Brake fade myths.....

Muzza80 · Apr 17, 2014

I see a lot of posts around brakes and upgrading them from standard due to brake fade when driving hard.

Most of the time I read people advising that the only advisable route is upgrading to an expensive, multi piston, big brake kit.

They are a lot of myths around brakes and "warped discs" plus causes of "brake fade" are probably the biggest of them all.

I've been shot down when I advise people that from my experience a good pad and fluid upgrade is all they may need, people jump on stating that "the standard discs are the problem" or the "one piston caliper is rubbish" when in fact that's probably not the main factor at all (for the vast majority of fast road/occasional track users). Many people claim to have tried upgraded pads with little success but I question wether they have also changed their lines for a firmer pedal feel or bled the system with fluid that's capable of withstanding the temp increases caused by the different friction material of upgraded pads.

Anyway, there's an extremely good article from StopTech here

The "Warped" Brake Disc and Other Myths of the Braking System

-Warped- Brake Disc and Other Myths

Personally what I find most interesting and useful in that article is the following:

MYTH # 3 - A SOFT BRAKE PEDAL IS THE RESULT OF PAD FADE

The all too familiar mushy brake pedal is caused by overheated brake fluid, not overheated pads. Repeated heavy use of the brakes may lead to "brake fade". There are two distinct varieties of brake fade:

A) When the temperature at the interface between the pad and the rotor exceeds the thermal capacity of the pad, the pad loses friction capability due largely to out gassing of the binding agents in the pad compound. The brake pedal remains firm and solid but the car will not stop. The first indication is a distinctive and unpleasant smell which should serve as a warning to back off.

B) When the fluid boils in the calipers air bubbles are formed. Since air is compressible, the brake pedal becomes soft and "mushy" and pedal travel increases. You can probably still stop the car by pumping the pedal but efficient modulation is gone. This is a gradual process with lots of warning.

Ok you could argue that the standard discs being one piece does not dissipate the heat as well as a 2 piece disc which causes the pads to overheat, you would be right to an extent, a 2 piece discs is clearly better but a solid 345mm x 30mm disc as on the S3 8P is a meaty enough size to cope with a lot of abuse.

I would respectfully suggest that the main reasons the bulk of people get "brake fade" are not down to the disc, they're more likely poor pad/fluid choice more than anything.

Anyway.... food for thought?

S3_Mat · Apr 17, 2014

I suffer from B) more than A) so based on that I would guess a brake fluid change and upgraded pads and lines would be a cheap and worth while first step at least for me. Interesting read mate, Ill give it a shot and let you know the results! If it enables me to do what i want to do without having to get larger calipers and potentially larger wheels then its a big cost saving.

Muzza80 · Apr 17, 2014

S3_Mat said:
I suffer from B) more than A) so based on that I would guess a brake fluid change and upgraded pads and lines would be a cheap and worth while first step at least for me. Interesting read mate, Ill give it a shot and let you know the results! If it enables me to do what i want to do without having to get larger calipers and potentially larger wheels then its a big cost saving.

Another point to note in that case:

MYTH # 4 - BOILED BRAKE FLUID WILL BE SERVICABLE AFTER IT COOLS.
Once the brake fluid inside the caliper has boiled, it has lost a significant percentage of its original boiling point and should be replaced.

Once boiled, it's fubar'd basically and you're more likely to get fade, earlier, again thereafter.

S3_Mat · Apr 17, 2014

Its due a change its nearly 3 years old. Its a common step missed on services i feel and i regret having not had it done the last time it went in for a service. Last owner before me hadn't changed it either. I have some parts to go on soon, so ill get the Haldex/diff oil done and brake fluid done at the same time.

Muzza80 · Apr 17, 2014

The problem is they (Audi) will flush the system with DOT4 brake fluid.

You need DOT5.1 or Super Dot 4 racing fluid to withstand boiling (fade) at high temps, the only thing is it really needs to be changed annually as it absorbs water quicker than DOT4 does.

batch · Apr 17, 2014

I've always maintained that good improvements can be had from upgrading to decent pads, good quality hi-spec fluid and braided lines. I've had two Golf VR6s, a 1.9 205 GTi and a bonkers, race-spec Mk1 Fiesta which have had the treatment.
My first VR6 got Black Diamond discs, Mintex 1144 pads, AP DoT5 fluid and Goodridge hoses, all done in one hit and the improvement was massive.

S3Alex · Apr 17, 2014

What a good idea for a thread.

