When to replace the brake pads?? - 986 Forum - The Community for Porsche Boxster & Cayman Owners

BoomerRoadie · 12-01-2016, 07:11 PM

Hi.

I noticed my front pads appear to be about 1/8" thick (maybe a bit more) and the rears look to be about 3/8" thick (also maybe a bit more).

I'm thinking that the front should be done soon, but how thin it thin enough?

Also, I have never done a break pad job on any car before, but doing it on my 1997 Boxster seems like a fun, rewarding and major cost saving project. I've watched some videos and it really seems simple to do.

So, thoughts on how thin I can wear those pads down? and thoughts/guidance on doing it myself.

Any help will be great!! Thank you all.

Adam

thstone · 12-01-2016, 07:40 PM

The easiest way to know when to replace the pads is when the brake pad warning light illuminates on the dash. Each brake pad has a "sensor" that consists of an electrical loop of wire that is inserted into the brake pad and when the pad wears down far enough the loop is broken (which breaks the circuit) and the light on the dash turns on.

Alternatively, you can manually inspect the pads and replace them just before they wear down to the pad sensor hole that is molded into the edge of the brake pad. This will also save the cost of a new brake pad sensor.

Also, be sure to measure the thickness of the rotors to be sure that they are still within allowable thickness.

Brake pads are a fairly straight forward DIY and there is a lot of experience and help available here on the Forum.

Here you can see the pad sensor holes on the edge of this new set of pads...

Here is a completely worn set of pads - don't wait this long!

JayG · 12-01-2016, 09:05 PM

From new to gone in one track day
That some pretty heavy braking Tom

jcslocum · 12-02-2016, 04:06 AM

Rule of thumb is when the friction material is the same thickness as the backing plate, then it's time to replace.

Measuring the rotor thickness is more tricky. The ridge and grooves make it hard to get a real accurate measurement of the thickness. There is a special gauge for this:

How many miles on the car??

BoomerRoadie · 12-02-2016, 04:58 AM

Ok cool.

I'm a little confused then....

When I said I have about 1/8" in the front and 3/8" in the rear, I estimated this by looking through the wheel on an angle to see what I thought are the pads.

Are you saying/showing me that in order to really see the remaining pad thickness, you need to take the wheel off and look at it face on?

I can send a picture of what I think is the pad, but not until tonight. But basically I'm looking at the part that comes in direct contact with the silver disk. I can only see the outer pad.

Assuming I have this correct, based on this statement: "Rule of thumb is when the friction material is the same thickness as the backing plate, then it's time to replace." I should replace the front pretty soon, like as in the next 1000 miles or less.

The car has 37,000 miles on it.

Anker · 12-02-2016, 05:10 AM

There are several DIY articles available on replacing pads and other common repairs. I would also recommend two books: 101 Projects and the Bentley book. Both are available on Amazon. I bought mine used.

I bought all the needed parts from Pelican. Lots and lots of choices. I buy parts from manufacturers that are OEM suppliers to Porsche, not the grossly overpriced Porsche branded parts.

Its actually quite easy. Take care that you get a long reach, low profile floor jack and decent jack stands. It is not safe to do repairs with the car held up by the scissor jack.

Anker

jcslocum · 12-02-2016, 05:19 AM

At 37,000 miles the rotors (silver round thing) should be fine.

Yes the backing plate is a steel piece that the friction material is bonded to. When you look in there you can see 1 side and if it's 1/8 of an inch, then replace NOW.

Just to be perfectly clear, ( we are talking brakes here ) the backing plate is the outer yellow piece that has the silver pin in the center running thru it. OK? The friction material is also yellow but smaller and the pin does not go thru it.

Now, we are talkin about a MAJOR safety system that keep you safe but also those around you. If you do not have the knowledge, skills or tools, please ask for help or take it to a shop and watch. I have no idea where Fountain Hills is, but if I were close I would come and help you learn this simple but very important task. Please take no risks with this work!

JayG · 12-02-2016, 06:48 AM

If you don't have calipers with the pins, an easy el-cheapo way to measure the rotors is to use a couple of thick washers on the rotor surface, measure and then subtract the thickness of the washers
Yuo can buy a decent digital caliper from Harbor Freight for around $10. Mine look just like the ones Jon posted, but without the pins

Brake pad changes are probably one of the easiest DIY you can do.
It takes more time to jack the car and remove the wheel than to change the pads.
Once the wheel is off, it takes me maybe 90 seconds to swap out the pads

BoomerRoadie · 12-02-2016, 12:25 PM

Ok here's what I'm going to do, I will post a photo of what I'm looking at and first see if it's what I think it is. I'm I'm correct, the front is about 1/8th inch remaining.

Here's the deal though, when I take the picture, the wheel will be on the car. I cannot take the same picture as shown above with the yellow pads (unless there's a way to get up under there, I guess I can try that too.

Anyway....hold this thought. I'll update this page with some pictures.

Thanks all...oh yeah Fountain Hills, Arizona. The weather is awesome this time of year!!

Meir · 12-02-2016, 12:28 PM

Quote:

Originally Posted by jcslocum

Rule of thumb is when the friction material is the same thickness as the backing plate, then it's time to replace.

Measuring the rotor thickness is more tricky. The ridge and grooves make it hard to get a real accurate measurement of the thickness. There is a special gauge for this:

How many miles on the car??

nice tool.
i went mcgiver, and made main from a $10 HF caliper, 2nuts and hot glue.
on a second thought, the original macgyver would probably use chewing gum instead of hot glue

Anker · 12-02-2016, 12:30 PM

I don't understand why you can't take the wheel off?????

You need to do that to examine the pads.

