(If you are just looking for my review of Pepboys Pro-Stop pads, just scroll to the bottom of this posting. Also note that this post fits in with the previous posting “My recent headache with brakes”. If you want more info, read that as well.)
Brakes are the most important system on your car. If your engine stops, big deal… you can just pull over to safety. But if your brakes stop working, well, things get a lot more exciting. It has been said that brakes are often forgotten about when modifying a car; but, I guess the people that forget about brakes have never raced on a road course, because there’s no way you could forget anything after going into the second corner with factory brakes.
Well, I guess if you have a modern sports car, it’s not so bad. A lot of progress has been made with brake systems and cars are stopping better now than ever before. But anyway, in my last post I was saying how I didn’t have the time to properly bed-in my Pepboys Pro-Stop Ceramic pads.
To summarize what happens when a pad beds: The material of the brake pad actually transfers to the rotor surface. This is known as the Transfer Layer, and this layer is what provides the real meat-and-potatoes friction that stops your car. Without this layer, your braking ability is reduced drastically. (The StopTech Company has a really great write up about how this whole process works that I suggest you read here. )
But here’s the interesting part. To bed in your pads, the pad and rotor have to be brought to a temperature range where this transfer happens. And this transfer doesn’t happen all at once when you get to that range, and takes a few cycles to get applied and is done gradually. Before this transfer layer is applied to the disk, your braking ability can be reduced. I have noticed that some pads are more reduced than others with the Prostop pads being about the most drastic I have seen.
So here I was at the track with pads that weren’t bedded in, what happened next? The pads transferred to the rotors. But because the rotors (and pads) were at such an elevated temp due to racing, this didn’t happen very evenly and made large uneven smears of pad on my rotor. This uneven buildup is usually what causes vibrations in brakes, not warping.
My front rotor now a few hundred street miles after the event:
The uneven transfer layer is visible in the form of radial bands. If viewed in person, these bands are much more pronounced. It’s not as bad now since the abrasiveness of the pad has worn away the really high spots. These bands happened to form over the vane pattern of the rotor, with the dark bands over the hotter parts of the rotor surface. You can also see that these rotors have straight vanes, and that they don’t run the full width of the swept area.
I also have some cracks that formed on the surface of the rotors. These cracks formed right next to a vane where the temperature differences are the greatest. I have also noticed that the vents of these OE style rotors have a very square profile; I’m sure the corners of this profile also contribute to uneven heating and cooling.
By contrast, my buddies brakes don’t even look like they saw a track day:
These are absolutely massive 8-piston calipers on 14.4″ rotors. I couldn’t tell you for sure that the factory pads on this Gallardo are semi-metallic or ceramic, but they have very little dust. My friend is a very inexperienced driver and most likely, he did not brake hard enough to really tax the brake system and create dust. But, the Lambo pads can squeak every now and then on the street, suggesting a more aggressive compound than a typical street pad.
High end sports cars like this continue to use cross drilled rotors even though they serve no benefit other than looking cool. Cross drilling actually weakens the rotor, but these are just so big that it doesn’t matter for light track work. Though, just like any other car taken to the track with drilled rotors, they will crack prematurely when pushed hard
So, overall, how would I say the track day went with the Pro-Stop Ceramic pads?
Well, pretty good actually; and it was my fault for pushing everything so hard. I ran the full 3.5 mile configuration at autobahn and did up to 4 laps at a time. That’s 14 miles of racing abuse put on these street pads in just one session alone, and I’m surprised they took the punishment.
After they bedded-in, I didn’t experience any problems with fading, this is actually quite an amazing feat, but might actually be a problem with these pads. Clearly, these pads were never made to endure the high temps of road racing and started to melt down and apply to much pad material unevenly to the rotor. After my track day, I had quite a bit of vibration from my rotors that slowly decreased, but never went away as I put more street miles on them. Looking through my wheel I didn’t notice anything wrong; but later, I removed my rotors for inspection and noticed that the surface facing the inside of the car contained all of the uneven buildup.
After that, these rotors were pretty much toast and needed to be replaced.
