I feel like I start off every blog post with "It's been a while..." And, well, this one isn't any different. It's been a while since I posted Part 1 of my brake pad comparison. Looking back at that post, I made a few easy predictions. I knew I'd be right about each one, but the main reason for doing the comparison test is to determine just how much of a difference there is in each category: cold performance, hot performance, dust, and noise. So here's what I noticed going from the Porterfield R4-S street pads to the Porterfield R-4 track pads on my 2007 Aston Martin V8 Vantage.
Brake Pad Temperatures
Brake pad operating temperatures have a range. When discussing hot and cold performance, that doesn't mean whether it's hot or cold outside (say, winter vs summer). It is about the temperature of the pads themselves. For most street-use pads, that range is starts somewhere around 50-100F. It doesn't matter if it's 30F or 95F, you're still around the minimal operating temperature for the brake pads and having such a low minimum for that range means that the pads will usually be warmed up when used for the first time during that drive. In simple terms, cold temperatures are generally a non-issue for normal street pads.
Pads made for track use have higher temperature thresholds, but they also have a higher minimal operating temperature. A track pad needing to be at 300F before it starts working might not be able to stop your car until they've been heated up. That makes using track pads very risky on the street. If you're sitting at a red light and your brakes cool off, you'll have to heat them back up again. In traffic, that might not be too easy or safe.
The other side of this is the maximum end of the heat range. When a brake pad exceeds its operating temperatures, it is no longer able to function properly and will lose its ability to stop the car. Track pads sacrifice cold performance so they can better handle extreme heat.
This is an important thing to consider for people that drive their car year-round, especially in normal commuting traffic. Cold performance addresses how well the brake pads perform when they're still cold. That isn't limited to ambient temperatures during the winter. Rather, it means whatever the temperature the pads are before being heated up to their operating temperature by being used. Street pads have a lower temperature range than track pads, so they warm up almost instantly and are suitable for year-round driving in almost any street conditions.
Porterfield's R4-S pads are designed to be street pads so cold temperature performance is a non-issue. How well the R-4 pads worked when cold was the real question. The R-4 pads have an "optimal minimum" temperature of 450F, which is fairly warm. When I found is that the pads were adequately warm for normal stop-and-go commuting after a few stops. So I was comfortable driving these around in normal driving - I just had to remember to do some easy warming on my way out of my neighborhood. Cold performance is a huge safety issue for using track pads on the street, and brake pad manufacturers will recommend against that usage, so this was a pleasant surprise.
NOTE: While the Porterfield R4 pads might be usable on the street, Porterfield and myself both recommend against it!
If you drive your car aggressively or go to the track, this is a massively important topic. I was very happy with the R4-S pads in most situations until I used them in situations where I was going over 100 MPH. I found that speed to be the limit of my comfort zone with the R4-S pads, which is why I switched over to the R-4 pads (and which is how this comparison came about). I felt serious brake fade during hard braking at the end of Summit Point's main straight, and again going into a downhill hairpin at the end of a fast section. I also experienced brake fade when slowing from high speeds during highway runs.* In spirited driving, the R4-S pads are just fine. But once you start hitting higher speeds, especially if you're doing a lot of repetitive braking, you'll need a more suitable brake pad.
*Professional driver on a closed course in Mexico. Please obey all posted traffic signs.
The R-4 pads don't have a high temperature problem. In fact, these things are absolute monsters when hot. Your tires are going to hurt your braking performance more than these pads. I found them to be very easy to modulate when warm, and felt wonderful under extreme braking. I used these at Lime Rock and found myself diving deeper and deeper into braking zones, and my only worry was whether or not my tires could handle the braking I subjected them to each time.
Let's face it, brake dust is embarrassing. It's also one of the biggest complaints Aston owners have with their V8 Vantages. The OEM brakes (which are Pagid 4-2-2 pads) dust like crazy, even when driving the car at a casual pace. This is one of the reasons why I recommend the R4-S pad so highly - there's practically no dust. It's freakish how little dust there is! The R-4 pad, on the other hand, dumps buckets of dust. It's constant, it's everywhere. It's thick and it's offensive. But these pads are made for track use, and performing in that environment is the primary concern. Although I expected there to be a clear difference in the amount of dust from the R4-S and R-4, the difference between the two is just amazing. They're on opposite sides of the dust spectrum, a veritable dust feast-vs-famine.
