Brake judder

[ricof]

I had the front disks and pads replaced on my 987.1 Boxster recently to try and cure some pretty substantial brake judder, on the advice of my indie. Pad shadow and blueing was reported to be the cause of it.

It has not solved the issue at all. Speaking to some learned Porsche drivers over the Le Mans weekend and it was mentioned that a suspension bush may be the culprit.

Any other advice on how to check this? Or indeed any other causes? Could the rear disks need replacing too?

[Jaybmw]

Feel it in the wheel or peddles? Are any of the calipers binding ? Can you feel the wheel vibrate say on a motorway. Yes it can also be a bush, it can also be a shock, hat etc . It can be many things unfortunately. But the simplest one first is check for binding

[Cankicker]

Get it on a ramp, get a guy to go round the suspension with a pry bar. 987 suspension is very straight forward. Two control arms, a strut, a spring & an anti roll bar. If anything's up with it, it'll be easy to find.

[Slippydiff]

Worn suspension bushes/components won’t cause blueing of the discs ...
I have no idea what pad “shadowing” is ?
As suggested, I’d be checking for seized pistons in the callipers, or a problem with the mater cylinder/brake pedal linkage, causing the brakes to stick on and overheating the pads.

[roboxm3]

I had this on my 986; took calipers off, pads out, discs off, double-checked all the mating faces and that the pistons were moving freely, checked disc runout, all the bushes, alignment etc. and it was still there.

I was having a read up on the possible causes and uneven transfer of pad material to the disc was mentioned. I struggled to believe it as there was nothing visible on the disc and even running a finger nail over the disc felt completely smooth.

Turned out to be true though and the best part is, the cure is a) free b) fun.
Get out and do some normal driving to get everything up to temperature, then do some very "brisk" driving and use the brakes very, very hard. Then do a few more miles at a sedate pace to let everything cool back down, using the brakes smoothly and try not to sit with them on until fully cooled.

Never came back after that, even with daily driving in traffic, where you would naturally hold the car on the brakes at a junction etc. I think it was just the case that I hadn't followed the break-in procedure to the letter and they (Porsche / Brembo, I don't know) didn't like it.

ps. Don't hold back...brake late and hard and smooth!

[ricof]

Since they have been bedded in, i've been driving the nuts off the car and including some very hard stops.

The trouble is, at high speeds, the vibration is so bad that really hard braking feels like its going to end in trouble. From moderate speeds, its easy to lock the wheels.

[Slippydiff]

ricof said:

Since they have been bedded in, i've been driving the nuts off the car and including some very hard stops.

The trouble is, at high speeds, the vibration is so bad that really hard braking feels like its going to end in trouble. From moderate speeds, its easy to lock the wheels.

What procedure did you use for bedding the new pads/discs in ?

[roboxm3]

ricof said:

Since they have been bedded in, i've been driving the nuts off the car and including some very hard stops.

The trouble is, at high speeds, the vibration is so bad that really hard braking feels like its going to end in trouble. From moderate speeds, its easy to lock the wheels.

I had exactly the same...took a few "sessions" to sort it completely but if you can rule out everything else, I'll bet hard and heavy braking will sort it.
You're not aiming to lock the wheels by the way and if they're locking easily from moderate speed I'd suggest something else may be amiss.
Despite the judder and horrible feedback through the wheel / pedals, I was still confident in the brakes to stop me from X2Xmph to 15mph or so in as short a distance as possible (15mph because I didn't want to stop with the brakes on while they were hot e.g. rolling into a roundabout).

[ricof]

Slippydiff said:

What procedure did you use for bedding the new pads/discs in ?

Moderate braking from 60mph to a near stop and letting disks cool then repeating a number of times. No harsh braking. No sitting on the brakes. Only after 400 miles or so did I start to push them.

The trouble is, it was exactly the same before the disks and pads were replaced so i'm a little naffed off at the indie as they were so sure that replacing them would solve the issue.

[SV_WDC]

Is that the correct breaking in procedure for 987 brakes/discs?

Pretty sure the documentation instructs no hard braking (except in emergencies) for 200-300 miles.

But as you say the judder was there before and after. Have the rear discs been checked?

[gwsinc]

Wheel vibrations can be a ballache to get to the bottom of. When I had a wheel refurb/tyre/brake change combo earlier in the year I found tyre balancing to be at fault, despite 'normal' balancing machines showing the wheels as balanced.

I had to find a garage with a Hunter Roadforce balancer top sort them out. I paid £25 a wheel which is the going rate for this, but it fixed it. :-)

[Slippydiff]

ricof said:

Moderate braking from 60mph to a near stop and letting disks cool then repeating a number of times. No harsh braking. No sitting on the brakes. Only after 400 miles or so did I start to push them.

