D52 pad coeff.

[Skip Fix]

I thought there was a thread awhile back on a guy asking about different brand D52 pads.

Off my shelf
Hawks HPS-FF
Raybestos Advanced Tech(look identical to the Hawks)-FF
Raybestos PG Plus EE
Wagner Thermo Quiet-EE
Old Bendix Semi metallic-EE
Old Bendix organic -FE another EE
Wilwood BPs no letter code

Go figure the organics a better rating than the semi metallics. Tjose old semi metallics didn;t liek being cold and sure ate rotors and caused dust.

For you guys running D52s the 614 Impala SS/Police pad fits the calipers and is slightly larger.

[woody80z28]

Thanks. This says my HPS pads should be good, but I do not like them.

[Skip Fix]

I would assume just because a pad has a decent coeff that still doesn't say all about feel, warmup, longevity or dust.

[woody80z28]

Mine just will not bite. My brake PSI gauge shows 1100psi, but they just do not stop the car with any force.

[Skip Fix]

I was shocked when I looked at my old Bendix semi metallics vs the organics ratings-better for the organics I know when i used the "better" semi metallic they sure didn't grab when cold.Even many of my autocrossing friends used organics as they work better when cold- a short autocross cource you rarely get the heat in the semi metallics.

[Ron Sutton]

Hi Skip & Woody,

I design a lot of brake systems for race cars. Inputting the CF # into the formula is key to designing an optimum braking system for an application. Most brake pads do not have the same CF # "across the board". They look more like a dyno curve. To be accurate, you need to use the CF # from the expected or experienced operating temperature for that specific application.

If I know the front brakes are going to operate in a real world temperature range of 500-700 degrees, then I input the CF # from the middle .. 600 degrees. The rear brakes are going to operate at lower temps. If I know they're going to operate at 150 degree less, then I'm using the CF # at 450 degrees.

Please don't lock in on these numbers or use them as a baseline. This was just a real race car example. These temps vary with driving style, car weight, type of racing, etc, etc. At the track, we ALWAYS use an infrared temp gun to shoot the brake rotor temps immediately after a run to know what we're working with.

Most of our "high end, cost is not an object" racers ... run Performance Friction pads or Brembos. Most of my "mid-budget" racers ... and some high end racers ... run Wilwood. (This is our biggest group) And most of our "budget conscious" racers run Hawk pads. In our own race cars, we have had good success with Hawk pads & Wilwood pads ... and have not seen a measurable advantage with PF pads. We have however seen incredible braking out of the Brembo brakes in multiple applications. The cost is simply out of reach for most racers.

Unfortunately, Hawk does not offer "Pad Compound Graphs". They make good brake pads, but somewhere up the chain of command, they decided not to release these graphs to racers or dealers. (My race shop offers 10 brands: AP, Baer, Brembo, CPP, Hawk, Howe, Performance Friction, Red Devil, SSBC, US Brake & Wilwood)

So ... the only way to see if Hawk pads meet your needs ... or more accurately, "Which Hawk pads" fit your needs is to test them. For racers that are at the track 20+ times a year, going through several sets of pads, this isn't difficult. For most Pro Touring guys & gals who "occasionally go to the track" this isn't practical. When you go to the track, you need to focus on learning the track, finding the limits of your car, tuning the suspension, etc. Sorting out the brakes on a RARE track day is not a good use of your time.

Again, I am a fan of Hawk brake pads. Specifically the Black pads & Blue MT-4's for competition. But the only way to work out a combination with Hawk pads is testing.

On the other hand, Wilwood brakes makes their "Pad Compound Graphs" available to everyone. You can review them in their catalog or online. From these graphs, along with their "Pad Compound Selection Guide", You can choose pads that should work optimally for your application the first time. For this reason, for most Pro Touring guys & gals that only see occasional track days & don't want to spend those days struggling with improper brakes, I recommend Wilwood pads.

In their brake pad catalog, you can study the "Pad Compound Selection Guide" on pages 4 & 5 ... and the "Pad Compound Graphs" on page 6.
Here is the link: http://wilwood.com/Pdf/Catalogs/BrakePadCatalog.pdf

[Skip Fix]

I agree testing is probably the only real way to tell what pads perform for your likes. And I would also bet most of us would have a hard time even looking at the graphs what pads still fits their needs of stopping the car,feel, and wear of pad and rotors.

[Ron Sutton]

When you get some experience with the pads ... and you're clear on the goals for your application ... using the pad compound graphs help a lot to pick the right pads. When you're on page 6, look at the BP-20 pad graph. At 100 degrees (first brake application in turn 1 of an autocross) it has a .37 CF# ... then goes up to .53 CF# at 900 degrees. This is not a good autocross pad.

Look at the BP-10 & E compounds with flatter graphs, higher initial bite, then flatter curves. (BP-10 range from .40 to .45 & the E pad goes from .40 to .47) These are better Autocross pads. Look in the 400-500 degree range & it's clear, of the two, the BP-10 is on the low end of brake clamping force with .42-.43 CF# ... and the E compound is .46-.47 in the same range ... meaning the E pad offers much more braking force.

Don't let these small CF#'s fool you, the difference between those 2 pads is 10% in braking force. To compare that, changing from 12" rotors to 13" rotors is an 11% difference in braking force. In other words a car with 13" rotors & the BP-10 pad would have only 1% better braking than if the same car had 12" rotors & the E pad.

Many Autocross winners run the E pad. Some want a more aggressive pad, and run either the J, H or B pad. (The A, BP-30 & C pads have too much of a warm up to be an optimum Autocross brake pad. They are much better at long runs like oval track & road racing.) In the same 400-500 degree temp range, the J has a CF# of .56-.57 . the H has a CF# of .60-.61 ... and the B CF# is .56-.59.

We have raced with the H pad a lot, on lightweight race cars, and it is a great pad when you have a driver that goes in deeper than everyone else & outbrakes them on corner entry. Too aggressive for the street & too much wear. The BP-30 is similar, but experiences higher degrees of brake fade when the brakes get real hot ... and has too much CF change in the lower temps to be the best autocross pad. (but it costs less)

The J pad is a bad-to-the-bone Autocross brake pad, but crazy expensive, with selected availability based on the caliper you're running. (Not available for the D52 Caliper - only available for certain Brembo, AP & Wilwood IR-GT calipers) Awesome brake force, but real predictable, with a flatter brake torque curve than most pads. (Too expensive & too much wear for the street.)

The BP-10 is the most economical of the Wilwood performance brake pads. A good choice for most street cars, and has slightly more brake force than the Hawk HP Plus pads ... No CF#s to go off of, but our testing indicates .39-.41 in the 400-500 degree range ... and significantly more brake force than stock replacement pads.

