MK5 Golf GTI
All Things Mk5 => Modifications & Technical Area => Track Day Technical => Topic started by: gobbleplease on September 22, 2011, 10:27:48 pm
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Ive seen a few posts reguarding brake fluid recently so i thought id post this up to help out. :smiley:
There is a lot of misinformation about which Brake Fluid is the best to use so thought i'd post this to clear a few things up!
The trouble comes when people start quoting DOT ratings with sweeping statements like a DOT 5 or DOT 5.1 fluid is better than a DOT 4 fluid, well I'm afraid you can't make statements like that because in most cases it isn't true, you get lots of opinions about whats the best brand so here is my opinion based on some facts!
Firstly to set a few things straight.
Castrol SRF is DOT 4 rated and is definitely not DOT 5.
DOT 5 rating is reserved SOLELY for Silicone based brake fluids and these should not be used in performance applications. Basically any moisture entering the system will stay in small bubbles or pockets as water cannot be absorbed into silicone fluids. As soon as the fluid reaches around 100C (pressure dependent) the trapped water will boil. As gases can be compressed and fluids can't your brake pedal will become softer. Separated water in the system can also lead to corrosion on metal components (pistons etc.). Silicone fluids should not be mixed with other DOT rated fluids as they are completely different chemically.
DOT 3, DOT 4 and DOT 5.1 brake fluids are Glycol-ether based fluids. Glycol-ether is hygroscopic which means it absorbs water into the fluid (water combines with the fluid, water doesn't sit separately as with Silicone fluids). As water is absorbed into the fluid it will gradually reduce it's overall boiling point. For this reason fluids are rated with with two boiling points, one with no water absorbed into the fluid (Dry Boiling Point) and one with 3.5% water absorbed into the fluid (Wet Boiling Point).
The Wet and Dry boiling points are the MOST important factor when deciding what brake fluid to use, DOT ratings set the minimum requirements for these two boiling points. The higher the DOT rating, the higher the minimum boiling point requirement.
HOWEVER that is not the whole story as the DOT requirements also stipulate other criteria that the fluids must pass including acidity, corrosion protection etc. but the most important one for us after boiling points is viscosity.
With the introduction of high tech ABS/TCS/ESP systems there was a need for thinner brake fluids so they could pass easily through the micro valves used in these systems. The main reason why the DOT 5.1 rating was introduced was to set a standard for these thinner fluids.
DOT 5.1 criteria dictates that the fluid will be thinner in viscosity than a DOT 4 fluid.
If your manufacturer says you only need a DOT 4 rated brake fluid (as mentioned above, all BMW's only need DOT 4) then you don't need a DOT 5.1 fluid. In fact there aren't many cars that specifically require a DOT 5.1 fluid.
If you check the Wet and Dry boiling points of the most popular DOT 4 and 5.1 fluids you will find the best performing fluids (like Castrol SRF) are in fact DOT 4 rated. The reason they are DOT 4 rated is they are too thick to pass the DOT 5.1 viscosity criteria even though they surpass the DOT 5.1 wet and dry boiling point criteria by miles!
The really important numbers (to me anyway) are the Wet boiling points, SRF wins hands down with this and you can see why it is so widely regraded as the ultimate brake fluid. What the wet boiling points don't tell you however is how quickly the brake fluids can absorb moisture, some fluids are more hygroscopic than others and will get to the wet boiling point quicker than others. Manufacturers can get around this by treating the fluid with Boric acid to help neutralize any water entering the fluid and makes the fluid slower to drop to the wet boiling point. Castrol use this method with their 'Super Dot 4' giving it a longer life. ATE 'Super Blue' is also a very good performer over a long period and I believe was the OEM fluid for BMW's for a while (I have used it in the past and it's been excellent).
Whatever fluid you chose change it AT LEAST every two years and preferably annually.
SRF is expensive and the next alternative is Motul RBF 600 at half the price its worth considering when SRF is approx. £40/Ltr. especially if you do change every year its add's to the already high running costs we all experience...!
A few general tips about brake fluid...
Only buy enough fluid for what you need at the time. Fluid sitting on shelves just absorbs moisture from the atmosphere so when you come to use it, it maybe no good. Incidentally that is why decent fluids come in metal cans (ATE for example and SRF used too), moisture cannot pass through metal where as it can permeate through plastic.
