Brakes Experts: Larger Disk / Smaller Pistons vs. Smaller Disk vs. Larger Pistons ?

[waid786]

I recently completed 5.3/4L60E swap in my 1998 Sonoma/S10.

For now I am keeping stock 15" wheels so I have couple of options for better brakes. Blazer's Brakes, C4 Corvette Brakes or keep stock brakes.

Blazer's rotor diameter is 10.8" with twin 1.8" pistons caliper. The C4 rotor diameter is larger at 12" but the caliper has smaller twin 1.5" pistons. The stock front brake rotor is 10.5" with a single large 2.5" piston caliper.

Which will provide more stopping power. C4 or Blazer setup?

The stock rotor diameter is almost same as Blazers but much larger single piston. Is Blazers still better ?

Thanks

Waid

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[c4racer2]

I think you probably know without doing any hard math that a C4 has better performing brakes than a s10 blazer.

[cornfedbill]

The area of the pistons times the pressure times the number of pistons on one side of the caliper gives you the force. The force times the coefficient of friction times the working radius gives you the braking torque.

A bit of math should answer your questions.

What is the purpose of the build? Daily driver with occasional autocross? Road racing? What do you need?

If you are not racing, I would go with the 2 piston Blazer brakes and a good set of pads - unless you have the Corvette brakes or money you are dying to spend.

[c4racer2]

10.8” is pretty tiny rotor and it’s very thin. C4 is hands down better. C5/6 would be better still.
You just need a master cyl bore size that matches the caliper piston size to optimize clamping force. If using power then going with a C4 master or equivalent would be a natural choice.

[c4racer2]

Here is where things get tricky.
Stock brakes have a PA (piston area ) of 4.9 sq in.

C4 is 3.5

As a point of reference the popular 6 piston wildwoods have a PA of 4

So with a smaller PA you need a smaller master to give you the equivalent clamping force at a given pedal travel.

Again - start with a C4 master or something similar size. I want to say they use a 1” bore size but check that as it’s from memory.

Assuming power assist and also check your pedal ratio compared to what a C4 uses.

The real advantage of the C4 setup is rotor size. Since you use radius in brake calculations you have 7.5 vs 5.4 in radius. That literally gives you a 39pct improvement in braking force.

Piston area is somewhat irrelevant to clamping force since you can completely adjust by picking the bore size on the master.

So I am not doing the exact math but something along the lines of a stock master with a 1.25” bore and a PA of 4.9 will be equivalent to a 1” PA of 3.5. For example don’t take those as actual numbers.

[waid786]

What is the purpose of the build? Daily driver with occasional autocross? Road racing? What do you need?

If you are not racing, I would go with the 2 piston Blazer brakes and a good set of pads - unless you have the Corvette brakes or money you are dying to spend.

The truck is for street and strip (1/8 mile) but not a daily driver. I already have Blazers Calipers/Spindle & C4 Calipers. All I need are rotors.

The C4 Master Cylinder is 0.875". The S10 & Blazers uses same Master Cylinder which is 1". If I go with Blazer's setup, I can keep my Master & not mess with Line Lock & other brake lines which are all plumed in.

Would I have to change the master if I go with C4 setup ?

Waid

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[waid786]

Interestingly, the 3rd gen Camaro's had 1LE package and used very similar Calipers with same 1.5" twin pistons and 12" rotors. The master cylinder was a duel bore design (1.25" & 0.945").

Waid

[stab6902]

Here's some back of the napkin math going off of your piston diameter numbers:

Stock Piston area = pi*2.5^2/4 = 4.9 square inches

Blazer piston area = (pi*1.8^2/4)*2 = 5.1 square inches

C4 piston area = (pi*1.5^2/4)*2 = 3.5 square inches

The Blazer setup would have slightly more braking power than what you have now. Most people probably wouldn't be able to feel the difference between the Blazer and S10 brakes (assuming equal brake pad compounds). We're talking a difference of (5.1/4.9)*roughly(10.8/10.5)] equates to a 7% improvement in brake torque.

The C4 brakes would have better thermal capacity (and way less braking power unless you switch the master cylinder), but you said you're running 1/8 mile drags, not road racing, so that's not really a factor.

[malibudave]

Plug in your numbers into the brake calculator spreadsheet at the bottom of this the page on this thread.

https://www.pro-touring.com/threads/104584-Brake-sizing-and-selection-tutorial-featuring-Ron-Sutton-and-Tobin-of-KORE3/page7

Using the same variables (master cylinder bore size, tire diameter, pedal ratio, pressure input), you can have a good comparison. All you need to do is change the caliper bore diameters and rotor diameter.

Blazer caliper will be
Bore 1: 1.81
Bore 2: 1.81
Effective rotor diameter: 10.8

Corvette caliper will be
Bore 1: 1.50
Bore 2: 1.50
Effective rotor diameter: 12.0

Your truck should come with a 1.0" bore master cylinder, but the C4 corvette came with a 15/16" bore (0.937")

With all things being equal, the Blazer Setup is better on paper. If you reduce the master cylinder down to a 15/16" bore to see how it improves the Corvette numbers, the improvement number after this change is still less than the Blazer brake setup with the 1.0" bore.