A better "overall" brake pad for Autocross, is the E Pad. Mid-level pricing, good wear, predictable braking & aggressive braking for a street car being autocrossed. For many Pro Touring cars, this pad could be the just the ticket to increasing braking force for autocrossing ... instead of putting bigger rotors on. (*I'm not recommending the E pad for the front of cars that are street driven or driven on big tracks, as the brakes will fade & fail if ran above 600 degrees for extended periods of time.)

Hope this helps. Happy motoring.

[Ron Sutton]

Another note ... in testing & racing we found the Hawk Black to perform very similar to the Wilwood BP-30. Both are good budget brake pads for oval track & road course racing with a CF# at .58 in the 500 degree range.

[Skip Fix]

I think what you mentioned is something many folks here don't think of-yes their pad might be good rating for a track day-but at the autocross that first stop or two is rough! You have to decide what you are really doing with the car-how many hard track days vs street and autocross.

Back before there were as many choices many autocross folks pulled out those semi metallics and put organics back in.

[woody80z28]

Thanks, Ron. According to your description and the PDF provided, the BP-10 sounds like it would be best. I am running manual brakes and the Hawk HPS just do not have good pedal feel or stopping power on the street. And there is no way I would feel comfortable with them on a road course to test.

[Ron Sutton]

Woody,

If you change from the Hawk HP Plus pads to the Wilwood BP-10 Pads ... that may not solve your issue ... as the CF difference is small. If you need substantial more braking from a pad change, I'd suggest the E pads. But I would also look at other factors in your braking system first.

Not having "good pedal feel" is usually not a pad issue, but a pressure issue. Meaning you could be experiencing air in the lines, a failing master cylinder, Brake calipers with pistons way too small or a master cylinder with a piston(s) simply too big (which lowers brake line pressure).

I would seriously look into these areas & not just change pads. Braking is obviously important to safety (yours & everyone on the road around you) and performance.

If I were in your shoes, my questions would be:
1. Does the pedal feel spongy at first ... then get stiffer as you pump it up and/or use the brakes?
(Clear sign of air in the system)

2. Does the pedal feel spongy always?
(Could be air in lines, could have a miniscule air leak, could be a failing M/C ... or a combination of small pistons in the calipers & big piston(s) in the M/C.)

3. Is the pedal always firm/hard ... but it just doesn't stop well?
(Means the Coefficient of Friction (CF#) is weak/low "somewhere". Could be rotors glazed and/or brake pads glazed/burnt ... or simply too hard of a pad. This is the time to simply step up in brake pad CF ... like to the E-pad in your case.)

4. Are the brakes "good" initially ... then get worse (fade) with use?
(overheating the pads, rotor and/or brake fluid)

Don't be afraid to ask questions as you look into your car's brakes.

[sccacuda]

Good info Ron. I have a question though. Looking at the charts, it seems that the BP-30, A, and B pads would be a better street/autocross/road course pad. They all have better low temp CF than the E and much better high temp. Seems these would make the better autocross/road course/street pad because of the good temperature extremes/CF.

What am I missing?!

[Ron Sutton]

Hi Craig,

No worries. You may have it backwards in your mind. In long run racing (oval & road course) ... usually with warm up lap(s) ... the driver can get heat in the brakes (rotors & pads) and get them up to a decent temp before actually needing them (turn 1 green flag).

In Autocross ... after the car has been sitting in between runs (the brakes are cool) ... and you start the run from a standing start ... the brakes are not warmed up going into turn 1 (and barely by the 2nd turn).

You need the brakes to work "pretty good" right from the get go ... and not change so much over the course of the short autocross run as heat rises in the brakes. BP-30, A ... and BP-20 & C compounds ... have too much CF# change from 100 to 500 degrees to be optimum for Autocross. The B pads don't change too much from 100-500 degrees (.49-.55) ... but continue to change all the way to 900 degrees (where it is .63). As long as the driver keeps the brake temps within the 100-500 degree window, the B pad will work fine in Autocross.

Any pad can be "made to work" ... just know the braking force is going to change as the brakes heat up during the run. The driver could compensate for pads that change a lot from 100-500 degrees, but would need to change their braking pressure & braking duration dramatically over the course of the run. That's not ideal for the front end handling.

When racers work out a front end geometry & suspension set up ... how far the front end travels in "dive" ... and how long it stays down in dive entering & rolling through the corner ... plays a HUGE role in the optimum front end geometry & suspension setup. If the driver has to brake softer part way through the run ... that's affecting (reducing) the car's suspension travel into dive mode. That changes roll center, camber, load on the front tires, etc, etc.

If the driver has to change the duration of braking ... because the pads are gripping way more & slowing the car down too much ... that is affecting when the front end is going to come back up.

Racing shocks are like timing devices. The rebound valving (and specifically the bleed valving) in the front shocks is going to hold the front end down for a short & precise amount of time after the driver steps off the brakes. (How long is determined by a combination of spring rate & shock bleed valving.) Then the front end is going to ... slowly or quickly, depending on the rebound valving ... come up, allowing the car to transfer weight front to rear for better forward bite (corner exit traction). If the driver needs to get off the brakes earlier (so they don't kill their corner speed) then the front end will "pop up" at an earlier point in the corner. When the weight comes off the front tires, they will reduce grip & the car will then push/understeer through the middle of the corner.

It is hard enough for racers to dial in the optimum front end geometry & suspension setup with brakes that are consistent. Having brakes that change dramatically during a run makes that goal monumentally harder. BP-10, E & J are all brake pads that have "flatter curves" for more predictable & consistent braking in autocross competition. Make sense ?


P.S. BP-30, A, and B pads (and C Pads) do work great as road course brake pads. The wear rate (and cost) may be too much for street driving, unless you're ok changing them often.

[woody80z28]

Woody,

If you change from the Hawk HP Plus pads to the Wilwood BP-10 Pads ... that may not solve your issue ... as the CF difference is small. If you need substantial more braking from a pad change, I'd suggest the E pads. But I would also look at other factors in your braking system first.

Not having "good pedal feel" is usually not a pad issue, but a pressure issue. Meaning you could be experiencing air in the lines, a failing master cylinder, Brake calipers with pistons way too small or a master cylinder with a piston(s) simply too big (which lowers brake line pressure).

I would seriously look into these areas & not just change pads. Braking is obviously important to safety (yours & everyone on the road around you) and performance.

If I were in your shoes, my questions would be:
1. Does the pedal feel spongy at first ... then get stiffer as you pump it up and/or use the brakes?
(Clear sign of air in the system)

2. Does the pedal feel spongy always?
(Could be air in lines, could have a miniscule air leak, could be a failing M/C ... or a combination of small pistons in the calipers & big piston(s) in the M/C.)

3. Is the pedal always firm/hard ... but it just doesn't stop well?
(Means the Coefficient of Friction (CF#) is weak/low "somewhere". Could be rotors glazed and/or brake pads glazed/burnt ... or simply too hard of a pad. This is the time to simply step up in brake pad CF ... like to the E-pad in your case.)