I've got to admit I'm probably not a good example here but a lot of what's said above makes very good sense.

I did have problems on a trackday with the brake kit on my car and the cause was much as DaveB1970 had said elsewhere in that the pads themselves were ******.

I have the fluids changed regularly and get the rotors etc changed when indicated.

The only thing I can say about pads was based on trying a set of aftermarket pads with the stock brakes and coming away disappointed but that's I think down to my own preferences.

Muzza80 · Apr 17, 2014

S3Alex said:
What a good idea for a thread.

I've got to admit I'm probably not a good example here but a lot of what's said above makes very good sense.

I did have problems on a trackday with the brake kit on my car and the cause was much as DaveB1970 had said elsewhere in that the pads themselves were ******.

I have the fluids changed regularly and get the rotors etc changed when indicated.

The only thing I can say about pads was based on trying a set of aftermarket pads with the stock brakes and coming away disappointed but that's I think down to my own preferences.

Cheers, I hope it's useful to some people.

I guess if all you did at that stage was change the pads and retain the old brake fluid, not upgrade to one with a higher boiling point then I'm not surprised you were disappointed Alex. The OEM Dot4 fluid cant take the heat generated sometimes by the standard pads never mind upgraded compounds (which by their nature generate more heat), it boils, you get fade.

Brake fluid boiling point ranges:

Wet boiling point

DOT 4 230 Â°C (446 Â°F) 155 Â°C (311 Â°F)
DOT 5.1 260 Â°C (500 Â°F) 180 Â°C (356 Â°F)

Take the Ferodo DS2500 compound for example, it has a claimed ideal working temp range of up to 500 degrees C but will go beyond that.
You would need to be doing some very very hard driving to "cook" a set of DS2500's, I'd have to assume you would be off the track into a wall, barrier or gravel trap due to having boiled the fluid long before reaching those temps. (and yes I realise pad temp is not directly in line with fluid temp but you get the idea)

People may have found it a very different story with a fluid like the Motul RBF600 with its very high wet boiling point (216Â°C / 420Â°F)

I just think some people, speccing a good pad, lines AND fluid option would find this a drastic improvement over standard and probably way more capable than some would believe.

EDITED: All in my opinion and personal experience of course, clearly I'm no master brake engineer lol

S3Alex · Apr 17, 2014

When we tried a set of different pads the fluid etc was changed but I could certainly understand DaveB's comments about the DS2500s after a lot of hard braking efforts from over 120mph.

I do understand the point about fluid temps as well but to put it another way changing to a different pad and rotor has made a huge difference to the way mine works now.

I admit I'm spoilt from past setups from AP and Alcon and I think that has a lot to do with my own expectations.

Muzza80 · Apr 17, 2014

S3Alex said:
When we tried a set of different pads the fluid etc was changed but I could certainly understand DaveB's comments about the DS2500s after a lot of hard braking efforts from over 120mph.

I do understand the point about fluid temps as well but to put it another way changing to a different pad and rotor has made a huge difference to the way mine works now.

I admit I'm spoilt from past setups from AP and Alcon and I think that has a lot to do with my own expectations.

That's some serious work for a set of road/occasional track pads, probably way more than they were intended for.

I personally love the DS2500 and am looking forward to trying the Brembo HP2000 but this is a daily drive with the odd track day, clearly not anything like im sure your car sees Alex.

Now if some company would make a 2 piece standard size rotor for the S3! I'd be interested in that!

Anyway, the point of this thread before I went off on a (mediocre experince & google based) tangent was simply this, unless you are building a track car or have the money burning a hole then don't totally discount a good pad upgrade but make sure you do fluid at the same time or, ultimately you will probably be disappointed

S3Alex · Apr 17, 2014

Agreed!

It was asking too much and produced the predicted result.

But you're right,there's no point shovelling money at brakes or suspension or whatever unless you have a clear aim in mind.

S3_Jacko · Apr 17, 2014

Great write up Muzza... Very interesting and enjoyable reading...

I'm must say i'm not one for driving the car really hard (most times) and on the occasional times that I have, I must say that i've suffered mostly from 'A' on the above listing....

So whats your recommendations then for the 'fast road/occasional trackday use' setup then?

Ferrado pads
Dot 5.1 Brake fluid (any particular brand?)
Braided lines

Are there no grooved or drilled discs that are made in the standard size for the 8P to help with the heat issue, or is that just overkill if you have already fitted the above?

