Hi All,

Enjoying the new to me 2005 car much and have a question. Under light braking I am getting some vibration/feedback through the steering wheel, stops straight, no pulling, but some vibration like a warped rotor. Under hard braking there is none. Is this normal?

The PPI from Porsche dealer was clean.

Vehicle only has 12,000 miles on it, no PCCB.

Thanks!

 

It is normal only in the sense the rotors have varying friction coefficents around their working surfaces that account for uneven braking action.

I've never had this problem with my Porsches but I had it once with my VW Golf TDi. What happened was I washed the car and then let it sit. The rotors of course rusted up.

I drove the car and had to make an emergency stop before I had used the brakes, which would have removed the rust. The hot pads/rotors remained in contact with the rust (dust) present and from then on the brakes would pulse lightly under light braking.

I tend to use a harder more agressive braking technique so the symptom ever hardly appeared. In fact I sort of forgot about it until I went to sell the car -- with the original brakes -- at 140K miles and the buyer, a woman, who engaged in very light braking noticed the pulsing right away.

Oh, the dealer even though the car was under warranty refused to fix this: a light clean up skim of the rotors should have done it.

Also, I tried a brake rebedding operation which didn't help.

If the symptom is not too bad, maybe you can live it, get around it, by adapting a slightly more agressive braking technique which will have the added benefit of prolonging brake life.

If you can't live with it then you can try a brake bedding in operation but my WAG is this will not help and could -- it didn't in my case but... -- make things worse.

Another alternative is to see about having the brake rotors cleaned up, lightly resurfaced. You can keep the old pads if they have good life left but you'll have to bed them in to the resurfaced rotors.

Or if the rotors are too thin they'll have to be replaced.

Always after you wash the car drive it and use the brakes to get them hot and dry before you park the car.

If the car has sat for a while and the rotors have developed a bit of rust, use the brakes, but do not bring the car to stop, to scrub away the rust.

Also, keep the holes in the rotors free of any dust/rust buildup.

Sincerely,

Macster.

 

Don,

When was the last time the brakes were bled??

T2

 

Thanks guys.

When I bought the vehicle 2 weeks ago I had a full service done and brake fluid change so assume they bleed the brakes during the fluid change?

On 6 Speed they are recommending doing a brake bedding. Relative to brake bedding can it be done to a vehicle with 12,000 miles on it? Any potential negative after affects?

 

That is the first thing I thought. Go to zeckhausen.com and read up on the white paper on bedding.

"can it be done to a vehicle with 12k on it"?!?!?!?

She's not a child Don...DRIVE IT.

 

You can do a brake bedding in operation at any time, but the only time it is called for is when the pads or pads and rotors have been replaced, or in rarer cases when the rotors have been resurfaced whether the pads have been replaced or not.

There is a theoretical risk in doing this for pulsing brakes and that is because in your car's case the braking action is uneven under the hard braking during the bedding in procedure the very high and uneven heating that is results could make the pulsing worse afterwards.

This did not happen though with my VW. But the rebedding operation had no benefit either. But maybe in your car's case it will help.

It costs just a bit of time and a bit of gasoline. You want to pick a section of road where you can get the car's speed up to freeway or higher (safely!) speeds and apply the brakes very hard, but short of triggering the ABS. Be sure you avoid bringing the car to a stop wth the brakes hot from any of the bedding in hard braking operations (2 or 3 will suffice) and after the last hard brake drive the car long enough keep it moving long enough to get the brakes as cool as possible or you could make the symptom worse.

Sincerely,

Macster.

 

It's not hard to take the pads and rotors out. Get some emory cloth and brake cleaner then clean everything. Mic your pads and rotors, if you can't take them to a local Oreillys or Autozone and they'll do it for free. Do it in a couple of spots on the rotors to make sure it's the same on that rotor.
After all that ( being everything is w/in Porsche spec ) I'd try bedding the brakes.

But that's just me, I'm sure the extra work isn't for every1. But if you don't like it or it doesn't feel safe and you end up changing the pads & rotors out it won't hurt to try it because you'll have the same expense in the end for a new set.

