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Brake Pad and Rotor Wear Meaurements

skymast
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skymast Member

skymast

Posted
Posted

What is the correct way and appropriate tool to use to measure remaining brake pad and rotor thickness? TIA, Mark

ar38070 Member

ar38070

Posted
Posted

Rotor, use a micrometer. A dial caliper might work though it would depend on how much of a lip there is on the rotor.

Pad thickness use a ruler or using stock pads use them till the holes for the sensors are just worn into.

  • Admin
Loren Member

Loren

Posted
  • Admin
Posted

I think what is more important than rotor thickness is to inspect them for cracks. With cross-drilled rotors any crack 7 mm or more radiating from the edge of the rotor OR between the cross-drilled holes makes the rotor unsafe and not reusable.

post-2-1104973780.gif

1999Porsche911 Member

1999Porsche911

Posted
Posted (edited)

Or you can do it the way I did when I was a kid and couldn't afford new brakes. Simply listen for a loud grinding sound when applying the brakes, with probably one brake grabbing more than the other, causing the car to swerve into the other lane or off the shoulder of the road. No further testing is required to be sure that you need brake pad AND rotors.

OR you can to it the correct way....as Loren and ar38070 said above.

Edited by 1999Porsche911
  • 3 years later...
clay1067 Member

clay1067

Posted
Posted
Rotor, use a micrometer. A dial caliper might work though it would depend on how much of a lip there is on the rotor.

Pad thickness use a ruler or using stock pads use them till the holes for the sensors are just worn into.

How do you know when the sensors are worn into? Is it just increased brake noise or is there an actual warning light?

  • Admin
Loren Member

Loren

Posted
  • Admin
Posted
Rotor, use a micrometer. A dial caliper might work though it would depend on how much of a lip there is on the rotor.

Pad thickness use a ruler or using stock pads use them till the holes for the sensors are just worn into.

How do you know when the sensors are worn into? Is it just increased brake noise or is there an actual warning light?

The brake sensors are just a wire. When the wire wears through it breaks the connection and the light turns on.

  • 2 years later...
redcab Member

redcab

Posted
Posted (edited)

Sorry if my search technique didn't turn up an obvious answer to this....

What is the in spec measurement for front rotors on a 2001 996 ? 2-wheel drive cabriolet, if that matters. As far as I know the current set up is "stock" porsche.

My tech did a brake inspection and the pad came in at 3 mm (yes, I need to replace them) and the rotors came in at 1.037 without units, but I'm assuming that it's CM. What's the rotor spec?

Many thanks!!!

Jerry

Edited by redcab
  • Admin
Loren Member

Loren

Posted
  • Admin
Posted

Sorry if my search technique didn't turn up an obvious answer to this....

What is the in spec measurement for front rotors on a 2001 996 ? 2-wheel drive cabriolet, if that matters. As far as I know the current set up is "stock" porsche.

My tech did a brake inspection and the pad came in at 3 mm (yes, I need to replace them) and the rotors came in at 1.037 without units, but I'm assuming that it's CM. What's the rotor spec?

Many thanks!!!

Jerry

redcab Member

redcab

Posted
Posted

Thanks Loren, just a clarification for the neophyte in me....

The info you linked me to says the front wheels brake disk thickness is 28 mm new and at 26 mm wear it is gone. At 26.6 mm you've reached the spec limit.

The tech came up with a measurement of 1.037 for the rotor. I'm not any expert in brake anatomy, but it seems like he was measuring some other distance. How do I compare these 2 sets of numbers?

As always, thank you for sharing your expertise.

  • Admin
Loren Member

Loren

Posted
  • Admin
Posted

Thanks Loren, just a clarification for the neophyte in me....

The info you linked me to says the front wheels brake disk thickness is 28 mm new and at 26 mm wear it is gone. At 26.6 mm you've reached the spec limit.

The tech came up with a measurement of 1.037 for the rotor. I'm not any expert in brake anatomy, but it seems like he was measuring some other distance. How do I compare these 2 sets of numbers?

As always, thank you for sharing your expertise.

1.03700 inches = 26.3398 millimeters

So, I would change the rotors out.

  • 3 weeks later...
SA321 Member

SA321

Posted
Posted

how is this possible? i bouth my car with 10k km from Porsche dealer as porsche approved car. car now has 70k km (45k miles). I look at the front pads and there is about 8 mm left in them so half worn from new. the rotors to have groove on the edge which i can feel with a thumb (dont have the measuring tool yet but my guess is that both sides will be close to two mm together). even if I assume that the dealer has changed pads at 10 k km is it possible that the pads can last so long while the disks last so little? Porsche dealer would not put non-OEM pads is my thinking. Car is 2004 c4s.

Any thoughts?

  • 3 years later...
  • Admin
Loren Member

Loren

Posted
  • Admin
Posted

Is the minimum thickness for rotors the same for 996 and 997-1?  

 

996:  Fr = 28mm, Rr = 26mm.

 

Yes - since the 997-1 uses the same (iron) brakes as the 996 series.

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