HELP Master Cylinder upgrade

uneek1976

G-Body Guru
Jul 24, 2009
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Sugar Grove IL/ Chicago
Is there a certain or maximum bore size to use or look for when considering a master cylinder upgrade? Everything has been upgraded as far as the brake system accept for the master cylinder.
 

78Delta88

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Older post... Did you ever get this resolved?

Did you upgrade to bigger calipers? Or did you change from drum rear to disc rear?
 

307 Regal

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Oct 21, 2009
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It would be good to know the capacity or recommended master bore size of your calipers or wheel cylinders (if you have rear drums). Going above the recommended size would result in less required pedal travel, but more pedal effort. And you may need a pedal stop. And depending on your setup you may need a proportioning valve. If your front calipers aren't getting enough fluid pressure then you may have a rear brake bias bordering on "dangerous."
 
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Hurricane77

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Nov 11, 2020
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It would be good to know the capacity or recommended master bore size of your calipers or wheel cylinders (if you have rear drums). Going above the recommended size would result in less required pedal travel, but more pedal effort. And you may need a pedal stop. And depending on your setup you may need a proportioning valve. If your front calipers aren't getting enough fluid pressure then you may have a rear brake bias bordering on "dangerous."
Good advice. Very few people seem to understand the relationship of bore size and how it affects the rest of the system. They end up with a firmer pedal feel but not realizing they actually have less pressure in the lines
 
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Rt Jam

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Mar 30, 2020
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Good advice. Very few people seem to understand the relationship of bore size and how it affects the rest of the system. They end up with a firmer pedal feel but not realizing they actually have less pressure in the lines

Exactly and for the same reason a bore size change is not an upgrade. Bigger or smaller both have pros and cons.
You are just trading a firmer pedal for less pressure or more pressure at the cost of a softer pedal.
 
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78Delta88

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Hydraulics isn't a subject many know or understand. And as stated above sometimes you think you make an improvement yet instead you can make it worse.

I'm still waiting for response from the OP. He stated an "upgrade", just like to know what was the upgrade was.
 
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malibudave

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Mar 12, 2010
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Here is my opinion on master cylinders and calipers.
I do not like the 1982-1988 step bore master cylinders. I believe these master cylinders give you a spongy pedal because of the internal transition from a larger volume bore to a smaller bore. These are meant to work with LOW drag calipers.

If you have a stock 1982-1988 G-Body, with the original, never been replaced calipers, they are LOW Drag or Quick Take Up calipers. The 1978-1981 "G-Body" calipers are NON low drag or "normal" calipers.

That being said, these metric, D154 calipers were used from 1978-2004ish. Below are the vehicles that used the metric, D154 calipers.

1978-1981 "G-Body"
*Normal, NON low drag front calipers.
*24mm (roughly 15/16") strait bore master cylinder.
*Outlet ports on DS fender side of master cylinder.
*1/2-20 and 9/16-20 IF outlets

1982-1988 G-Body
*LOW Drag/Quick Take UP front caliper.
*24mm/1.25" Step bore master cylinder.
*Angled Reservoir.
*Outlet ports on DS fender side of master cylinder.
*1/2-20 and 9/16-20 IF outlets

1982-1997 S-10
*LOW Drag/Quick Take UP calipers.
*24mm/1.25" Step bore master cylinder.
*Flat Reservoir.
*Outlet ports on DS Fender side of master cylinder.
*1/2-20 and 9/16-20 IF outlets.

1982-1992 F-Body
*LOW Drag/Quick Take UP calipers.
*24mm/1.25" Step bore master cylinder.
*Angled Reservoir.
*Outlet ports on engine side of master cylinder.
*Metric bubble flare outlets.

1998-2004ish S-10 - Normal, NON low drag caliper.
*1.0" strait bore master cylinder.
*Outlet ports on engine side of master cylinder for left hand drive models.
*Both 1/2-20 IF outlets on Left Hand Drive Models.
**Outlet port on DS fender side of master cylinder on RIGHT hand drive models.
**1/2-20 and 9/16-18 IF outlets

ALL YEAR driver side CALIPERS WILL HAVE THE SAME PART NUMBERS regardless if they came with LOW drag calipers or NORMAL calipers.
ALL YEAR passenger side CALIPERS WILL HAVE THE SAME PART NUMBERS regardless if they came with LOW drag calipers or NORMAL calipers.

I believe, all calipers "should be" rebuilt to normal standards as they will be able to work with a strait bore master cylinder or a step bore master cylinder.
If a caliper was rebuilt to the LOW drag standards, you will get a LOW spongy pedal if using a strait bore master cylinder, so I suspect all calipers are rebuilt to normal, NON low drag standards.