Speaking of moisture permeating through plastic, tests have proven that the most moisture entering a brake system comes from...moisture permeating directly through the rubber of the brake hoses! Remember that the next time you drive through a puddle
The Importance of Braided Brake Lines
Installing stainless steel braided brake lines should be one of the first purchases for ANY sportscar. Replacing the crappy OEM rubber brake lines has two major benefits: eliminating brake fade and reducing your maintenance. This will help to reduce water permeating through the rubber only hoses, braided are still rubber in the centre so there is still the possibility water getting in but its deffinitely reduced with braided lines but not eliminated.. there are plenty of cheap Halfords sheit out there so make sure you spend a few bux and get DOT approved ones!
Safety first: Eliminating dangerous brake fade
Brake fade is the loss of braking power when your brake system overheats. When you apply your brakes, brake fluid is forced through the rubber brake hoses, squeezing your brake calipers and causing you to decelerate. A by-product of the braking action is HEAT which is bad for your brake lines. As the brake fluids heats up, so do your OEM rubber lines. Hot rubber lines will expand when the brakes are applied - instead of channeling the fluid towards your calipers, they expand outwards, robbing you of valuable braking power.
Stainless steel braided brake lines don't expand when heated by your brake fluid. You will get maximum braking power regardless of the time spent riding. These brake lines may save your life one day.
No Maintainence & Peace of Mind
Some manufacturers recommend their OEM rubber brake lines to be changed every couple years. Most stainless steel brake lines never need to be replaced - Most cases one purchase and guaranteed for life!
Thanx Mroad For Info!
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Nice one, very interesting. :congrats:
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Yup good info there.
Just changed my OE fluid to Millers 300+ which is DOT 4 but has higher dry boiling point than DOT 5.1!
Dealer wasn't gonna change my fluid till 3 years is up but I thought I ain't doing that!
Think I'll change it annually from now on :happy2:
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how many litres roughly does our cars take ???
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I bought 2 liters for a full bleed (upgraded calipers) had some spare though.
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I bought 2 liters for a full bleed (upgraded calipers) had some spare though.
thanks dude :happy2: can u recommend me some fluid for fast road with possible trackday???
thanks dawain
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Motul RBF600. I swear by it.
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cheers tony...... dont suppose u know the best place 2get it from do ya??/
thanks dawain
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Loads of places sell it - try Opie Oils for online sales and any decent motorsport shop for over the counter. Should be about £15/500ml.
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thanks tony ordered some this mornin from opie oils should b with me friday :party: :party:
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100% RBF 600, its the second best dot 4 available at 1/4 the price of the best !
Ill need to get some ordered up for my new BBK :party: :party:
What are opie charing at the moment ?
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i paid £56 for 2L worth including shipping :happy2:
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Hmm, I run on AP Racing brakes so I take their advice above anyone else's, including anyone on a forum. They say 5.1 for fast road use with their brakes and say it's ok for the occasional trackday.
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Nice read. :happy2:
I don't see the need of braided brake line though as the Mk.V brake lines are
much more advanced than on previous models.
I prefer Ate Super Blue and Motul RBF600 as Castrol SRF is too expensive imho,
but I personally never had any boiling fluid on any car.
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Hmm, I run on AP Racing brakes so I take their advice above anyone else's, including anyone on a forum. They say 5.1 for fast road use with their brakes and say it's ok for the occasional trackday.
Probably sitting on the side of caution, as VW spec DOT5.1 and they'd not want to tell you to use DOT4 and have the 0.00001% chance of it causing a problem.
Fact is RBF600 exceeds DOT5.1 standards, is absolutely fine in our cars and I've never managed to boil it in any car I've owned.
As with everything, Robin, if it's working for you - then leave it as it is. :happy2:
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Tony, advanced DOT4 fluids may exceed DOT5.1 boiling point, but DOT5.1 fluids
have a lower viscosity. This complements the fast moving ESP valves.
I don't want to say that ESP doesn't work with DOT4 but that doesn't affect
the difference in viscosity.
Does VW really recommend DOT5.1? Thought they just use DOT4 in our cars,
but I might be wrong of course.
:wink:
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I was working on the assumption they'd told him to keep stock spec stuff, not 100% what VW spec is though???
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To be honest I never read an official statement which fluid they fill from factory.
Maybe VW have their own fluid.
But of course all DOT4 and DOT5.1 work well in all modern VAG platform cars.
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Probably sitting on the side of caution, as VW spec DOT5.1 and they'd not want to tell you to use DOT4 and have the 0.00001% chance of it causing a problem.
