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Old Wed, Jan-04-2017, 03:50:25 AM   #54
PencilGeek
2008 M3 - Red
 
Join Date: May 2008
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Default Re: New m3 and rod bearings

Quote:
Originally Posted by Rez View Post
Not sure their logic for material change with no change in clearance for 2011.5 S65 bearing?!
EU regulations went into effect for 2011 that forbid lead in vehicle bearings. The irony was there's an exception for vehicles already in production. Anyways, that's why they changed the materials.

Quote:
Also what is the explanation for such small percentage failure on a design flaw that should result in much higher failure rate?
I think it is consistent. If you start with a design that is on the hairy edge, so long as there is no tolerance stack-up, then most vehicles will survive. But as soon as you take a rod journal that's on the large side but still within spec, and mate it with a bearing on the thick side also within spec, then the tolerances stack up and you end up with dangerous clearance. I believe that's why engines go boom within 20000 miles, or they don't go boom for a very long time. With tolerance stack up, they go boom; without it, they last much longer.
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