myblues

Today I changed my brake pads both front and rear from stock to Porterfield R4S. I also resurfaced the rotors.

The pedal feel is much softer, and the bite and stopping power seems much weaker.

Is it because it's the first day? Or do others also feel weakened stopping power when changed to R4S from stock pads.(Non p30)

BLKROKT

Did you bed the pads?

myblues

No. Does it really make a huge difference?
It's driving around 60 mph and applying full brake until near stop right? Repeating about 5~6 times...

BLKROKT

Why you should bed in your brakes: http://www.stoptech.com/tech_info/wp_bedintheory.shtml
How: https://www.zeckhausen.com/catalog/i...Path=6446_6443

More: https://grassrootsmotorsports.com/fo...e/72317/page1/
http://forums.viperclub.org/threads/...g-in-procedure

Skizz

I have an E63, but just changed to R4S' about 700 miles or so ago. I also changed rotors at the time as well, so YMMV. However, I bled the system in proper sequence with a Motiv bleeder and bedded the brakes and have noticed no real difference from OEM's I had on it before. Initial bite is about the same, but then Porterfield's aren't known for their spectacular initial bite. Pedal feel and stopping time/power for me is similar to OEM's if not a little better when you really get into them. The OEM brakes are pretty good, though, so I wasn't expecting a huge improvement in some of these areas. Dusting is certainly better than OEM's, but they are in no way dust-free.


There is a sequence to bleeding as I noted above; which bleeder valve to start with and which to move to next. It is by most accounts important to follow that pathway. Starting there and then bedding properly as members above noted should yield similar results to that noted above.
NOTE: The brakes on the P30 cars on the E63 are the same as the base E63's. Also, my note above on bleeding sequence is from my experience on the E. I assume it would be similar on the C, but you should investigate first.

myblues

Thanks so much BLKROKT and skizz!
I'll try bleeding and bedding and see how it improves!

zcct04

Changing pads and rotors doesn't normally require bleeding the brakes. I'd try bedding first. Links from BLKROKT are the best explanation I've seen of the why and the how of brake bedding.

Skizz

True, but (probably wrongly) assumed that the much weaker stopping power indicated change in brake pedal feel/travel. Not knowing what was done, by whom and when (even before OP), suggested giving it a try to see if it helps with what he is experiencing. Typically, if the lines aren't opened, no need to bleed, but as long as you know what you're doing and don't mind getting in there, it's not a bad thing to do anyway.


Caveat: I changed my lines and pulled the calipers for painting, hence the bleeding on my part. I probably would have done it anyways while I was in there.

speedking

If that's the process you went through with new pads on resurfaced rotors, you just glazed the sh*t out of your new expensive pads and likely overheated the freshly resurfaced rotors. Personally, I would pull the pads back out, sand the braking surfaces on 80 grit sand paper on a totally flat surface until the entire surface of the pad is uniform and no longer shiny, then reinstall the pads and follow in a proper bed in procedure as BLKROKT pointed to.

There is a high probability that you'll never get your pads to bed in now that you've glazed them if you don't.

If your brake pedal feels spongey/soft....it could be the process you went through to install the new pads. If you didn't crack the bleeder screw at the caliper when you compressed the caliper piston, then you forced fluid backwards up through the system....pushing moisture and debris/contaminants backwards up into the ABS valves and master cylinder. This can damage both the ABS and the seals in the master cylinder, causing a spongey feel to the pedal if not full on ABS failure. If you did crack the bleeder screw when compressing the caliper pistons, then you could have let air into the system and I'd recommend doing a brake fluid flush.

While it's not a requirement to do a brake fluid flush when replacing pads, keep in mind that brake fluid does need to be changed from time to time and there really isn't a better time than when you have the car up in the air with all the wheels off while servicing the brakes. Just sayin....

Just my $.02.....been a professional mechanic for the majority of my life.

zcct04

Interesting. Have never done that on any of my cars, and never suffered any negative consequences. Probably because I flush my fluid every couple years and have thus avoided getting any of that 'moisture and debris/contaminants' in my system.

Just my $.02.....been a clumsy amateur mechanic for the majority of my life.