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Old 28th March 2009, 13:15   #1
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Default Anyone using DOT 5.1 brake fluid??

It like to know if our indian cars can run on DOT 5.1
(non silicone based fluid). I'v heard some really good reviews about it wrt braking performance/endurance.

While i have no braking issues on the OHC, the Innova suffers from brake fade during spirited driving.

Both cars use DOT 4 as of now. And while DOT 4 has a dry boiling point of 230 Deg C, DOT 5.1 can handle temps upto 270 Deg C.

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Old 28th March 2009, 13:38   #2
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It can't be just because of brake fluid. After all, DOT4 is all I can find here.
Brake fade could be because of the brake pad material. Why don't you try sourcing uprated pads like EBC green stuff or Hawk HPS or Tarox?
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Old 28th March 2009, 22:49   #3
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Dude! brakes are the things that can't be joked about. Stick to the recomended fluid of your car.
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Old 28th March 2009, 23:01   #4
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Subscribed.

Need to pick up DOT 5.1 for a friend. Please post here the Name and Address of any supplier that you come across.
Thanks
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Old 28th March 2009, 23:59   #5
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Quote:
Dude! brakes are the things that can't be joked about. Stick to the recomended fluid of your car.
Cmon dude, its just a fluid change. If we can go from mineral 15w40 to synthetic 5w50 for the engine, i dont see the harm in going from dot 4 to dot 5.1

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Old 29th March 2009, 00:46   #6
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There is absolutely no harm in going for a higher DOT rating than recommended. It's lower that's the issue.

DOT 5 improves pedal feel IMO, It's the fluid used in my BMW, but I get that from BMW themselves, so can't help you source it sorry.
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Old 29th March 2009, 02:36   #7
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Quote:
DOT 5 improves pedal feel IMO, It's the fluid used in my BMW, but I get that from BMW themselves, so can't help you source it sorry.
Actually DOT 5 is a silicone based fluid. It is not compatible with "polyethylene glycol" based fluids (DOT3, DOT4 and DOT 5.1).

If you have to move from DOT 4 to DOT 5, you will need to flush the entire brake system. Most websites advise against using DOT 5 in cars running DOT 3 / DOT 4.

DOT 5.1 is the prefered upgrade on such cars.

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Old 29th March 2009, 02:59   #8
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I would think you ought to check pads/rotors/lines as potential sources of fade, before moving to the fluid itself.
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Old 29th March 2009, 04:32   #9
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I use ATE Super Blu and ATE Typ 200 in my Lotus Sport Elise for which I need fluid that is as good as it can get for the track, while still being good for road use. The ATE fluid is DOT 4, but its wet and dry boiling points are well in excess of those of most DOT 5.1 fluids, and are higher than just about everything except the most exotic super expensive racing fluids.

However, that having been said, I can't see any reason for 99% of the people to upgrade to DOT 5.1 unless they have worked through their other braking problems.

If your current brake fluid is not boiling off and filling with bubbles, then your fluid is not responsible for your brake fade, and it will make no difference to your braking performance or feel.

What people need to realize is that brake fluid is designed to absorb water because the water is very insidious, and at a rate of molecule by molecule, it will make its way into the braking system, even when there are no leaks, by going in through atomic sized holes in seals where liquid water or fluid cannot pass. Overtime, this entering water vapor would cause corrosion. to prevent that, fluids are designed to absorb moisture so prevent it from cauding corrosion.

This is happening ALL the time. It accelerates sharply during monsoon and wet seasons.

As the fluid absorbs water, its viscosity changes, and its boiling pressure comes down. therefore the pedal feel changes, and if you perform hard braking, such as when a man runs across the highway as you are going at high speed and you brake hard, you can cause localized boiling of the moisture laden brake fluid. This causes the moisture to boil out of the fluid and form bubbles. THese make the brake pedal squishy because the bubbles compress when you apply pressure on the pedal and not enough pressure is transfered to the pads.

So if your existing fluid has become moisture laden, and perhaps boiled at some stage, changing the fluid will make the pedal feel much better. If you happen to replace it with a higher grade fluid, it will feel like that fluid is responsible for the improved feel, but it is not. it is the newness rather than the spec that improve the pedal feel.

This constant absorption of moisture by the fluid is the reason why you should replace your fluid atleast annually.

Of course it never hurts to go to a higher spec fluid, because that will ensure boiling doesn't happen so easily, wether the fluid is wet or dry. but do not look upon higher spec fluid to cure fade problems if your problem is not caused by fluid that boils too easily for the pace at which you drive.

get some fresh fluid, make it DOT 5.1 if you want (though ATE Super Blue and ATE Typ 200 DOT 4 are the best), and fit better pads and discs. fit stainless steel brake lines.

and oh yeah, another big deal. most brake fluid is sold in plastic containers. this is stupid because just as water molecules make their way into the braking system (which is why the fluid is designed to absorb water), water molecules also make their way THROUGH the plastic walls of the container. This sounds absolutely ubelievable, but believe me, it is true, and in this critical application, the extent to which it happens is enough to matter. If the fluid is used soon after packaging, there is no problem, but if its been shipped by sea, then sat on the port, then got shipped and sat in the warehouse then sat in the shop, well its been absorbing water all this time. reducing how much more water it can absorb once it goes in your car, in effect already being wet by the time it goes in the car, and already suffering from a reduced boiling point and greater prospensity to boil.

This is why the really quality fluids come in metal containers.

Also, when you get new pads and/or discs, you have to follow a bed in procedure. virtually nobody does and it doesn't matter for the average bloke, but if a spirited driver doesn't follow the bedding in process, he'll end up with pads that are prone to glazing and fading and cannot develop solid consistent friction on the discs, and will get inadequate braking.

