Is there is benefit to using the flange type bolt heads (stock mazda) instead of using a regular or socket head bolt with the proper washer. I am ready to mount the redrive and need to purchase bolts for the flexplate. The local mazda dealer has them in stock but would like to charge me $30 for the set. Grade 12.9 socket head bolts are less than a  $1 each with washer.

Any opinions?

Bobby

Not that they wouldn’t work, but grade 12 is going to be quite brittle, so a lower grade would be better.  I’m guessing that the flange head bolts are forged, and the standard socket head may be machined.  The forged head is stronger because of grain orientation.  Someone else may know; but when I’m guessing I prefer to err on the conservative side and go with the flanged.  You may be able to find the same bolts that the Mazda dealer would sell you somewhere else (McMaster-Carr?) for considerably less.

AL