With regards to the above and from being a pretty much noob, with regards to my understandment of braking engineering ... When would a higher piston caliper become more beneficial over the single piston unit? I only ask this as knowing me, track day use, I would probably push the car extremely hard (Isn't that the point?) would a higher piston caliper reduce stopping distance (quicker braking), more spread load over the friction material? what are the benefits over single piston....

I like to learn....?

S3_Mat · Apr 17, 2014

I think the point of multi-piston calipers is so you can have larger brake pads and spread the load more evenly over the larger proportion of the pad and disc, the resulting increase in contact = better braking bite and feel. It was mentioned in another thread though that this does not necessarily improve stopping distance because it is more dependent on contact patch and the quality of the rubber you have on.

Muzza80 · Apr 17, 2014

As I understand it bigger caliper =

More pistons = more power (clamping force on the disc)
Bigger pads = more surface area so more power & less heat produced
Bigger rotors = again more surface area & less heat produced

Also and more importantly (and excuse my rubbish way of explaining it) the further away from the hub centre the caliper sits (i.e the bigger the rotor) the less actual braking force required to stop the rotor spinning, it'a all about the leverage the caliper/pad has over the rotor, the same way a long breaker bar cracks a stubborn nut much easier than a short one which is closer to the nut in the middle?

Does that even make sense?

No doubt a BBK is the ultimate in braking but having had Alcons myself on a previous car and Brembo GT's on another they were overkill for me and my few track days a year.

Plus bits are SO expensive to replace, pads, rotors, bobbins kits and so on.

Jack, any DOT5.1 is better than DOT4, Halfords sell DOT 5.1 but you may as well spend a little more and get some "Super DOT4" racing brake fluid such as the Motul from Opie oils or the likes, the price difference aint much.

DS2500 are excellent but they're quite expensive, I'll be trying the Brembo HP2000 which they claim is better than the DS2500.
I also read that the Tarox Strada compound is actually DS2500 rebranded but that's internet info, I know they're supposed to be good anyway and again cheaper than the DS2500.

Discs, look at MTEC brakes, I've used them for previous cars and for the money they're superb, you can have grooved, dimpled, drilled or a combination. They guarantee them too. Cheap but good discs, like any new disc or pad they need to be bed in properly though. (note you need to search for MK5 R32 on Mtec site for F&R discs, they dont list rears for the s3)

Braided lines is a nice upgrade if you like a firm pedal.

warren_S5 · Apr 17, 2014

Really good thread, and an interesting one as people are often preconditioned to think certain things (e.g. if you upgrade your brakes the only route is BBK, if you upgrade your suspension the only route is coilies).

I do very little track time these days, so wouldn't want the expense of a BBK, I'd rather look to upgrade serviceable parts at point of failure / end of life, so would rather look to uprated discs / pads / fluid / braided hoses.

I had EBC yellow pads on last car (on OEM discs with DOT 5.1) and it was an improvement, but I only ever ran that config at Combe and it's hardly like the Nurburgring as you only really have 2 'proper' braking zones. A lot of people don't rate them, but I'd tested them on Revo's S4 a couple of years before and they seemed fine so I gave them a shot. There are likely better, but there is one thing that worries me about brakes and I shall explain below.

I want uprated brakes without the 'race brake' compromises (squealing / crap from cold / rattling pads / inordinate costs of consumables). Basically I want OEM when I'm driving by the rules of the road, with OEM feel, but with an extended capability on track to cope with slightly more aggressive braking (I don't go all out, I just go faster). I also want a better pedal feel. The hard part with so much car stuff is it's near impossible to try before you buy. It's not like a Naim CD player at £2k where you can go and test it for an afternoon in a plush hi-fi shop and make an informed decision, you're expected to part with £3k on blind faith which unnerves me a bit. But that's how the car industry has always been, so I get the challenges.

Intrigued to see if we can get three Utopia specs (e.g. low price upgrade / mid price upgrade / high price upgrade) that fits all needs and pockets from analysis within this thread! (not hoping for much then!).

PS: Don't recommend doing a similar thread on coils vs. spring / damper, I did it once and offended a LOT of people who blindly choose coil overs like sheep as they follow the 'in' crowd!!! (on SEATCUPRA.net!)

Muzza80 · Apr 17, 2014

Well I'll be able to report on the cheaper end of the upgrade scale shortly.

I need new discs and pads all round in the new few thousand miles ideally and will be going OEM, Pagid or MTEC discs with Brembo HP2000 or Tarox Strada pads along with braided lines and Motul 600 fluid.

