Well, I just tried the Porterfield R4S yesterday at Homestead and it wasn't exactly what I was hoping for. I was looking to replace the Hawk HP Plus with something which dusts less (for general maintenance) and which offers a bit higher operating range (800 deg. for HP Plus vs. 900 deg. for R4S).

Switching from the HP Plus to the R4S, on the street, I first noticed that the pad had much less initial bite. It stopped equally as well, and linear in response, but the feel is somewhat mush.

At the track, same thing. The R4S hauls you down perfectly fine, are fade free enough, but the feel is mushy and not reassuring. Easing into the brakes with less initial stab had cured the squirrely tail under threshold braking with the HP Plus. The R4S is less prone to get that tail wagging under hard braking under equal circumstances due to its lack of initial bite.

On a positive note, the R4S does dust less than the HP Plus. That's good, as the HP Plus brake dust was wearing away at the wheel finish.

So far, the best compromise street/track brake pads in terms of feel and response which I've driven on have been the Cobalt Friction GT Sport on my friend's RX8 at the track, hands down.

 

Update:

I just had the driver's rear Porterfield R4S outer pad come off its backing plate. It sheared off after the car sat for a few days through Fay's downpours with the e-brake on. When I released the e-brake this morning to pull out of the driveway; POP! the pad's compound (what was left of it, as there were only a few mm of compound left) sheared right off, as it was stuck to the rotor.

As for the performance of the R4S, I've been less than impressed. Pad wears very quickly (pads went on in April and I only got 3 track days out of the rear set) and there's simply no bite. The only positive thing about it is that the car won't pitch forward with too much weight transfer to the front if you're aggressive with the pedal.

Time to try another brand.

 

Nice post. Thanks for your input.

 

I've never had any problems with the Porterfielf pads.

Sounds like you put the E brake on after you heated up your brakes too much.

Didin't they teach you not to use it at HDPE?

 

Rear pads stuck to the rotors while it sat in the driveway during Tropical Storm Fay.
Last time the car was driven before the storm was on a run to the grocery store to get batteries and water. Last track day I drove was back in July. And, of course I don't engage the e-brake at the track after running hot, lol.
If anything, I'm glad the pad sheared off in the driveway on my way to drop off the kid at school, instead of having it delaminate at the track.

 

To be fair, R4S are marketed as trackable street pads, with an operating range of ambient to 900 deg..

 

The tendency is that a street pad will glaze over at the track.

I've pushed the limits of both the Hawk HP Plus and the Porterfield R4S. They will each give me about 20-30 minutes of track time before showing signs of giving up. I credit them for at least holding up for that long. Any less of a pad would turn to paste.

 

get the R4-1 compound, from the graph I posted a while back it stomps all the other Porterfield compounds into the dirt WRT friction coefficient from cold to 1000 degF

it will dust more than a street pad, but it seems to clean off easily

 

I posted in the other thread about braking but to improve my chances for a response I'll ask here too.

Whats a great pad to use for autocross? I doubt I'll see anything close to the temps track guys are pulling.

 

The R4 pads are noisy (squeaky/squeally) and dusty. You need to warm them up before they reach max-grab, so the first stop or three in the morning can be exciting, as well as coming off a freeway exit ramp.

I pulled the R4 pads back off my car and put them back on the shelf. I'll put them back on when I bleed the brakes for the next track day.

 

Hmm, never had any of those problems with the R4S.

Yes they have less initial bite as the Hawk HP+ (which requires very minimal pedal pressure to generate a lot of torque), but the R4S is a very linear pad - the harder you press, the faster the car decelerates.

I guess the feeling of 'performance' is relative. Their are tons of race compounds that vary from high initial bite, to others which require more pedal pressure to generate more braking force.

I've really liked the modulation and release characteristics of the R4S and got over 30,000 miles out of a miata that saw the track every other weekend and about the same in a MR2 Turbo. I now have them on a Lexus LS400 and they're working great.

0.02