[JLMounce]

Call me a believer.

For 10 years or so and specifically in the last 3 years I have really chased performance issues with the braking of my Firebird. It had basic stock type components on it to create a 4 wheel power disc system.

It consisted originally of a single 9" diaphragm power booster which clamped GM D52 calipers on 11" rotors in the front and GM Metric calipers on 11" rotors in the rear. In this configuration, the braking was adequate. It would stop decently, but never really wanted to lock up the wheels.

In 2022 the power booster failed and the decade + aged calipers had started to leak and really just looked like crap.

Last year I replaced the calipers with Wilwood variants of the D52 and Metric calipers and had a rough time with it. This is what led me to discover the power booster was failed/failing. I had determined through speaking with several different people that the booster just wasn't adequate for the type of vacuum I was pulling. On the edge, so the single 9" diaphragm just wasn't adding enough pressure to the system.

I opted for a TuffStuff dual 9" designed around the C3 braking system. With the massive 6.28" front and 4" rear piston areas, combined with the larger power booster, the car stopped very well, now able to lock the wheels when needed. However the pedal feel as atrocious. The booster worked so well that it slammed all the pressure into the calipers as soon as you touched the pedal. Very little firmness from the pedal and zero feedback. It was like the first time you try left foot braking and your foot is asleep at the same time.

You can imagine, in traffic this was pretty terrible to deal with. You were going or stopping, not really anywhere in between.

I've been wanting to change the wheels and tires on the car for a while for a bit different look and figured if I was going to do that, now would be the time to re-engineer the brake system, in case my track widths changed.

With a bit of trepidation, I opted to go with an upsized Wilwood package in the front and rear and matched it with a 15/16" manual master. The system consists of a 12.88" front rotor with the Forged Narrow Superlight 6 piston caliper in the front and a 12.19" rear rotor with the Forged Dynalight 4 piston caliper in the rear.

I was able to get the system bled out and the pads bedded in yesterday and got some drive time in. I can tell you, I should have done this years ago.

Yes, the pedal effort is increased, but not in a bad way. It's nothing like a hard pedal with a bad power booster where it's just needless hard with no stop. You feel the pads come on to the rotor and you can feel the adhesion of the tires to the ground. It's super easy to modulate what you want the car to do. Actuation is quite linear and the pedal is always doing what you expect it to do and how you expect it to feel.

If you're on the fence about going with a manual setup over a power setup, the only thing that might sway me away from manual at this point is if the car is daily driven in stop and go traffic. The increased pedal firmness isn't that much of an increase. In fact I don't think my pedal is much firmer than the pedal on my wife's '13 Corvette. The feel is just so good as to override any issues with the firmer pedal.

As an added bonus, I now have zero vacuum accessories that I need to worry about having an engine support.

[JSchmitz]

I did similar many years ago and love it! I hated having the factory booster and, of course, 4-wheel drums. I went with manual master and 12" GM discs in front. I think I have 15/16" master also. Pedal effort is absolutely fine. It's very linear and predictable.

[b-man]

Originally Posted by JSchmitz

I did similar many years ago and love it! I hated having the factory booster and, of course, 4-wheel drums. I went with manual master and 12" GM discs in front. I think I have 15/16" master also. Pedal effort is absolutely fine. It's very linear and predictable.

I did the same using a 1-1/16” master, pedal effort was fine and braking was predictable.

Manual brakes are great.

[Greg Reid]

Would it be at all advantageous to go with a bigger than stock MC and keep the drums? My '66 has manual drums which I may keep but I want to upgrade to at least a dual master.

[Scarebird]

If you go dual - go 1967; same bore size so it will match your drums fine.

Sorry about the giant size...

[59safaricat]

Drove manual brake cars for years and never bothered me. Just be aware when going back to a vehicle with power brakes. I drove my brothers truck with power brakes and him in the passenger seat and almost put him through the windshield on my first stop.

[65madgoat]

Swapped out a hydroboost for manual set up a decade ago. LOVE THE MANUAL BRAKES. Only way to go!

[JSchmitz]

Slight correction. I have 1" bore master: https://www.summitracing.com/parts/WIL-260-8555P

This is a very nice piece! A little pricey...

[Scarebird]

Waaaay too much.

1974-80 GM 1/2 ton manual w/1" bore. Looks factory, works factory. $40 https://www.rockauto.com/en/moreinfo...t=1836&jsn=914

[JLMounce]

The Wilwood masters are spendy. I did go with one, primarily for the look. A factory master is more than adequate as scarebird points out.

