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      11-09-2019, 02:57 PM   #118
F87source
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Drives: Bmw M2
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Quote:
Originally Posted by MR RIZK View Post
I actually disagree with this. If the primary purpose of the CBC is to stop the bolt backing out because overtime it moves a fraction here and there then it would make sense to do the install sooner than later. Otherwise you are just stopping the bolt backing out any further at a later date which the bolt may of already moved a bit and hence locking it in a compromised position.

If you are going to get rid of the car before warranty runs out and not modding I agree don't waste the time.
You have to retorque the crank bolt before you put on the CBC so it won't matter if it got a bit loose (a nm less etc. Otherwise if it did get too lose your hub would've slipped) as long as the friction disc didn't slip which means the hub didn't move. The bolt just sandwiches the whole assembly, whether or not it is in the correct position shouldn't really matter so long as the hub itself doesn't move.

I guess it's up to the end user what they do but for me if the bolt slipped and BMW saw that CBC they would probably have reasonable grounds to deny warranty.

Quote:
Originally Posted by 1mm2 View Post
So why wouldn't BMW just recall the vehicles for this fix and give everyone piece of mind?
1) it's actually quite a rare issue.
2) if it isn't happening frequently enough it is cheaper to fix motors as they go vs. perform a recall. Just like on the sti with ring land failure.
3) the CBC isn't a complete fix, the friction disc can still spin.


Quote:
Originally Posted by cntzl View Post
CBC is not a 100% solution as friction discs can still fail and cause a hub spin. However, the fact that there is not a single failure reported with CBC installed might be indicative of bolt becoming lose being a common reason for SCH in my opinion. The chance of SCH happening is very low already when you look at all the reported cases vs number of S55 cars produced so far. I think CBC lowers this risk even more and costs a fraction of what a keyed hub would. Therefore, I thought CBC was a nice safety net (even though being not 100% fail proof as mentioned earlier) and decided to go with it. I have been running it since I hit 5K miles. I currently have nearly 11k miles and 9 track days. I have been on BM3 CS+ map since I got the CBC installed and so far so good. I'm not planning to do a keyed hub anytime soon either. If you look at all the SCH cases, almost all of them resulted with just a timing loss (only seen one case of piston hitting the valves and it might be a money shift). I'm aware of the fact that forums in general aren't a 100% representation of the real statistics but I still think SCH is such a rare occurrence. Btw some of those 6MT SCH cases reported online are due to money shift but obviously owners rarely come forward and admit it for various reasons.
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