What is the consensus about whether the brake pad warning sensor gives adequate notice to replace? I have 34k on my pads and no sign of a sensor light yet.

I've read in another thread that by replacing the pads "early" heat damage to the rotors can be avoided. In yet another thread it indicated that several hundred miles are still left once the light goes on.

My plan is to wait for the light and then replace the pads. Are those sensor lights reliable?

 

doesn't porsche measure your pads when taken in for service? (sorry, not sure because I haven't hit the miles for my first service)

on all my previous cars, I always replace them all before the brake lights warning actually turns on, I know the widths of the pads from each service

another reason is that, once the warning light is on, you have to spend additional money to replace the sensors

 

Good points, kechang. The problem is the dealer often wants to replace the breaks early...

 

The flashlight and finger technique never fails
If you wait till the light comes on then they will already be down to the end.

 

Sensors ARE reliable. No need to worry. On pre2011 Cayennes usually received brake pads replace warning for the FRONT pads first at about 34Kmi. On an after2011 Cayenne received the same warning message for the REAR pads FIRST at about 52Kmi. ...for the same driving style and tires...

No need to worry for the heat damage. There is plenty of pad material/protection left AFTER warning indicator goes off- about 2mm to be exact. It's enough for 1000-2000 additional miles of driving...

...good plan. I've always done the same. Dealer wants to make MORE money by replacing components too early.

 

The sensors don't cost much and should be replaced with the pads regardless if the light goes off or not. The sensors are not damaged when they go off, but if you keep reusing them they are likely to fail without you being aware until you are eating your rotors. Pads that are supposed to have sensors typically don't have the squealer tabs so you get no warning until you are grinding you rotors (and consequently have crap braking ability). I have seen people (including myself) skip the sensors and then have them fail before the next pad change.

Now Porsche wanting us to replace the rotors with every pad change regardless of thickness is another matter.

 

I agree with everything else you are saying but all the sensors I have used on my three Boxsters are destroyed when it goes off. It is an 'active' system and when the sensor is worn it breaks the circuit.

Here is one that monitors both pads on one caliper:

 

Ahh. Thanks for the updated info. The 996 and BMW sensors (haven't needed brakes on the P!g yet) I'm used apparently work a bit different as they appear to use a range finder of some sort.

Still, they are cheap and not worth "saving"