Discs & Pads

[Teutonic_Tamer]

....Didn't someone post that the Seat(?) brakes were a much better alternative to the R32. Seat? Skoda? - I don't know the difference.

The Seat Leon Cupra, the R32, the Audi S3, the TT quattro, amongst others, all use the same 345mm disc and caliper.  The only difference is the colour of paint which fritz has on his brush! 

Regarding weight, then the OEM 345mm setup will be slightly heavier than the OEM 312mm GTIs, but this will be outweighed by much better performance.

[Teutonic_Tamer]

I think (unless something comes up) I wil be going zerosixty's and standard pads - which are made by ATE.  In fact ATE also do some grooved discs for the GTI  - similar design to brembo discs





ZeroSixty front discs - £125 + vat

Is that for a pair?  Anyway, still expensive. 

If these zero sixtys are the same dimensions as OEM, then forget them.  They will not give any improvement in braking performance.  Stick with OEM discs at £33.88 each plus vat, and instead go for some quality uprated pads.

[RedRobin]

T_T may know what's best, I reckon. Though if I recall correctly, he may not have agreed with AP Racing's use of Dot 5.1 fluid for road use.

I think I previously stated (though it probably got lost when the forum went down) that virtually all DOT5.1 fluids are snake oil, and are completely un-necessary on a road car.  Furthermore, from model year 2008, ANY brake fluid which does not meet VW 501.14 spec will invalidate the VW warranty.

Lets take the specific AP Racing 5.1 - it has a wet boiling point of 187°C, whereas the genuine VW brake fluid has a wet boiling point of 172°C - so not much difference.  Furthermore, the VW fluid is a specific "low viscosity" brake fluid, for use in ABS and ESP systems.  The AP 5.1 is not, therefore will make the ABS/ESP slower reacting.  Both the AP 5.1 and the genuine VW fluids have a normal service life of two years, but the real killer is the cost.  AP 5.1 costs about £40 per litre, whereas the VW stuff retails for £7 per litre, with 10-15% discount just for asking. 

....TT - Then, would you advise me to use (genuine) VW fluid instead of the Dot 5.1 when I next service my AP brakes?

Quite honestly I am not prepared to sacrifice/compromise any safety for the sake of cost [Not said in anyway contradicting your post].

I had experienced brake fade on my stock brakes and was lucky that the truck took avoiding action! It's what prompted me to take up AP Racing's generous offer.

AP said to me exactly what you have said about drilling and how there are companies out there that take advantage of a market where Jo Bloggs simply fancies the cool look on his discs and he doesn't have a clue.

[gazbutmk5gti]

I can only go by my own experience T T, I know when I fitted the zerosixty discs to the ED30 there was a deffinate inprovement. Its my understanding that the grooves and dimples can help release gases that are built up between the pad and disc when things are getting hot and can also help prevent the pad becomeing glazed with heat by cleaning them every time the brakes are apllied more so than a standard disc because it is then just polished surface against polished surface

[RedRobin]

Its my understanding that the grooves and dimples can help release gases that are built up between the pad and disc when things are getting hot and can also help prevent the pad becomeing glazed with heat by cleaning them every time the brakes are apllied more so than a standard disc because it is then just polished surface against polished surface

....That's also my understanding. Plus that grooves help to disperse brake dust.

[Teutonic_Tamer]

T_T may know what's best, I reckon. Though if I recall correctly, he may not have agreed with AP Racing's use of Dot 5.1 fluid for road use.

I think I previously stated (though it probably got lost when the forum went down) that virtually all DOT5.1 fluids are snake oil, and are completely un-necessary on a road car.  Furthermore, from model year 2008, ANY brake fluid which does not meet VW 501.14 spec will invalidate the VW warranty.

Lets take the specific AP Racing 5.1 - it has a wet boiling point of 187°C, whereas the genuine VW brake fluid has a wet boiling point of 172°C - so not much difference.  Furthermore, the VW fluid is a specific "low viscosity" brake fluid, for use in ABS and ESP systems.  The AP 5.1 is not, therefore will make the ABS/ESP slower reacting.  Both the AP 5.1 and the genuine VW fluids have a normal service life of two years, but the real killer is the cost.  AP 5.1 costs about £40 per litre, whereas the VW stuff retails for £7 per litre, with 10-15% discount just for asking. 

....TT - Then, would you advise me to use (genuine) VW fluid instead of the Dot 5.1 when I next service my AP brakes?

If AP Racing, or indeed anyone else brings out an "ESP" rated DOT5.1, and you are out of warranty, and you must have a 5.1 fluid, then go for it.  But as far as I have researched, no 5.1 fluid is ESP rated, so I would recommend using the VW fluid.

Quite honestly I am not prepared to sacrifice/compromise any safety for the sake of cost [Not said in anyway contradicting your post].

Absolutely.  And I didn't take as a contradiction - just an honest and friendly question. 

I had experienced brake fade on my stock brakes and was lucky that the truck took avoiding action! It's what prompted me to take up AP Racing's generous offer.

But brake fade has nothing to do with brake fluid.  Brake fade is when the friction lining on the pad overheats - this then gives off a "gas" (which is why drilled discs are good at preventing genuine brake fade).  This brake fade then makes the brake pedal feel very unresponsive.  Sometimes the pedal can feel quite "hard", but travel a long way (sometimes nearly to the floor), and other times, the brake pedal feels very "wooden".

