For assorted reasons I'm looking to upgrade my brakes, but am not willing to limit myself to larger wheel sizes. Currently my '87 TA has the stock disk/drum setup.

I am trying to weigh my options and would appreciate suggestions and thoughts about my current plan. What I want to run:
- stock TA/Formula "hi-tech" 16" wheels
- Z06 wheels (these should pretty much be no problem
- 15x3.5 and 15x9 Draglites
- in a perfect world but not absolutely necessary 15" firebird wheels (sort of a cool stealth look but _much_ lighter and faster in a straight line than the similar looking 16's)

 

I think in the front that limits me to Corvette C4, 12" brakes (they're the only ones that will fit the stock 15's), or possibly the LS1 11.xx" brakes (which funny, supposedly will not fit 15's and I hear may or may not fit the pontiac 16's, even thought they're slightly smaller OD than the C4 brakes. I don't believe that there are any other choices.

If that's the case I think I prefer the C4 brakes since they have a slightly larger diameter and should in theory stop slightly better, and are significantly lighter than just about any other option. My only concern is if they're durable enough, at .7x" thick rather than the 1.xx" that most other options have.

 

I think in the back wanting to run 15's pretty much limits me to later 3rd gen rear disks or LT1 rear discs. I think that the third gen ones are actually something like .2" larger OD, but I'm not sure that they are really any better, I believe that the calipers are the same. I don't believe that they typical LS1 swap will fit.

I have most if not all of a set of LT1's sitting around, I also have the stock '87 rear disks on my parts car which are also in good shape (I actually put fresh rebuilt calipers on it before it got parked).

Now I'm wondering if the LT1 or stock '87 rear disks are a better choice.

 

I think many members would agree that the 89-97 PBR system is superior to the 82-88 Delco-Moraine system. The 89-92 design has, IIRC, 11.7" rotors and alum calipers (I assume the 93-97's are similar) while the 82-88 has 10.5" rotors with iron calipers. Real distance stopping power between the two? Who knows. Though I personally never experienced issues with the latter, they do have a bad reputation on TGO, FWTW.

JamesC

 

Honestly, I'm more concerned with input about what to do with the fronts. It looks like the C4 vette brakes make the most sense for me, but I'm not sure if they are really worth the effort and if they would be durable in hard use.

As far as the late vs early 3rd gen rear disks, I think that real world most people don't have a setup that taxes _any_ of the rear brake setups available and the real reason that the early Delco disks got such a bad name was because of the parking brake adjusters freezing in them. If you get a set that have been updated with the replacement parts and/or use the parking brake regularly regularly they work fine. In this case my bigger issue is that they'll be visible with the Z06 wheels and are just ugly.

WRT to the sizes, I was under the impression that the early ones were 10.5, the later ones were 11.7x" and the LT1 ones are actually smaller at 11.5x"

 

On the money, according to Lukestaff (diameter/thickness/weight):

89-92 = 11.67
93-97 = 11.54

.78
.79

12.5
11.0

JamesC

 

Yea, like I said, I'm not that worried about the rears... any thoughts about the fronts?

 

FWIW, I'm swapping my 84 from the Delco Moraine rear discs to the PBR setup, LS1 fronts and will be running the 16 inch High Tech Formula wheels. The LS1 setup as far as I can see will fit fine under those wheels. Its the crosslace wheels where it seems people are running into problems, but even then that is solved with a small spacer. I used the Formy wheels because that was the closest option I had to a stock appearing wheel, while going bigger with wheels. I used bigbrakeupgrade for the LS1 mods (spindle, hub, bracket). I have rotors on order, still need to get the rear calipers, hard lines, and pads for all four corners.

 

I forgot to add, there is a picture floating around somewhere on here that shows the pad differences between the iron stockers, 1LE PBRs, and LS1 fronts. The LS1 pad is noticeably bigger than the other two, bigger pad, more stopping power.

 

Nope. Bigger pad is only good for pad life and lowering pad temp.

The braking torque or "power" as you call is the (braking force) * (radius from center of the spindle to roughly the center of the pad). Braking force is determined by the hydraulic advantage in the system. Force = (piston area) * (fluid pressure). Fluid pressure remains the same when swapping brakes, so really only the piston area matters.