No they don't. VW used to spec DOT4 upto 2007, but they now have their own unique spec - VW 501.14 - which exceeds DOT4 wet and dry boiling points by some margin, but more importantly, is a special low viscosity fluid. :happy2:
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VW sometimes go the 'exclusive' route.
Why don't they use a common 'industrial standard' DOT5.1 ??
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VW sometimes go the 'exclusive' route.
Why don't they use a common 'industrial standard' DOT5.1 ??
Because, despite that clear 'copy and paste' in the orginal post of this thread - DOT5.1 does NOT include any 'low viscosity' specification. The Conti Teves MK60 ESP (and all Teves ESP units) are notorious for failing - due to fluid which is beyond specification (non low visc fluid, dirty fluid, old fluid, water contamination, etc).
VW has their own exclusive spec, as does Mercedes-Benz (http://bevo.mercedes-benz.com/bevolisten/331.0_en.html and http://bevo.mercedes-benz.com/bevolisten/331.1_en.html), Renault, BMW, Fiat, and probably many more.
It must be remembered that 'DOT' is a United States specification, and just like the yankie API engine oil standards - are basically way too inferior for European spec motors - hence all the OEM specs.
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VW sometimes go the 'exclusive' route.
Why don't they use a common 'industrial standard' DOT5.1 ??
Because, despite that clear 'copy and paste' in the orginal post of this thread - DOT5.1 does NOT include any 'low viscosity' specification. The Conti Teves MK60 ESP (and all Teves ESP units) are notorious for failing - due to fluid which is beyond specification (non low visc fluid, dirty fluid, old fluid, water contamination, etc).
VW has their own exclusive spec, as does Mercedes-Benz (http://bevo.mercedes-benz.com/bevolisten/331.0_en.html and http://bevo.mercedes-benz.com/bevolisten/331.1_en.html), Renault, BMW, Fiat, and probably many more.
It must be remembered that 'DOT' is a United States specification, and just like the yankie API engine oil standards - are basically way too inferior for European spec motors - hence all the OEM specs.
And whats your point ?? It was a copy and paste and if you noticed at the bottom i thanked the original author for the info !
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Posted this already on another thread: :wink:
AP Racing 551 - DOT 3 - 527°F (275°C) / 302ºF (145ºC)
AP Racing 600 - DOT 3 - 590°F (310°C) / 410°F (210°C)
AP PRF Racing - DOT 4 - 608°F (320ºC) / 311°F (155ºC)
Ate SL6 - DOT4 + ISO6 - 509°F (265°C) / 347°F (175°C)
Ate Super Blue - DOT 4 - 536ºF (280ºC) / 396ºF (194ºC) (Tipp)
Ate Super 200 - DOT 4 - 536ºF (280ºC) / 382ºF (194ºC) (Tipp)
BMW OEM - DOT 4 - 446*F (224°) / 311*F (156°)
Bosch - DOT 3 - 491ºF (255ºC) / 288ºF (142ºC)
Bosch - DOT 4 - 509ºF (265ºC) / 329ºF (165ºC)
Bosch - DOT 4+ - 536ºF (280ºC) / 356ºF (180ºC)
Brembo LCF 600+ - DOT 4 - 601ºF (316ºC) / 399ºF (204ºC) !!!
Brembo EVO 500+ - DOT 4 - 520ºF (271ºC) / 336ºF (169ºC)
Castrol GT LMA - DOT 4 - 509ºF (265ºC) / 311ºF (155ºC)
Castrol SRF - DOT 4 - 590ºF (310ºC) / 518ºF (270ºC) !!!
Endless RF-650 - DOT4? - 612°F (323°C) / 425°F (218°C) !!!
GS610 - DOT 4 - 610°F (321°C) / 421°F (216°C)
Gunk HD - DOT 4 - 510ºF (266ºC) / 311ºF (155ºC)
Motul DOT 5.1 - DOT 5.1 - 509ºF (265ºC) / 365ºF (185ºC)
Motul RBF 600 - DOT 4 - 594ºF (312ºC) / 421ºF (216ºC) (Tipp)
Motul RBF 660 - DOT 4 - 617ºF (325ºC) / 400ºF (204ºC) (Tipp)
Neo Super DOT16 - DOT 4 - 610°F (322°C) / 421°F (216°C)
Pentosin Super - DOT 4 - 500°F (260°C) / 338°F (170°C)
Pentosin RBF - DOT 5.1 - 572°F (300°C) / 392ºF (200°C) (Tipp)
Prospeed RS683 - DOT 4 - 683°F (360°C) / 439°F (224°C)
ValvolineProSyn - DOT 3/4 - 527ºF (275ºC) / 347ºF (175ºC)
Wilwood Hi-Temp 570 - DOT 3 - 570ºF (299ºC) / 284ºF (140ºC)
Wilwood EXP600 Plus - DOT 4 - 633ºF (330ºC) / 417ºF (213ºC)
VW has it's own spec J 1704 FMVS16 Audi/VW 501.14. At least Ate SL6 meets this spec.