So brake fade is a result of not being able to get rid of the heat quick enough.  Did you have your open fog grilles then?

Regarding brake fluids, and the different "boiling points" - well that is the fundamental issue - between the obsolete DOT3, the current DOT4 - and the so called high performance aftermarket DOT5 (nasty, evil shyte) and DOT5.1.  However, the ONLY reason to "upgrade" to a 5.1 fluid is if you can boil your exisiting, and fresh DOT4.  Boiling brake fluid creates air bubbles in the system.  If you have a basic understanding of hydraulics, you will know that all liquids (ie brake fluid) can not be compressed, whereas gasses (ie the air in brake fluid) can be compressed.  Boiling brake fluid is sometimes referred to as "vapour lock" - but basically, if you get air in the brake hydraulics (from either boiled fluid, or simply letting the level drop too far in the master cylinder resevoir) - then the actual brake pedal will feel very "spongy".  The pedal may, or may not go all the way to the floor, but the actual braking efficiency of the wheel brakes will not be altered (providing there is enough pedal to pressure the system).

A very simple way to determine between brake fade (overheated pads) and vapour lock (air in the fluid) - is to repeatedly "pump" the brake pedal.  If you are able to pump the pedal back upto a normal height, then it is air in the system.  With brake fade, you can pump away like a cherry boy in a brothel, but the pedal will not change.

AP said to me exactly what you have said about drilling and how there are companies out there that take advantage of a market where Jo Bloggs simply fancies the cool look on his discs and he doesn't have a clue.

Absolutely.  But don't forget, many peeps do mods purely for looks, and not any improvement in function!  I think you sit on both sides of the fence in that.     

[Teutonic_Tamer]

I can only go by my own experience T T, I know when I fitted the zerosixty discs to the ED30 there was a deffinate inprovement.

But is that down to "placebo" effect.

If these ZeroSixty discs really were an improvement, why then do quattro GmbH not fit them to the monstrous leviathon which is the Audi RS6 V10, or why don't AMG use them.

And how can you dismiss the fact that you had just stripped down, cleaned, and probably put some fresh copaslip on the brakes when you had fitted them.  This can have a big effect, even simply stripping down and refitting existing brake pads.

Its my understanding that the grooves and dimples can help release gases that are built up between the pad and disc when things are getting hot

Sorry, but groves and dimples are purely cosmetic, and for the "fashion-consious".  The claim that grooves release the gases is pure fairy-tale physics, and simply marketing hype.  Dimples must be the worst thing going, because they dont actually do anything, yet reduce the mass of the disc, which then reduces the ability of the disc to absorb the heat from the pad.

and can also help prevent the pad becomeing glazed with heat by cleaning them every time the brakes are apllied more so than a standard disc because it is then just polished surface against polished surface

And what, exactly, is "pad glazing"?    I know, but grooves, dimples, or otherwise wont clear glazing. 

Sorry, but the "grooves" on a disc surface do absolutely nothing.  If they did, then why arn't F1, or DTM, or MotoGP, or LeMans cars using groved discs?  Why doesnt the Audi Q7 V12 TDI, or the RS6, or the Bugatti Veyron use groved discs?  Thay all don't use grooved discs because they do not provide any increase in brake performance. 

The only reason grooved discs sell is simply because they look good. 

[Teutonic_Tamer]

Its my understanding that the grooves and dimples can help release gases that are built up between the pad and disc when things are getting hot and can also help prevent the pad becomeing glazed with heat by cleaning them every time the brakes are apllied more so than a standard disc because it is then just polished surface against polished surface

....That's also my understanding. Plus that grooves help to disperse brake dust.

Nope, the normal rotation of any conventional disc, along with airflow over the disc/pad/caliper area from normal vehicle motion is what clears pad dust.

In fact, grooved discs have actually been found to cause excessive and aggravated pad wear.

[RedRobin]

....Yep, I'm out of warranty. I have the Dot 5.1 fluid because it's what AP supply with their BBK. I am on very good terms with them and will ask their opinion too on the 'ESP-rated' VW fluid being used in their kit. Having spent time with them I am naturally inclined to trust and take their advice, but also I always take notice of your advice.

....Did I have my open fog grills when I experienced brake fade? - No I definitely didn't - They were still closed versions - I have checked my photo dates and I converted to open grills 9th Sept 2006 and it was earlier in that Summer I had brake fade because AP installed my BBK the day before I drove to Berlin in early November. I just had to spend some serious time looking that all up but it's useful to know.

....Do I sit on the fence? In life I have been accused of that, but it's only because I always endeavour to see both sides of an opinion. Regarding modding, yes, some of my mods are purely cosmetic (wing mirror skins for example), some are cosmetic but have the bonus of some small/tiny advantage, others are purely performance. And some, such as open fog grills, have very debatable benefits and there are those who say they are a definite disadvantage

[pridders]

Ok I think from what Teutonic has mentioned (wow,  wealth of knowledge there pal  ) I will now look at getting normal stock Discs and maybe look at an up rated pad for front and back. Any recommendations for a pad of should I just stick with stock all round?

Normally you lot make me spend spend but I think in this instance I will have saved myself some $$$ Right what I have just saved what shall I spend it on now!