone is going to be able to say for sure. One thing is for sure, there is A LOT of marketing on this forum to sell you a “fix”.
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