So many times we have been
asked this question about bearing clearances that we thought it would be
informative enough to post. We relied on our friends at Callies
Performance for their opinion. As it turns out, there is no exact answer but
rather a range depending on the user.
this chart graph,
there are 3 major considerations Clearance vs. Oil Flow Rate, Clearance vs.
Bearing Temperature Rise and Clearance vs. Load Capacity. Just as with
everything else in life, there are trade-offs. As you can see from the
attached chart, most likely the decision a Competition Eliminator racer
would make would be different from the decision a performance street racer
The question most often is asked as it applies to coated bearings.
Dry film coatings used on engine bearings is
typically 0.0002" to 0.0004" thick and generally speaking does not need
extra clearances. A benefit of coated bearings is the allowance for tighter
clearances, keeping in mind that bearing clearances of .002" to .003" are
typical for High Performance applications.