http://www.ate.de/generator/www/com/de/ate/ate/themen/10_produkte/30_bremsfluessigkeiten/download/bf_flyer_pdf_de.pdf (http://www.ate.de/generator/www/com/de/ate/ate/themen/10_produkte/30_bremsfluessigkeiten/download/bf_flyer_pdf_de.pdf)
Ate SL6 has a dry boiling point of 265° C and a wet bp of 175° C. The low temp is at max.
700 mm²/s (Super 200 and Super Blue Racing are at max 1400 mm²/s).
:drinking:
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I think 5.1 is not the right brake fluid.
4.1 is the right one.
DOT5.1 is fine (DOT5 would NOT).
There's not "4.1", just DOT4 which is also fine.
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I use this one, with no issues at all - Fast or Slow
Ate Super Blue - DOT 4 - 536ºF (280ºC) / 396ºF (194ºC) (Tipp)
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some more added
Make..........DOT Rating......dry and wet boiling point
AP Racing 551 - DOT 3 - 527°F (275°C) / 302ºF (145ºC)
AP Racing 600 - DOT 3 - 590°F (310°C) / 410°F (210°C)
AP PRF Racing - DOT 4 - 608°F (320ºC) / 311°F (155ºC)
Ate SL6 - DOT4 + ISO6 - 509°F (265°C) / 347°F (175°C)
Ate Super Blue - DOT 4 - 536ºF (280ºC) / 390ºF (194ºC)
Ate Super 200 - DOT 4 - 536ºF (280ºC) / 390ºF (194ºC)
BMW OEM - DOT 4 - 446*F (224°) / 311*F (156°)
Bosch - DOT 3 - 491ºF (255ºC) / 288ºF (142ºC)
Bosch - DOT 4 - 509ºF (265ºC) / 329ºF (165ºC)
Bosch - DOT 4+ - 536ºF (280ºC) / 356ºF (180ºC)
Brembo LCF 600+ - DOT 4 - 601ºF (316ºC) / 399ºF (204ºC)
Brembo EVO 500+ - DOT 4 - 520ºF (271ºC) / 336ºF (169ºC)
Castrol GT LMA - DOT 4 - 509ºF (265ºC) / 311ºF (155ºC)
Castrol SRF - DOT 4 - 590ºF (310ºC) / 518ºF (270ºC)
Endless RF-650 - DOT4 - 612°F (323°C) / 425°F (218°C)
GS610 - DOT 4 - 610°F (321°C) / 421°F (216°C)
Gunk HD - DOT 4 - 510ºF (266ºC) / 311ºF (155ºC)
Motul DOT 5.1 - DOT 5.1 - 509ºF (265ºC) / 365ºF (185ºC)
Motul RBF 600 - DOT 4 - 594ºF (312ºC) / 421ºF (216ºC)
Motul RBF 660 - DOT 4 - 617ºF (325ºC) / 400ºF (204ºC)
Neo Super DOT16 - DOT 4 - 610°F (322°C) / 421°F (216°C)
Pentosin Super - DOT 4 - 500°F (260°C) / 338°F (170°C)
Pentosin RBF - DOT 4 - 572°F (300°C) / 392ºF (200°C)
Performance Friction RH665 - DOT 4 - 617°F (325°C) / 395°F (195°C)
Project µ G-four 335 - DOT 4 - 634°F (335°C) / 429°F (221°C)
Prospeed RS683 - DOT 4 - 683°F (360°C) / 439°F (224°C)
TAR•OX Roadrace - DOT 4 - 583°F (314°C) / 401°F (205°C)
ValvolineProSyn - DOT 3/4 - 527ºF (275ºC) / 347ºF (175ºC)
Wilwood Hi-Temp 570 - DOT 3 - 570ºF (299ºC) / 284ºF (140ºC)
Wilwood EXP600 Plus - DOT 4 - 633ºF (330ºC) / 417ºF (213ºC)