Good Replacement master cylinders for most stock type disc/drum or stock type disc/disc setups.
Replace your factory stock, never been replaced calipers to use these master cylinders.
1998-2004ish S-10 Right Hand Drive, master cylinder
*1.0" bore
*1/2-20 and 9/16-18 IF outlets like all G-Bodies

2005 Chevrlet SSR
1.0" Bore
1/2-20 outlets. Use Adapter (AGS PN BLF-26C) for the line going to the rear brakes.

If using a 1990 B-Body vacuum booster, step up to a 1-1/8" Bore master cylinder.
2000 Chevrolet Express Van 1500 Master Cylinder with a 1996 Chevrolet Caprice Reservoir (sold separately)
The Express Van master cylinder has the correct 1/2-20 and 9/16-18 IF fitting for stock G-body Brake Lines
The 1996 Chevrolet Caprice Reservoir is angled to work with the angle of the G-Body Firewall.

Let me know if you have questions.

Dave
 
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Sweet_Johnny

Has A Face For Radio
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Oct 4, 2022
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Here is my opinion on master cylinders and calipers.
I do not like the 1982-1988 step bore master cylinders. I believe these master cylinders give you a spongy pedal because of the internal transition from a larger volume bore to a smaller bore. These are meant to work with LOW drag calipers.

If you have a stock 1982-1988 G-Body, with the original, never been replaced calipers, they are LOW Drag or Quick Take Up calipers. The 1978-1981 "G-Body" calipers are NON low drag or "normal" calipers.

That being said, these metric, D154 calipers were used from 1978-2004ish. Below are the vehicles that used the metric, D154 calipers.

1978-1981 "G-Body"
*Normal, NON low drag front calipers.
*24mm (roughly 15/16") strait bore master cylinder.
*Outlet ports on DS fender side of master cylinder.
*1/2-20 and 9/16-20 IF outlets

1982-1988 G-Body
*LOW Drag/Quick Take UP front caliper.
*24mm/1.25" Step bore master cylinder.
*Angled Reservoir.
*Outlet ports on DS fender side of master cylinder.
*1/2-20 and 9/16-20 IF outlets

1982-1997 S-10
*LOW Drag/Quick Take UP calipers.
*24mm/1.25" Step bore master cylinder.
*Flat Reservoir.
*Outlet ports on DS Fender side of master cylinder.
*1/2-20 and 9/16-20 IF outlets.

1982-1992 F-Body
*LOW Drag/Quick Take UP calipers.
*24mm/1.25" Step bore master cylinder.
*Angled Reservoir.
*Outlet ports on engine side of master cylinder.
*Metric bubble flare outlets.

1998-2004ish S-10 - Normal, NON low drag caliper.
*1.0" strait bore master cylinder.
*Outlet ports on engine side of master cylinder for left hand drive models.
*Both 1/2-20 IF outlets on Left Hand Drive Models.
**Outlet port on DS fender side of master cylinder on RIGHT hand drive models.
**1/2-20 and 9/16-18 IF outlets

ALL YEAR driver side CALIPERS WILL HAVE THE SAME PART NUMBERS regardless if they came with LOW drag calipers or NORMAL calipers.
ALL YEAR passenger side CALIPERS WILL HAVE THE SAME PART NUMBERS regardless if they came with LOW drag calipers or NORMAL calipers.

I believe, all calipers "should be" rebuilt to normal standards as they will be able to work with a strait bore master cylinder or a step bore master cylinder.
If a caliper was rebuilt to the LOW drag standards, you will get a LOW spongy pedal if using a strait bore master cylinder, so I suspect all calipers are rebuilt to normal, NON low drag standards.

Good Replacement master cylinders for most stock type disc/drum or stock type disc/disc setups.
Replace your factory stock, never been replaced calipers to use these master cylinders.
1998-2004ish S-10 Right Hand Drive, master cylinder
*1.0" bore
*1/2-20 and 9/16-18 IF outlets like all G-Bodies

2005 Chevrlet SSR
1.0" Bore
1/2-20 outlets. Use Adapter (AGS PN BLF-26C) for the line going to the rear brakes.

If using a 1990 B-Body vacuum booster, step up to a 1-1/8" Bore master cylinder.
2000 Chevrolet Express Van 1500 Master Cylinder with a 1996 Chevrolet Caprice Reservoir (sold separately)
The Express Van master cylinder has the correct 1/2-20 and 9/16-18 IF fitting for stock G-body Brake Lines
The 1996 Chevrolet Caprice Reservoir is angled to work with the angle of the G-Body Firewall.

Let me know if you have questions.

Dave
Excellent information. Now what if I want to upgrade the rear drum wheel cylinders to the larger units from an '82-'86 S10 w/manual brakes or '95-'97 S-10 (same part #)?

These cylinders have a 1/8" larger bore as well as bolt-in retainers. Should they be paired with a 1990 Caprice brake booster and large bore master cylinder (without switch) or would a small bore be better? Proportioning valve changes would be required, of course.

And just for fun, what if I upgraded to 1LE ('88-'92 Camaro) or LS1 ('98-'02) brakes for the front? Can I do either of those in conjunction with the S10 cylinders out back? I understand swapping to rear discs is the obvious answer but these upgrades tend to happen in stages.

