CanadianBiker32

I

Need to bleed my Hydraulic brakes

Have AVid brakes which require dot
oil

would i be able to use the auto version pictured here

Iride01 

SRAM only list DOT 4 or DOT 5.1 fluids. https://www.servicearchive.sram.com/...lish_final.pdf

It's always been my policy not to use old opened bottles of DOT fluid of the correct type in my motor vehicle brakes. When needed I get an brand new unopened bottle.

In the many days you've spent trying to decide what to use, wouldn't just going to the auto parts store or LBS that has SRAM brake fluid have been quicker?

CargoDane

Dot oils are hydrophilic. They will absorb moisture from the air (even in your brake lines). So not using old opened bottles seems like the prudent thing to do!

As for dot 5, it is not backwards compatible with lower numbers (it's silicone). However, dot 4 is backwards compatible with dot 3 etc.

CanadianBiker32

I just ordered the Sram brand. maybe be safe

CargoDane

Dot4, I hope. But that was the correct choice.

Iride01 

But DOT 5.1 and DOT 4 are compatible. Who'd have thunk that DOT 5 and DOT 5.1 wouldn't be compatible? But DOT 5 as you say is silicone based and DOT 5.1 is glycol ester based.

I wonder why SRAM went with DOT fluids, given that they can be a skin irritation for some. And I have to wonder why they didn't go with DOT 5 since it is not considered hydrophilic. But I suppose there isn't much fluid in a bikes hydraulic system for water absorption to be an issue. But I've had vehicles with rust inside the steel brake lines that was an issue.

CargoDane

True, it get's confusing quickly!

Yes, I prefer mineral oil brakes etc. (well, on bicycles, anyway).

Amt0571

DOT fluid has more resistance to heat than mineral oil. Moreover, when water enters a DOT brake, its dissolved evenly on the fluid, so the chances of it boiling are few.

On a mineral oil system, if water gets on the system it tends to accumulate in the caliper because it's heavier. If it boils, you could suddenly find yourself without brakes.

You should change brake fluid regularly in either system.

I have bikes with SRAM and Shimano brakes and I prefer to wrench with Shimano because they're easier to bleed and I don't have to worry about corrosive fluids.

BTW, in theory DOT 3, 4 and 5.1are interchangeable. DOT 5 is not.

Avid / SRAM recommends DOT 4 or 5.1, so that's what I would use. Personally I always use Motul DOT 5.1 fluid.

CargoDane

Unless your mineral oil system is leaking, water will not go into it. And you will know if it's leaking because it will spurt oil the moment you pull the brakes. I can't see how water would get into your mineral oil brakes at all. Never had water in my bicycle brakes, and I don't change the mineral oil "regularly" either.
In fact, when I can swing it - next year: After christmas at least, I will most likely swap my shifters (Cinq5 shifters for Rohloff) to a hydraulic shifter from: Inbus5 GmbH | Sven Jan Hiltbrand
Never had my mineral oil brakes boil. Never. And I much prefer hydraulic whatever to wires.

CanadianBiker32

cables are so much cheaper and easier maintenance

cxwrench

Mineral oil and most bicycle DOT 4-5.1 can have pretty much exactly the same boiling temps. Obviously you can get racing/hi perf fluid w/ MUCH higher boiling points. DOT fluid will absorb moister from the air as soon as you open the bottle and get worse from there. Mineral oil obviously won't.

CargoDane

Cheaper maybe, but what about "zero maintenance" on mineral oil systems? I don't "maintain" my brake lines. I install them, bleed them, and that's that.
And although you found it difficult to figure it out this first time, bleeding brakes when installing them is not hard at all. To make it even easier to bleed your brakes, buy a syringe kit from https://epicbleedsolutions.com/

CanadianBiker32

Question how much fluid are you supposed to put in the system?

CargoDane

Till it's full and no more air bubbles are coming out.

cxwrench

I will repeat my recommendation that you have a shop do this for you. It doesn't sound like you know what you're doing (not trying to be a dick, but they're your brakes). There is no specified amount in any brake system. When it's properly bled it's 'full'. That's like trying to answer 'how long is a piece of string?'

CanadianBiker32

Update. I took the bike to the shop to get it done. All will be fine now. Just closure for you all here. of course. thanks for all your advice, you been helpful

grayEZrider

DOT3 is very hard on paint.

Amt0571

If that was true, nobody would be bleeding brakes because no air would get inside. If air is getting inside, that air has some degree of humidity, and that water has to go somewhere.

I've had air bubbles appear from nowhere on Magura HS11 hydraulic rim brakes which are much simpler as they have no reservoir and are basically the equivalent of a couple of syringes connected by a spring. So it's not surprising air ends up getting inside much more complex hydraulic disc brakes.

In any case It's really strange for a bicycle disc brake to accumulate enough water to pose a serious risk even if you don't change the fluid, but I've seen it happen once. My friend who was riding the bike was not happy.

