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Pads AND rotors?

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Old 03-10-2018, 09:00 PM
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mdsarch
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Default Pads AND rotors?

I am into my second year of ownership of my C4S. When I bought the car I replaced pads and rotors all around. I put on pads for 80/20 Street/track use. I canít remember the pads but I just had them replaced and was told I needed new rotors as well. Is this normal? The tech said thatís what they typically do. I had a 964 prior to this beauty and have to say I would get 3 pads/rotors replacement. Anyways, thought I would ask the community here. Thanks
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Old 03-10-2018, 11:01 PM
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Unless the pads you were using were too agressive (metal?), the rotors shouldn't need to be replaced that soon.
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Old 03-10-2018, 11:58 PM
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2nd. You should get several sets of pads per set of rotors unless your pads are exceedingly aggressive, which it sounds like they're not.
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Old 03-11-2018, 08:01 AM
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If the rotors need to be changed you should be able to feel a lip on them. It's an easy enough job if you have an impact driver in your tool kit. Go for it.
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Old 03-11-2018, 10:25 AM
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Thanks for the confirmation as it seemed excessive. I will check to see if there is a lip on the rotors.
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Old 03-11-2018, 11:36 AM
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IMHO the best method is to measure the thickness of your rotors using a micrometer (Harbor Freight makes an economical 3-tool set which is plenty accurate enough for this purpose). Provided the rotors are above minimum thickness and show no significant cracks linking up between ventilation holes, you're perfectly fine reusing them. The minimum thickness is cast or stamped into the rotor (factory ones, at any rate) or you can find this info in the service manual.

Brake rotors are a wear item and WILL develop a "lip" in use. It's how big the lip is--or, conversely, the thickness of the rotor in contact with the brake pads--that really matters.

Good luck.
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Old 03-11-2018, 10:22 PM
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Originally Posted by 02TX996Cab View Post
IMHO the best method is to measure the thickness of your rotors using a micrometer (Harbor Freight makes an economical 3-tool set which is plenty accurate enough for this purpose). Provided the rotors are above minimum thickness and show no significant cracks linking up between ventilation holes, you're perfectly fine reusing them. The minimum thickness is cast or stamped into the rotor (factory ones, at any rate) or you can find this info in the service manual.

Brake rotors are a wear item and WILL develop a "lip" in use. It's how big the lip is--or, conversely, the thickness of the rotor in contact with the brake pads--that really matters.

Good luck.
With the amount of track time you have planned, they'll crack up pretty fast and need replacing long before they wear down. So unless they are already close to wear limits, I'd say reuse them. Also, every time you remove & reinstall the calipers to change the rotor you are getting closer to the inevitability of stripping the threads on the upright.
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Old 03-13-2018, 08:46 AM
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I'd say change the pads, leave the rotors and find a new shop
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Old 03-13-2018, 01:53 PM
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Originally Posted by jayzbird View Post


With the amount of track time you have planned, they'll crack up pretty fast and need replacing long before they wear down. So unless they are already close to wear limits, I'd say reuse them. Also, every time you remove & reinstall the calipers to change the rotor you are getting closer to the inevitability of stripping the threads on the upright.
Agreed. As already stated, if they are cross drilled rotors, unless the cracks are actually connecting holes, you are fine.

For the caliper bolts, use a little PB blaster and always start them by hand to prevent this. If you can’t get them started by hand, remove the brake pads and try again. After having two wheel carriers cross thread on me I’ve learned to be extra careful. Haven’t had a single problem since doing the above. The bolt for the front brake line bracket is even worse. I swap it out for an m6 stud on any car I plan on keeping.
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Old 03-13-2018, 11:06 PM
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Every driver, every mission, every car is different. It's a use-case determination and there is no right answer. Measure them with a mic, look for cracks, and propagation. Decide if you need that N-th limit of brake authority. No right or wrong answer here.
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Old 03-14-2018, 02:42 AM
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The wear limit is 1mm per surface, 2mm total. So if they are 28mm new, the wear limit is 26mm and should be replaced.
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