Just my .02$ worth.

 

Also, with the front wheels jacked-up test the "play" in the wheels via the wheel bearings. I don't know what is allowable, but it is an easy adjustment if out of spec, and this can lead to vibration while stopping.

 

Do you have a shred of support for this blowhardy thesis you've concocted to support you initial post? (That bedding in only called for when replacing pads or rotors? (Or even better the theoretic risk???)

By extension, your thesis would be if someone inadvertently rested pads against super hot rotors and got uneven pad deposition they only fix is new rotors or resurfacing???? Rebed, done.

 

I would think if anyone had any grasp of basic laws of physics that the possible ramifications from doing a brake bedding operation with brakes that were already exhibiting pulsing due to uneven pad/rotor material deposition would see the potential that this would cause uneven heating of the rotor and generate hard spots that would further degrade the brake's performance.

We have seen a flywheel, at least I have, more than one too, that has hard (blue) areas from localized overheating and the clutch's engagement is affected to the point the car was brought in for this or we would not otherwise have the clutch hardware spread out to view.

The bedding in operation could also result in unparallel wear as the pads slide over the harder areas and then abrade the less hard area. However, this is less likely given the mass of the rotor. It would overheat and a large portion of the surface would harden and braking action diminished.

I was just being thorough. I did a brake rebedding operation with one of my cars and while it didn't help it didn't hurt.

But I do not want to be the one to say do X when Y can result (not a desired Y either) and have this time X result in while rare, Y, without at least giving the other person fair warning that Y was possible.

It is up the person to whom I'm addressing what he wants to do. I just want him to have as accurate as I can be foreknowledge for the risks albeit sometimes small regarding the suggested course of action.

Always, though, the best source of advice and counsel for these cars and their problems is a professional technican. I make no claims I'm that.

Even if one wants to try the rebedd operation he can always check or should check first with his trusted auto tech to get his input.

Oh, bedding in is called for when pads or pads and rotors are replaced, or when the rotors are resurfaced, because the mating pad and rotor surfaces may not almost certainly will not be making full/even contact.

The bedding in process helps accomplish this under controlled conditions and to develop or bring forth maximum braking action to have this available if an emergency braking situation arise.

In the case of new pads as they go through a couple of high heat cycles this generates and forces out gas that will as it being generated form a high pressure layer of gas between the pad and rotor surfaces. This gas layer can really make for lousy braking action. The bedding in operation heat cycles the pads a few times and their gas output falls to below a level of bother.

The best time to experience this is while one is bedding in the brakes under controlled and safe circumstances, not when he's emergency braking for his dear life.

Sincerely,

Macster.

 

Thanks all for your input.

Well I tried rebedding and that did nothing, no better, no worse.

Took the car to Porsche and they checked the brakes and unfortunately the rotors are toast. They believe that because the car sat for a couple years being used very little that washing the car and simply putting back in garage caused rust to eventually kill the surface which lead to the surface being unsavable.

New brakes going on today and UMW tune tonight. Cannot wait to drive with the new tune and no vibration.....

 

Oh, yeah, that kind of treatment will ruin brakes in no time.

I like you took the car to a pro. Brakes are very important and you do not want to be guessing if they're ok.

Check with the tech about what if any bed in he recommends and follow his recommendation.

Then never wash the car without a drive immediately after to dry the brakes.

Sincerely,

Macster.

 

I would think if anyone had any grasp of basic laws of physics...

in process helps accomplish this under controlled conditions...

under controlled and safe circumstances...

Macster, I assume by those statememts you don't have a lot of freinds who sit on tailgates w/ a 12 pk of keystone light arguing over who's gonna light the M80 on the ant hill , do you?

.

 

In case it needs to be pointed out, Mac is totally in the bag for anything "Porsche":

Keep it stock

Take it to the dealer.

Spend as much as possible, the more you spend the better it must be.

Do whatever they say..after all if it has Porsche on it, it must be better.