Technical GM metric low drag calipers *FIXED*

Thanks for following up. That's good to know about the AFCO calipers, but it puzzles me as why they would advertise them as being "low drag". I'm going to try changing from a 2 psi residual valve to a 10 psi to keep more pressure on the pistons. I think that will keep them from retracting so far and possible provide a cheap alternative solution to the issue.

Bob

 

Thanks for the update and the results of your new AFCO calipers. Good info in the discussion on the caliper differences and master cylinders.

 

Al of my Ford OE power master cylinders have deep push rod bores, ie Mustang/Mustang 11, F-trucks and more I can't remember application. IIRC, shallow bore masters were used with attached/retained push rods in manual mode, and with guided booster push rods with power. Non-guided booster output rods generally use deep master counter bores.

 

Does anyone make aluminum calipers in the GM bolt pattern (OEM, aftermarket, low-drag or non low-drag)?

- EM

 

OK. I'm seeing several: SSBC, Wilwood and Afco for starters. Were the late 80s OEM Corvette calipers also aluminum?

 

This Stainless steel brake line spring should help hold it in place .

 

An additional truth is that, even in a sealed system with a mix of fluid and air, the pressure will be equal at any point.

@WZ JUNK you probably don't have any air in the system. Air doesn't magically have different pressure than fluid if they are in the same sealed system, because of the above truth. You have a component that is causing the pressure drop. Is your proportioning valve plumbed properly? Do you have two gauges so you can measure two different points in the system at the same time?

 

On the S10 master cylinder in your link, which port goes to the front brakes and which goes to the rear brakes.? Thanks

 

The port next to the firewall [rear port] goes to the front brakes.

 

Thank you!

 

As S-10 MCs are mounted on the firewall. and a lot of hot rods have underfloor MCs mounted backwards, maybe it would be best to designate front and rear ports as the port closest to the flange or furthest from the flange. Just to eliminate confusion.

 

In the case of an underfloor system with 2# residual pressure valves, how bad would it be to put a higher # rating rpv in place of the always recommended 2# rpv. They make a 4# rpv. Recommended for high vibration applications such as circle track. Of course, there is the common 10# rpv for drums. I'm just wondering if either the 4# or 10# rpv might hold against the retracting seal of the low drag calipers without putting TOO much drag on the rotor?

 

What would happen..........if the hook-up was reversed and the front bowl goes to the front brakes ?
That is the way it's hooked up on my 91 S-10 ! (from the factory and stops great)
Could THIS be why I'm getting a low pedal?
6sally6

 

What would happen if the hook-up was reversed..front bowl to front brakes....rear brakes to rear(nearest firewall) bowl?
On my 91 S-10....the front bowl serves the FRONT brakes.
I wonder if....this is why my pedal is so low on my hot rod?!
6sally6

 

Allied Signal. The Bomb Factory.
They had a factory in KC, it was Bendix then Allied Signal. They made brakes in the front where the general public had access, in the back they made fusing mechanisms for uh, well fusing mechanisms. They claimed that all they did was design them there. But now the property is unusable for a few centuries.

Sorry I could not resist.

my understanding is that the low drag brakes were or are extremely component sensitive. Not just the pieces for the calipers but also the master and proportioning valve. I would not try and mix n match components on them especially rebuild parts for the calipers.

 

Please post a picture of your master cylinder, so we can determine if it was intended to be used with low-drag calipers.

If it was, yes, that can cause issues.

If it is not, and you don't have low drag calipers, you might run out of fluid in the reservoir as the pads wear.

On a disc/drum combo, where the master cylinder bore is the same all the way through, the disc calipers are attached to a larger reservoir, as the pistons, combined, are much larger than the wheel cylinders, and the friction material is a lot thicker.

As the friction material wears, and the pistons move out, the front brakes will need more fluid volume to make up for that.

If you simply kept up with topping off, you might not notice, until you changed your pads!

 

Could be,
Usually the floating piston [in the M/C] will bottom out because low drag calipers require more volume.
In some cases it will initially be soft pedal, then hard pedal when the piston bottoms out BUT with very poor clamping pressure on the front.

A step bore [quick uptake] M/C needs to look like this
note the different sizes....

 

What is the P/N / application for the M/C pictured? (Disregard, I see that its an S-10 cylinder)

 

How to check your calipers.

https://www.idmsvcs.com/2vmod/brakesystem/hydraulic/disassembly/calipers/pdfs/mpbrakes_lowdrag.pdf