996 TT BRAKES.....Help!!
Discussion
I've always had somewhat of a brake fetish (don't ask) and the first thing I would do when buying a used car (performance or everyday) is to whip the old brakes out (discs and pads minimum) and get some new ones on there, whilst checking the piston seals and that the pistons themselves are moving freely. In the case of 6-10 year old 996 Turbo's, that's the first thing I would do, and probably consider a full caliper overhaul in the process. I'm handy with a set of spanners so do all the above myself, but a specialist wouldn't charge the earth to do it either. There are kits avail with new dust seals and all the grease etc... that you need to overhaul the calipers.
Brembo (road) calipers have a rubber dust seal which has a finite life span. I've seen seals tear on relatively young calipers, and it would not surprise me that some of them would be shot on a good proportion of 996 Turbos whose calipers have never been off and which have been through a few sets of pads. When these dust seals tear, you get crap into the cylinder and the pistons can start to corrode/stick. As soon as this happens, the caliper (4 pot in the case of 996 Turbo) will not be distributing even force to the pads and your braking performance will suffer, and the feel of the brakes will change. This can also explain why one side of a brake disc is shiny and the other side is rusted and worn out, you're not getting even distribution of pressure applied to your pads. Some calipers tend to have less force aplied to the inside edge of the disc (especially single piston floating calipers) and this is even true of Brembo brakes also, but not to the extent that the inside friction surface can be chipped away with a screwdriver, there is something wrong there or the disc is FUBAR. Change immediately!
A 330mm front disc (and 300mm+ rear disc), 4 pot brembo caliper and decent pad area should be more than enough for a 996 Turbo driven on the road even in full anger. I would suggest that a pad change (race pagid compounds would be my only choice) and fluid change (Motul RBF 600 or Motul RBF 660, or Castrol SRF would be my only choices) along with the standard Porsche disc would also be enough for track work, although an upgrade to the GT3 350mm 6 pot setup would be better it's more unsprung weight - and I don't think it's fully necessary unless you are a complete track w
e. The pad/fluid upgrade would be my first step if I found the standard setup wanting on the road, but you would need to be driving like a total lunatic in my view to warrant this on the road.
I had a Fiat Coupe 20V Turbo in my younger days, and that had Brembo 4 pots on the front with 305mm discs, not too dissimilar to the brakes on our Porsches. My car was 5 years old with 40k on the clock when I bought it, and after investigation one of the calipers was shot (a few dust seals went, piston seized etc..). Brakes felt ok, but not fantastic. I replaced one caliper, refirbed the other one with new seals, new discs and pads (Ferodo DS2500 also a good fast road pad IMO, proven on the track/and used in number of motorsport applications), some Motul RFB 600 and it was a night and day difference. I used and abused that car on track and on the road to the limit, and whilst only 250bhp and 1300kg its performance was similar to a Boxster S, the brakes never had a problem from then on. Another chap who I met on a trackday had a similar car but hadn't touched the brakes, and could only do 2 laps of Brands Indy before having to come in from boiling fluid, same car - massive difference in condition of the brakes. I could stay out as long as I wanted.
I'd suggest a similar action with your 996 Turbos, maybe a specialist on here can offer a brake service package? All four calipers off, fully checked over, pistons taken out, new seals/grease, rebuild and refit with new fluid (Motul RBF660 maybe?) new Porsche OE pads and discs. I challenge anyone to get this done and come back and say that the brakes on a 996 Turbo are inadequate!
Brembo (road) calipers have a rubber dust seal which has a finite life span. I've seen seals tear on relatively young calipers, and it would not surprise me that some of them would be shot on a good proportion of 996 Turbos whose calipers have never been off and which have been through a few sets of pads. When these dust seals tear, you get crap into the cylinder and the pistons can start to corrode/stick. As soon as this happens, the caliper (4 pot in the case of 996 Turbo) will not be distributing even force to the pads and your braking performance will suffer, and the feel of the brakes will change. This can also explain why one side of a brake disc is shiny and the other side is rusted and worn out, you're not getting even distribution of pressure applied to your pads. Some calipers tend to have less force aplied to the inside edge of the disc (especially single piston floating calipers) and this is even true of Brembo brakes also, but not to the extent that the inside friction surface can be chipped away with a screwdriver, there is something wrong there or the disc is FUBAR. Change immediately!