[george kujanski]

Scaebird...that master looks like the front brake connection is the rear of the master vs. the OEM in the front. or am I wrong?

george

[Scarebird]

Correct. Mid-70's GM did a flip-flop on the reservoirs for simpler valving.

Some masters are still being made for the older style but more expensive and less effective.

Drum/drum work fine too but watch the fluid level.

[Murf]

Originally Posted by Scarebird

If you go dual - go 1967; same bore size so it will match your drums fine.

Sorry about the giant size...

Hi Scarebird! Partial threadjack but.
I’ve got LS Camaro discs on all 4 wheels on my wife’s 65. I have a leaking M/C and a bad booster right now.

Could you recommend a reasonably priced M/C for manual brakes? Also what M/C & booster combo would you recommend if I stay with power brakes?

I’m have a 1 inch M/C with the booster now. Is that wrong.

Thanks,
Murf

[Scarebird]

What year Camaro is this?

[Murf]

Originally Posted by Scarebird

What year Camaro is this?

2000-2002. 4 wheel discs. From what I could find when I put it together they used 1” bore M/C & all had power brakes. I used an aftermarket 1” bore M/C with a booster.

It’s leaking now & I thought I might go manual when I fix it.

Thanks
Murf

[RocktimusPryme]

Thats interesting. Ive never been happy with the 4 wheel disc setup in my 67. Now mine already is manual and they work fine, but I feel like the effort is too high. Ive always been worried that if a deer ran out in front of me I would have to put my foot through the floorboard to get it to stop in a hurry.

IIRC I have the 1" corvette type (equal reservoir) MC that came with my kit from Right Stuff for my original disc drum, setup. (I did swap the proportioning valve when I changed to discs)

Ive been wondering if I switched to a 15/16th" MC made for manual disc/disc if it would make a notable difference. I dont want to do it for no reason because I loathe bleeding brakes.

[Scarebird]

Murf - the power 2000 master is 1" bore; I am thinking you will need a smaller bore for manual but I do not know of a good one stock.

[JLMounce]

With a full manual setup, you can run the math pretty easy.

The First gen F-Body has a nominal 6:1 pedal ratio.

50 lbs of force on the end of the pedal is transformed to 300 lbs or force at the MC piston

A 1" bore MC has an area of .785sq". Divide that by the 300 lbs of force at the piston and you've now created 382 lbs of force leaving the MC.

If your front calipers are the standard 2.75" single piston caliper, you multiply that 382 lbs of force leaving the master cylinder, by the area of the caliper piston which is 5.94sq". You have an effective clamping pressure at the caliper piston of 2268 psi. Of course you aren't factoring in pressure loss through line bulge, caliper flex, pad crush etc, but you can see how the math works.

Now do the same thing with a 15/16" master.

The bore has an area of .689sq". We divide that by that same 300 lbs of pressure that your 6:1 pedal ratio is giving you with 50 lbs of force on the pedal. Now you're producing 435 psi at the outlet of the MC. Now plugin the numbers for the calipers and the MC change produces 2586 psi of clamping force on the rotor. A bit more than 300 extra psi at the calipers, or a bit more than 12% extra clamping force for the same pedal effort. The trade-off is that your volume goes down by the same amount, so the pedal will have to be depressed a bit more than 12% further to achieve the same volume of fluid movement.

None of this takes into account swept area of the rotor, pad volume or pad friction coefficient, which all plays a roll in how much stop the car will have at a given pedal pressure. At some point simply raising pressures reached diminishing returns due to caliper flex.

In your case going to the smaller bore MC may relieve some of the effort necessary by the driver, but the car probably isn't going to actually stop any faster. Selecting a brake pad with a higher friction coefficent like the Carbotech 1521 will translate more of that clamping force into stopping power. Also important to note that higher heat range pads, don't necessarily have a higher friction coefficient, they just work at a higher temperature. So when selecting pads, pay attention to that detail.

[RocktimusPryme]

I like that, thats well explained. It might be a winter project I take up, since it would be relatively affordable to swap. It would also give me an excuse to cut and reform my rear end brake lines, which are functional but a disaster to look at. I didnt have a flare tool at the time so I had to live with the pre-cut lengths available over the counter.

I think it might actually be more of a feel thing for me. Again, the car has never actually stopped poorly I just feel like I have to try hard. It is difficult to seperate the feeling from the reality there. Makes me afraid to drive at night around here in deer country.

[JLMounce]

factory type master cylinders are fairly cheap. It's more work than anything to try out the smaller bore master. You might consider changing out the brake pads at the same time as part of a brake service and see how you like it. If you hate it, you've still got the old stuff.

I'm assuming you have the D154 calipers for the rear?