4. Are the brakes "good" initially ... then get worse (fade) with use?
(overheating the pads, rotor and/or brake fluid)

Don't be afraid to ask questions as you look into your car's brakes.

Thanks, Ron. I'll explain my situation and perhaps a fresh set of eyes will help. I've gone over a LOT of possible issues with Tobin and everything we have come up with checks out.

Master is 1" bore with 2.38 single piston front calipers and 1.87 single piston rears. 12" rotor front, 11.6 rear. Hawk HPS pads, not HP+. 6:1 pedal ratio.

Pedal is always spongy. And the bite just is not there, even with heavy pressure it won't lock the wheels unless you are 5mph.

Tobin's first thought was air. System has been bled and bled and bled. Bought a pressure gauge and there is no difference in PSI between one step on the pedal and pumping it (1100psi). In theory, this should mean there is no air in the system.

Checked pads for glazing. Looked possible, so I scuffed the pad surface and rotor surface and re-bed them just as Hawk recommended. No change. Tried to find friction numbers online and stumbled across some threads complaining about the HPS pads:
http://forum.e46fanatics.com/showthread.php?t=192931
http://www.audizine.com/forum/showthread.php/413738-Hawk-HPS-pads-are-crap!!!
http://forums.tdiclub.com/showthread.php?t=254999
The mushy pedal and low "initial bite" is exactly what I'm feeling. It's like they took the words right out of my mouth. Except even getting on them hard it still doesn't stop well. I think this may be due to my manual brakes line pressure (1100psi) vs boosted which would probably be more. The pads would make sense as the issue, because they are one of very few constants in this system. I've tried a few different master cylinders and even different front calipers. I thought about throwing some cheap Napa pads on it just to test and see, but I'd rather go with good ones from the start.

[Ron Sutton]

Woody ... OMG! Dude ... you don't have any brakes !

I knew the instant when I saw those ridiculously small caliper piston sizes. But I ran the calcs anyway. With 100# of input at the pedal (from your leg) … with the HPS pads … you have a braking force of:

Total 1714#
Front 1076# 62.8%
Rear 638# 38.2%
* Not quite enough front brake percentage, IMO. Ideally, you need in between 65/35 & 70/30.

That would be "ok" if your car weighed 2200 pounds. If this is for your Camaro, I'm guessing it weighs 3400-3800 pounds. OMG, that's not enough for safety, let alone performance. I'm assuming you have to practically stand on the brakes to get her whoa'ed down (that’s a technical term).

Your Master cylinder, brake pressure, pedal ratio, etc, are all good. No booster is necessary. The issue is you simply have WAY too small piston size in the calipers. You have options that will get the job done at various price points.

-------------------------------------------------------------

Least expensive / Combination #1: Utilizing "Stock Type GM cast iron” calipers.

Front: Large GM Caliper with single 2 15/16" piston (OEM, OEM Replacement or Howe Racing Products Part # 3370) About $75 each

Rear: Metric GM Caliper Single 2” piston (Wilwood is only source with 2” piston part # 120-9333) About $80 each

This combo, with the HPS pads, will provide you with braking force of:
Total 2369#
Front 1639# 69.2%
Rear 730# 30.8% * Good baseline of front to rear balance
This is a gain of 38% for about $310 plus tax & freight

If you stepped up to Wilwood BP-10 Pads front & rear (about $55 per set/$110 for both ends of the car), your braking force would be:
Total 2681#
Front 1855# 69.2%
Rear 826# 30.8%
This is a gain of 56% for about $420 plus tax & freight

Of course, if you go with bigger rotors … or up on CF# on the pads, such as with the “E” compound, the braking force will increase from these #s.

-------------------------------------------------------------

Medium expense / Combination #2: Utilizing Wilwood Aluminum billet, direct replacement calipers for D52 & D154. (They come standard powder coated red or black for around $178 each)

Front: Wilwood Large Dual Piston, aluminum caliper, with two 2" pistons

Rear: Wilwood Metric Dual Piston, aluminum caliper, with two 1.625" pistons

This combo, with the E pads in front ($95) & BP-10 ($55) in the rear, will provide you with braking force of:
Total 2894#
Front 1880# 65.0%
Rear 1014# 35.0% * Good baseline of front to rear balance

This is a gain of 69% for about $862 plus tax & freight

*** 3 Big advantages here are:
a. Aluminum caliper for heat dissipation
b. Dual pistons make pads run flatter.
c. Powder coated pistons add cool factor.

Of course, if you go with bigger rotors the braking force will increase from these #s. Going up to 13” from 12” will add about 11.5% in braking force.

-------------------------------------------------------------

I’m sure there are many, many other options & if your budget is unlimited, you can step up Wilwood’s 6P & 4P combo’s with big rotors, but the gains will be small from here.

[woody80z28]

That's a POV I haven't heard before. I started with the stock D52 2-15/16 calipers and I went to 2-3/8 Wilwood GMIIIs up front to decrease pedal travel because I was almost at the floor. Braking was poor before & after the change, but pedal got better. In rear I have a 2000 Blazer setup that is not compatible with the "metric" setup. Both are aluminum.

And if my math is right I actually have more piston area than a C5 setup. 4.44 vs 3.98 front, 2.74 vs 2.46 rear. My rotors do have a little less leverage compared to C5, but not horrible: 12.0/11.6 vs 12.8/12.0. Car is down to 3300lbs...not too far from a C5.

[Ron Sutton]

Speaking of different POV's ... I haven't heard of someone picking a brake system to decrease pedal travel. Most racers don't want the pedal travel too short, or it will act like an "on/off" switch, which wouldn't be good for street driving or racing. Most veteran race drivers want to be able to have a "fine control" over the brakes & therefore desire 4-6" of brake pedal travel (at the top of the pedal).

If your pedal traveled too far before (to the floor) ... it is most likely you had a failing, worn out master cylinder and/or worn out pads ... and maybe a little air in the system.

I'm going to stand by my recommendation that what you have now, will not produce enough brake force without changing things ... either smaller M/C piston, bigger caliper pistons, more aggressive pads, bigger rotors ... or some combination. You simply have too little braking force for a 3300 pound performance car.

Best wishes !!

[Skip Fix]

Heck to rule out pad issues get some cheap organics that take no heat to grab-yea they may fade on multiple hard stops but a cheap trial. But probably is going to be a piston size issue.

Even the Malibus etc that used the metric D154 pads used a 2.5 piston.

[woody80z28]

No air could be found in the system, so smaller caliper pistons or a larger master piston would be the only way to get the pedal off the floor. From what those threads say, the Hawk pads must actually be compressible and attribute to the soft pedal feel. And being a manual brake setup magnifies the issue. But with more piston area and comparable leverage and overall vehicle weight, my setup shouldn't behave much differently than a C5 manual brake system.

Pads I think are the next thing to try. Then I can get my own experience on the issue rather than internet posts.