My Cutlass needs the booster and master replaced soon so I'd like to get this all planned out. Thanks guys.
 
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malibudave

Greasemonkey
Mar 12, 2010
204
235
43
Houston, TX
Excellent information. Now what if I want to upgrade the rear drum wheel cylinders to the larger units from an '82-'86 S10 w/manual brakes or '95-'97 S-10 (same part #)?

These cylinders have a 1/8" larger bore as well as bolt-in retainers. Should they be paired with a 1990 Caprice brake booster and large bore master cylinder (without switch) or would a small bore be better? Proportioning valve changes would be required, of course.

And just for fun, what if I upgraded to 1LE ('88-'92 Camaro) or LS1 ('98-'02) brakes for the front? Can I do the either of those in conjunction with the S10 cylinders out back? I understand swapping to rear discs is the obvious answer but these upgrades tend to happen in stages.

My Cutlass needs the booster and master replaced soon so I'd like to get this all planned out. Thanks guys.
In my opinion, the wheel cylinders size is not that important. I believe the stock drum brakes should have plenty of stopping ability. I would add the wheel cylinder brackets to "lock" the wheel cylinder to the backing plate. With this type of wheel cylinder, they tend to move a little front to back when braking without the bracket to lock it, which should reduce your braking performance slightly.

If going to a B-Body Booster, I would go with the 1-1/8" bore master cylinder with almost any front and rear brake setup. Usually, larger bore will give you better pedal feel and control of the brake.

Keep in mind that your brakes are only as good as your tires. If you can lock your tires up with your stock brake system, you don't need better brakes, you need a tire with a "stickier" compound. Usually, you will get better braking out of a stickier set of tires than going to a "big brake" system.

If you get brake fade (usually not in a daily driver), you usually need a rotor with more mass to absorb the additional heat.

A fluid flush will make a difference if your fluid hasn't been changed in years.

For the money, a brake pad upgrade is the better investment, IMO, even with the stock brakes.

Change out your 40 year old rubber lines with new rubber lines or stainless steel braided lines. Older lines will balloon with age.

Usually, the larger the piston area the better.
Usually, the more rigid the caliper is the better.

Unless you have them, a 1LE caliper (1.5" diameter pistons) is not worth the money. It has a much smaller piston area vs the LS1 (1.77" diameter piston). So with the same 12" rotor and the same leg input, you get less braking performance.

The LS1 brakes have a nice 12" rotor and a caliper with a normal sized diameter (1.77" diameter) pistons. But IMO, I think the LS1 calipers "clamshells", more than it should with pressure, which would reduce braking performance. If you are going for looks and for something to fill out the wheel better, I would go with the LS1 setup as the best budget swap that looks pretty good.

I like the 1998 and up S10 Blazer dual piston caliper spindle assembly. It gives you a little larger diameter rotor (10.5" v 10.75") and a caliper that has a larger piston area and is more rigid than the stock g-body caliper. The S10 Blazer spindle and hub assembly lends itself to "big brake" upgrades without modifications vs a stock g-body spindle. Add a EBC Yellow Stuff or Hawk HP+ pad to the stock S10 Blazer setup and I think you would be impressed with the braking.

The B-Body big brake conversion upgrade is the best big brake upgrade for the money. It's overkill for most tires. 12" rotor with a huge single piston 3" diameter piston caliper. You'll need a aftermarket upper a-arm. People take about dumpsteer issues, but for a daily driver, this shouldn't be an issue.
 
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Sweet_Johnny

Has A Face For Radio
Supporting Member
Oct 4, 2022
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Thank you for the detailed response, the information is much appreciated. Copious amounts of research on this forum and others has led me to formulate a rough plan over the course of a few years and I might utilize parts of that plan for my current ride.

I have none of the new parts yet but the plan was to machine the factory G-Body rotors down to be hubs, then either use 1LE 12" rotors and dual piston calipers or the LS1 finned PBR calipers so it would look great and fit under 15" wheels. The proposed setup would also accept the 14" Vette rotors but would then require a 17" rim and I'm not going down that road.

I'd considered new pads from EBC or Hawk but there's also a drilled/slotted rotor & pad combo from Power Stop for the LS1, specifically the Z26 Street Warrior kit. https://www.powerstop.com/product/p...rior-brake-kit/#y=2000&mk=CHEVROLET&mo=CAMARO I've used Russell stainless lines and would again any day, and that was also part of the plan.

"Usually, the larger the piston area the better.
Usually, the more rigid the caliper is the better."


So the 1LE calipers have smaller, less desirable pistons but the LS1s push open like clamshells? Would the former not be more consistent and reliable in a harsh environment? As for filling out the wheel, my only goal is to have the things you can't hide to be pretty, e.g., nice rotors & either polished finned calipers or ones painted an accent color, and try to stuff it under 15s so I'd have multiple options around the garage.

I'm one of "those people" that has absolutely no desire whatsoever to get into B-Body or Blazer spindles. Just a personal preference is all.
 
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