Kirk930

Car is an '87.......97000 miles.

I just changed the front rotors and pads. Zimmerman rotors and Hawk HPS pads. I've changed brakes many times, including an SC and a 928, but never this 930.

I tightened the wheel bearings with the recommended method.....screwdriver pressure to move washer without using hub as a lever.

I broke in the pads according to Hawk instructions.

Car has a slight pull to the right and a "grab, release, grab, release" feel under light to moderate braking. If I let go of the steering wheel as I apply brake pressure I can see the "grab, release" and the wheel begins to turn slightly right.

Also, when driving there is a slight pull to the right....I would assume because of the brake drag.

Have I installed something incorrectly? Warped new rotor?

Ideas?

Kirk

DeWolf

Sounds like a sticky piston/pistons in the caliper. You can remove the caliper, pull back the piston seal carefully and run a little bit of brake fluid around the top of the piston. This worked on my old girl.

Dave 86 930 Fl

I've been fighting brake problems since last December, finally removed all of the brakes and the problem went away.

Regards, Dave

Geoffrey

So Dave, you have no brakes on your car at all?

PorschePhD

Push the pucks back in and bleed the system. Do it two or three times and see if it goes away. Sometimes they just get sticky.

Kirk930

Great idea....never thought of that! Why the bleeding?

None of the pistons were stuck when I replaced the pads though......they all moved in very easily.

I'll try it and see.

Thanks.

ferraripete

kirk,

when i was racing back in the imsa firehawk days, we were always told never to bed in new pads and new rotors at the same time. under proper bed in, the pads are to be run to fade with a few aggressive stops and then cooled to ambient. this is obviously done at high interface temp and thus can be a bit hard on a green rotor. under most street bed in practices...the green pad , green rotor issue is less likely but should always be considered.

best,

pcb

Kirk930

Hmmm......I did do one "spirited" stop shortly after bedding the pads from about 120 mph

I had just installed a wastegate pipe (without muffler) and was blasting around some deserted farms roads (don't worry - perfectly straight and no crossroads!) laughing at the afterburner noise.........

Could the ONE high speed stop have warped the rotor? They're made to do that kind of thing all day aren't they?

I'll check the pistons tonight........I guess my focus should be on the right wheel.

Dave 86 930 Fl

Dry humor, sorry.

Geoffrey

No, you won't warp a 930 rotor.

Kirk930

Good! That's what I wanted to hear.

Anything special about freeing up a sticky piston? Caliper rebuild necessary? I'd like to avoid that if possible. There was no indication of a sticky piston prior to the replacement. I guess pushing the pistons all the way back in the bore may have caused the problem.

SGOGT4

Is that comment specific to factory rotors or does it also apply to OEM aftermarket (zimmerman)?

gr1275

Kirk,
You mentioned a slight pull to the right... I had that problem along with a "sticky" piston symptom that ended up being the right hand flex line going to the caliper. Although it looked and felt fine, it was coming apart inside and restricting the flow of fluid both in and out of the caliper.

125shifter

I've also seen a stock Porsche flexible line fail, so that could be it.

When I rebuilt my calipers, the pistons were actually in very good condition so maybe just working them in and out would fix a sticking piston.

Kirk930

I just had the wheel off and tried pushing the pistons in with the pads removed, and pushing them out with the pedal and pads in. One of the four (top outboard) seems slightly harder to move, but not stuck. Maybe that's all it takes. I repeated this three times and took the car for a drive. The problem is still there but seems to come and go now. It seemed to improve after a couple of hard stops, but eventually returned. ?????

I've ordered new bearings and rubber hoses. The front lines are stainless and I have no idea how old they are. I guess I should rebuild the calipers too. Why the high price compared to other rebuild kits? I realize there are more pistons but..........