Hi all-not long ago I had the brakes done, new pads and disks front and rear. Genuine saab for both on the rear, Black Diamand drilled AND grooved disks front with Predator pads.
So, as the pads have worn in, more and more if I step on the brakes (as in a fairly rapid slow from 70-80 down to 20-30), I get a noise from the brakes-it's kind of a rumbling, but if you brake harder or don't let off it becomes more of a scraping sound. Typically if I step hard on the brakes from motorway speed it's quiet until about 50 then gets louder as you keep stepped on it.
I would say that no noticable loss in brake performance is noticed though.
Is this some strange effect of drilled/grooved disks with my pads? Because the only time I've heard brakes making an even remotely similar noise was on my sister's car when the pads were so bad the mechanic wouldn't let her drive it away from the garage before swapping them, and obviously all my pads/disks are brand new (well, about 1000 miles old).
The sounds you describe are commonn with hard pads and grooved or drilled rotors.
The main effect of drilled or grooved rotors is excessive pad wear. Noise is the additional bonus if the engineering isn't done perfectly. They are pretty much useless for street driving,a fashion item like large wheels and rubber band tires.
Hmm, fair enough. Well I've got them now, so as long as that noise is normal (just a bit annoying, rather than something I should be worried about), I'll put up with it. Cheers.
Factory parts are often not drilled or grooved and their pads are fairly soft partly because of these noise issues.
In return for the grumbling you get marginal improvement in braking grip in wet weather and some benficial effect if you would likely reach brake fade temperatures with ungrooved rotors. Grooves are easier to make quiet than drillings.
Those fancy rotors also wear the pads faster, which is what that noise is actually caused by.
Yo Chris, I had to change my front pads last week to the BD Pred pads. The OE Porsche ones just don't work with the BD discs. However, I don't hear any rumbling sound yet from mine. I've done about 150 miles from Last Monday, still quiet.
Hmm. Can't remember if your disks are grooved, drilled or both? Mine are both. Anyway, I'd say the noise didn't start for me at 150 miles-it was a chunk more than that, I'm guessing when the pads were more worn in. I THINK it was something like 500-600 miles in, because I know I'd been to Leeds and back by this point. See how you go and let me know.
I am just picking my car up from the shop today for that exact reason, with the rumbling and scraping noise, etc. Apparently the disks were a bit rusted because the hydraulic fuel wasn't being distributed across the disk. Check the hoses.
I am just picking my car up from the shop today for that exact reason, with the rumbling and scraping noise, etc. Apparently the disks were a bit rusted because the hydraulic fuel wasn't being distributed across the disk. Check the hoses.
AFAIK the 9000's stock brakes are actually pretty nice... but what rakusfraku has said doesnt make sense to me...
i have changed the pads myself, once, on a rear wheel that I left the brake engaged on lol, and i dont understand the part "the hydraulic fuel wasnt being distributed across the whole disc"
Doesnt the fluid jump pump a caliper's hydraulic cylinder which squeezes the brake pads on both sides of the disc? where does the fluid have to "spread across"? And did your mechanic really call it fuel? From my knowlege it sounds like ur getting screwed buddy... Rumbling and scraping is usually the noise of just a worn down pad.
SAAB uses single piston calipers which means the fluid enters the cylinder and moves the piston which presses the brake pad onto one side of the rotor then this pressure operates through the rigid caliper to pull the pad onto the other side of the disc.
Unless the hoses are falling apart internally then all fluid exerts the same pressure throughout the hydraulic system. bear in mind that the front left and right rear calipers are on one circuit and the other pair are on the other. Brake balance is achieved by using a floating piston in the Master Cylinder to equalize pressure across both circuits.
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