Replacing the fluid from time to time is cheap and better than crashing your head into a tree, so in my opinion it's worth it.

CargoDane

If you shorten the tubing you will get air in, or if you damage your seals. Mineral oil (unlike Dot oils) does not absorb moisture.

I do have two different bleed kits. But that's because I installed two sets of different brakes on two different bikes and the tubing had to be shortened. There is a huge difference between Dot oil brakes and mineral oil brakes.

Then you had a leak. Having a reservoir is not "more complex" than not having a reservoir.
Unlike most Magura brakes, the HS11 uses mineral oil. And mineral oil does not absorb moisture from the air or otherwise.

Again: Mineral oil does not absorb moisture. Dot oils do (except the Dot 5 which is silicone). There is no "accumulation of water" with mineral oil brakes.

Completely unnecessary on mineral oil brakes.

Amt0571

Well, just inform yourself better.

Mineral oil does not absorb water. That's true.

That means than when water gets inside a mineral oil system, it accumulates at the lowest part, since it's heavier than the oil. The lowest part is the caliper. If there's water in the caliper and it boils when you're braking, you're in for a nasty surprise. It's rare, but I've seen that happen once and it wasn't beautiful.

DOT fluid, meanwhile absorbs the water so it gets "diluted" in it and the probability of it affecting your brakes is lower.

Do whatever you want with replacing the fluid on your brakes, it's your teeth, not mine.

By the way, no: I don't have a leak on my Maguras, and it's a relatively common occurrence with this brakes as anyone that has been involved in bike trials will tell you. Air tends to get inside even if it's a slow thing. Like it or not, and it happens too in disc hydraulics.

Finally, not al disc brakes are "sealed". Some use a bladder to allow expansion, others are built like an open system. But since you speak like you know everything, I'll let you do your own research.

CargoDane

Great that you now realise this.

No, still wrong on every level:
1) Since the water in the air is not absorbed by the oil, it will not "accumulate at the lowest part", because it will still be in the frigging air.
2) The moisture in the air is not seperated from the air and then sink to the lowest part of the brakes.

You haven't seen water in the caliper on a mineral oil system, nor have you had that water boil. See above as to why you haven't seen that with anything else but Dot oils.


Haha, no. Just no. The water that is absorbed by Dot oils will lower the boiling point so in the end you will have "boiling brakes".

This is beginning to resemble Preventec/Cubewheels style of commenting.

Yes, I know what I'm talking about and I know what I'm doing.


Never had that problem with my mineral oil brakes, apart from once when my seal had a notch in it when I installed it. That was quickly fixed.

LOL, depends on what you mean by "open". Hydraulic brakes work because fluid does not compress. However, I can't see what that has to do with anything at all.

Edited to add:
As for bike trials, I did that for more than 10 years when I was younger. I used Magura HS33 brakes back then (also mineral oil), never had a problem. If I were to do it again (i.e. if I was young again), in this day and age I'd use some mineral oil disc brakes instead.
And really, bike trials is possibly the only biking "scene" where "boiling brakes" will never be a problem. I bet you could use demineralised water in the brakes with no ill effect whatsoever.

Amt0571

There's a thing called condensation. Maybe you have heard about it.

I'm not going to argue with you anymore. I've got better things to do with my time.

Meanwhile, you can read what some experts about this have to say: https://epicbleedsolutions.com/blogs...s-mineral-oil#

CargoDane

Yes, I have. That won't have any effect in your brakes - especially not when it comes to "boiling" brakes. None whatsoever.

Suits me fine.


LOL, you really do think that that link somehow supports your claims, don't you? Spoiler: It doesn't.

The one thing that surprised me in that link is this:


120 degrees boiling point of the Royal Blood!? I'm glad I haven't use Magura brakes for anything other than trials and now use Shimano and Shimano oil.
Maybe that's why you thought you had "water" in the brakes. You boiled the exceptionally low boiling point Magura oil.

That truly surprises me. Seriously, I knew it was lower than Shimano's but 120 degrees? With that new-found knowledge, I will warn people about Magura's mineral oil and their mineral oil brakes. I consider that to be quite dangerous for anything other than trials riding.

gsa103

One of the big differences is the intended operating environment for automotive vs bicycle brakes. With bicycles, the calipers rarely get above water's boiling point. So if you get a little bit of water in a Shimano brake, you'll get some minimal fade, and the solution is bleeding the brakes. DOT fluid is designed for cars, where the pad operating temperature can exceed 600F, and on a mountain road the calipers will easily exceed water's boiling point. Any free water in an automotive system is a recipe for disaster.

SRAM's DOT system will slowly adsorb water from the air as air permeates the seals. Shimano won't, unless air permeates the seals and then condenses. Annually bleeding a SRAM system is probably safer than Shimano, but we're splitting hairs at that point.

Personally, I find the lower maintenance and less toxic fluid better, so I run Shimano. But that's largely because my bikes aren't heavily ridden, and aren't exposed to a lot of bad weather, so they don't get water in.