The trouble is, it was exactly the same before the disks and pads were replaced so i'm a little naffed off at the indie as they were so sure that replacing them would solve the issue.

That sounds excessive, and as someone else has said, the recommendation is to avoid heavy/hard braking for the first 100-150 miles, as initially you’re attempting to bed the face of the disc and pads, once that’s done, you’re aiming to cure the resins and bonding agents within the pad by increasing the pad temperatures.
You’ve effectively missed out the bedding the pad/disc faces to each other, and gone straight to the curing process.
If there was an issue with the disc mounting (ie a hub not running true or similar) you’ve effectively reintroduced a/the same problem into the new disc.

My concern is you said your Indy stated the discs were blued, so either you’re driving the car hard (no harm in that by the way !!) and getting uneven pad transfer (as a result of the pads working outside their temperature range) OR the blueing is caused by the pads overheating for another reason. Be that a sized caliper or a problem with the master cylinder, the servo or their linkage/s.

[ricof]

SV_WDC said:

Is that the correct breaking in procedure for 987 brakes/discs?

Pretty sure the documentation instructs no hard braking (except in emergencies) for 200-300 miles.

But as you say the judder was there before and after. Have the rear discs been checked?

The ex-Porsche service manager recommended that method, so I did as he said! When I say moderate, I don't mean hard by any means.

[ricof]

Slippydiff said:

That sounds excessive, and as someone else has said, the recommendation is to avoid heavy/hard braking for the first 100-150 miles, as initially you’re attempting to bed the face of the disc and pads, once that’s done, you’re aiming to cure the resins and bonding agents within the pad by increasing the pad temperatures.
You’ve effectively missed out the bedding the pad/disc faces to each other, and gone straight to the curing process.
If there was an issue with the disc mounting (ie a hub not running true or similar) you’ve effectively reintroduced a/the same problem into the new disc.

My concern is you said your Indy stated the discs were blued, so either you’re driving the car hard (no harm in that by the way !!) and getting uneven pad transfer (as a result of the pads working outside their temperature range) OR the blueing is caused by the pads overheating for another reason. Be that a sized caliper or a problem with the master cylinder, the servo or their linkage/s.

I was not doing hard braking by any means. Moderate braking in that I actually reduce speed, rather than feathering the brakes for half a mile or so. I've just had the old disks out and I can't see any evidence of blueing, actually.

From my materials engineering knowledge I believe the curing process in similar compounds is done in advance of heat cycling (i.e bedding in). But I did drink a lot during my degree though.

[Slippydiff]

You need to check the discs for runout with a DTi gauge. If they’re within tolerance, you’re more than likely experiencing “inconsistent pad transfer” either due to incorrect bedding in procedure, or you’ve overheated them in use. If it’s the latter, you’ll need to fit some upgraded pads and fluid, if it’s the former, you need to ignore your service manager and just drive “normally/sensibly/a bit gently” for the first 150 miles after you’ve fitted new pads.
I presume you’ve used OE brake pads and discs ... ?

[ricof]

Slippydiff said:

You need to check the discs for runout with a DTi gauge. If they’re within tolerance, you’re more than likely experiencing “inconsistent pad transfer” either due to incorrect bedding in procedure, or you’ve overheated them in use. If it’s the latter, you’ll need to fit some upgraded pads and fluid, if it’s the former, you need to ignore your service manager and just drive “normally/sensibly/a bit gently” for the first 150 miles after you’ve fitted new pads.
I presume you’ve used OE brake pads and discs ... ?

Genuine Porsche disks and pads were installed - the units that came off were Pagid disks and Textar pads. Cost a pretty penny too so do not want to replace again.

I was led to believe that the 'inferior' non-Porsche parts were to blame, now I am not sure. I am inclined to suspect rear disks or suspension components. I am confident that the pads were bedded in correctly. Have bedded in many new sets of pads the same way on previous cars!

[Slippydiff]

Nothing wrong with Textar, they’re part of the Pagid group, and OE suppliers to Porsche. The Pagid discs have come in for some criticism, but I’ve never had a problem with them.
If the discs that came off the car aren’t blued, it pits a very different perspective on the problem.

[ricof]

Slippydiff said:

Nothing wrong with Textar, they’re part of the Pagid group, and OE suppliers to Porsche. The Pagid discs have come in for some criticism, but I’ve never had a problem with them.
If the discs that came off the car aren’t blued, it pits a very different perspective on the problem.

There is no evidence of blueing that I can see. What are your thoughts?

[Slippydiff]

ricof said:

There is no evidence of blueing that I can see. What are your thoughts?

If you’ve got the old discs, take a decent picture of both of them (both inner and outer faces) and post it up.