A 330mm front disc (and 300mm+ rear disc), 4 pot brembo caliper and decent pad area should be more than enough for a 996 Turbo driven on the road even in full anger. I would suggest that a pad change (race pagid compounds would be my only choice) and fluid change (Motul RBF 600 or Motul RBF 660, or Castrol SRF would be my only choices) along with the standard Porsche disc would also be enough for track work, although an upgrade to the GT3 350mm 6 pot setup would be better it's more unsprung weight - and I don't think it's fully necessary unless you are a complete track w
e. The pad/fluid upgrade would be my first step if I found the standard setup wanting on the road, but you would need to be driving like a total lunatic in my view to warrant this on the road.I had a Fiat Coupe 20V Turbo in my younger days, and that had Brembo 4 pots on the front with 305mm discs, not too dissimilar to the brakes on our Porsches. My car was 5 years old with 40k on the clock when I bought it, and after investigation one of the calipers was shot (a few dust seals went, piston seized etc..). Brakes felt ok, but not fantastic. I replaced one caliper, refirbed the other one with new seals, new discs and pads (Ferodo DS2500 also a good fast road pad IMO, proven on the track/and used in number of motorsport applications), some Motul RFB 600 and it was a night and day difference. I used and abused that car on track and on the road to the limit, and whilst only 250bhp and 1300kg its performance was similar to a Boxster S, the brakes never had a problem from then on. Another chap who I met on a trackday had a similar car but hadn't touched the brakes, and could only do 2 laps of Brands Indy before having to come in from boiling fluid, same car - massive difference in condition of the brakes. I could stay out as long as I wanted.
I'd suggest a similar action with your 996 Turbos, maybe a specialist on here can offer a brake service package? All four calipers off, fully checked over, pistons taken out, new seals/grease, rebuild and refit with new fluid (Motul RBF660 maybe?) new Porsche OE pads and discs. I challenge anyone to get this done and come back and say that the brakes on a 996 Turbo are inadequate!
Just to add: I belive that brake calipers are generally a neglected area on cars. When the majority of people (even enthusiasts) buy a car, they check the tyres, brake pads/discs, interior, check for damage etc.. etc... but rarely do they consider the condition of the brake calipers/dust seals. It's like people expect them to last the lifetime of the car, they are not considered a servicable part of the car.
Fact is, that they are a servicable part of the car, they are a moving part, and they should be examined thouroughly when changing discs and pads (or every 10k-20k if you don't change pads/discs often). Every time you change a set of pads, consider that the dust seals have gone from being full compressed (new pad means piston is fully embedded in caliper) to being fully extended when pad is worn (piston sits further forward as resting point now, as pad material has been worn away). Then when you stick a new pad in and push the piston back, the dust seal goes back to being fully compressed. The rubber will only last so long before it either tears or degrades. With brake fluid/grease on the inside of the seal, and brake dust/water/stones/etc... on the outside, there's a good chance the seal can tear within every few applications of new pads, and that's what I've seen in my experience.
I'd suggest that this is the main reason for the disparity in braking performance when driving the same model of car, some cars have been lucky or are better looked after, some aren't. It's also why after you can read examples of changing calipers for new GT3 items, owners see a massive difference in braking feel/performance. But - if they refirbed or replaced their own old/worn calipers for the same I'd suggest they would see a similar improvement. Also, as per the initial press reports - when driving a brand spanking new example with new capliers, there are no complaints. When driving an old example, we hear about poor performing brakes. It doesn't take an expert to figure out why this is.
Hope the above helps!
Fact is, that they are a servicable part of the car, they are a moving part, and they should be examined thouroughly when changing discs and pads (or every 10k-20k if you don't change pads/discs often). Every time you change a set of pads, consider that the dust seals have gone from being full compressed (new pad means piston is fully embedded in caliper) to being fully extended when pad is worn (piston sits further forward as resting point now, as pad material has been worn away). Then when you stick a new pad in and push the piston back, the dust seal goes back to being fully compressed. The rubber will only last so long before it either tears or degrades. With brake fluid/grease on the inside of the seal, and brake dust/water/stones/etc... on the outside, there's a good chance the seal can tear within every few applications of new pads, and that's what I've seen in my experience.