From my experiences and what I have heard about ceramic pads, I get the impression that ceramic pads, in general, seem to lack the initial cold bite that semi-metallic pads have. How bad is it with these pads? I’m not able to bring on the ABS at all when I floor the brake pedal when these pads are cold. These pads increased my stopping distance so much that I felt that safety could be an issue. When they are warm, they have a lot of bite, but they are bound to cool off if you are not on the brakes for a while – like on a highway.
Just to summarize my experience with the Pepboys Pro-Stop Ceramic pads:
- They have much less initial bite than my OE pads when cold, and can take a few stops to warm up. This leads to longer cold stopping distances. I feel this is the weakest point of these pads. This gets better after they bed in, but it’s never as good as OE.
- These pads seem to perform about the same or better than Hawk’s HPS pad and are much cheaper.
- Overall friction coefficient is lower than the OE pad.
- Very clean; the dust does not stick to the wheels at all.
- They are an excellent value at half the price of OE pads and come with very nice anti-squeal shims built in.
- Have a life time warranty that I hear is no questions asked!
- Expect a few hundred miles before they completely bed in.
- Completely quiet.
- Overall, I do not like this pad because the cold performance is so poor. I found it possible to floor my brake pedal and being nowhere close to bring on the ABS.
Food for thought:
- Pads designed for racing are generally not ceramic pads.
- Even though ceramic pads are often advertised as dustless, they do in-fact create dust. This dust has a lighter color and does not stick to your wheels like the dust created from a semi-metallic pad.
4 Comments to "Ashes to ashes brake dust to brake dust. A track day on Prostop Pads."
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Unfortunately I have had massive brake fade even with pads on my Z car that are supposed to be light track duty. It certainly doesn’t help that the Z cars don’t have any brake ducting what so ever to help cool the rotors.
Which pads are you using? Some years ago when I was running my RX-7, I was conned into getting some pads that could handle “some light track duty”. The pads were absolutely horrible and could only take 1 or 2 racing stops. The company that made those was Rotex, but that was some years ago so hopefully their formula has changed for the better.
With these pro-stop pads, I was surprised that they didn’t fade at all as temps increased; instead, the amount of friction increased. I wish I had an IR thermometer or something so I could measure the rotor temps because all of that force slowing my car down had to go somewhere, and I expected that my rotors were getting pretty hot due to the pad meltdown. I seem to crack my rotors a lot when I push these cheap street pads hard, it might be do to quality of metal in my Centric Rotors, or it might be because of uneven heat buildup, I don’t really know.
Shockingly, the pro-stop pads really remind me of full-out race pads due to the lack of friction when cold and how they get so much better as temps build.
If you do a lot of auto-x or solo events with your car, I would consider running Hawk blacks. I have driven them on the street and they did well while still performing at the track.
I actually ran Porterfield R-4 pads, their race compound pads, my last few events. My previous experience I mentioned was with some Hawk pads and which compound it was with escapes me right now. There wasn’t a hint of any fade, and the ability to modulate the brakes (which sometimes fails to happen with race compounds) was pretty good as well.
Remember that just because your brakes are very hot, doesn’t mean that is the reason they are cracking. What also goes into that equation is also the thickness of the rotors. What I mentioned before was pad fade, where the pads get so hot that they become malleable and start to effectively melt. The brakes with the R-4’s were so hot that I could feel the heat coming off of them from about a foot away through my jeans. I should also mention that the event was in Texas on about a 90 degree day.
The pads worked ok on the street but never really hit temps that were required so they started to really eat into the rotor. As a result I decided to buy their street compound, R-4S, and have been alternating that with the track pads. The R-4 compound will effectively turn the rotor so you don’t have to turn the rotors every time.
I will look into the Hawk Blacks. I drove a Pontiac Firebird with some HT-10’s on the car, the brakes were able to apply so much torque that it felt like the nose of the car was going to scrape the ground (yes I know this is impossible).
Cross-drilling provides someplace for the water to go when driving in the rain, so you don’t lose your brakes after hitting a puddle. They aren’t about cooling, never were.