[Ron Sutton]

Woody,

Before you redid your brake system ... and the pedal was going almost to the floor ... was that with an older, used master cylinder? Also, is the master cylinder in the car now ... new or used?

I ask, because as a master cylinder wears over time, it produces less pressure, even though there is no leak. The brake fluid is getting past the M/C piston seals, back into the reservoir. This is when & why many people replace worn out M/C's.

[woody80z28]

Woody,

Before you redid your brake system ... and the pedal was going almost to the floor ... was that with an older, used master cylinder? Also, is the master cylinder in the car now ... new or used?

I ask, because as a master cylinder wears over time, it produces less pressure, even though there is no leak. The brake fluid is getting past the M/C piston seals, back into the reservoir. This is when & why many people replace worn out M/C's.

The old master cylinder with stock brakes was fine - pedal and stopping power.

During my brake "upgrade" I changed the stock 11" front rotors to 12" 1LE and changed the drums to 11.6" Blazer disc with a brand new 79 Vette 1.125 disc/disc MC with HPS pads and it felt soft and the stopping power was reduced. Chased my tail to remove air with no results. Converted to manual brakes with a brand new 70 Vette 1" MC and all braided hoses and the pedal was still soft and the travel was almost on the floor. Swapped the stock D52 front calipers for 2.38 Wilwood GMIIIs and it was still soft, but it reduced travel. Tried re-bedding the pads...no change. Tried a used aluminum Mopar MC with no change. That's where I'm at now.

I know it still sounds like air in the system, but I have bled and bled and bled and even had two different shops bleed it with the same results: no air. And my brake pressure gauge does not read any higher when pumping the brakes than a single step. MC's pass the lock test with the ports plugged. When my car comes out of storage I plan on trying new pads as an easy test. Many people on those Bimmer & Audi forums have complained about pedal feel with the HPS pads and at this point I'm willing to try it. If that fixes the problem I will be overjoyed to chuck them in the dumpster, and at the same time I'll be annoyed they were the cause of all this aggravation...haha I never would have suspected my new "High Performance Street" pads would have been the cause of my brake issues, but I'll be happy regardless if I get it sorted out.

[Ron Sutton]

Good, detailed info Woody. That helps a little to see where the problem is not, by process of elimination.

I think trying to compare your car & brakes to the C5 is misleading. Your car originally had Large GM calipers with 2 15/16" front pistons & a 15/16" M/C with 11" rotors and stopped good. (you also the help of a power booster)

If we use the same CF# we have using for HPS pads, we come up with front braking torque number of 1679#.

Remember earlier in this thread, I posted the calculated brake torque #s for your current brake set up to be:
Total 1714#
Front 1076# 62.8%
Rear 638# 38.2%

When you went from Large GM calipers with 2 15/16" front pistons & a 15/16" M/C with 11" rotors ... to the Wilwood calipers with 2.375" pistons & a 1" M/C bore with 12" rotors ... you reduced the braking torque from 1679# to 1076#. That is a 36% decrease in braking torque (assuming same pads) in the front of the car, where the majority of braking is. That's a huge reduction.

The best solution would be to install brake calipers with larger pistons and/or a master cylinder with slightly smaller bore. Then you could still run a longer wearing street type brake pad and have great performing brakes.

If you you don't want to replace the Calipers and/or M/C ... and want to fix it with a pad compound change only ... you'll need to step up to a pad compound with a CF# around .54 to .57. These are racing brake pads. They will cost more & wear quicker. Wilwood B or BP-30 compounds would achieve this. Also the Hawk Black compound would too.

Happy testing !

[woody80z28]

Thanks for the continued interest in the topic, Ron. I've been fighting to get to the bottom of this for a couple years! Originally I hadn't even considered larger calipers...and I'm still a little sketchy on that due to my mushy pedal. The pedal is not on the floor now, but with bigger piston calipers it might be. It'd would be nice to borrow a pair of D52s for the front to try. (Mine ended up on my dad's 63 Impala and that car has since been sold.)

Here are a couple of things that make me doubt that changing the calipers would remedy the problem, though. The stock master was 1.125, same bore as the Corvette disc/disc unit I installed. And even with the stock booster, stock bore size master cylinder, stock front calipers, and 1" larger front rotors...the pedal was still soft and braking power was reduced. It was after this that I converted to manual brakes with a smaller bore master cylinder. So the only real changes from adequate stock brakes to poor "upgraded" brakes was the larger front rotor, Hawk pads and rear disc conversion.

When I finally do get the situation sorted out I will post back with the cause and remedy.

[Ron Sutton]

Ok. Best wishes !

[sccacuda]

Thanks Ron. You are a brake knowledge guru!

Would you mind if I ran my brake setup by you and see if you agree with what I have?

[Ron Sutton]

Hi Craig,

Thanks for the kudos. I'm not necessarily a "brake guy" ... but more a complete race car designer/builder with years of experience at winning races. I wouldn't mind helping you at all. Please include the following info for the front & rear brakes ...

1. Caliper model, with # & diameter of pistons per caliper
2. Bore/piston size in master cylinder
3. Rotor diameter (true #, not advertised) * Most 12" rotors are 11.75 or 11.875. Most 13" are 12.88"
4. Brake pad you have planned to use

This will give us a place to start out conversation.
** Knowing the pedal ratio is important in completely custom built applications. But if you are swapping brakes in a car & keeping the same pedal, we can just use a constant #.

[sccacuda]

Hi Craig,

Thanks for the kudos. I'm not necessarily a "brake guy" ... but more a complete race car designer/builder with years of experience at winning races. I wouldn't mind helping you at all. Please include the following info for the front & rear brakes ...

1. Caliper model, with # & diameter of pistons per caliper
2. Bore/piston size in master cylinder
3. Rotor diameter (true #, not advertised) * Most 12" rotors are 11.75 or 11.875. Most 13" are 12.88"
4. Brake pad you have planned to use

This will give us a place to start out conversation.
** Knowing the pedal ratio is important in completely custom built applications. But if you are swapping brakes in a car & keeping the same pedal, we can just use a constant #.

Thanks Ron,

I'm using Wilwood SL6 calipers in the front. 4.04 piston area w/ 1.62, 1.12, and 1.12. The rotors are a true 14". SL4 in rear. 1.96 piston area w/ dual 1.12. The rotors are a true 13". I'm using a Wilwood pedal assy with a 6.25:1 w/ no assist. My M/C are 3/4", 13/16", and 7/8" for clutch and MC. I wanted to see what bore you thought would be appropriate for what (and to see how far i'm off!). I'm looking at A, B, or BP-30 pads.