I've a track day planned for the end of May & two in June so I should have a good amount opinion to share soon.

XFi · Apr 17, 2014

I have TTRS calipers still yet to be fitted and for me it's more about the look in all honesty with the added benefit of stopping faster. Yes I do a few track days and yes I have had bad brake fade but only on long straights when slowing from 100mph+

The stopping power of the TTRS brakes is a big benifit but I think a lot of people upgrade calipers for the look.

perazzi · Apr 17, 2014

I don't get this.

I've never replaced a set of discs in my driving life; 40+ years, yet there were periods during those earlier years where engines would pop with way too much regularity.

I drive an old fiat as a daily banger with 170k on it (been thrashed to within an inch of its life from the get-go) and my S3s on 68k 'spirited' miles. Both brake true, tightly, and on-line with no wobble or judder - What happens, or causes discs to need replacing so often? :blink:

P

manor13 · Apr 17, 2014

there's the weight factor to if you have lifted the mk5 r32 callipers and discs they are very heavy, for me and my driving style they are fine but I can see the need for a BBK setup as well. for my sline i would go to the r32/s3 setup and try diff pads discs.

S3Alex · Apr 18, 2014

perazzi said:
I don't get this.

I've never replaced a set of discs in my driving life; 40+ years, yet there were periods during those earlier years where engines would pop with way too much regularity.

I drive an old fiat as a daily banger with 170k on it (been thrashed to within an inch of its life from the get-go) and my S3s on 68k 'spirited' miles. Both brake true, tightly, and on-line with no wobble or judder - What happens, or causes discs to need replacing so often?

P

Engine reliability has improved dramatically,and I've had some cars where you may as well have tossed a coin to decide if it would run or not.

Why do discs need replacing?......

There can be a lot of reasons,from things like warping or uneven wear etc,down to plain old wear and tear,which is the usual reason.

If you use an aggressive brake pad compound,the trade off for good feel and bite may be increased wear,and it's pretty easy to see when a set of rotors need replacing.

You may be a bit kinder to your car!

S3_Mat · Apr 18, 2014

One of the main reasons discs warp is keeping your foot on the brake pedal when stopped a junction, especially after getting them exceptionally hot. It holds heat in the disc where the pad is and the rest of the disc cools and can warp them.

Best to use the handbrake or no brake at all if your on a flat surface.

c_w · Apr 19, 2014

Even that 99% of time isn't disc warp but pad deposits on the disc leading to vibration and the feeling of warped discs.

c_w · Apr 19, 2014

warren_S3 said:
Really good thread, and an interesting one as people are often preconditioned to think certain things (e.g. if you upgrade your brakes the only route is BBK, if you upgrade your suspension the only route is coilies).

I do very little track time these days, so wouldn't want the expense of a BBK, I'd rather look to upgrade serviceable parts at point of failure / end of life, so would rather look to uprated discs / pads / fluid / braided hoses.

I had EBC yellow pads on last car (on OEM discs with DOT 5.1) and it was an improvement, but I only ever ran that config at Combe and it's hardly like the Nurburgring as you only really have 2 'proper' braking zones. A lot of people don't rate them, but I'd tested them on Revo's S4 a couple of years before and they seemed fine so I gave them a shot. There are likely better, but there is one thing that worries me about brakes and I shall explain below.

I want uprated brakes without the 'race brake' compromises (squealing / crap from cold / rattling pads / inordinate costs of consumables). Basically I want OEM when I'm driving by the rules of the road, with OEM feel, but with an extended capability on track to cope with slightly more aggressive braking (I don't go all out, I just go faster). I also want a better pedal feel. The hard part with so much car stuff is it's near impossible to try before you buy. It's not like a Naim CD player at £2k where you can go and test it for an afternoon in a plush hi-fi shop and make an informed decision, you're expected to part with £3k on blind faith which unnerves me a bit. But that's how the car industry has always been, so I get the challenges.

Pagid RS29 is the best road/track pad IME. I have them in my BMW, they don't squeal as long as they are used hard ocassionally.

Brake fade myths.....

Registered User

Registered User

Registered User

Registered User

Registered User

Registered User

Rarely neutral

Registered User

Rarely neutral

Registered User

Rarely neutral

Registered User

Registered User

Registered User

Moderator

Registered User

In need of a V8.

Registered User

Registered User

Rarely neutral

Registered User

Registered User

Registered User

Similar threads