Kaizu

Sorry for crossposting this, but I know this is THE forum with 996 porsche track guys

Okay I’m back at home from this springs Ring trip.

Everything was awesome as usual BUT…

Both 996 Turbos we had there from Finland had a mysterious braking problem.

It happened in 8 min laps (= going fast), when braking to a corner the brakes (and thus wheels) lock up for 0.5-1.5 seconds and the brake pedal doesn't lift up to its normal position. Only after that you’re able to steer the car, and trying to avoid a crash in to a barrier. That’s why we had a lot of close calls and we had to quit “the faster driving”….otherwise there would have been some real nice lap times... now we just couldn't push them...

Both cars had semi slick tires, some suspension mods and 500hp+. Of course we used racing pads from Pagid and Carbopad and racing fluids from Motul and Castrol…didn’t help.

When driving fast a modded Turbo the stock brakes aren’t enough…we would have upgraded both cars brakes in Manthey to GT2-version but they didn’t have any in stock.

Anyway, that’s not the problem because the stock brakes have been quite good with race pads and fluids. Both drivers and cars have quite a lot of experience with their cars on different race tracks. The problem might happen in the beginning of the lap, for example in Aremberg corner after Schwedenkreuz. And that's really strange, how the f*** the brakes can't handle a couple of corners...

First we started braking sooner and less aggressively but the problem was still there.

So, WHAT THE HECK IS THE PROB?

Have the ABS-sensors gone mad and bad? Of course both cars are driven PSM OFF at the Ring but we found an interesting thing when driving PSM ON, the PSM interfered a lot when it’s not supposed to be… for example cutting the power at 120mph+ when accelerating on a straight line…

ps. Both cars are from 2001 and there's no abs/psm failure light or anything...

Thanks for all the feedback!!

Nordschleife

you have experienced the bumpy track syndrome

R+C
PS - remember to breathe through the nose

Kaizu

I immediately thought that the famous R+C himself would have a nice answer to this

What? With both cars we've driven that speed at the Ring before, without locking the front wheels badly.

And without touching the barriers.

Nordschleife

well, if you brake whilst airborn, the ABS/PSM system can have a hiccup and the easiest way of fixing it is to stop, turn off the engine, remove te key and then restart the car.

Perhaps, you know the track better and are starting to drive harder. In general, braking whilst airborn is a bad idea. However, what you describe is a recognised condition. It would be worth discussing the solution with Olaf M, but it might not be worth it with PSM and AWD.

Braking hard under extremely bumpy conditions can upset the system too.

Interestingly, I found the brakes on the 997 Turbo to be weak compared with what I am used to.

R+C

Kaizu

Thanks for the info.

I heard from Manthey that the problem might be with the ABS. Olaf (actually I don't know, the sales guy went to ask the chief) said that when you're pushing more than 80 kg of weight to the brake pedal with your feet the stock ABS system stops or might stop working. They said try to brake sooner and less aggressively but my front wheels still locked up one time when taking a bit sooner and easier braking...and that's when I stopped lapping.

I understand the problems while airborn. But the actual corners where the wheels locked up badly are like Aremberg, Kallenhard, Eschbach and Brünnchen. As you know, these places aren't that bumpy...but yes all of them need hard braking.

Anyway, I (and the other Turbo owner) have to upgrade the brakes...I'm really anxious to see is it the final solution to our problems (too bad Brembo has a lot of delivery problems, also with the 997TT PCCBs...the season has started and the tracks are waiting!)

Nordschleife

well, call Guido Frensmeyer at Mov'it in Achern. His excellent 6 piston monoblocs have been put on more than one fast P-car, including 24 Hour race cars.
The real problem is in software.
R+C

Ed Newman

Common problem in the 996's. Mine has done it a few times, mostly at Pocono and LRP. Has not done it since I put the GT3 brakes on. I believe Synergy totalled a 997S at LRP because of this problem.

Mr. C4

80kg pressure is a lot of pressure, no wonder the wheels lock up. Sounds more like a driver error than mechanical/electronic failure/glitch to me.

Kaizu

Update after changing both cars' brakes:

Both had this front setup with problems:
Stock 4-pot Turbo brakes, Pagid Yellows, Motul racing fluid, semislick tires (other had 19" Pilot Cups which might have caused the problem but the other had 18" R888's with original diameters!)

Now both cars have:
GT2 6-pot brakes, Pagid Yellows, Motul racing fluid and GT3 Cup brake ducts, other car has 18" Pilot Cups and other car has 18" R888's.

After the upgrade the other car's braking problem has disappeared! My car still has it!!

So what should I do? Go through the whole system? It's NOT a driver's error, or if you think so everyone is welcome to take a passenger ride...Or at least tell me HOW I do this error with my braking?

Also being airborne has nothing to do with it, it has happened usually in flat sections of Nordschleife and happened also in our local circuits too.

What it strange that this mysterious locking of the front brakes usually happens only with smooth braking during otherwise very aggressive driving (for example seeing a yellow flag or taking a curve slower than usual because cars ahead...)

I did a new trip to Ring last autumn and I still managed to do theoretical 7.48 min BTG lap (friend compared track data from PBOX) with this problem...But couldn't brake too late.

I spoke with Olaf Manthey himself and what was very surprising that he has not heard of this kind of problem! He thinks the stock ABS has some problems but doesn't know what. They don't sell racing ABS system to Turbos, only 2WD GT2's and GT3's but he also mentioned that it might not be the answer for my problem...

What all parts should I go through, just in case ??

Is it possible that there's too much dirt from racing pads in the wheel hubs or something strange like this? The car's on winter storage right now so I can't check...

Help me guys...All comments are appreciated, I've heard this is the board where all the fast guys are

Ed Newman

Maybe change the ABS computer and pump.

Kaizu

Thanks a lot Ed for the advice. Let's hope the parts aren't expensive...Any ideas?

Also this brake talk is A LOT confusing for a guy that tracks a 1550kg 996 Turbo. With GT3's it seems people are doing multiple track days with stock disks and racing pads?

The stock GT2 disks straight from the package lasted only a couple of days with Pagid Yellows in this Turbo. I'm very disappointed because at the same time I also added the GT3 Cup brake ducts which help tremendously the rotor life at least in the GT3 Cups but nope, the cracks are too large now...

After some searching I'm going for Performance Friction disks and pads (01 compound) Hopefully they'll last the whole season both street and track. Knowledgeable comments appreciated about this choice too!

zoomzoom

Have you tried braking less? In the fastest laps sub-8min laps I've been in (as pax), the driver has been very gentle on the brakes and the speed is found by through the bends and by perfect car positioning for balance. A fast lap at the 'Ring doesn't need exceptionally powerful brakes, but it does require smoothness and exceptional car control...

ArcticFox

If you are also having the PSM doing weird things when on, I would think the issue is more electronic than mechanical. I would be looking at sensors and the ABS computer and pump. Just my thoughts.

Rassel

Can you post the PBOX data and point out where you have problems?

hammerwerfer

Kaizu,

You mention locking the front wheels.

That is the opposite of the bumpy road, or jump, situation where the ABS has a brain fart and just doesn't apply the brakes. It gives you avery hard pedal that just doesn't do anything. Rather disconcerting to say the least.

That problem would show up at Quiddelbacher Höhe, and Pfalntzgarten 1, when the car is unweighted or in the air whilst braking. I've experienced that in numerous cars, but never on a smooth piece of tarmac.

I have never experienced a locking tyre in an ABS equipped car. I would look to the sensors or their wiring.

Are you actually flatspotting tyres? If they lock for even a fraction of a second they will flatspot, and you will notice the rough ride.

Ed