[Ron Sutton]

Nice Craig ! This hot rod is going to have a lot of braking. Here are the #'s

If you use the BP-30 pads (more on pads later) and put the 7/8" M/C on front & the 13/16" M/C on the rear:

Total 3566#
Front 2347# 65.8%
Rear 1219# 34.2%

That's looking sweet for a baseline. Most stock street car brake systems have 2200-2800# braking force. You are at 3566#, now into race brake system territory (3000-5500#). This layout of M/C sizes provides you with a good baseline ... near 65/35 brake balance front to rear. (use the 3/4" M/C for your clutch.)

Now that you have a good baseline, you will want to work out some other factors. For this, I need to know total car weight (estimate) & front to rear weight balance (estimate) ... tire type & sizes front & rear ... and the driving environments you plan for this car. Then we'll dial it in better.

While I'm waiting on your response, I'm going to add some posts for "Reference Material" to be used later in our conversation.

[Ron Sutton]

Reference Post #1

Craig, let's talk brake pads, so you have a better feel of how critical a role this plays on the braking force.

We use the "A" pad a lot in racing. I have racers that "love" the A pad in oval & road racing, and I have racers that feel it is too "mean" (too aggressive) in their race car. It has a steep ramp up ... and down. It changes too much from cold to be an optimum Autocross pad. It has a narrow "sweet spot" it needs to run in for optimum braking, then LOSES braking force if over heated. Not a good pad for an inexperienced race driver. I feel most people would not enjoy it as a street pad ... especially the high wear rate & cost.

The "B" pad is the most common race pad Wilwood sells. It has a safe feeling, because it brakes better all the way up to 700 degrees ... then stays pretty consistent to 1050 degrees ... then fades slightly. (Boiling the brake fluid will be the bigger problem if the car continues to see those temps in the run/race.) I recommend the B pad for most rookie racers in oval & road racing, until they get enough experience & skills to know if they want something different. For Autocross, if the driver wasn't getting the brakes hotter than 500 degrees on a run ... the "B" pad would be "ok". From 100 degrees to 500 degrees, it changes from CF# of .49 to .55. This is a good multi-purpose brake pad for autocross & track days. It would make a good "street fighter" pad, but wear & cost are kind of high.

The BP-30 pad has similar characteristics to the "B" Pad, but with higher initial "bite" when the rotors are cold ... then a steeper ramp ... going from .52 to .62 at 500 degrees. That is not the characteristics we want in an Autocross pad. This pad compound does provide a lot of confidence for rookie race drivers because, even when cold, the brakes grab "right now" & just gets better as the driver stays on them ... and then flattens out. Braking force trails off when the driver over uses & over heats them, but it is gradual. This is a good race pad for rookie race drivers on road courses and even a good "mean" street pad. Cost is lower than then the B pad.

[gsxrken]

Ron, great insights on this thread. I run Wilwood SL6 on 13" and Wilwood 4 piston rears on 12" rears with Hyrdoboost. I landed on the E pads myself for my 3100lb Mustang on the street and autocross after some trial error. However, they didn't hold up on a track day at NJMP... Fronts overheated and left deposits on my rotors that created an impressive pedal chatter from "warped rotors". I don't have cooling ducts yet.
I should mention that a set of A compound pads driven around on the street cleaned up the deposits and the brakes don't pulsate anymore. I now run the A in the front and E in back for track days, and E all around for street.
My only complaint with the brakes is no travel. Hydratech booster requires big toe only braking or they're locked up.

[Ron Sutton]

Reference Post #2

Craig, I misspoke earlier. The original #'s I gave you were with the "B PADS" ... Not the BP-30 Pads.

Now, let's play with some #s utilizing different brake pads & you can see your system with different pads. Don't jump to any conclusions yet ... because there is more to consider than just brake torque numbers.

Here is your baseline with B pads, operating at 500 degrees. Let's use the 500 degree temp throughout our comparisons.

Total 3566#
Front 2347# 65.8%
Rear 1219# 34.2%


Here it is with BP-30 Pads

Total 3948#
Front 2598# 65.8%
Rear 1350# 34.2%


Here it is with A Pads

Total 4330#
Front 2849# 65.8%
Rear 1481# 34.2%


Ok, now lets go the other way on pad selection ...


Here it is with E Pads

Total 2993#
Front 1969# 65.8%
Rear 1023# 34.2%


Here it is with BP-10 Pads

Total 2674#
Front 1760# 65.8%
Rear 914# 34.2%


Here it is with Hawk HPS Pads

Total 2420#
Front 1592# 65.8%
Rear 827# 34.2%

What most people learn from this exercise, is that brake pads play a bigger role than they thought. In many situations (many ... not all) A brake compound change, can be a bigger change to the car's braking force than going to a bigger rotor or different calipers.

I urge you not to get lost by just looking at static CF#'s. That's like looking at cam lift numbers. Two cams can have the same maximum lift, yet have very different characteristics in the engine. Same with picking brake pads. You will want to look at the whole big picture, to get the optimum performance. (With cams, brake pads & most other performance items.)

[Ron Sutton]

Hi Ken ...

Thanks for chiming in. As a race car designer & builder, I don't have any experience with boosted brakes, hydroboost or otherwise. That may be why your brake pedal is an on/off switch. It may not be too. I simply don't know.

You didn't list your pedal ratio or master cylinder sizes, which all play a role. But I am absolutely sure that having the brakes act "on or off" ... with very little pressure control ... is not optimum for performance driving.

If running autocross and/or track days were a one time thing ... you may not care. If you plan on continuing, or increasing your participation, in performance competition events, I would address it for sure. Having more precise brake control will make you a better driver, you'll perform better, be safer & have more fun.

As far as the E pad goes, it is a GOOD Autocross pad. I would NOT run it on ANY track events longer than 1 lap. Because as this pad heats up past 600 degrees, braking force goes away. That is when the pad is getting eaten up. When you ran that track day at NJMP, the brakes were probably fine for the first lap (maybe). But as they heated up ... you "probably" had to apply more pressure to "whoa the car down" on corner entries ... and that shot the temperatures even higher, making the pads fail.

Go look at the brake graph on page 6 of the Wilwood brake pad catalog here:
http://wilwood.com/Pdf/Catalogs/BrakePadCatalog.pdf

Pay special attention to when a brake pad compound CF graph GOES DOWN as brake temps rise. That is when the pad is being used outside it's "Happy Window" and all kinds of bad stuff happens ... pads fail, rotors glaze up, brakes fade, etc. etc. You usually find out what it costs to repair crashed cars at that point. :-(

Look at the graph ... the E pads falls off rapidly past 600 degrees. Which means ... don't use this pad in applications above 600 degrees. Autocross ... if the car handles well ... should not see above 600, so it is a good Autocross pad. But a "scary" pad for oval or road course racing, where on long runs the possibility of temps getting above 600 is there in the rear ... and more than possible ... it is probable in the front.

I, personally, wouldn't run the E pad "long term" on the street ... maybe in the rear ... maybe. I would have a set of E pads that I put on the car for Autocross events ... drive to the event ... run them ... and take them off when you get home & put your street pads back in.

