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New Rotors installed


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Today I installed 4 new rotors (dealer direct, Porsche OEM). Used Loren's DIY, piece of cake, all rotors came out without any strugles. While the wheels where off, I did a thourough cleaning, and sprayed the inside with the silver metallic paint (2 coats) and enamel(2 coats). Amazing how the wheels look like new. All the black marks are history now. :clapping:

But here is the problem, did a quick drive up and down the street, and to my surprise the brakes where very weak. The pads are mid-life, the fluid is a week old. With the old rotors, the car stops on a dime. With the new ones, I have to drive like with a minivan. Is this normal? and if so, any idea of how long (miles) for wearing-in?

I am heading to Road Atlanta this weekend and don't want to fly into the wall with poor brakes :eek: . The old rotors where exactly and the low wear thickness. Thank you

Izzy

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I don't know how Porsche protects their rotors, but many manufacturers place a coating on the surface of the rotor that keeps it from rusting. You need to get this off before your brake pads will grab the cast iron. I always sand new rotors until the sandpaper quits skidding on the the iron and digs in, you'll see scratches at this point. Be sure to degrease them well with brake cleaner before you finish, one thumb print will cause chatter and uneven braking. Good Luck!

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Today I installed 4 new rotors (dealer direct, Porsche OEM). Used Loren's DIY, piece of cake, all rotors came out without any strugles. While the wheels where off, I did a thourough cleaning, and sprayed the inside with the silver metallic paint (2 coats) and enamel(2 coats). Amazing how the wheels look like new. All the black marks are history now. :clapping:

But here is the problem, did a quick drive up and down the street, and to my surprise the brakes where very weak. The pads are mid-life, the fluid is a week old. With the old rotors, the car stops on a dime. With the new ones, I have to drive like with a minivan. Is this normal? and if so, any idea of how long (miles) for wearing-in?

I am heading to Road Atlanta this weekend and don't want to fly into the wall with poor brakes :eek: . The old rotors where exactly and the low wear thickness. Thank you

Izzy

New rotors or pads are like brand new shoes for your feet. You need to wear them for a while before they get comfortable. Give them several miles and lots of stops, preferable light stops as not to generate too much heat too quickly. The pads have to wear in to the rotors. It's best to use new pads with new rotors as used pads even 10% worn do not usually wear evenly, but somewhat tapered or wedge shaped, and somewhat grooved. The pads have to wear in to be 100% in contact with the disc and it will take a little time, moreso with used pads rather than new. Another important consideration with worn pads and a perfectly flat new rotor, is the fact that the caliper pistons may want to cock or twist slightly in their bores as they follow an unevenly worn and beveled pad. This results in poor braking performance, accelerated wear of both pads and rotor.

Edited by nick49
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I looked at the thread... was it this one? If you didn't wash the rotors down with brake cleaner (i.e. Brakleen...this stuff, which I like), then your pads may be fouled.

They may also not be true to your new rotors; not as big a deal with multi-piston calipers. But, if you swap pads for track or other reasons, then keep them paired with the same rotor.

I've changed rotors and pads on numerous cars over the years; never had the condition you describe. You could mosey around for 100 miles or so to see if they improve, but I think you're heading to new pads, especially if you didn't clean the new rotors.

--Brian

Edited by Q-Ship986
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Looks like some people clean the rotors prior to install, others get new pads to go along.

I have used break cleaner solvent on BMW,Honda, and Volvo rotors, they did come coated with some cosmoline or other like coat. But the Porsche ones did not feel at all like they had a coating, no residue on the box or on my hands. They felt totally dry. So I didn't think to spray them.

The pads are probably half life OEM's. I also use Pagid oranges for track day. Thinking about driving this week the long highway way to work and back, light braking. If they are still garbage by Wednesday, probably change to the Pagids, which are only used on track and have a couple hundred miles only.

Or should I change to Pagids tomorrow, more aggresive bite will bed-in the rotors faster?

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But here is the problem, did a quick drive up and down the street, and to my surprise the brakes where very weak. The pads are mid-life, the fluid is a week old. With the old rotors, the car stops on a dime. With the new ones, I have to drive like with a minivan. Is this normal? and if so, any idea of how long (miles) for wearing-in?

Izzy

Izzy,

I notice that at the end of his pad change DIY, Loren says new pads need to be bedded in, and that it takes 125 miles before they are fully effective.

It makes sense that if new pads have to bed into old disks, then old pads need to bed in to new disks ....

Kim

2000 Cab

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Thank you guys. This morning I mounted the Pagid oranges on the front and new Porsche OEM on the rear. Breaks fine. Pagids are always amazing, and I mount them a week before track day to get use to the fast braking. All seems fine, will keep them until after track weekend.

Wheels look great too, don't know why I didn't do this sooner. Don't know how long it will last, or how it will stand to the soap and scrubs.

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Thank you guys. This morning I mounted the Pagid oranges on the front and new Porsche OEM on the rear. Breaks fine. Pagids are always amazing, and I mount them a week before track day to get use to the fast braking. All seems fine, will keep them until after track weekend.

Wheels look great too, don't know why I didn't do this sooner. Don't know how long it will last, or how it will stand to the soap and scrubs.

I would be very careful about mixing matching different brake pads under any circumstances.

There is not much difference between a panic stop on the street at 60mph and hard braking on your favorite racetrac.

IMHO, different pads on a f/r basis will probably throw off whatever braking bias the good doctor has already built in.

Have fun, but be safe on track----

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Good point Dave. However I have been tracking with Pagids upfront for a while after trying different setups, and found that for my driving, the added front transfer gives me more agressive turning, less chance of ending up butt first on the grass (done that plenty of times!)

But I always go back to OEM street pads after tracking.

Izzy

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