The Definitive Brake Thread for 8L A3/S3 Owners(and other Golf4 Platform cars).
This info was taken from UK-MKIVs forum with permission.
A full guide on brakes for the Golf4 Platform all within one thread.
Heres all the brake sizes on the VAG range, and what they are fitted to as standard.
VW Golf R32 | Audi TT 3.2 Quattro
- The Front brakes are 334mm x 32mm Vented 2-piece Discs, Twin piston(32mm/42mm) calipers
- The Rear brakes are 256mm x 22mm Vented Discs, 38mm Lucas singles
Seat Leon Cupra R
The Front brakes are 323mm x 28mm Vented (grooved/drilled option) discs with 4 piston(34/38mm) Brembo calipers
The rear brakes are 256mm x 22mm Vented , with 38m Lucas single piston calipers
Audi S3 Quattro | Audi TT-Quattro (225hp) | VW Golf anniversary | Golf GTI AUQ | Skodá Octavia VRS | VW Golf V5 170 | VW Golf V6 4 Motion
- The Front brakes are 312mm x 25mm Vented Discs, 54mm ATE single piston calipers
- The Rear brakes are 256mm x 22mm Vented Discs, 38mm Lucas single Piston calipers
Audi TT (180hp)
- The Front brakes are 312mm x 25mm Vented Discs, 54mm ATE single piston calipers
- The Rear brakes are 232mm x 9mm Solid Discs,
Audi A3 1.8/1.8T | Audi A3 1.8T Quattro | Audi A3 TDI 130 & Quattro | Golf GTI 1.8T | Golf 130/150 TDI | Golf V5 150 | Seat Leon 130/150 TDI and 20VT
- The Front brakes are 288mm x 25mm Vented Discs, 54mm ATE single piston calipers
- The Rear brakes are 232mm x 9mm Solid Discs
Audi A3 1.6 | Audi A3 TDI 90 | Golf 2.0 8v | 1.8 | TDI 115 | TDI 110 | TDI 100 | TDI 90
- The Front brakes are 280mm x 22mm Vented Discs, Single piston calipers, caliper carrier integrated into hub (FS III's)
- The Rear brakes are 232mm x 9mm Solid discs
Golf 1.4 16V | Golf 1.6 16v | Golf 1.6 8v | SDI
- The Front brakes are 256mm x 22mm Vented Discs, single piston calipers, carriers integrated into hub (FS III's)
- The Rear brakes are 232mm x 9mm Solid Discs
BRAKE DISC INFO
Heat capacity is the amount of energy that can be absorbed by the disc before the temperature gets high enough to cause brake fade. The mass of the disc is proportional to the heat capacity. Therefore, a lighter disc will not allow as much energy to be absorbed as a heavy disc.
Solid vs Vented
Vented discs are hollow with internal vanes. This increases the surface area of the disc and allows air to cool the disc mass more effectively. A 5Kg vented disc will cool much quicker than a 5Kg solid disc. In many cases, a vented disc can weigh less than a solid disc and still provide more effective braking because of the cooling effects alone.
Curved vs straight vanes
The vanes inside vented discs provide structural integrity to the disc itself as well as cooling. There are several different styles of vanes:
Straight vanes are the most common because they are easy to manufacture.
Curved vanes are common in higher performance cars as they promote better cooling better than straight vanes.
Where does the air go?
For solid discs, all the air travels over the surface of the disc - the same surface as the brake pads.
For vented discs, a considerable amount of air flows through the interior. Because it's spinning so fast, it creates a vacuum and air is sucked into the center of the disc and forced out through the edges. The air follows the pattern of the internal vanes.
A common misconception is that the purpose of drilled discs is to promote cooling. This couldn't be further from the truth, The real purpose is to reduce weight.
Drilling can allow brake dust and gases to escape, but with modern brake pads, this usually isn't a problem. Choosing a drilled disc for that purpose doesn't make a whole lot of sense.
Many high performance cars like Porsche and Mercedes AMG come with drilled discs from the factory. For these cars, the drilling is mainly about the looks, just like bright red calipers. When people do serious high-performance driving on a trackdays, they usually swap to regular plain discs.
Drilled discs generally wear out brake pads faster and produce much more brake dust as a result.
Drilled discs have a shorter service-life than plain discs and tend to develop stress fissures/cracks over their lifetime
Grooved discs keep the pad surface clean and allow certain gasses to escape which improves performance. not too many grooves though, you only need 6 or so, anymore and it it just for looks(e.g tarox cheese graters)
For street driving they may make a marginal improvement in initial brake "bite"
Grooved Discs are great for shedding water and mud off the rotor surface as in Rally racing or wet-weather racing.
Grooved Discs do accelerate pad wear and produce more dust just like drilled discs do. They also add noise and vibration into the system. For many these issues are annoying enough to not choose grooved discs, unless you do alot of rallying!
Two piece discs have several advantages including lower weight while maintaining most of the heat capacity and better cooling by having a more open center section
Two piece discs increase costs and generally a poor choice for street cars. For racing, they are great!