Let me know if you need any help.

[sccacuda]

Nice Craig ! This hot rod is going to have a lot of braking. Here are the #'s

If you use the BP-30 pads (more on pads later) and put the 7/8" M/C on front & the 13/16" M/C on the rear:

Total 3566#
Front 2347# 65.8%
Rear 1219# 34.2%

That's looking sweet for a baseline. Most stock street car brake systems have 2200-2800# braking force. You are at 3566#, now into race brake system territory (3000-5500#). This layout of M/C sizes provides you with a good baseline ... near 65/35 brake balance front to rear. (use the 3/4" M/C for your clutch.)

Now that you have a good baseline, you will want to work out some other factors. For this, I need to know total car weight (estimate) & front to rear weight balance (estimate) ... tire type & sizes front & rear ... and the driving environments you plan for this car. Then we'll dial it in better.

While I'm waiting on your response, I'm going to add some posts for "Reference Material" to be used later in our conversation.

Thanks Ron,

Seriously appreciate you looking over my shoulder on this setup.

Weight. It's a pig. 3650 guesstimate. Balance is all wrong as well. Probably 60/40, but I have lots of nose weight (turbos, a/c, intercoolers and assorted heat exchangers). I built this car as a compromise. Never going to be a good auto crosser, but a street/trackday/land speed car.

Tires are 295 rear and 275 front Falken Azenis on 18" rims. 200 tread wear.

[Ron Sutton]

Reference Post #3

Craig, let's talk brake bias. When you run this car at track, optimum lap times will only be achieved with optimum braking. In racing, many factors come into play with brakes. Consistency, warm up, fade, along with total braking force and brake bias (front vs rear). For this portion of the conversation, let's talk brake bias.

First, let's define optimum brake bias. It is when the driver can brake hard into the corner ... and I mean HARD, threshold braking ... without one end of the car locking up the tires prematurely. If the front tires lock up under threshold ... the car will push/understeer on corner entry. If the rear tires lock up under threshold ... the car will be loose/oversteer on corner entry. Neither is optimum for car control or lap times.

* You know the difference between push & loose ... right? Push is when you hit the barrier with the front end. Loose is when you hit the barrier with the rear end. :-)

Ultimately, you will want to get the brakes balanced front to rear ... meaning that neither end locks up the tires ... or, if you have too much total brake force ... the brakes lock up at the same time, putting the car into a 4-wheel drift. (More on total brake force later).

People can tell you that you absolutely need XX% front & xx% rear ... but no one really knows what a car needs "exactly" unless they have ran that car that day. There are too many factors that determine the correct front/rear percentage for that car. Heck, it even varies throughout the day as the track changes ... or if you make suspension tuning changes.

Softer front springs, softer compression valving on the front shocks or softer rebound valving on the rear shocks (amongst other tuning changes) all make the car transfer more weight onto the front tires under braking ... giving the front tires more grip ... and the rear tires less grip ... requiring a slight adjustment to the front/rear brake bias. (There are many, many more tuning situations that affect tire grip. Anything that affects tire grip, affect braking capabilities.)

THANK GOODNESS ... you have the Wilwood pedal assembly that is adjustable for bias. :-) It won't change your total braking force, like proportioning valves do. It will allow you to easily & quickly adjust the brake bias either direction. It has a lot of range, so as long as you start in the middle, and have both master cylinder rods even, you'll have a lot of adjustability. You can do it by hand, right at the bias bar, or you can add a cable with a knob, and do it by hand from just about anywhere in the cockpit, including the drivers seat, which is how most race cars are set up.

I suggest the cable, in a spot easily reachable from the driver's seat. After you have run enough corners to get comfortable ... and start to brake harder ... when you find one of the car's brakes locking up ... simply dial brake bias away from that end. Do this on straights ... when you have time. This is also why I suggest putting the brake bias knob in a comfortable spot, that you can put your hand on easily, without even looking.

Continue sneaking up on the braking force into corners ... and continue to adjust the bias on straights until the car is "happy" ... with neither end of the car locking up, under hard, threshold braking. Not only does this make the car produce quicker lap times, but it also inspires confidence in the driver.

As the day goes on, and track conditions change, you will notice the brake bias needs to be adjusted slightly to be optimum for the track conditions. Again, if you make a suspension tuning change, the brake bias may need to be adjusted to stay optimum.

Somewhere in the 65/35 to 70/30 front/rear brake bias is a good starting point. But you'll need to tune from there. If you find, and many racers do when building a new car or new set-up, that you run out of bias adjustment and still need more bias correction, this can be handled easily with a master cylinder change. It is relatively low cost & VERY predictable.

Bias can also be corrected with a caliper change (more expensive) and by mixing pads front & rear. I have done it all of these ways, in different situations.

Mixing pads requires a thorough knowledge of pad compound characteristics. If all pads were linear in their friction gain ... this would be easier. But they are not. Each brake pad has its own unique "curve" ... just look at the compound graph ... so mixing the pads causes the front & rear brakes to behave differently. Throw in the fact the rear brakes should be operating at cooler temps than the front brakes ... and you have a complex scenario.

Mixing brake pads can be done ... and has been done successfully for years. But it requires knowledge, experience and/or testing. I don't recommend it for racing rookies or anyone if they don't have much time at the track to test & sort out a combination. (Unless you have a veteran racer/brake guy advising you). Pick your path.

[Ron Sutton]

Hi Craig, just got your info ....

3650# is a typical heavy street car. It will need more than normal braking force to be optimum, and I'd say you have a good start with the system you laid out.

The 60/40 balance is going to hurt it for Autocross & hinder it for road racing track days too ... but it can still be made into a decent handling performer. Let's make sure you get the brakes dialed in, so you're not chasing brake issues at the track & have time to focus on tuning your suspension set-up at the track.

The Falken Azenis (200 tread wear) is a good tire. Running 295 rear and 275 fronts will compound the problem of your 60/40 weight balance. Remember, heavier cars need more tire. Heavier ends of the car, can benefit from more tire too. Running smaller tires on the heavy end = not optimum. If you have ANY WAY to run bigger tires in the front, to match the rear, I would.

A key theory to understand in handling is = force applied to tires creates grip. Tires with softer or better compounds, or more contact patch, that provide increased adhesion ... increase grip. After you have selected the tires ... it's now up to the suspension setup (and aerodynamic aids if they are on the car) to determine the actual force put on each tire during transition stages (braking, turning & acceleration). Actual weight, weight transfer & aerodynamic lift and/or downforce all play a role in determining the total force on each tire. Steady state, straight line driving is less complex than what happens … and what needs to happen for optimum handling … during the transition stages of braking, turning & acceleration.

This next part gets a little complex.

You need weight on the tires. With no weight, there is no grip. More weight (whether actual weight, weight transfer or down force) provides more grip from that tire. Engineers use the term “force” instead of weight, which is correct. It doesn’t matter which term you & I use, as long as we both understand each other.

