C5 Brake Master Cylinder Taken Apart

[BBShark]

I looked around the net for a rebuild kit for a C5 brake master cylinder and found that there are no rebuild kits and that a replacement is waaaaaaay to expensive. It got me thinking about what was so special that some of the replacements sell for $300. So, naturally, I had to see what is inside.

What I found is a pretty conventional master cylinder with the exception of a pressure "delay" built into the front port with a spring in between the rear seal and the front seal. So when you push the pedal, the rear port is directly coupled to the pedal and the front port is coupled to the rear piston with a spring. The spring takes about 30-40 lbs to completely bottomed out where the front and rear pistons are directly coupled to the pedal.

So it looks like the front port (which I assume go to the front brakes) only receive full pedal pressure AFTER the rear port.

 

[Twin_Turbo]

Actually most tandem cylinders are like that with a spring between the front and rear pistons. C3 is like that too.

There's more to it than you'd initially think...read this:

http://www.tegger.com/hondafaq/mastercylinderreplace/howworks.html

 

[BBShark]

That is the same except for the yellow piece (in their diagram). They call that a "solid spacer". The C5 master has a spring there which compresses ~15-20mm (5/8 inch) before bottoming and pushing on the front piston.

Makes me wonder if the front port goes to the rear brakes and the back to the front?

 

[Twin_Turbo]

The yellow piece is the entire front piston, the rear one is gray in the diagrams. Look more closely at the drawing. It's confusing because of the working, the front seal of the 2nd circuit is the rear V seal on the front piston because the spring sits in the center of the 2nd circuit, to build pressure there, that spring has to compress.

 

[badbirdcage]

Rear port goes to front brakes. Front port goes to rear brakes.

Rich

 

[mrvette]

Rear port goes to front brakes. Front port goes to rear brakes.

Rich

That is an interesting question on this topic.....when replacing the m/cyl on my '72, I noted the front section went to the rear brakes, and so the new aluminum m/cyl from aftermarket hotrod shop, the REAR goes to the rear brakes as most other cars, like the motor home....

only difference I can see is that the motor home is rear drum/front disc....

but on the shark the stock brakes are obviously 2 sizes, so curious as to if it really makes any difference how that is all hooked up....and IF it does, what would be the effect of having it 'backwards'....??

:bonkers:

 

[badbirdcage]

Rear port goes to front brakes. Front port goes to rear brakes.

Rich

That is an interesting question on this topic.....when replacing the m/cyl on my '72, I noted the front section went to the rear brakes, and so the new aluminum m/cyl from aftermarket hotrod shop, the REAR goes to the rear brakes as most other cars, like the motor home....

only difference I can see is that the motor home is rear drum/front disc....

but on the shark the stock brakes are obviously 2 sizes, so curious as to if it really makes any difference how that is all hooked up....and IF it does, what would be the effect of having it 'backwards'....??

:bonkers:

The effect will be that your rear brakes become your primary brakes instead of the other way around.

Since the front brakes take more of the load than the rears that would not be good.

I don't understand your statement that the 72 has different size brakes in stock configuration. They use the same diameter rotors and the same size pads front and rear.

Rich

 

[mrvette]

Rear port goes to front brakes. Front port goes to rear brakes.

Rich

That is an interesting question on this topic.....when replacing the m/cyl on my '72, I noted the front section went to the rear brakes, and so the new aluminum m/cyl from aftermarket hotrod shop, the REAR goes to the rear brakes as most other cars, like the motor home....

only difference I can see is that the motor home is rear drum/front disc....

but on the shark the stock brakes are obviously 2 sizes, so curious as to if it really makes any difference how that is all hooked up....and IF it does, what would be the effect of having it 'backwards'....??

:bonkers:

The effect will be that your rear brakes become your primary brakes instead of the other way around.

Since the front brakes take more of the load than the rears that would not be good.

I don't understand your statement that the 72 has different size brakes in stock configuration. They use the same diameter rotors and the same size pads front and rear.

Rich

RONG, the sharks have smaller pistons in the rear, I think pads too, I pretty sure the caliper castings are smaller also....

 

[badbirdcage]

Rear port goes to front brakes. Front port goes to rear brakes.

Rich

That is an interesting question on this topic.....when replacing the m/cyl on my '72, I noted the front section went to the rear brakes, and so the new aluminum m/cyl from aftermarket hotrod shop, the REAR goes to the rear brakes as most other cars, like the motor home....

only difference I can see is that the motor home is rear drum/front disc....

but on the shark the stock brakes are obviously 2 sizes, so curious as to if it really makes any difference how that is all hooked up....and IF it does, what would be the effect of having it 'backwards'....??

:bonkers:

The effect will be that your rear brakes become your primary brakes instead of the other way around.

Since the front brakes take more of the load than the rears that would not be good.

I don't understand your statement that the 72 has different size brakes in stock configuration. They use the same diameter rotors and the same size pads front and rear.

Rich

RONG, the sharks have smaller pistons in the rear, I think pads too, I pretty sure the caliper castings are smaller also....

OK. You know everything. I don't understand why you are asking the questions you are asking. When you look up the brake pad application for a 72 Corvette you come up with the same part number for front and rear replacement pads. Check NAPA Online. I did. That means the same swept area for your stopping power.

The application of hydraulic pressure to the calipers is controlled through the master cylinder. Hook it up backwards and your pressure is applied backwards. Just physics.

I hope you figure out what you need or want to figure out but I am finished with this one. My intent was to attempt to provide assistance to you. Your response is to be argumentative. That's not why I give responses to other persons on this forum.

I am 60 years old, I grew up in garages working as a mechanic trainee in the late 1960's prior to going into the automotive machine shop business for 15 years.

I do NOT know everything. My experience with Corvettes is my ownership and wrenching on a 59, a 64, a 78 and my current modified 63 as well as assisting friends with their cars.

While I do NOT know everything I also am not an idiot and I detect BS really quickly.

Best of luck to you with your 72.

Rich

 

[mrvette]

I am a truth seeker, part of being what I am....IF I am rong, fine, so be it....

what do others say???

I remember the pistons being different size....pretty damn sure of that...

I think the caliper castings too....

pads...not all that sure of....

I do know the swept area/diameter of the rotors is the same......

but the front and rear rotors are NOT the same.....

and so what is the difference between them???

 

[BBShark]

Rear port goes to front brakes. Front port goes to rear brakes.

Rich

I can see that full hydraulic pressure to the front port could be delayed (maybe milliseconds) until pressure is balanced but even that seems unlikely. If so, what would be the logic to hooking the rear to the front?

Also, I found some information that the ~2001 C5 was changed to a crisscross pattern. One port operates RR&LF and other LR&RF. This is without a change in the master cylinder.

 

[Twin_Turbo]

The change is in the ABS unit on those cars.