Stock
piston area: 4.43 sq in
effective radius: ~9.5"
Torque = P * 4.43 * 9.5 = 42.1 * P (P is brake fluid pressure)

LS1
piston area: 4.81 sq in
effective radius: ~11"
Torque = P * 4.81 * 11 = 52.9 * P

So the LS1 setup has about 25% more braking torque than stock at the cost of ~9% longer pedal travel to generate the same fluid pressure. Not a bad trade off for a setup that has to fit in a 16" wheel.

 

I'm probably running on a common misconception. Thanks for the mini lesson. In a way it is an improvement regardless.

 

No problem, we are here to learn. I would imagine the LS1 brakes feel much better than stock. The bigger rotor really help.

 

http://www.summitracing.com/parts/SSB-A181/

 

Those have a piston area of 3.5 in^2. That means that caliper will produce 21% less clamping force than stock. Not exactly what I would want, but they sure do look pretty.

 

Just figured i'd mention it... I was asking Matt (mw66nova) about this the other day when he was helping me get my brake swap done a few weeks ago, and he runs 15 inch front wheels on his LS1 brakes, but he said he runs either a spacer or an adapter, to push the wheel out a little farther to get the clearance he needs. Wouldn't work with factory 15's, but with the skinny 15's like he and you have, the LS1 swap is still a viable option. Doesn't look bad or anything either, you can see all the current pics in his car of the month thread.

 

Is it so that upgrading from Delco Moraine iron rear calipers to lt1 style bpr calipers is actually downgrading by brakeforces(at same brake line pressures).Delco calipers have 48mm piston ,and bpr calipers have 40.5mm piston.How is it?

 

Going with the dual piston setup while in fact is theoretically less piston area, does have a wider spread contact area. Which aids in even pad wear and theoretically larger pad contact surface with the rotor. There was some pretty bad math going on in this thread people need to look up some formulas before they start posting nonsense.

Though the two piston calipers by ssbc have a smaller piston diameter going from old worn calipers, pads, rotors to new ssbc caliper with new pads, rotors, ans braided lines are of course going to show an improvement.

If those SSBC dont tickle your fancy, why not try Willwoods d152 replacements. They have an upgraded 2.5" Diameter piston. Brings piston area up to 4.9 and from what I am hearing that is what you are concerned about.

From my experience stock brakes when set up and maintained "correctly" are more than enough for these cars. Slotted rotors, the right pads per application, recon. calipers, bled per sequence, can perform very well. I know guys running low 11's on these stock brakes with just a pad upgrade.

I agree they arent as pretty as some aftermarket setups and the rotors look tiny behind larger wheels, but in your case you have 15's I dont think that should be a concern.

I would consider the willwood kit. at just under 400$ from summit, you can do both fronts. They come with pads even though I would recommend some ebc's. I believe its 75$ extra for the braided like kit. They seem to be what you are looking for.

 

Yes, for the same fluid pressure (same amount of pedal effort) the Delco Moraine's will produce more pad force. However pad force is not what stops the car. Whats stops the car is brake torque. Torque is force * moment arm. Just like using a breaker bar it is much easier to tighten a bolt with a longer breaker bar than a short socket wrench. The PBR setup uses a larger rotor than the DM's.

So assuming 1000psi of fluid pressure.

piston area = pi*(d/2)^2

DM = pi*(1.89/2)^2 = 2.80 in^2
PBR = pi*(1.57/2)^2 = 1.93 in^2

brake force = piston area * fluid pressure

DM = 2.80*1000 = 2800 lbs
PBR = 1.93*1000 = 1930 lbs

brake torque = brake force * moment arm

Moment arm is the distance from the center of the rotor to roughly the center of the pad. Assuming the pads are about 2" tall.

Moment arm = rotor diameter/2 - 1

DM = 10.5/2 -1 = 4.25"
PBR = 11.67/2 -1 = 4.84"

Brake Torque

DM = 2800 * 4.25 = 11900 lb-ft
PBR = 1930 * 4.84 = 9340 lb-ft

So the DM setup will produce 27% more braking torque than the PBR setup for the same pedal effort. Now rear brakes are way more forgiving than the fronts since pressure to the rears is stepped down by the proportioning valve. I would guess that the PBR proportioning valve allows more pressure to the rears than the DM prop valve. Maybe someone can confirm. This is why it is really important to use the correct prop valve.

