I was drive a nice 996 TT with x50 and PCCB brakes as I like to buy TT Porsche, I I have several Porsche in my garage but never have or drive with PCCB brakes.
OK question when brakes were cold I find that brake pedal pulsate a little during soft braking? It is normal or could have some disc issue? When brakes going hot this problem going to be less visible but still some oscillation on pedal but maybe not enough hot?
I don't like to invest to new discs just after buying this car - so any advise invited

Tommy

 

A pulsing brake pedal with cast iron brakes is often a sign of unequal pad material deposition which generally can only be removed/eliminated by resurfacing (or replacing) the rotors. Once in a while a brake bed in procedure resurrects the brakes.

Less often a brake rotor mounting issue or even a wheel mounting issue is at fault.

A pulsing brake pedal in a car with PCCBs is something I do not think I've come across in my PCCB research. Even in Total 911 and its 3 article coverage of PCCBs I do not recall pulsing as one of the issues PCCBs can have.

Thus I'm a bit concerned you may be facing big brake repair bill due to at least rotor replacement.

Generally what I advise for a some acceptable issue like worn brakes would be to get a quote to address the issue and then adjust your offer price by that quote amount. Given the high cost of PCCB replacement you want to be darn sure the quote is accurate.

However, given the high cost of PCCB rotors the seller is not likely to discount the car that much and if you agreed to buy the car without the full or nearly full adjustment you would be taking on a big risk potentially costing thousands of dollars.

Now you might be tempted to buy the car remove the PCCBs and unload the PCCBs hardware and fit cast iron brakes. While of course it would be your car and your decision I think PCCBs bring with them superior braking and just all around performance gains that replacing them would be comparable to because of one bad turbo removing both.

While the car would run and be close to its factory spec, well, not that close with the turbos removed, it would be considerably diminished in my opinion.

Sincerely,

Macster.

 

Macter: Thanks, yes this issue is interesting as discs are exchange and know it has 20k miles on it only!
And current owner drive take them off for 2 years to drive with steel ones, they have been installed 2k mls ago. And they dont look bad. Maybe this is other story?
Impotrant! : this car make last 3 years only ca 6k miles and all together is 40k miles car. I need to make decision today sign contract.
Fro other side could I exchange discs only on front or back or 4 corners at once? With steel ones dosen't matter but with PCCB I don't know?

 

PCCB brakes are made for the high heat situation. I would take it out and run it hard and get the brakes really hot. This may alleviate what you are dealing with. To replace parts on the PCCB will cost you big time. I favor the steel rotors for everyday driving/

 

Pccb are good ....in a box !! For road use they are rubbish as they don't bite quick enough as they only work well when properly hot. On track they deteriorate badly when really hot !!!!Only good thing is they don't make the wheels dirty.....Girodiscs, Alcon or simply 997tt rotors all round !!! Just did it on mine , brake much better. if there is some pulsing with pccb brakes need to be checked . something loose , dirt behind the bell, broken bolts and cracks around bolt heads on inside of the front pccb rotors is very common. Rear pccb always stay in good shape . Inspecting the pccb mounted on the car is not enough, rotors need to come off to inspect the inside side where the bolt heads are.

 

With cast iron brakes you know the extent of your exposure should they need replacing. As long as the condition of the brakes is not a sign of other trouble or usage (extensive track usage say) that puts you off the car, then one can make an offer to buy a car with the offer price adjusted down to allow for the cost of doing the brakes.

In this car you are considering if I read you right the PCCBs were replaced ("exchanged") and on top of that have been off the car for while iron brakes have been on the car.

Removing PCCBs to substitute cast iron brakes is used by those who track their car and wish to preserve the PCCBs and then when they are ready to sell the car remove the cast iron brakes and of course refit the PCCBs.

Now the pulsing may not be a brake issue. I don't want to get your hopse up but it could come from a mismounted wheel (bent wheel or wheels even), a tire or tires problem.

However, some of the above explanations bring with them some concern about the car and its condition. Bent wheels could just be potholes but it could be a sign of accident damage/bad repair.

As for moving rotors around I doubt the front and rear rotors can be exchanged and in fact IIRC the rotors are not even exchangeable side to side. They are marked which side of the car they belong on.

As I think I touched upon in a previous post you could buy the car and remove the PCCBs and fit cast iron brakes. This of course adds to the cost of the car and since you are removing the PCCBs because they are not up to spec this has to lower the car's value some.

To me removing PCCBs from a car that came with them from the factory to replace them with cast iron brakes diminishes the car in my eyes by more than the cost of the cast iron replacement brakes.

Anyhow, while you are in a hurry to make a decision I think given the situation as I read it you might want to take a step back and reconsider.

The car could be ok but you need to nail down that brake issue, understand whta is the underlying problem and what it would take to address it, the cost.

Sincerely,

Macster.

 

A bedding in of the PCCBs - provided they were subjected to a thorough ispection by a qualified tech beforehand to ensure there was no mechanical or installation explanation for the pulsing -- might make the symptoms go away.

IIRC (from the Total 911 article on PCCB) the recommended PCCB bedding in procedure is a bit intense. High (100mph) speed slowdowns and more than a few are required. For cast iron brakes the PCCB bedding in process would be brake abuse nearly.

But we are talking about PCCBs and I believe the source of the PCCB bedding in procedure is an official one.

However, I'm always leery of a car being offered with a condition that could easily be dealt with before the car was put on the market.

Either the seller is woefully naive or he knows something he's not sharing iwht the buyer.

Thus in this car's case given the potential high cost of making things right I'd like to have the pulsing dealt with beforehand or know for certain that the problem is not expensive to address (and does not arise from deeper issues) or if it is expensive to address (yet still doesn't arise from deeper issues) in either case knowing what it would cost so I could adjust my offer down accordingly.

Sincerely,

Macster.

 

So thanks a lot - I going to pick up this car tomorrow, and will post how is my filling after 300 km journey ( 200 miles) So cross finger and will see what we have