Brake line

[wrightz28]

Can someone enlighten me as to why in the world would GM use a 3/8" steel line with a 3/8 fitting from the master t-off and a 10mm on the hose end?

Had to make a new line for my 87 the other day and when I dissassembled it I thought it was strange, blew it off as corrosion on the nut, but when it came to to buying new fitting, sure enough the hose end IS a 10mm fine thread.

just been eating at the back of my mind. and made bending and flaring a small pita, plus 45 minutes digging through adapters, because not only was size different, but the 3/8 side was double flared where the 10mm "bubbled".

[HotZ28]

My first guess, at the logic (if any) behind this, would be that the 3/8” fitting screws into a substantial aluminum or cast iron body and does not require as many threads per in to give the required torque on the flare. The hose end however, would have less “body” and would require more threads per inch to supply the same torque. The same logic applies to the type of flare.

Now, for another possibility, let’s look at the corporate purchasing process that could be behind such a “bizarre” fitting and flare combo. The engineer in charge of “master cylinder design”, issues a purchase requisition for 1M master cylinders, with the attached specifications and 3/8” female flare fittings. The purchasing agent sends the design and specifications out for bid. Once the bids are returned from the suppliers, he makes a supplier choice, based on the largest kickback to him, and then he issues a P.O. Now, 10 days later, the design Engineer in charge of “rubber brake lines”, sends a purchase requisition for 2M rubber hoses with a 10 mm hex hose end. The same purchase process takes place and the order is complete. Once all parts have arrived, the two proud design engineers take a sample of their parts to the engineer in charge of “brake line design”. That engineer looks at both parts and sends an Email to the other two engineers telling them what a bunch of “dumb asses” they are and the problem they created by not communicating their design specifications with each other. The “brake line design” engineer voices his concern to his superior, who is more concerned with “stock options” than design! The “chief design engineer”, simply sends an Email back, advising him to make a brake line that will work on both ends and not to bother him with such trivial design issues in the future.
“Corporate America” inside operations exposed!!

Could this be one of the many reasons GM is failing to compete in the international market?

[wrightz28]

Corporate America = If it makes sense don't do it.

That's kind of what i was thinking. Originally I thought it was a hack job form the a preivous repair. But while I was getting my supplies, I had the parts counter grab a replacement right rear hose and sure enough it was a 10mm.