big brakes

[Teutonic_Tamer]

Are there any potentially adverse affects on the rest of the 'stock' OEM brake system if you uprate the front discs an calipers?

....No (if I've understood your question correctly) - The sensors etc will continue to smartly react to whatever is going on.

Hmmmmm . . . that is only going to take into account the 'last case' scenario - ie, when the wheels are about to lock up, and the ABS needs to intervene.  But these wont be able to take into account the difference in bias which will result from say just upgrading the fronts. 

However, some big brake kits such as AP's no longer activate the car's pad wear system. But visual pad inspection is more reliable anyway.

So how did you disable the pad wear warning?  Just leave the existing wear sensor connected, but just taped to the strut? 

If you mix and match brake components - Such as simply changing to better aftermarket pads and ss hoses and fluid etc - The feel of the brakes will improve but improvements will be limited by the oem disc [So I am led to understand].

Braided hoses do NOT offer any gains in braking performance, and neither do these so-called uprated brake fluids.  And virtually all 5.1 fluids are not ABS/ESP compatible (not to mention will void your warranty, and may well ruin your ESP unit).

However, uprated pads on the standard disc can offer some valuble increases in performance, though with pads alone, the gains wont be large.

But for the biggest improvements in braking, then larger discs, or even standard sized discs, but with improved cooling, such as better integral vanes or drilling, along with uprated calipers - are really what is needed.

VAG factory cars are well known for their relatively soft brake pedal feel. The pedal response from a good aftermarket brake kit adds to your confidence in that extra stopping power. Unless I'm being closely chased into a roundabout by a much higher performance car driven by someone who knows what they are doing (in which case I make sure to let him pass at the first safe opportunity), I find that my brakes allow me to apply them late so I'm slow into the corner and then the Quaife helps my traction to power out......Et voila, they are very small in my rear view mirror and they don't tailgate me again!

BUT! Remember that your only points of contact with the road surface are 4 patches each only the size of a CD, so in other words your tyres are critical!

Yup, brakes just stop the roadwheels from rotating.  It is simply the grip between the tyre and the tarmac which stops the actual vehicle.

[MummRa]

However, uprated pads on the standard disc can offer some valuble increases in performance, though with pads alone, the gains wont be large.

But for the biggest improvements in braking, then larger discs, or even standard sized discs, but with improved cooling, such as better integral vanes or drilling, along with uprated calipers - are really what is needed.

The two common reason to upgrade your brakes (apart from the looks) are

- Have experienced fluid fade (soft pedal)
- Want better feel

As the only things that can affect actual braking force (assuming the tyres are good enough) are the diameter of the disc, the area of the pistons (both for a mechanical advantage from the pedal) and the coefficient of friction between the disc and the pad; if you are looking to improve on feel and get a little better response, upgrading the brake pads can make a decent difference.

Of coarse the faster you stop your car, the more heat that is generated, which normally leads to fluid fade

If you are upgrading because your current brake set up cannot handle the heat of all your braking (ie track use, or maybe following the upgraded pads ) then you need a larger lump of iron (disc) for a heat sink and/or better cooling to your brakes, and while you are at it, you slap on some bigger calipers as your old ones wont fit properly anyway

It is important to note, that brake pads (especially high performance ones) want to be hot in order to work properly, so cooling your brakes doesn't make them 'better' as such, simply less prone to fluid fade, ideally they want to be kept at just the right temperature. This is also why recommended 'fast road' pads such as DS2500 are a bit of a compromise, as they have to work well enough from cold to be any use on the road where are full race pads like DS3000 sequel like a pig untill you get them warm enough.

Also upgrading the front brakes alone as you point out will always affect the bias, so it is ideal to to something with the rears, such as match up the pads

So, basically, I agree with you I just think that pad choice is critical to getting the 'feel' that you desire from any brake set up and now realise that I have rambled on some what 

[RedRobin]

Thanks, but I've gone off the OEM 345mm S3/R32/A3q route - they are just too heavy.  Reducing unsprung mass plays a massive advantage to general handling too - which is why I'm seriously considering ceramics. 

