Brake fluid recommendation
Discussion
I need to do a clean and flush of the brake fluid in my (new to me) GTR. I use ATE blue in my Porsche, but am reading good things about Castrol SRF DOT4 synthetic. Just a bit worried whether this stuff (the Castrol) would be rough on seals and gaskets? There seems to be some undercurrent that it can be problematic. It's not clear if the Factory recommends a specific brand, or recommends against any brands.
Can anyone who is an owner and/or knowledgeable about the car offer some advice?
Thanks,
V
Can anyone who is an owner and/or knowledgeable about the car offer some advice?
Thanks,
V
Edited by Verde on Sunday 30th October 03:46
ROWDYRENAULT said:
Factory delivers the A.P. brakes with A.P. Formula 5.1. By the way, bravo for changing the fluid, people forget how cheap fluid is versus anything to do with rebuilding the brakes. Lee
Thank you. Truth is that I had a small problem with a brake fluid leak and since some air might have gotten in to the system, I likely have to flush it. But in general, I agree with the value of yearly (or so) flush. Good for the components, help harden up the pedal feel, and gives a better sense of safety. The builder of the car is quite a genius but this was just a simple problem that might have occurred in shipping.But I'm rather surprised about recommending DOT 5.1. I'm getting a bit confused in that I thought all 5.x fluids were silicon based and could not be mixed with 4's and 3's. This one is a 5.1, but is not silicon based, and can be mixed. Do you know how long Ultima has been using this? This kit was purchased on 2004-2005 or so.
Thanks again,
V
Verde said:
Thank you. Truth is that I had a small problem with a brake fluid leak and since some air might have gotten in to the system, I likely have to flush it. But in general, I agree with the value of yearly (or so) flush. Good for the components, help harden up the pedal feel, and gives a better sense of safety. The builder of the car is quite a genius but this was just a simple problem that might have occurred in shipping.
But I'm rather surprised about recommending DOT 5.1. I'm getting a bit confused in that I thought all 5.x fluids were silicon based and could not be mixed with 4's and 3's. This one is a 5.1, but is not silicon based, and can be mixed. Do you know how long Ultima has been using this? This kit was purchased on 2004-2005 or so.
Thanks again,
V
It can be confusing with the numbering of DOT. I don't get it either why they named it 5.1But I'm rather surprised about recommending DOT 5.1. I'm getting a bit confused in that I thought all 5.x fluids were silicon based and could not be mixed with 4's and 3's. This one is a 5.1, but is not silicon based, and can be mixed. Do you know how long Ultima has been using this? This kit was purchased on 2004-2005 or so.
Thanks again,
V
DOT 3,4 and 5.1 are glycol based brakefluids.
DOT 5 is the only silicone one.
Never mix DOT5 with any other of the 3,4,5.1 fluids. It will gell if you do.
DOT 5 is more used in racing applications, specially motorcycles.
You can identify DOT5 by it's purple color.
Said all of this, I changed the braking system on my Caterham from DOT4 to DOT5, but you need to flush the system very, very good and take the calipers of and take them apart to clean them. I had to change because I had to change to viton seals, which don't work with glycol.
UltimaCH said:
Castrol SRF is tops and the Ultima deserves it any and all the time despite the cost. Just know that it absorbs humidity faster that lesser brands, so your brakes need more regular bleeding than most other applications.
+1 Castrol SRF is absolutely the best but as above, has to be changed more often & costs a fortune. Use it (maybe) if you plan to be a track day regular. Otherwise ATE Super-blue (which I think is available in Blue and Non-blue which makes it handy to see what's going on when you bleed the thing) or either Comma or Lockheed 5.1. Those should last the 2 years unless you boil them.harry b said:
It can be confusing with the numbering of DOT. I don't get it either why they named it 5.1
DOT 3,4 and 5.1 are glycol based brakefluids.
DOT 5 is the only silicone one.
Never mix DOT5 with any other of the 3,4,5.1 fluids. It will gell if you do.
DOT 5 is more used in racing applications, specially motorcycles.
You can identify DOT5 by it's purple color.
Said all of this, I changed the braking system on my Caterham from DOT4 to DOT5, but you need to flush the system very, very good and take the calipers of and take them apart to clean them. I had to change because I had to change to viton seals, which don't work with glycol.
Almost - DOT 5 is silcone based as you say, but it is not used in racing applications. It is basically not hygroscopic, so it does not absorb moisture like the glycol-ether based Dot 3, 4 and 5.1, however it does not disperse moisture present in the system and (I believe) that it has a much lower boiling point, not making it suitable for race use. It is more often than not used in military vehicles etc. as it is essentially 'maintenance free'.DOT 3,4 and 5.1 are glycol based brakefluids.
DOT 5 is the only silicone one.
Never mix DOT5 with any other of the 3,4,5.1 fluids. It will gell if you do.
DOT 5 is more used in racing applications, specially motorcycles.
You can identify DOT5 by it's purple color.