For sake of simplifying this conversation, let’s take aerodynamics out … and that leaves us focusing on weight (actual) & weight transfer … which added together creates the force #.

On corner entry … too little weight transfer to the front tires will cause them to break traction, making the car push/understeer. Too much weight transfer will cause the rear tires to lose grip, making the car loose/oversteer on corner entry.

As a Racer, Tuner, Race Engineer or Crew Chief (just titles) the goal is to utilize the tunable parts of the race car’s suspension to control the amount of weight transfer … to achieve the maximum amount of force on the front tires for optimum turn in … without transferring too much from the rear tires … as to create a loose condition.

Follow me closely here, because this is where you get a curve ball. The more weight (force) applied to the front tires … the more grip the front tires will have … and therefore the car’s turning ability will be improved ... up to a point.

As a car goes faster & faster into & through the corners ... the g forces pushing the mass of the car towards the outside of that corner ... are going to overcome the grip the tires have. This is what determines the corning limits of a given car’s set-up.

Here is where your 60/40 weight bias car has its issue.

When a car with balanced handling (from tuning) reaches its cornering limits … the end of the car with the greatest weight is the end that breaks free (loses grip).

I have been involved with many types of race cars that have F/R weight balances of 58/42, 55/42, 53/47, 51/49, 50/50, 48/52, 46/54 & 42/58. You can make any of these cars handle “neutral” up to their limits. (You can also make any of these cars push/understeer or loose/oversteer with tuning.)

But when they exceed their limits … the heavier end will lose grip first … and go towards the outside of the corner.

So inherently, front heavy cars will push/understeer when driven past their limits. You can improve the handling of your car and make it a "pretty good" handling machine … up to a point. But … so you are prepared for what is going to happen ... with that much front weight ... the front tires are going to have more grip ... until they don't … and then the front end is going to push/understeer towards the outside of the corner, barrier, wall, etc.

Anytime you can achieve … or get closer to … a 50/50 weight balance, that car is going to handle better. And when it does reach its limits … the result will not be as dramatic.

The further a car is away from the optimum 50/50 balance … the more the heavy end is going to limit the car’s overall performance capabilities. And when it breaks traction, the more abruptly it will do so.

Theoretical example:
If we had two similar cars ... both set-up & tuned to their optimum & balanced handling … except one had weight balance of 60/40 and other was 55/45 … the 60/40 car is going to lose traction with the front tires at a lower speed than the car with 55/45. So when building cars, ideally, we want to control the weight placement as much as is practical for you, and get as close to the 50/50 balance as you can. Just because your car is estimated at 60/40 … don’t stop working on ways to make it better. 59/41 is better. 58/42 better yet, etc.

Now, back to brakes … :-)

The optimum F/R brake bias is ultimately going to be decided based on how much weight transfer you build into the suspension. If you run a "conventional setup" with stiffer front springs, shock valving, etc … to reduce weight transfer to the front … you’ll end up needing more rear braking force. If go the opposite route and run what is known as a “high travel” front with softer springs & a big sway bar … you’ll end up with more front brake bias.

Regardless, I think you’re on the right track with your current set-up … and you’ll need to adjust & tune it at the track.

From what I see so far, I would add the brake bias cable adjuster, start with the BP-30 Pads & make sure the pedal ratio is close to 6-1.

[sccacuda]

Thank you for the details!!

I've had race cars and finally got to the point where I wanted one I could drive all the time without sacrificing too much comfort. I'm building this car to do everything pretty good, but not one thing exceptional. With comfort comes weight. My crutch was more power and big brakes (and I already have the remote cable knob adjuster). I am very much a "high travel" guy. I set it up with a splined swaybar setup from the Cup teams (bought a huge lot of different diameter sway bars cheap), and have good anti-dive designed in the front. Also have double adjustable front and rear shocks. The rear is a decoupled 3-link with torque arm (a tuning nightmare!) but another crutch for the heavy car. I can get some crazy IC's with this. When I get a little closer to putting the car on scales, I'd like to pick your brain a little more.

Sorry for the thread hijack!

Really appreciate all your information.

[Ron Sutton]

Your project sounds awesome & fun.

If you go with the high travel front end set-up, I have a little secret weapon to allow you to run more brake on corner entry without locking up the rear brakes.

I am intrigued by your project. Can you tell me/us more about the engine. What model engine? How big? How much power do you estimate?

Thanks !

[sccacuda]

Your project sounds awesome & fun.

If you go with the high travel front end set-up, I have a little secret weapon to allow you to run more brake on corner entry without locking up the rear brakes.

I am intrigued by your project. Can you tell me/us more about the engine. What model engine? How big? How much power do you estimate?

Thanks !

I have a build thread: https://www.pro-touring.com/showthread.php?86743-just-another-twin-turbo-Cuda-build

The engine is a 422 c.i. twin turbo dry sump R3 SB Mopar. 16 injector Holley Dominator EFI with traction and boost control. Still setting up the EFI, but should make 750-ish on pump gas and shooting for 1700 HP on race gas for Bonneville and Monster Mile. The 750 number is where the engine will spend 99% of its life.

[Ron Sutton]

Craig, I went to your build thread & caught on your project. Holy cow. That is awesome.

I see lots of stock car influences, quality parts through out & a lot of care! This is going to be a really fun hot rod.

[Ron Sutton]

Reference Post #4

I didn’t want to leave this in-depth brake conversation without covering Total Brake Force. This only matters when we are in search of optimum track performance & therefore optimum braking performance.

We already covered, when you run at the track, optimum lap times will only be achieved with optimum braking … and optimum brake bias (front vs rear). This was discussed in Reference Post #3 ... but just to make sure everyone is clear … optimum brake bias is when the driver can perform HARD, threshold braking ... without one end of the car locking up the tires.

If the front OR rear tires lock up under threshold braking ... the front to rear braking bias needs to be adjusted. Once the bias is correct, Total Brake Force will be the final frontier affecting the car & drivers ability to achieve optimum lap times.

How do you know if you have too little total braking force … or too much ?

If the driver applies the maximum pressure their legs are capable of … to the brake pedal … assuming the F/R bias is worked out … and all 4 brakes don’t lock up … you don’t have enough total braking force … for that driver, car & set-up.

If the driver applies moderate to high pressure … but significantly less than the maximum pressure their legs are capable of … to the brake pedal … assuming the F/R bias is worked out … and all 4 brakes DO lock up … you have TOO MUCH total braking force … for that driver, car & set-up.

Before we move forward on the technical side, let’s get clarity on the human side. Assuming our goal is optimum track day performance, we have to take into account many factors about the car & track ... but also the driver. We don’t want to build a brake system that causes the driver to wear themselves trying to threshold brake.

