Quote:
Originally Posted by regular guy
Unfortunately no they don't. VAC uses Calico Coatings to coat factory bearings. According to the Calico web site, the coating will add an extra0.0002 - 0.0004 inch thick coating. To put this into real numbers, that would mean your bearing clearance would be reduced from 0.0010 to a range of 0.0006 - 0.0008.
Here's a link to the Calico Coatings FAQ on bearing coatings. Note they recommend 0.0020 - 0.0030 bearing/journal clearance.
http://www.calicocoatings.com/faqs/Calico's CT-1 dry film lubricant used on engine bearings, valve springs, oil pump gears, timing and transmission gears is 0.0002" to 0.0004" thick and generally speaking does not need extra clearances. A benefit of Calico Coated bearings is the allowance for tighter clearances. Keeping in mind that bearing clearances of .002" to .003" are typical for High Performance applications.
|
Thanks for the information. But we are assuming VAC takes a OEM bearing and then coats it... Is this a correct assumption or do they machine it so the aftercoating measurements are the same as OEM (.001").
I understand the coating might hold up to wear better than the metal, but that is crazy if they lessen clearance... I would also like to see the properties on oil flow across the surface of the coating versus the metal.
And Tom, thanks for posting.
Lastly, my 2 cents (meaning my opinion - flame suit on):
But must I remind everybody we are on a forum. Forums are where people post when things go south (small part of the population). So without having insight on a full population (aka dealership data for the non-entusiast M3 owners), it is hard to say if this really is a problem. I would believe BMW does endurance testing on their engines of cycles more severe than "mostly highway miles" (no offense please) so I have
some faith in the BMW engineering (though I still would have changed the clearences...). So I have a hard time understanding if this is truely a problem based on my two previous comments (an accurate population and durability testing).