What size master cylinder do I need with my manualbrakes.com KIT?
These are the master cylinder bore sizes I would recommend to customers.
G-Body / S10 / 3rd Gen F-Body
NOTE: Most of these vehicles came stock with the same size 10.5" front rotors, metric front calipers, and rear 9x2" drum brakes.
2nd Gen F-body
4th Gen F-body
Silverado / Sierra
Call David at 832-264-5566 or email to firstname.lastname@example.org to ask ANY brake question.
Is it OK to reach out with questions about a manual brake conversion?
YES. Call David at 832-264-5566 or email to email@example.com to ask ANY brake question.
Why is the MANUALBRAKES.COM conversions the best?
Manual brake conversions parts are all we do and are engineered to optimize your manual brakes. This is what we specialize in. We know what will work on for any given brake setup regardless if it is stock or modified with a different brake setup.
MANUALBRAKES.COM conversion parts are engineered with:
Call David at 832-264-5566 to discuss your setup.
Why do you recommend a smaller bore master cylinder versus a larger bore master cylinder?
We recommend smaller bore master cylinders to generate high line pressures. High line pressure maximize the clamping forces of the calipers which is essential for great performing manual brakes. When you go up in bore size of a master cylinder, you greatly reduce line pressures, and this means the driver will have to exert more effort on the pedal to stop the car. The MANUALBRAKES.COM KIT comes standard with a 7/8" bore master cylinder and will work the stock brakes of the vehicles we have developed KITS for. BUT, if you go to a rear caliper that is not stock, you may need to up size the master cylinder to a 24mm bore master cylinder so that it can handle the extra volume larger bore rear calipers require. 99% of manual brake cars will NOT need a 1.03" bore or a 1.125" bore master cylinders. ANY of the MANUALBRAKES.COM KITS have the option to upgraded to larger 24mm bore master cylinder at NO EXTRA CHARGE if your brake requirements need it.
Call David at 832-264-5566 to discuss your setup.
What will I need besides the Adapter Plate and Adjustable Pushrod Assembly?
1. Master Cylinders that can be used, by vehicle using stock brake set up (see Low Drag Calipers FAQ below)
2. Brake line adapter if using 1993 Dodge Shadow master cylinder or new brake lines if your current stock lines will not adapt
3. Optional Recommended Upgrades:
What modifications will need to be done to my “G-Body” or S-10 truck or Blazer to install the MANUALBRAKES.COM master cylinder brake plate?
When using the standard MANUALBRAKES.COM adapter plate without the retention cup, slight upper bolt hole clearancing are necessary for “G-Body” cars and 1st generation S-10 trucks (1982-1993) and S-10 Blazers (1983-1994). If using the MANUALBRAKES.COM adapter plate with retention cup, then there will be some trimming of the firewall to fit it properly on 1st generation S-10 trucks and Blazers. If done correctly, this will not cause any problems if converting back to power brakes. All vacuum boosted power brake equipped “G-Body” cars and all 1st generation S-10 trucks and Blazers have provisions in the brake pedal for manual brakes. This brake pedal provision is an extra hole drilled into the brake pedal from the factory to allow the use of manual brakes. The MANUALBRAKES.COM adapter plate uses these factory provisions to convert your vehicle to manual brakes.
On 2nd generation S-10 trucks (1994-2003) and Blazers (1995-2005), there is a need to have modifications done to the firewall because these years where never equipped with manual brakes from the factory. A 9/16 inch hole for the adjustable push rod will need to be drilled in the firewall between the top two vacuum booster bolt holes.
What is the piston size of a “G-Body”, S-10, and 3rd Generation F-Body caliper?
Stock piston size is 2.5” on 1978 to 2004 vehicles. 1982 to 1997 calipers are a LOW drag design. 1978 to 1981 and 1998 to 2004 calipers are a conventional, NON low drag design. All 3rd generation (non 1LE) F-Body calipers are LOW drag.
Caliper Specifications of Aftermarket "Metric" Calipers
Caliper.................................................Part Number........................Advertised Bore Size.......Actual Piston Size.........Weight
US Brake / AFCO Caliper (rebuilt)......PN 7241-9004/9003............ 2.50".................................2.50"............................6lb 4.7oz
CCP Big Bore Caliper (new)...............PN CP412526......................2.75".................................2.565"..........................6lb 11.2oz
Wilwood 2.75" Bore Caliper (new)......PN 120-8926........................2.75".................................2.704"..........................4lb 8.6oz
AFCO Caliper (new)............................PN 6635003/6635004..........2.50".................................2.50"............................6lb 4.7oz
Does Caliper Piston Size Matter?