I'd suggest that this is the main reason for the disparity in braking performance when driving the same model of car, some cars have been lucky or are better looked after, some aren't. It's also why after you can read examples of changing calipers for new GT3 items, owners see a massive difference in braking feel/performance. But - if they refirbed or replaced their own old/worn calipers for the same I'd suggest they would see a similar improvement. Also, as per the initial press reports - when driving a brand spanking new example with new capliers, there are no complaints. When driving an old example, we hear about poor performing brakes. It doesn't take an expert to figure out why this is.
Hope the above helps!
Sunnysidebb said:
There is nothing wrong with standard 330mm 996tt brakes and back in 2001 they were the largest brakes fitted to a production road car, so they cant be that bad and at the time we didn't hear anyone moaning about them however we all know there is better available just do you drive you car that fast on public roads to justify buying them.
Your having a laugh Frank... thought you were some kind of Rally driver?Edited by Sunnysidebb on Monday 11th July 22:24
I can honestly put my hand on heart and say one of the best upgrades for a 9TT is a 6 pot front Caliper
Rockster said:
Everyone drives his car differently. I subject my cars to a mix of various types of driving from high speed (I won't state how fast but just leave it at 'high speed') driving to navigating with spirit curvy roads in various mountain (or hilly) in my area and at various other locations about the southwest and midwest areas of the USA. Google Tesla/Corral Hollow Road, Mines Road, Patterson Pass Road (to name a few) in the Livermore CA (USA) area (in fact at one time or another I've been on almost every 'interesting' road in this area south of the nothern portion of SF bay anyway (I don't get north of the bay for some reason)) and various roads in other areas like for instance Highway 20 in eastern Oregon from I-84 to Bend, Highway 7 in northern Arkansas starting south of Harrison Ark and countless roads across the midwest and southwest.
In some cases I've had the chance to really drive my cars in a spirited way to the point I've made myself near car sick in both cars and have never found the brakes wanting.
The cars experience all kinds of roads saved unpaved roads and believe me the UK has no lock on bad roads. It is a bit of a joke but over here every state it seems wants the title of the worst roads in the USA to justify higher taxes.
The bottom line is one can find horrible roads (as well as some pretty good ones) everywhere.
These cars are designed for high speed running on a variety of roads and have as a result superb handling, suspension and brakes. They also have I believe considerable over-engineering in these areas (heck just about every area I come in contact with I'm amazed at some of the things I find or are pointed to me by the local Porsche techs).
Thus my experience matches what I expected. I can pretty much drive the car like I want (within reason with the primary restraining factor being the desire to keep my license) and the car will not be the weak link in the car driver pairing.
But as I started with everyone drives his car differently. And have to add everyone encounters different roads. Now I have encountered some roads (one in particular was a freeway from Illinois into Michigan) that was one of the roughest roads I've ever been on. If I had to drive that every day well, maybe my car's suspension would be shot long ago. Well, check that. I remember now driving 50 highway between Lee's Summit in MO to Sedalia (about a 60 mile drive one way) sometimes as often as once a week) and that highway, particularly in one direction, was quite rough. God these pavement seams!. But the Boxster took it in stride even though my brother the few times he rode with me was cursing the road and its roughness. (Recently was on that road in my Turbo and found the seams had been ground down and the road made much smoother as a result.)
Anyhow, I could envision scenarios that might really tax the brakes over time and could result in accelerated wear, for instance if I had to commute daily back and forth over that Mines Road (for example) vs. using it for pleasure drives when the mood strikes me.
If the stock brakes under street driving conditions are proving inadequate I have to question their condition not that the basic design or implemenation is at fault. The brakes should deliver good, better than good, braking.
Now they do come in for some criticism when wet, some noting a bit of a lack of initial bite but the times I've remembered this and experimented in the wet the brakes quickly (almost immmediately) bite and I do not believe braking distance would suffer any. The tires are the limiting factor in the wet.
Switching to different pads generally is a trade off in that while sometimes one gets better braking performance but generally only when the brakes are being really used, hard, and getting extremely hot. But the trade off is almost always accelerated brake pad and rotor wear (and higher than stock parts prices too) and noise.
Many mod their cars in other areas so it is not surprising that brakes come in for this mod'ing as well. But for street driving even spirited street driving the stock brakes ain't bad, ain't bad at all is my experience.
