Brake Fluid

[zzz]

hey all,

I actually have a corolla XRS which is probably very similar to the GTS in terms of brakes. We share the same rear pads and rotors and I believe we share the same front rotors (the GTS pads are slightly thicker than the XRS ones).

I'm in getting a new clutch put in this week and I was wondering what to fill my brake fluid with. I have the factory stuff in there and I would like to upgrade it. I've boiled it once already and I know that majorly screws it up but I've been lazy to change it since.

My car does have ABS and has 4 disc brakes. Which fluid should I go with? I see most people going with Motul, but what are the different grades DOT 3, DOT 4, DOT 5.1 and their properties? I have read that 5.1 is not to be used in ABS systems, should I use DOT 4?

If I flush it completely, how much will I need to fill it back up?

All recommendations / advice appreciated! Thanks in advance!

[Mido]

Motul RBF600 or something like that, is the fluid to use.

i'm trying to find an install for that too.

[zzz]

RBF600 is DOT4, is that okay on the ABS system? I know the manuals say DOT 3.

[hellsyphon]

You can interchange DOT 3 and 4 and 5.1 fluids. You should avoid DOT 5 fluids. Personally I use ATE super blue and one can should be more than enough to flush the whole brake and clutch system.

[zzz]

Why should I avoid DOT 5? And is DOT 5 and DOT 5.1 the same thing?

nvm, just read that DOT 5.1 is DOT 4 that meets DOT 5 specs since DOT 5 is silicon based.

[renfield90]

nvm, just read that DOT 5.1 is DOT 4 that meets DOT 5 specs since DOT 5 is silicon based.
Correct.

I would avoid DOT 3. I've personally found DOT 5.1 hard to find; realistically, most of the best fluids out there are DOT 4 anyway.

Valvoline makes a good synthetic DOT 4. I actually know some racers who use the stuff. For a daily driver this fluid would be perfect - it's cheap, and has good dry and wet boiling points. ATE Super Blue is probably the next step up. Motul RBF600 is probably as close as you can get to bulletproof. There is a 650 that has a higher dry boiling point but that comes at the cost of a wet boiling point.

Assuming you're not changing your fluid monthly, it's the wet boiling points you should really be looking at. IMO, RBF600 is overkill for a street car. What caused your brake boiling in the first place?

[zzz]

I was basically running it down an airfield over and over and over again so the constant braking eventually made the pedal all mushy about 12 or so runs.

My deal is, the RBF600 isn't all that much more expensive and I flush my system maybe once a year at most. So if I got RBF600, it would be fine for my lines, brakes, and ABS?

[renfield90]

Yes, RBF600 will be fine.

[zzz]

okay sweet, thanks!

anyone else have anything to add?

[verbal272]

Dot 5.1 is silicone based, It's not hygroscopic which is good but it's great at retaining air which is terrible for ABS, pulsating brake lines full of air isn't a good thing as it can cause problems with the system.

Dot 3/4 are what I would recommend, if your manual says DOT3, then go for it unless you don't drive your car that much and go longer than average without changing your brake pads.

I would use DOT 4 if I stored my car for 6-7 months a year as I wouldn't be using my brake pads enough to change them every 2 years.

But again you can't really go wrong with DOT 3 or DOT 4. only in the instance above I would recommend DOT 4 over DOT 3

[zzz]

Why would DOT4 be better if the car is being stored and the pads aren't being changed? I daily drive my car and plan on flushing the system every year. I've had this car about a year now, which is why I ask. Thanks for your input!

[mozso]

^^^
Go with RBF600. It's track proven by us for many years with Cotolla TS (same as XRS) and my Corolla Turbo as well.

[mozso]

I also suggest Ferodo DS2000 / DS Performance pads. Good on track and still good on normal roads even in cold.

[renfield90]

Dot 5.1 is silicone based, It's not hygroscopic which is good
Incorrect. DOT 5 is silicone based, DOT 5.1 is the same as DOT 3/4 (polyethylene glycol).

The fact that DOT 5 is hydrophobic helps - only a little. The fluid lasts a lot longer, but whatever water does accumulate in the system gets concentrated together (versus in a hygroscopic fluid, the water will be evenly spread throughout). Since water is heavier than DOT 5, it tends to collect at the lowest place in the system: right next to the caliper. Water boils at 212 F; as soon as your brakes hit that temperature, you're going to have big air pockets.

DOT 5 is typically used in collector cars and other similar cars that don't see much driving action and are stored for long periods.

[verbal272]

Incorrect. DOT 5 is silicone based, DOT 5.1 is the same as DOT 3/4 (polyethylene glycol)


yes my bad I don't know why I put the .1, I believe I must have been writing something then changed my train of thought.

[verbal272]

Why would DOT4 be better if the car is being stored and the pads aren't being changed? I daily drive my car and plan on flushing the system every year. I've had this car about a year now, which is why I ask. Thanks for your input!

Just a little bit of background info, DOT 4 has a higher wet boiling point than DOT 3.

Brake fluid like any liquid has a boiling point. Water boils at 100C/212F. Pure brake fluid has a very high boiling point. The below numbers give the boiling point for DOT 3 and DOT 4 when you put fresh clean fluid in your car.

DOT 3 205

[zzz]

sweet, thanks for the info. I think you confused the boiling points there but I get your point.

Now, does brake fluid have an effect on pedal feel?

[verbal272]

sweet, thanks for the info. I think you confused the boiling points there but I get your point.

Now, does brake fluid have an effect on pedal feel?