Plain discs are the best choice for 99.9% of applications
Name brand vs non-name discs
Why pay double the money for a Brembo discs vs. GSF cheapo's? You guessed it there is pretty much no benefit. Its all the same stuff, Spend you money on brake pads
Specialist Discs (carbon, carbon-ceramic, carbon-kevlar, etc.)
Some really expensive cars come with an option for fancy brake materials. These brakes are excellent for trackdays since they are relatively lightweight but can withstand extreme temperatures without brake fade. This provides a competitive advantage for racing.
For the street, it doesn't help much at all, and they squeal alot and wear fast.
If your discs are warped its because you have heated them up too much during hard breaking. probably nackered but you might be able to get them skimmed.
BRAIDED BRAKE LINES
Braided Brake hoses
Braided brake lines don't expand or bulge out, therefore reduce pedal travel, and increase the force applied to the brakes. I have never tried braided lines before, I think they don't really do alot on modern cars (especially the golf) because the servo makes the pedal feel soft anyway. It is a FACT that they apply more power to the caliper, but the caliper can easily apply twice the amount of pressure to the discs than the tyres are capable of handling anyway, i mean unless you have a track car with wide slick tyres, these are not really necessary.
If you want to improve your braking power on a budget, try using a Performance brand of Brake fluid and bleed your brakes. it makes alot of difference!
Chances are your fluid now is old and has absorbed some water and air and is not as good as it should be so the pedal will feel spongy. Sort this by bleeding your brakes and use a decent brand of fluid, ATE Super Blue Racing sounds good, and it's blue! how cool is that! anyway, it does make it easier to see when the new fluid has come through, and it has a low viscosity, it resistant to absorbing water, and has a boiling point of 200°C, which means less brake fade. another one is Castrol SPF Racing, it's expensive though!
There's lots of different types of these on the market, EBC, Mintex, Tarox, Pagid, Black Diamond, Brembo to name a few.
They are just made better, and depending on what you go for, they will provide better braking power / low dust etc..
They come in different levels of agressiveness, for example the EBC range is as follows:
EBC Blackstuff - Standard use
EBC Greenstuff - Street
EBC Redstuff - Fast Street
EBC Yellowstuff - Track
EBC Bluestuff - Race
if you go for the "race"option be prepared to get more dust, squealing/vibrations and accellerated pad wear and a harsh feel to the brakes - unsuitable for normal driving so thats why theres a range.
buying performance brake pads will make a difference to your braking power, for not alot extra cash over the standard pads.
Ever wondered why the front brakes are always bigger? By design most original factory brake systems do not split the brake force 50/50 between the front and rear axles. This is because under braking the front tires offer increased traction as weight is transferred forward. This additional traction can be utilized by increasing the brake force applied to the front axle vs. the rear. The outcome is a bias split that is more in the order of 70 front/30 rear resulting in shorter and more controlled stops.
BIGGER IS NOT ALWAYS BETTER........
Putting bigger brakes on may not always be a good idea.
For chipped/re-mapped cars the obvious upgrade is 312mm fronts because it's so easy, and only requires carriers and discs for most models(not SDI, TDI 90, 100, 110, 115, 2.0 8v, 1.6 8v, 1.6 16v, 1.4 16v,).and because you have increased the power of the engine, the power to wheel will not be de-creased as it would if you just put bigger brakes on.
# But, putting the 312mm conversion on a 1.4 for example, along with bigger wheels than standard and you will be adding alot of weight to your wheels, and the engine will be put under more strain, therefore reducing your accelleration. and Big brakes, contrary to popular beleif, don't actually do as much as people think in terms of stopping power increase, it's mainly that the disc heats up less, cools faster and therefore can stop the car more effectively, corner after corner without getting brake fade. IMO, the best brake mod for the smaller engined cars would be Performance pads and Performance Brake fluid, I wouldn't bother with drilled and grooved discs they just make your wallet lighter.
312mm and 256mm Setup from an Octavia VRS
280mm FS-III Fronts
256mm FS-III Fronts
256mm vented rears
256mm Rear splash Guards 1J0615609 & 1J0615610
256mm Caliper Carrier right 1JO 615 425 E
256mm Caliper Carrier left 1JO 615 426 E
256mm Caliper right 8NO 615 424 C
256mm Caliper left 8NO 615 423 C
256mm Discs 8LO 615 601
256mm OEM Pads 4BO 698 451
Rear Wheel hub with bearing 1JO 501 477 A
Front left 312mm Shield 1J0615312B
Front right 312mm Shield N90305302
The easiest upgrade of all is the 288mm to 312mm front setup. All this requires is 312mm Carriers and Discs(splash guards if you want, but they are not essential)
Upgrading 280mm FSIII's (AKA un-moddable without major work) take a bit more work as you have to change the hubs. these can be acquired from a breaker for relatively cheap, if the bearings have a little bit of play in, thats OK they will tighten up once the driveshaft is in place. if in doubt consult a garage. You can get new bearings fitted for relatively cheap so it might be worth it in the long run to get them changed whilst they are off the car. then once you have the hubs, you will need 312mm Calipers, Carriers, Pads and Discs, and splash guards.