Another thing to consider is brake feel. I personally like a shorter firmer pedal feel. So I actually like brakes with smaller piston area. The brakes are still plenty to stop the car, I just have to push a little harder.

Case in point, the gigantic 2009+ CTS-V calipers I am putting on my car actually have less piston area than the OEM calipers. 4.27 in^2 vs 4.43 in^2. The beauty really comes in having a bigger rotor. The bigger rotor gives you a much better brake torque without sacrificing pedal feel.

 

Like I said, I actually like the feel of smaller piston area calipers. I am just pointing out that it is false to say that the SSBC calipers produce more braking force. OEM calipers are what, $16 each. I'd use those until I could save up for a real upgrade.

Agreed that the dual piston caliper will even out pad wear theoretically. However anyone crazy enough to road race on the OEM brake setup is asking for problems much greater than pad taper.

 

The front metric iron calipers have a 2.5" piston where the fluid pushes on it. So the area is closer to 4.9 sq/inches. The piston OD is stepped, with it being 2-3/8" where it contacts the pad.

So the loss in braking power is even greater.

RBob.

 

Several of the above posts were off topic and deleted. Others are off topic as well but do contain useful/interesting technical info, so those remain in place.

Back to topic please.

JamesC

 

With the Willwood d154 brake kit you can use this line kit. http://www.jegs.com/i/JEGS-Performan...ductId=1682813

I can not find Willwoods part number ATM.

 

Interesting. I have never looked at the OEM calipers closely. Thanks for the info.

 

Ok thanks for answer.Any idea how much more pressure will bpr prop valve give to rears?

 

I have no idea what the specs are on the stock prop valves. I use an adjustable one myself. James always seems to know a lot about third gen prop valves, maybe he knows?????

 

I put standard C4 brakes on the front and am using the StopTech high performance street pads (high side of the FF rating), #30904120. Huge improvement over the stockers. IIRC, they are .81" thick, but they are also 12" in diameter. Which provides more surface area to dissipate the heat.

They fit under the stock '92 RS 15" wheel with no issues (no grinding, no spacers, etc.).

Since piston area is being discussed here, they are less then the stock iron calipers. With the rotor diameter making up for some of that. Doesn't really matter though, these things stop the car.

RBob.

 

it's not about surface area alone. In fact, pad area has no effect on braking force. (look up formula for dynamic friction), the only affect is that the larger area does indeed provide a larger energy transfer area and as such a reduced temeprature across that area. In other words, smaller pads fade easier. If you had the same setup, same rotors, piston size, mc size, pedal ratio and pedal pressure you would have the same braking force with small and big pads if the conditions are such that there is no pad fade. Not saying larger pads aren't ebtter they are...

Now, the rotor mass determines the mean rotor running temp. A larger mass an hold more heat energy with a lower rotor mean temp. Directional vanes offer better cooling than straight vanes and so on... larger rotor mass -> cooler running brakes.

That setup may stop the car, but does it stop the car each and every time, reliable under hard use with a proper firm pedal that you can modulate? Run it hard, run it on the twisties..those things will start to fade and you will smell the pads. We have twisty roads here, it doesn't take a whole lot to get the brakes to become spongy. Didn't invest in these for nothing:

 

I never said a word about pad area. You need to also re-read the first post in this thread. Do those brakes pictured fit inside a 15" wheel?

As far as fading, I've done it with the stock 10.5" iron caliper brakes in rush hour traffic. Not so with the C4 brakes.

RBob.

 

No but Rbob did. I didn't say the brakes pictured fit a 15" wheel, I said I upgraded to those because the JL9 brakes are junk, it's a retrofit kit from Mov-It for C4 vettes.

 

Uhh, I am RBob, and I didn't say a word about the pad area. Since the brakes you showed don't fit in a 15" wheel, your post is worthless. According to you nothing short of NASCAR brakes should be used.

And your opinion of the C4 brakes being junk is also worthless. As they are a lot better then the stock brakes and do fit in a 15" wheel. Which is a criteria that the OP has for upgrades.

RBob.

 

Oh, so my contribution here is worthless? Good to know, please delete my account here including all my posts. I wouldn't want my worthless contribution to spoil your forum.

 

The thread appears to have run its course.

JamesC