But everyone is entitled to his own opinion. My input is just one point of view backed with some experience.
If the OP really believes the brakes are inadequate it is his decision what to do.
Sincerely,
Rockster.
Interesting. I googled the Tesla/Corral road, looks good In some cases I've had the chance to really drive my cars in a spirited way to the point I've made myself near car sick in both cars and have never found the brakes wanting.
The cars experience all kinds of roads saved unpaved roads and believe me the UK has no lock on bad roads. It is a bit of a joke but over here every state it seems wants the title of the worst roads in the USA to justify higher taxes.
The bottom line is one can find horrible roads (as well as some pretty good ones) everywhere.
These cars are designed for high speed running on a variety of roads and have as a result superb handling, suspension and brakes. They also have I believe considerable over-engineering in these areas (heck just about every area I come in contact with I'm amazed at some of the things I find or are pointed to me by the local Porsche techs).
Thus my experience matches what I expected. I can pretty much drive the car like I want (within reason with the primary restraining factor being the desire to keep my license) and the car will not be the weak link in the car driver pairing.
But as I started with everyone drives his car differently. And have to add everyone encounters different roads. Now I have encountered some roads (one in particular was a freeway from Illinois into Michigan) that was one of the roughest roads I've ever been on. If I had to drive that every day well, maybe my car's suspension would be shot long ago. Well, check that. I remember now driving 50 highway between Lee's Summit in MO to Sedalia (about a 60 mile drive one way) sometimes as often as once a week) and that highway, particularly in one direction, was quite rough. God these pavement seams!. But the Boxster took it in stride even though my brother the few times he rode with me was cursing the road and its roughness. (Recently was on that road in my Turbo and found the seams had been ground down and the road made much smoother as a result.)
Anyhow, I could envision scenarios that might really tax the brakes over time and could result in accelerated wear, for instance if I had to commute daily back and forth over that Mines Road (for example) vs. using it for pleasure drives when the mood strikes me.
If the stock brakes under street driving conditions are proving inadequate I have to question their condition not that the basic design or implemenation is at fault. The brakes should deliver good, better than good, braking.
Now they do come in for some criticism when wet, some noting a bit of a lack of initial bite but the times I've remembered this and experimented in the wet the brakes quickly (almost immmediately) bite and I do not believe braking distance would suffer any. The tires are the limiting factor in the wet.
Switching to different pads generally is a trade off in that while sometimes one gets better braking performance but generally only when the brakes are being really used, hard, and getting extremely hot. But the trade off is almost always accelerated brake pad and rotor wear (and higher than stock parts prices too) and noise.
Many mod their cars in other areas so it is not surprising that brakes come in for this mod'ing as well. But for street driving even spirited street driving the stock brakes ain't bad, ain't bad at all is my experience.
But everyone is entitled to his own opinion. My input is just one point of view backed with some experience.
If the OP really believes the brakes are inadequate it is his decision what to do.
Sincerely,
Rockster.
One thing I've noted whilst trawling around on US forums is how clean the underside of the majority of the cars are (some being 3 or 4 years old and still looking like new underneath)
I've not been to the US but imagine that your climate may lend itself better to keeping brakes and suspension in better condition than our roads which are frequently wet (and in the winter months covered in salt and grime)
As Simma has mentioned, faulty caliper dust seals rapidly lead to salt, water, general grit and road grime getting to the pistons and bores and in turn damaging the piston seals. On cars that get tracked AND used on the road these outer dust seals will become brittle and unable to withstand the piston being extended to its full extent without cracking.
It would indeed be an interesting experiment to try a 60k mile car with the same discs and pads used before and after a combined caliper overhaul and fluid change.
996TT_STEVO said:
Sunnysidebb said:
There is nothing wrong with standard 330mm 996tt brakes and back in 2001 they were the largest brakes fitted to a production road car, so they cant be that bad and at the time we didn't hear anyone moaning about them however we all know there is better available just do you drive you car that fast on public roads to justify buying them.
