My initial thoughts and pictures were posted
here, earlier in this thread.
This is my impressions of using Ferodo DS2500 pads on my car this past summer. I'm a noob with fancy brake pads, so this is primarily comparing these pads to the stock BMW pads on my M235i RWD. I had these pads on for 5 months, and about 4000 miles. This included 4 track days at BIR, 1 at DCTC, and some auto-cross practice events. I changed back to the stock pads for the winter, when I put the winter wheels on.
I had four goals for these pads:
1) Better than stock pads on the track.
2) Decent pad life, and easy on the rotors.
3) Quiet operation.
4) Acceptable street operation.
Overall, these pads definitely hit my goals. They never made a squeek. (I did use a thin layer of brake grease on the back, which I think helped.) The rotors still look as smooth and shiny as when I started. I didn't measure rotor wear, but it appears minimal. And most importantly, the pads didn't grind or groove the rotor surface. The smooth surface keeps it quiet, and makes it easy to change to other pads. I've also seen rotors with harsher pads be totally trashed in a short while. The discs on this car are expensive enough I'd like to make them last as long as possible.
On the street, these are definitely a higher temp pad than stock. The lack of cold grip was very unnerving when backing down my steep driveway first thing in the morning. (Especially when my neighbor kids GTI was parked across the way, and I felt like I was going to slam right into it.) This is a key reason I changed back to stock for my Minnesota winter. However, once I got out of my subdivision, a few gentle stops and normal brake drag warmed them up to operating temperature. After that they always felt great for routine street driving, although sometimes the inconsistency as they warmed up bothered me.
I did notice that after a lot of gentle street driving, the pads seemed to glaze. The brakes were not as grippy. But some hard bedding type stops would usually burn it off and they were back to normal. (Or some wheel cleaning with Sonax.)
On the track they did work better than the stock pads. I did two events at DCTC. One with the stock pads, one with the Ferodo. I had Motul 600 in the lines for both (more important than pads), so the brake fluid was not a factor. After a few laps the stock pads would get a bit, um, 'greasy'. They still worked well, but at maximum stopping pressure, they just didn't have the same friction. With the Ferodo pads I never felt that same loss in friction. They just worked. DCTC is a small driver training track, but depending on how it's configured the straights are long enough to hit 80+, with tight 20 mph corners. Brakes get a good workout, with little recovery time.
At BIR the brakes did everything I asked. Turn 3 is ~120 to ~40, and I could wait till nearly the #2 brake sign to jump on the brakes. No drama.
The only negative I've had with these brakes did happen at BIR. During my later sessions, I got some heavy pad transfer to the rotors, and I was getting some significant pedal pulsation. It faded slowly, but wasn't completely gone until days later. The pads do have some pockmarking on them. (pictures below) At this point my instructor really had me working on hard braking, and I think I may have been reaching the limits of these pads. But I can't rule out an inadequate cool-down and some transference at that point either.
Everyone always talks about 'bite' and 'modulation'. Not sure I can adequately answer that, but these are my impressions.
Bite: I think the stock pads actually have more 'initial bite' than the Ferodo DS2500. There onset of brake force with the Ferodo pads was actually softer, and didn't have that same grabbiness that the stock pads often exhibit. The Ferodo pads did have a steeper friction curve as you applied more pressure, once you were on them.
Modulation: I'm not sure which is better, but the modulation of the pads was different. Under light (street) braking I find the stock pads to be hard to control. The initial application is touchy, and the stopping point tends to grab (the 'rocking' some people complain about at stop). In contrast, the Ferodo pads were easier to drive on the street, with a softer initial onset, and easy to feather to a smooth stop.
On the track, under heavy braking, the Ferodo pads almost felt like air brakes. The harder and farther you pressed, the more they stuck. They responded well, and you could easily back off a bit to stop ABS, but it was more of a positional thing than any feel under your foot. In contrast, the stock pads had more feel under foot and took less pressure change to back off. The Ferodo pads felt 'gummier' under heavy braking, and felt like there was more ultimate stopping power, but it was harder to find that peak brake point.
Dust: These are at least as dusty as the stock pads on the street. And obviously massively dusty on track weekends. Wheels almost black at the end of the weekend.
Would I buy them again? I'm not sure. They fit my goals and did everything I asked of them. But I might see if something else might have a bit more headroom at the track, with a touch more feel. Then again, I spend 95% of my time off the track, and I really liked the impeccable quiet street manners.
They still have ~6mm of pad left, so I'll probably at least start the next season with them. At that point, the rotors will likely be worn enough that if I put on some harsher pads I won't feel so bad about using them up.
I also updated the google sheet with the correct part #'s.