Yes. A stock "metric" caliper with a single 2.5" diameter piston has, almost, the same piston area as a 1998-2002 Camaro/Firebird's 1.77" diameter twin piston caliper. A 2.5" diameter single piston caliper has 4.906 square inches of surface area. Dual 1.77" diameter pistons has 4.919 square inches of surface area. These calipers with these piston sizes work well with 7/8" bore master cylinders.
If you increase the caliper single piston size to 2.75", you will have to increase the bore size of the master cylinder. Most 7/8" bore master cylinders do not have the fluid volume to fill a brake caliper with a 2.75" piston. Though a caliper with more square inches of surface will have more clamping force, a larger master cylinder reduces brake line pressure and, in the end, you will loose braking performance when running manual brakes.
The bottom line for good performing manual brakes is a caliper with the largest piston area along with a master cylinder with the smallest bore. Calipers with larger piston area have greater clamping force than a caliper with a smaller piston area. A smaller bore master cylinder creates more fluid pressure than a larger bore master cylinder. In the end, the master cylinder will need to be matched to the caliper to create the most effective manual braking system.
What is the bore size of a master cylinder on a G-Body?
Manual brake master cylinders are 7/8” and are cast iron. Power brake master cylinders come in 24mm strait bore and a step bore version with a primary bore of 24mm and a secondary bore of 36mm. Most of the strait bore master cylinders where cast iron, though some power boosted versions where aluminum. The stock step bore master cylinder came in aluminum. Any new step bore master cylinder made today will be made of cast iron. The master cylinder brake line outlets were 1/2-20 for the front brake lines and 9/16-18 for the rear brake lines.
What is the bore size of a master cylinder on an S-10?
Manual brake master cylinders are a step bore design and have two different bore sizes. The bore sizes are 24mm and 31.6mm and where originally aluminum from the factory. Most power brake master cylinders came in 24mm and 36mm step bore and where originally aluminum from the factory. Any new step bore master cylinder made today will be made of cast iron. The step bore S-10 master cylinder from 1982 to 1997 had brake line outlets of 1/2-20 for the front brake lines and 9/16-18 for the rear brake lines. From 1998 to 2004, S-10 master cylinders had a 1.0" strait bore design with 1/2-20 outlets.
What modifications should be done to the stock braking system?
If using the stock brake components, make sure all parts of your system are in good working order. Vacuum assisted power brakes will mask some faults in the brake system that a manual brake system will not be able to cover up. It would be good to replace old rubber brake lines with good aftermarket stainless steel braided lines. Steel braided lines eliminates “ballooning” that can happen with rubber brake lines and will contribute to brakes that feel spongy. Quick take up (low drag) calipers that came on most “G-Body” cars, S-10 pickups and blazers, and the third generation Camaro/Firebirds will require a step bore master cylinder. The best option is to change to a NON low drag calipers and a standard, strait bore master cylinder in a 7/8" bore. Upgrade to a street brake pad and/or brake shoes with great friction properties when cold.
What are quick take up (low drag) calipers?
In the early 1980s GM introduced the quick take up (low drag) caliper on most of its vehicles. The reason for the quick take up (low drag) caliper was the energy crisis. The quick take up (low drag) calipers were designed to reduce the friction between the pad and the rotor to improve gas mileage.
The engineers at GM found that changing the square cut seal groove on the caliper could cause the caliper piston to be pulled back twice as much as the conventional caliper. The quick take up (low drag) caliper is designed with a 30 degree bevel in the seal groove as opposed to the conventional calipers 15 degree bevel. With twice the bevel, there is twice the seal flex. Flexing the seal two times as much pulls the caliper piston back into the caliper bore 2 times as far creating no drag of the brake pad on the brake rotors.
What’s the problem with using a quick take up (low drag) caliper?
The volume of fluid needed to take up the extra gap created by the quick take up (low drag) caliper exceeds a conventional master cylinder's capacity so a step bore master cylinder is needed. A step bore master cylinder provides a large volume of fluid initially to take up the gap and then internal bypass valve switches the master over to a high pressure system where it acts as a conventional master cylinder. Quick take up (low drag) calipers require a step bore master cylinder to function correctly.
How do you visually check if your calipers are a quick take up (low drag) design?
