So just checking on something weird. I replaced the wheel cylinders on my '73 F100. The brake line fittings were 3/8in but the bleeder valves were 10mm. Doesn't this seem very strange? Also, when I look on Summit Racing, they list the bleeders for that application as 3/8in. As an aside, the new bleeders are cheap crappy metal that rounds very easily, even with the boxed end of a wrench. The old brass bleeders from the discarded cylinders seem much sturdier, and they were also fit by the 10mm wrench.

Additional question- are front caliper and rear cylinder bleeder valves all the same?

 

The bleeder valves on replacement calipers and wheel cylinders have always been metric in my experience as well. Agreed that they are cheap and round off easily.

On my '79 F100, the bleeder is the same on all four wheels.

 

Welcome to the world of imported aftermarket parts ! I see that type of issue often . I even get wheel cyl,s and calipers with different size bleeders side to side . That is usually on reman though .

 

Minor Update:
I was in NAPA and asked what size bleeders the front and rear wheels take. Their parts book indicated 3/8 inch bleeders. I told them the parts they sold me were 10mm. They didn't believe me, pulled a wheel cylinder off the shelf, and they found out first hand that 3/8 wrench won't fit and a 10mm is a bit loose. Unfortunately, both 10mm and3/8 inch bleeder valves will screw into the calipers and cylinders. I think the quality control is just so poor the screws are supposed to be 3/8 but are oversized. Thoughts?

Also, how much does it matter? I ask because my front caliper bleeders came rounded and need replacement, but no one is sure what size to use.

Oh imported crap.

 

So long as the threads match the end size doesn't make a whole lot of difference...You should only be bleeding them once or twice anyhow if you do more than that you have other problems that need addressed.