Said all of this, I changed the braking system on my Caterham from DOT4 to DOT5, but you need to flush the system very, very good and take the calipers of and take them apart to clean them. I had to change because I had to change to viton seals, which don't work with glycol.
Motul RBF600 or AP600 brake fluid is perfect if you are using the car on track or road - the expensive SRF is overkill (£60/litre!!). Rather than looking at the DOT level, it is important to look at the dry and wet boiling points of the fluids - in general, the higher the better if used on track. If road only, generally most 'brand name' fluids such as the ATE blue you were using will be fine.
Jonny
macgtech said:
Almost - DOT 5 is silcone based as you say, but it is not used in racing applications. It is basically not hygroscopic, so it does not absorb moisture like the glycol-ether based Dot 3, 4 and 5.1, however it does not disperse moisture present in the system and (I believe) that it has a much lower boiling point, not making it suitable for race use. It is more often than not used in military vehicles etc. as it is essentially 'maintenance free'.
Motul RBF600 or AP600 brake fluid is perfect if you are using the car on track or road - the expensive SRF is overkill (£60/litre!!). Rather than looking at the DOT level, it is important to look at the dry and wet boiling points of the fluids - in general, the higher the better if used on track. If road only, generally most 'brand name' fluids such as the ATE blue you were using will be fine.
Jonny
Hi Johnny,Motul RBF600 or AP600 brake fluid is perfect if you are using the car on track or road - the expensive SRF is overkill (£60/litre!!). Rather than looking at the DOT level, it is important to look at the dry and wet boiling points of the fluids - in general, the higher the better if used on track. If road only, generally most 'brand name' fluids such as the ATE blue you were using will be fine.
Jonny
Don't want to start a rant here, the discussion about the brakefluid goes well beyond the level most people dare to push their car, so for everybody I would indeed advice take a DOT5.1 if you think you push the brakes to the limit, elsewise take a DOT4, it will be more than sufficient for roaduse, and the occasional trackday.
One could look further than only the fluid you use, for instance the seals and hygroscopic effects.
Indeed dot 5 has a lower dry and wet boiling point, but only compared to DOT5.1 Not a huge difference either, 10 degrees.
(260degrees to 270degrees and 190degrees to 180 degrees).
The military use it because it is the only brake fuid that can cope with harsh arctic like temperatures.
Being not hygroscopic has also it's downside, if you get water in the system it will collect in the lowest parts of the brakesystem, often a caliper and brake capacity will be near 0 with water in the caliper. So a system filled with DOT5 needs to be air tight closed.
Again, take a look at motorcycles, and yes also racing ones if you get a chance.
I don't want to advice people to use DOT5 either, it needs much more attention in terms of flushing and keeping moisture out.
You will need fluidcontainers with rubberseal and screwdown caps
On the other hand seals made of Viton will never fail.
Important on harsh long distance racing, rally and raid applications.
Also I'm from an period DOT5 was the only alternative.
I've just been through this after experiencing some serious brake fade at an SCCA track event. I can only assume the high BP fluid had absorbed water over time. I can't stress enough the need to change fluids regularly, it was quite the pucker moment.
The factory recommended AP600, but it does not mix with conventional DOT 3, 4 or 5.1 fluids and I wanted to flush through, so I opted for Pro Speed RS683.
Here's a comparison of top brands at Pegasus Racing;
https://www.pegasusautoracing.com/group.asp?GroupI...
Julian
The factory recommended AP600, but it does not mix with conventional DOT 3, 4 or 5.1 fluids and I wanted to flush through, so I opted for Pro Speed RS683.
Here's a comparison of top brands at Pegasus Racing;
https://www.pegasusautoracing.com/group.asp?GroupI...
Julian
JoulesCanAm said:
I've just been through this after experiencing some serious brake fade at an SCCA track event. I can only assume the high BP fluid had absorbed water over time. I can't stress enough the need to change fluids regularly, it was quite the pucker moment.
The factory recommended AP600, but it does not mix with conventional DOT 3, 4 or 5.1 fluids and I wanted to flush through, so I opted for Pro Speed RS683.
Here's a comparison of top brands at Pegasus Racing;
https://www.pegasusautoracing.com/group.asp?GroupI...
Julian
When you say fade - what were the symptoms?The factory recommended AP600, but it does not mix with conventional DOT 3, 4 or 5.1 fluids and I wanted to flush through, so I opted for Pro Speed RS683.
Here's a comparison of top brands at Pegasus Racing;
https://www.pegasusautoracing.com/group.asp?GroupI...
Julian
If the pedal goes to the floor, and you get no retardation, then the fluid has boiled and all you can do is pump the pedal furiously to compress any air that has formed. A fluid change and maybe higher temperature fluid is required.
If you have a firm pedal and there is no retardation, the pads are 'fading' which means that they are above their maximum operating temperature - when this happens most pads burn off some of their constituents, which results in gases forming and it causes the pad to essentially aquaplane across the disc. Cross drillings or slots can help as they let the gasses escape, but if the pads are getting too hot on a regular basis you need extra cooling, higher temperature rated pads (most likely) and/or bigger discs/callipers.
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