So in short, there is a lot to getting the best braking from your car, and just upgrading the fluid isn't going to do much on its own.

Last edited by Harbir : 29th March 2009 at 04:38.
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Old 29th March 2009, 21:01   #10
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Harbir, thanks man, that was one helluva detailed, enlightening discourse on braking systems and performance..
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Old 29th March 2009, 22:33   #11
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Quote:
If your current brake fluid is not boiling off and filling with bubbles, then your fluid is not responsible for your brake fade, and it will make no difference to your braking performance or feel.
Atleast in the Innova's case, it seems to be the fluid. Coz when the fade occurs, the pedal feels spongy and no matter how much i press the pedal, there isn't any increase in stopping power.

When pad fade occurs, the pedal feel doesn't change much.

In any case, will get the pads checked.

Shan2nu

Last edited by Shan2nu : 29th March 2009 at 22:34.
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Old 30th March 2009, 01:00   #12
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If you have real brake fade, it is not likely to be the fluid. Let me explain why.

THe first time you boil your fluid, you will get a pedal that suddenly becomes squishy, and travels much further. This is because bubbles have formed and the pedal pressure is causing these bubbles to compress instead of allowing the fluid to pass on the hydraulic pressure down the line. However, most of the moisture in these bubbles does not disappear back into the fluid when the fluid cools. The bubbles remain. Therefore the squishy pedal will remain even when the brakes have cooled off.

Brake fade, which is the loss of braking comes from a different reason. it comes from gas bubbles forming between the pad and disc surface, reducing the friction by a huge degree. It can also come from the pads heating up and losing their coefficient of friction. This local heating around the pads can cause the fluid in the calipers to boil to, forming bubbles there that reduce how much force is transmitted to the pistons that push the pads.

So, in summary:

1. if you have a soft pedal, you need a fluid flush. Going to a higher spec fluid (don't use DOT 5), will give you better resistance to fluid boiling, but fresh DOT 5.1 fluid will not make the pedal feel any better than Fresh DOT 4 would, because neither has any bubbles in it when fresh.

2. If you notice a difference in braking after a spiritied run, then its not the fluid. The fluid may ALSO need replacement, but the fluid, once ruined by boiling, will not cause the brakes to feel different in normal vs spirited driving. the pedal will be soft and squishy all the time. The reason you notice it especially during spirited driving is that you are demanding strong braking and you are not getting it because of the bubbles. but in normal driving, you don't put such a demand on the braking system so its weakness doesn't show.

It is possible that what you are calling fade is not actually fade. In brake fade, the pedal remains firm. the pads lose friction on the disc. braking distances lengthen exponentially. Thats fade.

If you are losing braking performance in spirited driving from a squishy pedal, it is almost certainly not brake fade, but bubbles in the fluid. Replace the fluid with fresh stuff.

Last edited by Harbir : 30th March 2009 at 01:04.
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Old 30th March 2009, 01:31   #13
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Quote:
Originally Posted by Shan2nu View Post

Both cars use DOT 4 as of now. And while DOT 4 has a dry boiling point of 230 Deg C, DOT 5.1 can handle temps upto 270 Deg C.

Shan2nu
As you are aware the most important part is the boiling point. But, dry boiling point is relevant only if you are changing brake fluids regularly. It's wet boiling point which is more important for regular car use. Wet boiling point means when the brake fluid has absorbed moisture to quite a higher extent, which happens over a point of time.

For racers dry boiling point is relevant, because the change brake fluids nearly after every race.

For street cars the dry boiling point.

I am personally using Ate SL which has boiling points a bit lower than 5.1 but you can use ATE TYP 200 which is nearly as much as 5.1, both these fluids are DOT 4. Specs here : ATE -Rapid transmission of brake pulses: ATE brake fluids

I personally DOT 4 as it gives the same performance at half the price for DOT 5.1.

Also, as seen here Brake Fluid Comparison has better Boiling point after six months compared to Motul DOT 5.1 which is more than twice the price.

My 2 cents worth.
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Old 30th March 2009, 02:49   #14
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Boiling point standards:

DOT 4 Dry: 230C Wet: 155C
DOT 5 Dry: 260C Wet: 180C
DOT 5.1 Dry: 270C Wet: 191C


ATE Typ 200 and Super Blue, though rated DOT 4 exceed the DOT 5.1 standard at 280C and 198C.

ATE SL is at 260C and 165C, dry and wet respectively. Its not very far off the dry boiling point of Super Blue/Typ 200, but substantially lower on the wet boiling point.

A huge advantage of using Super Blue and Typ 200 is that both are exactly the same fluid, but of different color (blue and amber, respectively). This is brilliant when changing the fluid. If you have one (say Super Blue), next time you change you use Typ 200. So when the fluid coming out of the bleed valve at the caliper changes in color from blue to amber, you know you've flushed the old stuff from that corner. next time, you go back to blue.

Last edited by Harbir : 30th March 2009 at 02:55.
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Old 30th March 2009, 07:08   #15
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Quote:
Originally Posted by Shan2nu View Post
Atleast in the Innova's case, it seems to be the fluid. Coz when the fade occurs, the pedal feels spongy and no matter how much i press the pedal, there isn't any increase in stopping power.

When pad fade occurs, the pedal feel doesn't change much.
After how many kms of spirited driving? you have to be literally coming down a mountain with 5 people to experience fade in a normal car. I would check the rubber lines to see if they are missing the reinforcement. A change to semi-mets will help too.
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