Brake pad wear sensor...

When a brake wear sensor is triggered, how many miles (normal driving) until the pad material is gone and the rotors start scoring? I know mine are getting there and I just bought new pads, rotors, sensors and caliper bolts. My pad material is about as thick as the backing plate right now on both fronts & rears, so sensors will trip soon. I may be splitting hairs here but here are 3 scenarios: 1. I could just replace pads and rotors now before the sensors trip and reuse the sensors (send new ones back for refund), eliminating having to replace them. Not that they are costly. 2. Let the brake pad sensors trip and then replace rotors, sensors, pads all around immediately. 3. Let the brake pad sensors tip and continue driving until the pad backing plate hit the rotors, then replace rotors, sensors and pads all around. (This is why I ask the first question.) Since I only put between 2,000 & 3,000 miles per year, option 3 may make sense. If once the sensors trip there is 5 or 6 thousand miles before the pads hit the rotors, that could be 2 or 3 years more of life in the old brake pads. If only 1 or 2 thousand then maybe just replace everything once sensors trigger. Any safety issues going with option 3?

Option 2 sounds like the best decision. When the sensor hits you are down to 1 or 2 mm left. It all depends on driving styles but usually less than 1k miles is expected.

Option 4, replace it all with the new parts, including new (and inexpensive) wear sensors. The idea of option 3, driving until you are into the metal backing, seems foolish and dangerous to me.

Quotes source posts: 15671370, 15671404

Only 2 responses so far, but I have a feeling option 3 is out.

Wait till you see sparks coming out of your rear wheels from the side mirror then you know for sure the pads are completely worn out Kidding aside, I like option 2 followed by option 4.

Let me also add that running he pads to metal to metal causes the caliper pistons to be pushed out further than they should be. It's not work the risk of damaging expensive calipers not to mention the safety aspect. Too many times i have seen cars come in with pads actually missing and the caliper piston is contacting the rotor - that's when the customer says "it only started making that noise a few hours ago".

Quotes source post: 15671461

That would be BAD ***, especially at night.

2 and 4 in that order.

If I recall correctly, my brakes squeaked pretty loudly as the sensor materials started just peeking through and touching the discs. I drove it about a week - it didn't trip the sensors and I was able to reuse the sensors.

I did my brakes last summer at option 2. I really like having brake pad material when stopping my car vs metal on metal. New rotors, pads, sensors and misc bits. Plus SS brake lines since was still on original rubber hoses.

New pads have about 10mm pad thickness, the wear sensor is set at about 2mm. I have seen people wear out a set of pads in a couple of DE track days, I have also seen people drive 100k miles on their original pads. For most people, when the wear light comes on(2mm), there is no need to re-arrange your whole life to get your brakes done, (ie. take off work, cancel your doctors appointment, ect ) but you should plan to get them done at your earliest convenience.

Why are you replacing your rotors? Are they worn thin past the wear limit or are your brakes pulsing in some way? To me, the normal thing to do, as long as your brakes are not pulsing/vibrating, is to run them until the sensors come on, then change the pads, and check the rotors for thickness and excessive scoring, etc, and if all is well, keep going. After you do this job once, you will see that Porsche has made it very easy to change pads. Once you have your wheels off, it's like a 2 minute job. What I'm sayin' is, no reason not to just have a look at everything before you buy, and then don't buy stuff you don't need. But, that's just me.

The OP says he already bought all of the parts. And wear sensors are so inexpensive that it seems silly not to replace them. At least to me.

Quotes source post: 15672448

I use the Boy Scout method, "be prepared." Over a year ago I inspected my complete braking system and determined my brakes were going to need replacing soon. Pads F&R were nearing minimum thickness. Rotor thickness both F&R were below minimum thickness spec. I buy parts proactively on sale and during deep discount holiday sales. So in a nut shell I knew what shape my brakes were in over a year ago, estimated about when they might need replacing, then shopped the parts that i knew would need replacing during the year before I estimated doing the job.

Just so everyone can sleep at night. Going with option #2. Let the brake pad sensors trip and then replace rotors, sensors, pads all around immediately.

When you do the replacement, make sure you use plenty of brake grease to prevent any pad knocking. Mine were quite loud and I had to redo to the pads to add more Cerami-Glyde. Though that may be related to my use of Akebono Euro pads instead of OEM.

So any videos or instructions on replacing the pads and sensors?

Rolex, Apologies if I sounded a bit critical. Didn't mean to be. Obviously, you have it well in hand with your inspections. I'm learning that I also should be planning ahead for tires and brakes! To attempt to say something more useful to your original question, I just replaced the rear pads in my '04 C2. I'll guess that it was 1000 miles between the first warning light and the replacement. (I drive the car 350 miles a week.) The pads still had material, but one of the warning sensors was half worn through at that point. Bottom line, I'm surprised at how fast the rears wear. I have about 30k on it since everything was new (when I bought the car 20 months ago) and the fronts are at ~ 50% ish, and the rears were gone. Just like the tires, come to think of it. Welcome to rear weight bias I guess. I drive at a "brisk" street pace, nothing crazy and no track time.

I'm with D.L. on changing rotors. I get at least two sets of pads out of one rotor. You can buy a cheap micrometer off the internet for $15. The fancy ones built especially for rotors are $40. I've got 35K on an 09 Boxster with 15 track days with the original OEM rotor on the rear. I ordered a new rotor and pads all around, but when I measured the rear it was no where near the minimum. The front is a different story. Put on a dedicated track rotor late 2017 and replaced last August. The brake pad dampers on the front are a pain. Took them out when we put on the track rotor. Saved the original OEM rotors and pads. Put the OEM pads back in if I'm going any extensive street driving since the track pads really squeak. Changing pads is now a simple job front and rear. I have new sensors but have been reusing the fronts. The rears practically feel apart when we took them off. Assume from engine and exhaust heat. Wire tied the rear ones out of the way but reinstalled the fronts. Many if not most who regularly track their cars have the brake pad sensors tied out of the way or on a shorted plug. Makes changing pads quicker. Pads and rotors are checked after almost every session but thoroughly each morning. You can't completely remove the sensors or you get an open circuit and a brake pad warning light. Get replacements for the two rotor retaining screws. They take a beating if you use an impact driver. If you are just beginning Harbor Freight sells an inexpensive low profile aluminum jack by Pittsburgh which is great for jacking up the car. Get a (hockey) puck to protect jacking points. The price from a dealer or even an indy to this work is all the motivation I've ever needed. 09 Boxster PDK w/Sport/Sport+ 00 BMW 320Ci-Gone and missed 85 Saab 900T autobahn cruiser for 5 years 65 Mustang 289 4 speed First love​​​​​​ 16 MB GLC 300 DD