This is for comparison with all the variables (pedal ratio, pressure, assist, master cylinder bore size, pad coefficient of Friction, and tire diameter) being equal.

[c4racer2]

ya - for that application forget the C4 brakes - no good reason to run them. And the only real benefit is the calipers can handle a 13" rotor, but you probably won't have a 17" wheel with clearance and you certainly don't need the capability of C4 brakes for your intended use

[waid786]

Most people probably wouldn't be able to feel the difference between the Blazer and S10 brakes (assuming equal brake pad compounds). We're talking a difference of (5.1/4.9)*roughly(10.8/10.5)] equates to a 7% improvement in brake torque.

The C4 brakes would have better thermal capacity (and way less braking power unless you switch the master cylinder), but you said you're running 1/8 mile drags, not road racing, so that's not really a factor.


Thanks you all for great info. I will keep the current S10 brakes as they are for now.

Waid

[waid786]

Well after little more digging, I found that 2000-2005 Cavalier uses Master Cylinder with 7/8" (0.875) bore (same as C4) with ports on same side and about same location as S10. The Cavalier uses Metric Bubble fitting where the S10 uses SAE inverted flare. AutoZone has fitting adapters. The C4 master cylinder is completely different with some kind of integrated proportioning valve. More importantly the Cavalier & S10 uses similar proportioning valve and ABS system. This should my pluming very simple.

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Waid

[stab6902]

If you put the C4 brakes up front (which provide about 18% less brake torque at a given pressure than your stock brakes assuming similar pads) but keep your rear brakes stock, the brake system bias will move rearward. Your ABS will more or less keep you out of trouble (even though you'd throw the calibration way off), but it'll still be a mismatched system and your rear brakes will wear and heat up much quicker than the front. You could add an adjustable proportioning valve to dial back the pressure to the rear brakes, but that has its drawbacks as well.

What is your end goal? Are you just looking for a little more stopping power? If that's the case, I'd look into higher friction brake pads for your stock brakes. You want pads with a good cold coefficient of friction, which a lot of people will call an autocross or street pad.

You said this is an 1/8 mile drag truck, so adding bigger brakes will just add to rotating and unsprung weight, slowing down your truck. People put big brakes on cars for thermal reasons to resist fade (very important on a road course), but drag racers usually go with the smallest, lightest weight brakes they can get away with.

[waid786]

As a point of reference the popular 6 piston wildwoods have a PA of 4


For my own future benefit, when you have 4 piston or 6 piston caliper, you only count the area for 1 side (2 or 3). Correct?

Waid

[malibudave]

For my own future benefit, when you have 4 piston or 6 piston caliper, you only count the area for 1 side (2 or 3). Correct?

Waid

Correct

[malibudave]

Well after little more digging, I found that 2000-2005 Cavalier uses Master Cylinder with 7/8" (0.875) bore (same as C4) with ports on same side and about same location as S10. The Cavalier uses Metric Bubble fitting where the S10 uses SAE inverted flare. AutoZone has fitting adapters. The C4 master cylinder is completely different with some kind of integrated proportioning valve. More importantly the Cavalier & S10 uses similar proportioning valve and ABS system. This should my pluming very simple.

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Waid

Keep in mind, will the Cavalier master cylinder bolt up to your booster? Is the mounting bolt holes the distance apart? Will the flange of the Cavalier fit on a S10 booster?
Is the piston face (where the booster's push rod contacts the master cylinder) in the Cavalier's master cylinder the same design as the S10? If not you may have issues push rod to piston clearance. This may lead to some preload on the piston, which may engage the brakes; or a space between the tip of the push rod and the pace of the master cylinder which may lead to excessive pedal travel.

In my opinion, you are doing a lot of work for minimal gains in braking performance (if any) and weight reduction.

If this is mostly a drag truck, the brakes in the front are only as good as the tire. If you are running skinny tires up front, there is no brake upgrade that would be beneficial (other than spending money on a light weight braking system), as almost all brakes should be able to lock those tires up easily with power assisted brakes. If you are launching off the line by foot braking your truck, it is better to maximize your rear brakes to hold the power coming through the axle shafts. A larger rear tire will help your braking because it has a larger contact patch with the road which is better for braking.

If you have rear drum brakes, maximize them. Larger wheel cylinders, two long shoes, and choosing the best shoe friction material. If you do not over heat the shoes, they work very well in a drag truck at holding it at the line and stopping on the top end. For the money, for a drag truck, there is not much of an advantage to going to rear disc, unless you already have them.

[waid786]

It a street / strip truck running 195's up front and 255 in the rear. It would be nice to have little better stopping power since its so cheap. I will check out the M/C carefully ensuring they mount the same as you suggested.

Thanks

Waid