Your having a laugh Frank... thought you were some kind of Rally driver?Edited by Sunnysidebb on Monday 11th July 22:24
I can honestly put my hand on heart and say one of the best upgrades for a 9TT is a 6 pot front Caliper
Nope I wasn't jocking about road use. My GPA Escort Cosworth wasn't quite as heavy 1300 kg and only had about 330 bhp/450ftlbs, but in 1992 315mm was the GPA disc size for the front and 285mm for the rears. Events like: Yellow Brick, Tour of Cornwall, Muller, Cheviot, The Orm could put some serious heat ino the brakes. So driving a 1600 kg 911 on the road has never been a problem. The only time I found the brakes to be a bit poor ok quite poor, was driving on the A386 Dornoch to Tongue. Hardly ever had her on boost, but the nature of the roads( blind crest after blind crest) and hardly getting much above 40/50 mph with so little brake cooling I did manage to cook the brakes on a number off occasions. to the extent i might have a marginally warped disc. That sort of road is exceptional and in the 65k miles so far I only ever get the chance to drive like that a few times. Apart from that I have never felt the need to change the brakes for larger.
I could be doing some track days shortly , once the car is back from Kens, so perhaps I might change my view. However for road use I stand by my opinion that 330mm in good condition are adequate for 90% of the time. Perhaps I don't rely on the brakes as much as I should, even with a Tip I use both engine braking and brakes in combination with each other.
James did notice that my Tip had started slipping when coming down gears as well as going up the gears .....no wonder.lol
Slippydiff said:
Interesting. I googled the Tesla/Corral road, looks good
One thing I've noted whilst trawling around on US forums is how clean the underside of the majority of the cars are (some being 3 or 4 years old and still looking like new underneath)
I've not been to the US but imagine that your climate may lend itself better to keeping brakes and suspension in better condition than our roads which are frequently wet (and in the winter months covered in salt and grime)
As Simma has mentioned, faulty caliper dust seals rapidly lead to salt, water, general grit and road grime getting to the pistons and bores and in turn damaging the piston seals. On cars that get tracked AND used on the road these outer dust seals will become brittle and unable to withstand the piston being extended to its full extent without cracking.
It would indeed be an interesting experiment to try a 60k mile car with the same discs and pads used before and after a combined caliper overhaul and fluid change.
Indeed. Something else worth pointing out (correect me if I'm wrong racers): race cars have race brakes, right? They look similar to our road car brakes, big 4 or 6 piston calipers, groved discs etc.., right? They are very similar, on the whole... but most have one ommission from the caliper design, the majority do not have dust seals. Why? Well - one reason is that brakes get very hot when used with pads that have a high operating temp range, what would happen to a rubber seal that gets repeatedly hot and cold, or what happens if the rubber gets too hot? It melts/degrades rapidly. So, race cars get their brake calipers rebuilt regularly instead, replacing the piston seal and servicing/replacing the pistons as needed. There's a few more reasons why they don't use dust seals e.g. piston area within a set caliper size etc... Have a look on the AP Racing website at the race applications and you can see they don't use dust seals.One thing I've noted whilst trawling around on US forums is how clean the underside of the majority of the cars are (some being 3 or 4 years old and still looking like new underneath)
I've not been to the US but imagine that your climate may lend itself better to keeping brakes and suspension in better condition than our roads which are frequently wet (and in the winter months covered in salt and grime)
As Simma has mentioned, faulty caliper dust seals rapidly lead to salt, water, general grit and road grime getting to the pistons and bores and in turn damaging the piston seals. On cars that get tracked AND used on the road these outer dust seals will become brittle and unable to withstand the piston being extended to its full extent without cracking.
It would indeed be an interesting experiment to try a 60k mile car with the same discs and pads used before and after a combined caliper overhaul and fluid change.
Our cars are somewhat in the middle used on the road and track, being very fast and heavier than the majority of race cars, on track our cars can give brakes more of a workout and generate more heat than even some race cars. We want our cars to operate on the road protecting the pistons from water/muck so they dont corrode, and also to operate to very high temps on the track. Something's gotta give? I recommend that calipers are rebuilt at least once a year/bi annually if you are super hard on the brakes on track, look after those dust seals. Changing to a larger disc and larger caliper will require more abuse to heat up, and allow you to use a pad with possibly a lower optimum (high coefficient of friction) temp range, which in turn would promote reliability of the rubber and would last longer than a smaller disc/caliper combo, but you are increasing unsprung weight which effects also shouldn't be underestimated...
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