Corrected my mistake in the last sentence for ya :)

Generally no, DOT 3/DOT 4 brake fluid (essentially hydraulic fluid) shouldn't affect pedal feel if there is no moisture in the lines, it follows the strict principals of hydraulics and Pascal's Law. The difference between most brake fluids is the special addatives that are added in after, sort of like the special cleaning addatives that are added into premium fuel that you don't get in regular at your local gas station. switching from DOT3 to DOT4 should not change how your pedal feels.

Once moisture/air gets into the lines it no longer follows Pascal's law as the air can then be compressed which can cause all sorts of problems, most noticably is a squishy/mushy/spongy pedal.

If you ever get a mushy/squishy pedal it usually means you have air in the lines which means you HAD moisture that boiled. Easiest way to correct this is to just bleed the lines, once bled problem solved (if air in the lines caused the problem) :)

[zzz]

okay, that is why I'm asking. My new clutch, despite using the same pressure plate as both my friends, is much softer than theirs. I have boiled my fluid once before at an event and I haven't changed the fluid. Let's hope this helps then.

From a daily driver point of view, if I go with a DOT4, which I find only marginally more expensive, would that mean I could get away with a longer flush interval?

[verbal272]

okay, that is why I'm asking. My new clutch, despite using the same pressure plate as both my friends, is much softer than theirs. I have boiled my fluid once before at an event and I haven't changed the fluid. Let's hope this helps then.





Well each car, even the same model may have a different clutch feel, parts wear differently in each vehicle. When you changed your clutch you should have replaced your transmission fluid too, if not that may be what's causing the issue, you can also try bleeding your clutch (a flush/replacement is reccomended over a bleed though)

From a daily driver point of view, if I go with a DOT4, which I find only marginally more expensive, would that mean I could get away with a longer flush interval?

Essentially yes, as long as you down leave your resevoir cap open for long periods of time.

To get the same wet boiling point as DOT 3, you would need more than 3.7% water in DOT 4 brake fluid. DOT 5.1 would require even more but the price goes up between DOT3, 4 and 5.1.

One thing you have to remember though is that once that moisture near your calipers boils off and leaves air in the lines, (All 3 brake fluid types suffer from this) you will still have a squishy/mushy/soft brake pedal feel and will need to bleed the lines. The moisture closer to the middle of your system might not get hot enough to boil but it will still reduce the over all boiling point of your brake fluid.


Manufacturers recommend changing the fluid each brake change or every 2 years. You'd be suprised how many people I've talked to who have owned their vehicle for 4,5,6 years without changing their brake fluid.


http://i13.photobucket.com/albums/a289/verbal272/Other%20Stuff/brakefluidb.jpg

[zzz]

Gotcha. I went ahead and ordered the Motul RBF600. I got two bottles, which makes 1 liter, that should be enough for a flush. I'm avoiding the 5.1 also because I read it's bad for ABS systems.

I hope this makes it a little nicer for me. I've owned my car one year but it was purchased used. They did change the transmission fluid when they did my clutch job. I'm going to look into stainless steel lines.

Do you recommend them for the clutch, and all 4 disc brakes? Why or why not?


Thanks again! You've been very helpful.

[verbal272]

Gotcha. I went ahead and ordered the Motul RBF600. I got two bottles, which makes 1 liter, that should be enough for a flush. I'm avoiding the 5.1 also because I read it's bad for ABS systems.

I hope this makes it a little nicer for me. I've owned my car one year but it was purchased used. They did change the transmission fluid when they did my clutch job. I'm going to look into stainless steel lines.

Do you recommend them for the clutch, and all 4 disc brakes? Why or why not?


Thanks again! You've been very helpful.

Unlike rubber brake lines the stainless steel lines wont expand in the heat/when your fluid heats up.

as the rubber heats up it expands more when you push on the brake, giving you a mushy/squishy pedal feel, you'll also notice your foot will be a little closer to the floor than normal when you finally get a hard pedal feel.

The steel brake lines prevent this mushy feel and should maintain a hard pedal so long as there is no air in the system.

[zzz]

so is it all just feel or would it improve performance at all?

If it's all feel, I'll just get the clutch line...

[gumber]

Gotcha. I went ahead and ordered the Motul RBF600. I got two bottles, which makes 1 liter, that should be enough for a flush. I'm avoiding the 5.1 also because I read it's bad for ABS systems.

Do you mind me asking where you read this from? I've seen alot of people miss-understand dot 5.1 as being dot 5 which it is not. Dot 5.1 is not suppose to containe silicone and should be abs safe.

[zzz]

I read it on some corvette forum I believe. Maybe they were mistaken.

In any case, I think DOT4 will do it for me anyway.

[verbal272]

Do you mind me asking where you read this from? I've seen alot of people miss-understand dot 5.1 as being dot 5 which it is not. Dot 5.1 is not suppose to containe silicone and should be abs safe.

I've heard from many sources that DOT 3/4 are generally considered safer for ABS than 5.1, I haven't read literature backing this up (proof) but I think most mechanics would agree. It may have something to do with the additives in 5.1 that raise it's DRY/WET boiling point that may cause an issue with ABS.

[gumber]

Wierd... the only thing I've heard is that the Brit's tend to relabel the DOT 5.1 as performance DOT 4 because they're afraid of the whole 5.1 notation or something... anyways, I'm very happy with my Motul 5.1 in my vehicles, expecially my Yamaha R1 where the resivoir sits right beside the exhaust pipe. Dot 4 would go a nasty burnt color in like just over a month. The Motul DOT 5.1 still looks as golden as the day I put it in. But I don't abs on my celi and beside motul specifically states they're abs safe like most of the other major brand names. Ok i'm done harping was just curious.

[rjohnson67]

Would this be a good manufacturer of silicone brake fluid (www.xiameter.com/en/ExploreSilicones/Silicone-Fluids/Pages/Fluids.aspx)?