....Music to my ears! - I've just ordered a set of lightweight OZ Alleggerita 8x18 wheels which weigh approx just over 7 kg compared with 12 kg of my Monza 18's (I don't have the exact weights to hand). It's the handling advantage of turn-in and feedback which has initially driven my choice but now I am learning from this thread discussion that the LeggyRita's open spoke design will also benefit my brakes - Yippee!

[RedRobin]

^^^^ Exactly what AP's Senior Race Engineer, Pete Collen, advised me - That 4-pots and fronts only were absolutely fine for fast road use and that the Golf did about 85% of its braking on the front. I found them awesome on The Ring though my rear end did get twitchy a few times!

That is a fundamental example of incorrect brake bias, because the rear brakes on the Golf need to work MUCH more than the '15%' - and this is borne out by the way the rear suspension is set up.  The Golf 5, just like the Mk4, and many similar modern road cars - have a much greater rearwards bias in the brakes - and whilst the fronts may actually do most of the actual 'braking', the rears play a massive part in the stability whilst braking.  Why do you think that some cars are now coming with larger REAR discs than fronts. 

....Methinks I need to do something about my rear brakes.

However, uprated pads on the standard disc can offer some valuble increases in performance, though with pads alone, the gains wont be large.

But for the biggest improvements in braking, then larger discs, or even standard sized discs, but with improved cooling, such as better integral vanes or drilling, along with uprated calipers - are really what is needed.

....Whilst I could simply go out and buy a pair of rear AP's I want to firstly investigate if there are any less expensive options such as just changing the rear pads to match the DS2500 fronts. I've put in a call to AP's Senior Race Engineer but he's away until later next week. I expect he'll advise the same as you, Sean, but the pads may be a short term compromise as I'm off to The Ring in a few weeks and am currently short of funds.

[RedRobin]

How often have you had the brake fluid changed?  I just think that as an earlier poster said, it seems to be as a result of more frequent fluid changes by the race teams.  But if you are into track days on a road car, and need to change the fluid regularly, then it just might become an 'issue'. 

....Fluid changed from stock > AP when brake kit fitted > VWR when working on suspension (accidently punctured a hose) - All over a period of 4 years exactly.

Re VWR's brakes - apart from being very expensive, they do snatch but have totally gobsmacking stopping power! VWR are apparently working on a cheaper and more road friendly version.

Oh yus - the VWR brakes have mighty stopping power, there is no doubt about that!    Cost-wise, well that really isn't a deciding factor for me, so it wouldn't have mattered if they were £500 or £2500.  The real big issue is that the SWMBO isn't very 'delicate' with the brake pedal  - so the brakes must have much greater progression than what VWR were offering, hence why I have to rule them out.  But if you say they are developing some newer ones - are they ready yet? 

As an aside, though, I was mighty impressed by their on-track racing operations, and have to say that Sam is a really nice, top bloke.

....I'm speaking to VWR later today (all being well) and also plan to be up there next week, so I'll ask how that is developing.

I'm sure that if you wanted to ask Sam anything he'd be very helpful but I know he's away until later next week.

[Rhyso]

 

[Teutonic_Tamer]

However, uprated pads on the standard disc can offer some valuble increases in performance, though with pads alone, the gains wont be large.

But for the biggest improvements in braking, then larger discs, or even standard sized discs, but with improved cooling, such as better integral vanes or drilling, along with uprated calipers - are really what is needed.

The two common reason to upgrade your brakes (apart from the looks) are

- Have experienced fluid fade (soft pedal)
- Want better feel

As the only things that can affect actual braking force (assuming the tyres are good enough) are the diameter of the disc, the area of the pistons (both for a mechanical advantage from the pedal) and the coefficient of friction between the disc and the pad; if you are looking to improve on feel and get a little better response, upgrading the brake pads can make a decent difference.

Of coarse the faster you stop your car, the more heat that is generated, which normally leads to fluid fade

If you are upgrading because your current brake set up cannot handle the heat of all your braking (ie track use, or maybe following the upgraded pads ) then you need a larger lump of iron (disc) for a heat sink and/or better cooling to your brakes, and while you are at it, you slap on some bigger calipers as your old ones wont fit properly anyway

It is important to note, that brake pads (especially high performance ones) want to be hot in order to work properly, so cooling your brakes doesn't make them 'better' as such, simply less prone to fluid fade, ideally they want to be kept at just the right temperature. This is also why recommended 'fast road' pads such as DS2500 are a bit of a compromise, as they have to work well enough from cold to be any use on the road where are full race pads like DS3000 sequel like a pig untill you get them warm enough.

