Porterfield R4-S -- initial review - RX8Club.com

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Porterfield R4-S -- initial review

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Old 08-15-2017, 06:42 PM
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Porterfield R4-S -- initial review

Just switched to this pad, hoping to correct some apparent pad compatibility issues with my RacingBrake front rotors.

I went for a bed-in run immediately after the install. The first 10 minutes were SCARY. Very mushy pedal, no bite. I managed a bunch of hard 60-30 decelerations near the ABS threshold, and got some nice billowing smoke from the brakes. But I'm assuming they then faded and/or the year-old OE fluid boiled, because the bite was even worse and the pedal was still mushy. Normal deceleration required a terrifying amount of pedal pressure, and the pedal just wilted under my foot.

After 10-15 minutes of cooldown (30-50 MPH with very little brake application and no stops), I warmed the brakes back up and tried a couple more 60-30 runs. Those were scary for the opposite reason; I basically had to peel my face off the steering wheel afterward. The pedal still felt mushy, though better than before.

Today, I replaced the OE Mazda fluid with ATE Typ 200 and bled the brakes. Pedal firmness is more or less back to where I remember it, though the feel around town is still equal-to-slightly-worse than OE just because there's not a lot of bite at low-to-moderate temps and pressures. Thankfully, the car still hauls down nice and hard when I want it to.

Not too happy with this pad as of now; I had wanted a more positive pedal feel than OE at low temps and pressures, and I ended up with slightly less. But I'm okay with it for now.
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Old 08-15-2017, 06:55 PM
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You have issues man, you need professional brake help.
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Old 08-15-2017, 09:51 PM
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I have the full F & R brake kit with those pads and love them, already expressed my other thoughts elsewhere, so yeah, what he said ....
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Old 08-16-2017, 07:23 AM
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Originally Posted by TeamRX8 View Post
I have the full F & R brake kit with those pads and love them, already expressed my other thoughts elsewhere
Thought you preferred the R4-1?
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Old 08-16-2017, 08:44 AM
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Oops, my bad. You're right; 4S is the street pad. My car has been on jackstands for 3 years with a newish set of R-41 pads so I hadn't bought a set in a while.

I haven't run the S pad since the mid 1990s on an FD3 street car. I have a post on here from back in 2008 where I showed this graph and stated why the S pad has low bite. Also why I use the 41. Well, you're going to have to make some compromises. If you want that right now feeling you'll most likely have to accept dealing with brake dust and noise ...



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Old 08-16-2017, 08:15 PM
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Originally Posted by TeamRX8 View Post
Well, you're going to have to make some compromises. If you want that right now feeling you'll most likely have to accept dealing with brake dust and noise ...
Or, from what I gather, a greater likelihood of pad transfer issues (e.g. Carbotech) -- which RB rotors apparently exacerbate.

I was a hair's breadth from getting the R4-1. Maybe I should have. If the only difference were a bit of noise and more dust, I would have in a heartbeat. But Porterfield told me it wears faster than the R4-S at low temps, in addition to the noise and dust. And the R4-1 costs as much for just the front as the R4-S costs for the whole set. Didn't seem super tempting at that point, especially when I wasn't even sure it'd fix the problem I was having, and I might have ended up ditching the RB rotors anyway -- in which case OE pads would have been fine. And anyway, I figured there was no way the R4-S could be that bad around town; like, maybe the naysayers were just super picky or something. There's no shortage of good reviews of it, and my brother loves it on his own car.

Oh well. Live and learn. :-P

To be clear, I don't think the R4-S is bad per se. I can still engage ABS on Super Sports, and it definitely seems better than OE when hot. It's just not what I want. Maybe after I regain my confidence in my brakes, I'll go for a more enthusiastic drive and see what they're like with some real heat in them. Might make me feel better...

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Old 08-16-2017, 10:30 PM
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I haven't noticed any compatability issue on my rotors and they've lasted through many sets of the R-41 pads without much wear, but it's not a street car. They will dust and squeal more than the typical street pad, but then my recollection of the S pad is that they weren't shy to dust either. I've been through many different kinds of pads and can relate to what you're saying. Always kept coming back to the R-41 because it's hammer down from the first touch of the brake pedal on cold rotors ... they might be touchy with lower grip street tires
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Old 08-16-2017, 10:46 PM
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The compatibility issues are only with certain brands, e.g. Carbotech and Ferodo. And apparently OE RX-8 pads as well, despite RB's initial insistence to me that they'd be fine. Porterfield is one of the brands that's known to work with RB rotors, per both companies.
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Old 08-17-2017, 02:21 AM
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Well obviously they can't know the exact makeup for every OE brake pad. That said, I'm pretty sure other people ran OE pads with those rotors here and don't recall anyone else saying anything. Not meaning to knock your experience, but it's possible Mazda even changed the exact material makeup somewhere along the way.
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Old 10-12-2018, 11:12 AM
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So these pads lasted 23k miles... and one track day, lol. It was my first real track day ever, so I wasn't exactly easy on them. The event took the front pads from ~50% to replace-right-now, and basically vaporized the rears. Can't fault them for that, obviously.

I think I finally understand this pad compound. The flip side of the lackluster-feeling bite is really progressive modulation. Being a street pad it can't take much on track before it starts to fade (or wear REALLY fast), but at higher-than-optimal temps the torque falls off pretty gradually. Its peak torque and fade resistance seem well matched to street tires AFAICT -- i.e. the pad's limits are in the same ballpark as the tires' limits. Overall, it just seems like a super forgiving pad compound in every way, and a decent one for a n00b to learn on. Bonus: the dust is non-corrosive and super easy to clean.

I still prefer the OE pad, which I'm back on now. It seems just a bit more positive at low and moderate pedal pressures. But I think it's safe to say the R4-S has its place.

As an aside, this pad did NOT solve the deposit issue I was having with the RacingBrake rotors. Zero deposit issues with OE rotors, though.

Last edited by IamFodi; 10-21-2018 at 05:19 PM.
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