“G-Body”, most S-10 Trucks/SUVs, and most 3rd generation F-Body vehicles use the same front caliper design throughout their 1978 to 2004 production. Conventional calipers where used from 1978 to 1981 on the “G-Body” and quick take up (low drag) calipers where used from 1982 to 1997 in “G-Body”, S-10, and 3rd generation F-Body. From 1998 to 2004, S-10 calipers used a conventional, NON low drag design.
How do you physically check if your calipers are quick take up (low drag) design?
To check if your caliper is a quick take up (low drag) engineered, perform the following test. Purchase or rent a pair of brake hose clamps at an auto parts store. Press the brake pedal as it is and then clamp off the two front rubber hoses. If the pedal returns and is high and firm, chances are you have quick take up (low drag) calipers. Be aware that this same of the same symptoms will occur if the bleeder screw is not in the 12 o’clock position when mounted on the spindle or there is still air in the caliper.
Can you use quick take up (low drag) and step bore master cylinder with manual brakes?
Yes. This is how it was done from the factory in the 1st generation (1982-1993) S-10 trucks, but they are not known to be very effective when braking. The 24mm secondary bore in a step bore master cylinder is great if your truck has power brakes. The 24mm secondary bore will cause a harder than normal pedal and there is insufficient clamping force produced by the system to make the braking effective. The stock S-10 step bore master cylinder is the smallest step bore master cylinder made. A 7/8” strait bore master cylinder is recommended, but cannot work with the stock front quick take up (low drag) calipers. A smaller bore master cylinder bore equals more brake fluid pressure at the caliper. NOTE: The manualbrakes.com adapter plate for the G-Body and 1st Generation S-10 will not work with a 1982-1997 GM step bore master cylinder. The housing of the master cylinder will not allow the master cylinder to fit inside the retention cup. The inside diameter of the retention cup is smaller than the outside diameter of the master cylinder.
What is a "metric" brake caliper?
A metric brake caliper where designed to be used on the GM metric chassis (1978-1988 “G-Body” cars). It is a floating, single piston design with 2.5” piston. The metric brake calipers where used on 1978-1988 “G-Body” cars, 1982-2004 S-10 trucks and most S-10 SUVs, and most 3rd generation F-Body (1982-1992 Camaro / Firebird) vehicles. Aftermarket metric calipers come in bore sizes of 2.75” bore, 2.50” bore, 2.38" bore, 2.25” bore, and 2.0” bore. Most aftermarket metric calipers are designed as conventional calipers and are not a quick take up (low drag) design. All metric calipers have a slide bolt center to center spacing is 5.50 inches and use a D154 brake pad.
What is a “G-Body” vehicle?
Technically, G-Body vehicles are the GM intermediates chassis designation made from 1982 to 1988. The GM intermediate vehicles from 1978 to 1981 also used the same chassis and are technically “A-Body” chassis. For simplicity and to avoid confusion, the 1978-1981 “A-Body” vehicles are lumped in with the 1982-1988 “G-Body” vehicles.
What kind of pad should I use?
If on a budget, cheap 100% organic pads with an FF rating are best for street/strip duty and manual brakes. Unlike semi metallic and ceramics pads and shoes, they do not require a lot of heat to operate effectively. The downside to 100% organics is that they dust substantially more than semi metallic and ceramics pads. They will also induce brake fade if they are subjected to high heat for a long period of time. There are other aftermarket brand alternatives, like EBC, Hawk, Wilwood, etc., that can be contacted to find a pad that is best suited for your needs.
WHAT ARE THE LOW DRAG CALIPER REPLACEMENT OPTIONS?
Any parts store replacement caliper should be a normal, NON low drag caliper. The part numbers are the same from 1978-2004. They rebuild the calipers to normal, NON low drag specifications because a normal NON low drag caliper will work with any 1982-1997 STEP bore master cylinder and any 1978-1981, 1998-2004 STRAIT bore master cylinder.
What vehicles came with LOW drag calipers?
1982-1997 Rear Wheel Drive S-10
What vehicles came with normal, NON low drag calipers?
1998-2004 Rear Wheel Drive S-10 with single piston front calipers.
What modifications need to be done to install the MANUALBRAKES.COM "KIT" in the 3rd and 4th Generation F-body?
For any questions, please email me at firstname.lastname@example.org or call (832) 264-5566
1919 West Sam Houston Parkway North
Houston, TX 77043
THE SUPERIOR MANUAL BRAKE CONVERSION