For optimum track performance, we need a brake system that allows the primary driver (you or whomever that is) to achieve threshold braking … meaning braking as hard as the car, tires & brakes will allow without locking them up … while only using 60-75% of the driver’s leg strength. If the brakes require the driver to use 90-100% of their leg strength … every corner … for xx laps … even well conditioned drivers are going to get tired legs. And tired legs lead to inconsistent braking & slower laps times.

On the other hand, we don’t want the brakes to be so “touchy” … that the driver is locking up all 4 tires with moderate to high leg pressure on the brake pedal. In a panic stop (wreck in front of them) they may lock up all 4 tires & lose car control at that point … crashing … versus slowing & steering around it. This is key ... the brakes need to have good feel to the race driver, so they can modulate the brakes by feel. We do not want them to act as "on/off" switches.

So, the goal for our brake system is to provide good, hard, balanced, threshold braking without the driver wearing themselves out. This is going to vary from driver to driver and is a very personal thing. I suspect for most of you … it is your car … you’re driving … so build it for you. I have ran cars the last 8 years for other drivers, and we were ALL happier when the braking was tailored to them. If someone else is the primary driver … I suggest you build the brake system tailored for them.

Now, let’s get technical …
My experience is mainly race cars, but all kinds … from Formula Fords (900# & 110 hp) … to Cup style stock cars (3500# & 900hp). I have seen brake systems with total brake force of 1600# on light race cars to over 6000#. It is possible to have too little braking force ... and possible to have to much braking force. I have dealt with both and neither situation is desirable in a competition vehicle.

What’s right on one car is wrong on another. Heck, what is right for one driver … can be wrong for another. There is no optimum # … or correct number … or formula to achieve optimum brakes for each specific car & driver combination. But there are guidelines that can help you dial in yours.

Here are some guidelines, tips & experience …
1. Lighter cars need less total braking force & heavier cars need more.

2. More traction/grip … allows you to use more total braking force.
3. Anything … and everything … that affects the GRIP … affects the total brake force needed to achieve optimum braking.

4. Install new softer and/or wider tires … with more grip … and now the car can use more braking force.
5. Change the suspension (physically with parts or by tuning) … giving the car more grip … and now the car can use more braking force.
6. Add some aero device that works at creating downforce … and now the car can use more braking force.

7. Make the car heavier (turbos, cage, frame stuff, stereo, etc) … and now the car NEEDS more braking force.

8. Smaller (ok, let’s say it) or weaker drivers … need more braking force built in. Bigger, stronger drivers require less braking force. It all has to do with leg strength & conditioning.
9. All of my brake force formulas are based on 100# of pressure applied to the brake pedal. If the driver can only push 75# comfortably … we just lost 25% of our braking. On the other hand, if the driver is a big ole strong boy and is comfortable pushing 150# all day long … we just gained 50%. That is a big swing, and why the driver ALWAYS needs to be factored in the equation.

Ok, once you know if you have too much, or too little, Total Braking Force … how can you fix it? You have a lot of options. I’ll outline them below with any major pros, cons or concerns . and you chose what works best for your individual situation.

To ADD total braking force:
A. Increase brake pedal ratio.
Con: requires buying or making a new pedal. Could have fitment issues.
Pro: Relatively low cost & no added operational costs.
Concern: Do the math to insure ratio is optimum. Pedal travel will be longer.

B. Install calipers with larger pistons.
Con: Expense of buying new calipers.
Pro: No added operational costs.
Concern: Availability, may require pad change, fitment issues. Pedal travel will be longer.

C. Install master cylinder(s) with smaller pistons.
Con: Expense of buying new master cylinder(s), but less than buying calipers.
Pro: Relatively low cost & no added operational costs.
Concern: Pedal travel will be longer. Don’t go so small the M/C lacks sufficient fluid volume.

D. Install rotors with larger diameter.
Con: Expense of buying new rotors… probable added operational costs from rotors that cost more to replace … and increased rotating weight negatively affecting performance.
Pro: Just the additional braking force.
Concern: Availability & fitment issues.

E. Install brake pads with higher friction numbers.
Con: Expense of buying new pads now … and probably added operational costs from pads that wear out quicker and/or cost more per set.
Pro: Smaller initial expense than buyer calipers. May, or may not, cost less than master cylinder(s).
Concern: Getting high enough friction pads to do the job … and not wear out in everyday street driving.


To REDUCE total braking force:
F. Decrease brake pedal ratio.
Con: requires buying or making a new pedal. Could have fitment issues.
Pro: Relatively low cost & no added operational costs.
Concern: Do the math to insure ratio is optimum. Pedal travel will be shorter.

G. Install calipers with smaller pistons.
Con: Expense of buying new calipers.
Pro: No added operational costs.
Concern: Availability, may require pad change, fitment issues. Pedal travel will be shorter.

H. Install master cylinder(s) with larger pistons.
Con: Expense of buying new master cylinder(s), but less than buying calipers.
Pro: Relatively low cost & no added operational costs.
Concern: Pedal travel will be shorter.

I. Install rotors with smaller diameter.
Con: Expense of buying new rotors.
Pro: Probably less operational costs & reduced rotating weight positively affecting performance.
Concern: Availability & fitment issues.

J. Install brake pads with lower friction numbers.
Con: Expense of buying new pads now.
Pro: Smaller initial expense than buyer calipers. May, or may not, cost less than master cylinder(s). Probable reduced operational costs from pads that last longer and/or cost less per set.
Concern: Some lower friction pads do not do well in high temperature environments. Study the compound graph & know your operating temperature range.

That’s all for now.

There’s still lots more to know about brake systems, from fluid characteristics, heat transfer, ducting, rotors types, bedding pads, rotors, proportioning valves, brake lines & much more. If someone has specific questions, feel free to ask.

[Skip Fix]

So a related update . The '81 TA I just test drove after a few years being down and redoing interior, and then dash and suspension. Just before I had thrown the old Bendix organics on the factory rear discs . Could lock them up easily and the original to the car fronts did not seem to be doing much. Figured old tired calipers and pads so threw a 1LE on and using D614 larger Hawk pads on the front. Even after a fair amount of stopping to bed in the fronts rears lock. So either the organics grab too easily or my factory prop valve is bad.

Options swap on some other rear pads, replace factory prop valve with a T and adjustable rear.

[woody80z28]

Skip, you sure the Hawk pads on the front aren't the problem? HPS? I never had a good feel with them.

I ended up going 13.4 Z51 front with some Advance "Wearever Gold" GG friction rated pads.

[Skip Fix]

Hawks could be but the other calipers and previous pads on the car originally when I got it and driving OK before the rear end and rear calipers got freshened had the same issue. So far only a few miles on the Hawks.

Granted these are old school organics from the 80s and have great cold stop. Back then the semi metallics were terrible cold. A buddy who was a mechanic and worked on those old ratchet rear calipers said sometime the rear semi metallics would expand with heat and since the piston can no go back any with the ratchet bind so organics were better.