(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.