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/showth...-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.