Also upgrading the front brakes alone as you point out will always affect the bias, so it is ideal to to something with the rears, such as match up the pads

So, basically, I agree with you I just think that pad choice is critical to getting the 'feel' that you desire from any brake set up and now realise that I have rambled on some what 

Whilst I was fully aware of the above, it will be a great help to other forum readers. 

So 'rambling' is good!

[Teutonic_Tamer]

Thanks, but I've gone off the OEM 345mm S3/R32/A3q route - they are just too heavy.  Reducing unsprung mass plays a massive advantage to general handling too - which is why I'm seriously considering ceramics. 

....Music to my ears! - I've just ordered a set of lightweight OZ Alleggerita 8x18 wheels which weigh approx just over 7 kg compared with 12 kg of my Monza 18's (I don't have the exact weights to hand). It's the handling advantage of turn-in and feedback which has initially driven my choice but now I am learning from this thread discussion that the LeggyRita's open spoke design will also benefit my brakes - Yippee!

Sexy wheels Red, but I'd recommend ordering a 'spare' too.  When you make alloys that light, there has to be compromises to get the weight that low - and if you happen to hit a pot hole at a particularly unlucky angle (or speed  ), then they have a tendancey to fold like origami.  The original Audi RS4 (or was it 6) was plagued with this problem.

[Teutonic_Tamer]

^^^^ Exactly what AP's Senior Race Engineer, Pete Collen, advised me - That 4-pots and fronts only were absolutely fine for fast road use and that the Golf did about 85% of its braking on the front. I found them awesome on The Ring though my rear end did get twitchy a few times!

That is a fundamental example of incorrect brake bias, because the rear brakes on the Golf need to work MUCH more than the '15%' - and this is borne out by the way the rear suspension is set up.  The Golf 5, just like the Mk4, and many similar modern road cars - have a much greater rearwards bias in the brakes - and whilst the fronts may actually do most of the actual 'braking', the rears play a massive part in the stability whilst braking.  Why do you think that some cars are now coming with larger REAR discs than fronts. 

....Methinks I need to do something about my rear brakes.

I can't agree any stronger!   

However, uprated pads on the standard disc can offer some valuble increases in performance, though with pads alone, the gains wont be large.

But for the biggest improvements in braking, then larger discs, or even standard sized discs, but with improved cooling, such as better integral vanes or drilling, along with uprated calipers - are really what is needed.

....Whilst I could simply go out and buy a pair of rear AP's I want to firstly investigate if there are any less expensive options such as just changing the rear pads to match the DS2500 fronts. I've put in a call to AP's Senior Race Engineer but he's away until later next week. I expect he'll advise the same as you, Sean, but the pads may be a short term compromise as I'm off to The Ring in a few weeks and am currently short of funds.

But just upgrading the rear pads on your set-up still wont provide the necessary bias improvement.

I honestly think that you need to be looking at the whole rear R32/S3 schebang - because not only does that set-up come with larger diameter discs, it also has larger diameter pistons in the calipers - and it is the piston diameter which will provide the greatest result in 'evening' the bias.

The rear end was something I spoke to Sam @ VWR with, at fairly great depth - but this is where a road car application and a full on race car differ the most.  Most race cars feature dinky little rears (for weight reduction), but use a manual bias adjuster in the cockpit - oh, and they completely do away with the ABS/ESP, which is a vital and fundament component of our road cars.

So I hope you understand why I 'earnestly' try and advise that race car 'products' can often be completely unsuitable for road cars.  In the past, this has always seemed to appear as though I was just having a 'dig' at the likes of VWR/AP racing and JKM (though  JKM arn't into racing in the same way that AP and VWR are) - when I was just genuinely trying to offer a more 'road car' biased opinion. 

Hope this all gives some genuine and helpful 'food for thought'. 

[jaydubveedub]

Yes it was the original RS4 that had the problem. I think Audi ended up replacing a great many wheels under warranty or maybe they even did a recall on it? It was a long while ago now......