Peterbuilt

Does this picture help?

Mike Ward

Yes it does, thanks!

oldalaskaman

based on that pic, if there's an issue with the fronts , there should also be an issue with the rears, based on the op's description , its common to both fronts, but not the rears.



something that hasnt been asked in this thread is what problems the op was having with his brakes prior to changing those parts. "If"....he was having similar issues prior to changing the parts, all of you folks gave excellent answers, this has been an interesting thread. many thanks to all of you for posting

noonie

That's the normal place to start, especially since "amount of drag" is subjective.

At this point, the easiest way to check the master, is to look into the reservoir while someone else pushes the pedal slowly. You should be able to see the piston seals move by and return past the compensation ports and physically see if they are returning all the way (or probe with a wire). The op said the master was changed by the previous owner, so assuming it's relatively new, I doubt the pistons are not returning, unless filled with a oil product to drastically swell the seals. The springs are very, very strong. Having a master rod too long will cause this, but the OP already dismissed it.
You may also look for a residual valve installed in error in the front port, stranger things have happened.

A word on Orings.
Depending on how the piston groove was machined, it might or might not need the return springs. At the very least, the crush tolerance for oring calipers are much tighter than the original and the combination of the two could lead to more drag.
The oring distorts on application and returns to normal in brake release, different than the oem seals. The oring pistons I use don't use the springs, but I believe VP style uses them for their pistons. You can't tell unless you took them apart.

Rebuilt masters are only 30 bucks or so and new are only 50.
Since you're more inquisitive, here are a couple pics of a c3 master I cut apart.

oldalaskaman

excellent tech.many thanks, bob

72 corvette roadster

I contacted VB and P this AM. Very friendly and willing to discuss. He also pointed twd. the MC not fully releasing, improper MC part (pwr MC in place std MC), and/or improper rod adjustment, and also mentioned that sometimes there is dragging due to too many shims behind pads (I will check this as well). He did not totally dismiss that the calipers themselves could be sticking, but thought it unlikely, especially both fronts at the same time. He was quite friendly and said if I had eliminated all other sources he would readily accept the calipers back and have a look. Just FYI for those considering VP and P it is good to have someone so willing to talk....

So, I guess at this point I am still looking at a MC as the culprit?

oldalaskaman

excellent

Mike Ward

And yet it happens that one system or the other does not release and the other does

Hey- ya think? Take the d*mn thing off, take it apart and clean it out. Inspect for damage and repair/replace accordingly.

oldalaskaman

could take it and get it reverse pressure bled, blow that crud out the top...if there is any.

lionelhutz

OK, I have to point out something stupidly obvious (well at least to me). This proves nothing. Manually pushing the pistons back doesn't prove the calipers are not sticking. 2 or 3 experts have jumped-in agreeing that this means the MC failed except the test was flawed and nothing was proven. You can't manually push the pads back.

72 corvette roadster

Yes you are correct, but that was just my first stab at the problem to make sure the bearing itself would turn freely. Afterward, I pumped the pedal several times which re-set the pistons/pads and re-created the difficult to turn the wheel issue. THEN, I went to the next steps of loosening the MC from firewall, then loosening front line from MC (which freed up the wheels).

Mike Ward

I can.

my 76 ray

Since loosening the front line at the master cylinder frreed up the front pads, then it is probably safe to assume that the master cylinder is not allowing the fluid to return when the brake is released.

Peterbuilt

When you get your new M/C make sure the holes at the end match the one you took off...


Don't forget to bench bleed the new one, here's how...

Ghunt

As said somewhere in this thread, These calipers pistons are spring loaded and keep pad contact with the rotor. Any pad contact will not allow the wheel to spin freely.
I have the same problem and bet that the spring suppliers are not paying attension to the specs or can't convert english into Chinise.

George

lionelhutz

I don't really care what you can do out of context....

72 corvette roadster

OK, new MC from ZIP in the car yesterday and voila! Wow, what a difference in the reduction of drag on the front brakes. The car now rolls freely in neutral and at stop lights on slight grades. Looking forward to a fuel economy boost as well-I was getting 14 mpg with a totally stock car and dragging brakes....maybe 15 or 16 now? Thanks for all of the comments help and opinions!

Mike Ward

Glad to hear it was an easy fix.