Weak brakes

[Mook613]

Car only has 177,000km.
New rotors (Zimmerman), new pads (Pagid), some new brake lines, and fluid flush.

When pressing the pedal while car is off it has a small bit of travel and then stays very stiff. Then if I turn the car on the pedal depresses another few inches (booster is working properly?).

The issue is that when I'm going slowly and press the brakes hard the wheels won't lock up/engage ABS.
The car stops, but not in a manner that inspires much confidence with spirited driving.

Any ideas as to why the brakes just don't grab well?
Perhaps a bad bleeding and there are still small air bubbles, perhaps the pads just aren't that great, or maybe a vacuum leak on the booster?

Help please!

[TobyB]

How many miles since pad change?
The pads take some time (100's of km's, on a manual driven on highways)
to bed to the rotors, and don't grab all that well until they're bedded.

I'd rebleed, and then go do some hard stops. Then drive a bit to cool, and do a few more.
Then maybe bleed again. And see how it is.

I haven't been all that impressed with Pagids on the M46. They just don't have the
bite that the ATE version did...

t

[Kershaw]

Did the car stop well before you did the brake change?

[Mook613]

How many miles since pad change?
The pads take some time (100's of km's, on a manual driven on highways)
to bed to the rotors, and don't grab all that well until they're bedded.

I'd rebleed, and then go do some hard stops. Then drive a bit to cool, and do a few more.
Then maybe bleed again. And see how it is.

I haven't been all that impressed with Pagids on the M46. They just don't have the
bite that the ATE version did...

t

Pad change was around 3,000km ago.

So, pad choice may have been the problem? Could the pads have such little bite that it takes a two-foot stomp to get the wheels to lock?

[Mook613]

Did the car stop well before you did the brake change?

When I bought the car it had old fluid, warped rotors, and some old pads that I didn't bother keeping.
Needless to say, the car didn't stop very well.

While replacing the parts has helped a lot, the brakes still aren't quite what I would expect them to be. I'm not expecting the car to stop as fast as my other car (which has rotors big enough that only 18+" rims will fit), but I do expect that I can drive without being nervous about the lack of stopping power.

[Kershaw]

My e30 will put you through the windshield if you aren't expecting it and strapped in. Normal rotors (may be vented I can't remember right now) and Hawk Ceramic pads. Direzza Star Spec II tires. Which the brakes can still lock up.

If you can't lock up your tires with one foot, then you definitely have an issue. Usually shitty brake pads will stop pretty well once, it's repeated stopping where they'll fail.

It sounds like your booster is the place to start.

[Mook613]

My e30 will put you through the windshield if you aren't expecting it and strapped in. Normal rotors (may be vented I can't remember right now) and Hawk Ceramic pads. Direzza Star Spec II tires. Which the brakes can still lock up.

If you can't lock up your tires with one foot, then you definitely have an issue. Usually shitty brake pads will stop pretty well once, it's repeated stopping where they'll fail.

It sounds like your booster is the place to start.

Thanks.
My impression was that the booster is tested by holding brake pedal down while starting and measuring the drop in the brake pedal. My pedal drops a few inches when starting the car.
Is it possible a small vaccuum leak would cause this (note that my idle is pretty steady and only a small shake to the car with the refurbished AFM that I just put in).

[Kershaw]

If you have a stable idle, you probably don't have any vacuum leaks.

http://www.chevelles.com/forums/16-brakes-suspension-steering/401420-firm-pedal-weak-brakes-cant-lockem-up.html#post3697838

[jeffnhiscars]

It's hard to lock the the wheels at low speeds which is probably why your abs hasn't engaged since they respond to lockup.

Other thoughts are calipers in need of rebuilding, contaminated brake fluid or old brake lines that expand rather than force fluid to the calipers