Anker

BoomerRoadie · 12-02-2016, 02:25 PM

Take a look.....

Now here is what I think is the pad.

Is that 1/8" thick section the brake pad? If so, I'm thinking that the brake light should be coming on pretty soon and that I should be ordering parts very soon.

Thoughts???

jcslocum · 12-02-2016, 02:30 PM

Yes, that is the pad material you have pointed out there. They are close to being in need of replacement as they look to be slightly thicker than the backing plate.

jcslocum · 12-02-2016, 02:34 PM

Quote:

Originally Posted by Meir

nice tool.
i went mcgiver, and made main from a $10 HF caliper, 2nuts and hot glue.
on a second thought, the original macgyver would probably use chewing gum instead of hot glue

It's a great tool and not expensive at about $35. I don't have one BTW. I do kinda like you but used ball bearings, flats ground on the back and the same HF calipers, so I can get into the grooves and get a truer min. measurement.

Anker · 12-02-2016, 04:14 PM

Harbor Freight has one for $25. For this kind of work their stuff is great.

Anker

MarkAP · 12-03-2016, 11:14 AM

Quote:

Originally Posted by BoomerRoadie

Ok cool.

I'm a little confused then....

When I said I have about 1/8" in the front and 3/8" in the rear, I estimated this by looking through the wheel on an angle to see what I thought are the pads.

Are you saying/showing me that in order to really see the remaining pad thickness, you need to take the wheel off and look at it face on?

I can send a picture of what I think is the pad, but not until tonight. But basically I'm looking at the part that comes in direct contact with the silver disk. I can only see the outer pad.

Assuming I have this correct, based on this statement: "Rule of thumb is when the friction material is the same thickness as the backing plate, then it's time to replace." I should replace the front pretty soon, like as in the next 1000 miles or less.

The car has 37,000 miles on it.

I develop the friction for a major brake pad manufacturer and we recommend that you change your pads when they reach 3mm of thickness left. The reason is that most companies use an "under layer" beneath the main friction material. Typically, these are 1.5 to 2mm thick in the OE pads (ours too). The under layer will have some stopping ability but do not wear too well so once you reach it it will be gone quickly.

Upshot is you should change the front pads soon. Rears are ok for a little more mileage.

Mark

lkchris · 12-03-2016, 04:31 PM

It's fun to use the special gauge to determine rotor thickness, and I have one, too, but it's not really a required tool.

Your rotors are allowed to lose no more than 2 mm thickness from new.

It's pretty easy to feel for a lip at the outside edge of your rotor, and if there is one it really can't be more than 1 mm higher than the rest of the rotor surface. Remember the same lip almost certainly exists on the other side of the rotor which is of course harder to see. So, 2 mm loss is 1 mm on each side. One millimeter isn't very much, and if you have any lip at all it's likely pretty close to 1 mm and it's time for new rotors. You've got a ruler or tape measure somewhere to remind you what 1 mm looks like.

And, it is senseless to put new pads on worn rotors.

And, to replace the rotors, you have to remove the calipers first and reuse of the screws that mount the calipers is forbidden.

All that being said, I'd have to add that for someone that's not sure where their brake pads are and (I assume) not really sure whether you even have wear sensors installed, I'd advise at the minimum finding a friend that's done it before to assist. Perhaps there's a VERY basic u-tube out there that would help quite a bit, but at your novice level it's pretty doubtful that a bunch a typed words from a forum will get you through it. In any event, attempting this and about any level of DIY maintenance without reference to a repair manual is not wise, to say the least.

Full disclosure: I used to produce repair manuals as a job. Mine was of course a Military situation and you were required to have someone read the steps EVERY time.

BoomerRoadie · 12-04-2016, 07:07 PM

Hi . Great info! Yes I am a novice. But I also know my limits. I posted the pictures to confirm what I knew from other cars just to be sure things were not more complicated which is what I keep expecting with this car. I think changing the pads and oil is easier on this car than on my Toyota 4Runner!!

And yes I have help too and I too have writen manuals and I am not wholly reliant on this forum for information. I'm using YouTube, manuals, books, experience, questing mentors and asking lots of question (many of which I know the answer too to test the answers I get, that's how I find the smart people).

I will order my parts tomorrow.

I think I'll follow up in this thread for a progress report.

Thx!!!

jb92563 · 12-05-2016, 06:06 AM

Boomer, once you have the brakes replaced and the wheel off you might also consider purging the brake fluid with new fluid.

I think the recommended interval is 3 years. There are 2 nipples at each wheel, on the calipers, to bleed and many of us use a pressure bleeding system like Motiv to make it quick and easy to do.

We alternate brake fluid colors at each change to make it easy to see when the new color starts coming out the bleed line so you know when you are done.

Note: The video only shows 1 of the 2 bleeder nipples being bled. You should bleed both nipples.

If you dont want to pay for the bleeder you can DIY and make one with a pesticide sprayer and a rubber stopper to fit your brake reservoir.

You need a small pressure guage as well as you don't want to over pressure the system and blow out any seals in the reservoir.

Anker · 12-05-2016, 06:22 AM

Good video, but

Get a good shop jack. The scissor jack is a pain in the butt, and you will need the shop jack to put the car on jack stands.

Why not use the impact driver to loosen the wheel nuts after jacking up the wheel?

The tool kit has a threaded guide in it to help put the wheel on. You can see what a pain it is to get the first bolt aligned if you don't use it.

I would never use an impact driver to tighten wheel bolts. Many impact drivers will over torque the bolts, even on the lowest setting. Easy to spin them in by hand and then use a torque wrench set at the proper torque.

He isn't tightening them in the right sequence. Always skip over one bolt going in one direction.

Anker