With proper installation and bedding, the R4-S is dead silent. Again, this is pretty much the ultimate street pad. If you toast the pads by exceeding their temperature thresholds a time or two, you might get a little bit of a squeal. But under any other circumstances, these things are super quiet.
If you even consider using the R-4 pads on the street, get some earplugs.
The number one reason I found why the R-4 pads to be incapable of using on the street is because of the horrendous brake squeal. Unless these pads are hot, the brakes will emit the most awful, high-pitched squealing noise ever when coming to a stop. I was fully expecting a priest to walk up to me at red lights to ask if my car needed an exorcism. It was unbearable, and even more embarrassing than the brake dust. There was usually no squeal when braking on track, but it was unavoidable on the street.
I honestly didn't pay too much attention to rotor wear. You're going to see more wear with the R-4 pads than the R4-S, but I didn't notice any unusual or concerning wear with either pad. If you're only using the R-4 pads during occasional track days, the pads will be rotor friendly enough that you shouldn't need to worry about extra wear.
Summary of Thoughts
The pads performed in line with my expectations. The R4-S is a street pad and does that very well. The R-4 is a track pad and does that very well. Each has its intended use, but can be used in limited capacity for the other's use. The R-4 pad was the real subject of this comparison. The R4-S has been my favorite street pad for a couple years now, and it made the perfect basis for comparison.
Predictions and Observations
I listed out some predictions in Part 1, and I was right about each of them (they were pretty standard assumptions for brake pads). The extent of each, though, is what I found interesting. The R-4 is better than I expected at cold braking. This is a huge concern for using track pads on the street due to the safety risks involved, so it's definitely worth noting. The main benefit of this is that the pads can be installed at home, then driven to the track. So you don't have to worry about bringing the tools to change them to the track. The other thing worth mentioning is that the noise is a dealbreaker for regular use of the R-4 pads on the street. It's just too much, too loud, and too often.
This has been a comparison, not a competition. There's no "winner" or "best pad" here, because it's comparing apples to oranges. The comparison is still valid, though, because some people want apples and some people want oranges, while others might need pears. I like to test out a wide variety of things to give a better understanding of each, not to say which is best. By comparing the R-4 track pad to the R4-S street pad, it helps give a better understanding of how different a track pad is to a street pad.
The Porterfield R4-S is a fantastic street pad. For my taste, I'd like a little more initial bite (this is me being pretty particular, though, because I'm an aggressive driver). Even so, it's my favorite street pad. If you don't usually hit speeds over 100 MPH, this is the pad to get.
The Porterfield R-4 is an eyeball-popping track pad. These things are beautiful on the track, but serious care needs to be taken if you use them on the street. Yes, they create a ton of dust, but more concerning is that the noise makes them unusable for street driving. They are capable enough at cold temperatures to drive on the street to-and-from the track, just be ready for some seriously unpleasant brake squeal.
If you want the best of both worlds, get both worlds. Changing out the brake pads isn't very difficult, so you can run around the streets on R4-S pads, then swap over to the R-4 pads for track days and return to R4-S pads afterwards. There's a risk you might get some brake squeal due to the R-4 material transferring to the rotor, but this is an easy way to get both dust-free street driving and hard-braking track driving.
But the comparison isn't quite over yet.
Next year I'll be hitting the track again, reusing my R-4 pads. But to make them more bearable when driving on the street, I'll be chamfering the pad material. An angled edge helps reduce brake squeal and chatter, so it might be enough to make the R-4 pad a slightly better all-around pad. (Of course, this won't do anything for cold performance, so keep that in mind!)
I've also been driving around on the Hawk HPS 5.0, which is a newer pad that bridges the gap between the R4-S and R-4 pads. Whether or not it can handle track duty will be seen next year, but so far they've done quite well on the street. The holy grail for me is finding a pad that can handle both street and track. I'll be adding the HPS 5.0 to the mix in an upcoming blog post discussing balancing brake pad requirements.