so my brakes started squealing occasionally so i figured i needed new brake pads. but when i run my fingernail along the brake disc starting from the center to the outer edge, i'll notice the outer edge has a distinct lip to it. maybe 1-2mm but theres def. an edge to it. . .

is this normal? they're not warped or anything like that (which is the only time i thought you had to change rotors).

please advise

 

You *should* change the rotors every time you change the pads. There is a minimum thickness that is allowable for a rotor, I don't know what it is for these rotors though. The ridge on the edge is how thick the rotors were when new, and as you can see, they are worn down now. How many miles do you have?

For $300 or so, I'd change them. Thinner rotors can't dissipate the heat as well.

Also, just cause your brakes are squeaking doesn't mean the pads are done. Have you checked and looked at the pad to see how much material is left?

- Anthony

 

i've honestly never heard of people changing the rotors along with the pads, is this a porsche specific recommendation?

so does a brand new porsche rotor not have the edge? it's weird that they'd design the pad not to contact the outermost edge

the brakes have ~30k of daily driving/cruising on them. ive never had a problem wtih brake fade, what else would cause the squeaking? it's intermittent

 

On most vehicles you should always change or machine (never machine your Porsche rotors) the rotors with new pads.

However, on your Porsche this is not necessary UNLESS your rotor thickness is less than the minimum rotor thickness spec'd by Porsche. Your Porsche can and is meant to be able to be pad slapped assuming rotors are in proper condition. If done properly there are no adverse problems.

About your squealing, cross drilled/cross cast holed rotors are prone to noise because brake dust will sit in the holes and at times may make noise when brakes are applied. You can try by cleaning only the rotors with brake cleaner. If you do this, you will already have your wheels off and at that time you can inspect pad thickness, measure rotor widths, and also look for any potential object that could be causing other noise.

Another nice feature about your brakes is that when your pads reach the nominal thickness, your red brake wear dash light will come on and tell you. This happens when the pads are thin enough that the wear sensor begins contacting the rotors. If you replace before this point, you can reuse sensors. If your dash light has come on, plan to replace the brake wear sensors.

 

It is pretty much a normal thing. Japanese cars can have the rotors machined/turned, but you can't do that with drilled rotors. German rotors are also a different composition and they don't turn well.

Correct. That is normal of every braking system, there is always a ridge on the edge from where the pad doesn't touch the rotor.

With 30k on the rotors I would replace them, especially if they are the fronts. It's really not that expensive...

- Anthony

 

Suncoast has a special on rotors this month. $259 for front set of OEM rotors: http://e-partssales.com/Merchant2/me...6BrakesCarrera

Great deal.

 

i've owned at least 6 different japanese cars and none of them have that leading edge on the rotor, they are all level from center to the edge

is 30k normal for porsche rotors?! i remember Car and Driver magazine had a long term 1999 911 and after 45k they estimated the pads and rotors would last till 80k

 

Yes. This is normal. Use a set of calipers and measure your rotor thickness. Brand new, rotors have thicknesses of: Front: 28mm Rear: 24mm. You noted 1-2mm of wear. This is getting close to the factory minimum wear limits of: Front 26mm / Rear 22mm.


IMO, you should only change rotors when you need to based on wear limits or cracking (7mm cracks or connecting holes), or any other factors indicating unsafe conditions. Depending on the type of pads and your driving style (street, track, traffic, etc), you may go through 2 or 3 sets of pads to a set of rotors. The rears and fronts may wear differently as well.


You can always replace them to be on the safe side, but you should measure them before you throw them out, as you can always use them in a pinch if they still have life in them. It is not unheard of to only get 30K, but it is also likely that 30K is only 1/2 of your particular rotor life.

Porsche rotors will not be level across the whole surface. The pads do NOT touch the entire rotor, which will result in a small lip on the outer edge. When you run your fingernail across the rotor and feel a pretty big lip, it is time to measure them.

Depending on what you do, and the type of equipment you have, you can get a long life, or a short life out of pads and rotors. More agressive pads used on the street (without a proper transfer layer as in a track application) will wear rotors down like sandpaper on a two-by-four. Less agressive pads (or OEM pads) will be kinder on the rotors AND the pads will last longer as well.

There are a few rotor options, but most use OEM/Zimmerman. You can also try PFC dimpled, as they last longer, but they'll set you back substantially more than OEM and you won't get any other benefit (besides longevity) unless you track your car.

-td

 

Recent (last 15 years, at least) BMW, VWs, and Mercs all have lips on worn rotors, as well. May be a European thing. If I had a 2mm lip on a rotor on the front, I'd check the back as well. Could be as much as 4 mm wear overall, as Tom said, have to use a caliper to be sure.

 

You have wear limits as posted above. If you're under, don't replace them unless of other issues with cracking etc. If you replace them prior to the wear limits, you're wasting money. Germans hate two things, wastefulness and something else....oh yeah, anyone who hates Hasselhoff.

 

Ditto that man... Get a set of measuring calipers and check for yourself. My rotars are down at 25.1mm (fronts) at 36kmiles, 30 laps of the Nurburgring, and 'several' hard on the brake trackdays. I doubt your lip is as big as you estimate but measuring is a black & white science, just watch those cracks more than anything else.

 

usually the fronts go quicker

 

996 BRAKES:

Timely topic - I too at 33k miles have the BRAKE WEAR light on in the dash. I plan to get to the shop this Saturday to learn more about rotors and pad replacement.

I would rather go to the dentist!

99C2

 

Goto Renntech.org and do it yourself!

 

yea, pad and rotor change is really not too hard to do. Might be worth attempting to do yourself or at least giving it a shot