Upgrading 256mm FS-III's to 280mm can be done by changing the hubs and discs alone, the calipers and pads are the same.
The standard 232mm Solids can be upgraded for the 256mm Vented setup, the bigger carrier/caliper just bolts straight on. If the calipers/carriers have come off a Quattro/4 Motion then you will need some 6mm spacers.
You will need to modify your standard splash guards as they curl in over the top of the std disc, and would catch on the new, larger disc. or alternatively you can fit 256mm splash guards, but the bearing has to come off, this can be tricky to do without spliting the bearings, a hydraulic puller and hammer chisel to free the race from the stub axle is what i used.
Upgrading the rear brakes does not do much in terms of braking power, reducing your stopping distance. The rear brakes only account for about 30%. Most people upgrade just for looks.
Porsche calipers are monoblock which means they are machined out of 1 solid peice of metal and are lighter and more rigid. LCR brembos are not monoblock, and heavier and not as rigid.
996 rears can be fitted on OEM 312mm discs with custom carriers which are available from DaveB1970. also available from him are some 325mm X 25mm discs which use the same carriers with another spacer to accomodate the larger disc. contact him for more info and prices. these calipers are readily available, and go on ebay for about £250 a pair which makes this a very reasonably priced upgrade. they have 28mm/30mm pistons thickest disc you can fit in them is 25mm.
The calipers you need are part numbers 996.352.421 and 996.352.422 but beware that this is the same part number as Boxster rears and DO NOT FIT! luckily you can tell the difference by just looking at the calipers, see the pics below:
996 REARS will be either red, silver or gloss black
BOXSTER REARS are a dull anodized black finish
There is an M6 hole drilled next to where the brake line connects on the 996 rears, shown in the photo below:
Part numbers for these calipers are 986.352.421 and 986.352.422, they are very similar in appearance to the 996 rears above, but have some subtle differences. the geometry is the same though, so the same carriers are used as above with the 996 rears. they also have larger pistons which are 36mm and 40mm
996 fronts / 996 turbo rears
The part numbers for these are 996.351.425 & 996.351.426 (996 fronts) or 996.352.425 & 996.352.426 (996 turbo rears)
piston sizes for the 996 turbo rears are 28mm and 30mm, and these use a slightly larger pad then the rest of the Porsche rear calipers.
piston sizes for the 996 fronts are .................
these require a 28mm disc, there is a 330mm disc available from DaveB1970 which is much taller than the 312mm or 325mm disc and means there's less chance of needing a spacer to clear the calipers
for the bigger calipers 429&430 and 431+432 then you need a 34mm discs.
Before you get excited and rush out to buy a BBK, you gotta think about your wheel clearance.
***NOTE*** rims are different sizes,different thickness walls, and therefore some may not fit.
these are the minimum wheel sizes, some may be very close, and may need the wheel re-balance with the weights put on the outside(not the rim face, but just not in the way of the caliper)
also some rim designs may require some spacer to fit around the caliper.
***alot of BBS split rims or deep dish rims will struggle to clear brembos or other monoblock calipers, normally a 10mm spacer is all thats needed to clear them***
334mm R32 brakes require 17"wheels
312mm TT brakes require 16"wheels
288mm Brakes require 15" wheels
280mm Brakes require 15" wheels
256mm Rears need a 16"to clear the caliper(15"spare doesn't fit)
Most porsche brakes need a 10mm spacer on the front
Most people paint there calipers to make them look better, the general consensus on the forum seems to be with big brakes go Anni Red or .:R32 Blue, but if you have standard calipers then a more subtle tone(black, silver, gunmetal grey) might be in order, because nothing looks more "max power" than small bright red/orange/yellow calipers.
before you paint them you will have to remove all the brake dust and the majority of the rust. then mask up the area you don't want paint on and paint. Hammerite smooth and B&Q Japlaq seem very popular. these are cheaper than a special caliper painting kit, which is just in a smaller pot and probably comes with a tin of brake cleaner worth a fiver, and costs more than twice the price.
give them a few coats and for best results don't drive in-between!
It's important to do this properly, having even a little bit of air in there and its negating the big brakes you've just put on! I reccomend using the Gunson Eezi-Bleed system, it costs about 10-15 IIRC.
you just fill up the bottle, fit the correct resevoir cap from the box, then connect up the bottle to the spare tyre (20psi works best). the system is now pressurised and as soon as you crack a nipple fluid will come out, just wait untill the new stuff comes through then close it off. simple!
bleeding the brakes the old school way (as suggested by haynes manuals :think:) can damage the seal in the master cylinder and cause the brake pedal to feel soft all the time and travel quite far. this is because under normal circumstances the piston only moves 5-10mm at most, but when the piston goes the full length of the cylinder it goes over the rough and pitted surface, this can damage the seal and sometimes flip it rendering the MC useless.
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