Magura brakes + shimano fluid = fail?

[Profpointy]

From my experience, the seals are mostly proprietary parts. If you look at the reservoir seals in my photos above, you'll see that each manufacturer has its own shape. The O-rings are obviously standard but then the piston seals proprietary.
As for bearings, Shimano makes each and every one of the bearings in its hubs itself. These are cup-and-cone bearings and proprietary, The bearings in its bottom brackets are cartridge bearings and at first glance standard. However, they're proprietary too, being 1mm narrower than the industry standard bearing with the same OD and ID. I don't know who makes those bearings for Shimano.

oh well, I stand corrected. And if it's anything like my other pursuit (diving) it's hard to identify even "standard" parts if you can't get the OE parts

 

[Smurfy]

There is no shortage of compatibility guides on the interwebs. Just google 'seal compatibility', or 'rubber compatibility'.

Here's two:

http://www.prepol.com/Ppe-Uploads/Elastomer_guide_chemical_compatibility.pdf

http://mykin.com/rubber-chemical-resistance-chart

 

[Smurfy]

oh well, I stand corrected. And if it's anything like my other pursuit (diving) it's hard to identify even "standard" parts if you can't get the OE parts

There's a huge number of standards, and not all standards are stocked by all suppliers. As a minimum you really need a vernier gauge to measure accurately, and then you need to deduce the correct type of rubber, as many seals come in different material options. I'm writing this from the POV of someone who discovered what I initially thought was a special seal was available off-the-shelf.

 

[Pale Rider]

Lots of mountain bikers use water instead of oil.

It works fine, which rather suggests worrying about types of oil is pointless.

 

[Yellow Saddle]

Lots of mountain bikers use water instead of oil.

It works fine, which rather suggests worrying about types of oil is pointless.

And a lot of people drink water instead of whisky, but that doesn't make it right. The boiling point of water is at best 100C, the boiling point of DOT Brake Fluid is 220C and that of mineral oil about 180C. There's a good reason why you don't want your brake fluid to boil - you don't want to get onto the Darwin Awards shortlist.

 

[Smurfy]

Hydraulic sounds like a lot of trouble compared to cable with rim or disc.

 

[Pale Rider]

And a lot of people drink water instead of whisky, but that doesn't make it right. The boiling point of water is at best 100C, the boiling point of DOT Brake Fluid is 220C and that of mineral oil about 180C. There's a good reason why you don't want your brake fluid to boil - you don't want to get onto the Darwin Awards shortlist.

We are talking about stopping a push bicycle, not an F1 car braking hard every few seconds for hours.

Boiling point doesn't really matter, as evidenced by the boiling point of Magura Royal Blood which is only 120C.

As I said, lots of mountain bikers use/used water with no braking problems.

http://www.epicbleedsolutions.com/blog/dot-brake-fluid-vs-mineral-oil/

 

[Yellow Saddle]

We are talking about stopping a push bicycle, not an F1 car braking hard every few seconds for hours.

Boiling point doesn't really matter, as evidenced by the boiling point of Magura Royal Blood which is only 120C.

As I said, lots of mountain bikers use/used water with no braking problems.

http://www.epicbleedsolutions.com/blog/dot-brake-fluid-vs-mineral-oil/

Water is not a good idea for two reasons I can think of offhand.

1) Boiling point does matter. It is relatively easy to boil your brakes on a bike, especially what you call push bikes which I'll take to be entry-level bikes not intended for racing. The discs are small and thin and store very little heat. Likewise the calipers. Thus the system heats up very quickly, especially with novices who like to drag their back brake down inclines. 200m on a steep incline with only one brake doing the stopping quickly boils the brake. An experienced rider will alternate brakes and get up to a higher speed where airflow cools the brakes. Novices do the opposite. The moment brakes boil it is asif they are switched off. Onset is sudden and precipitous and if you are not skilled in dealing with it, you're toast.
2) Water corrodes the uncoated aluminium/magnesium master and slave cylinders very, very quickly. The slightest bit of pitting in those renders the brake useless.

Hydraulic brakes are just about standard on most mountain bikes nowadays, not because they are better ( @Yellow Tim is absolutely right here) but because users perceive them as better and they're fitted as a marketing, not engineering decision. I concede that water works - just about any fluid will "work" but working and suitable are not the same. Let me put it this way. If a bike mechanic has to go to court because his customer's brakes failed and he had filled it with water. Will he have a case?
In other words, did he do a sensible thing?

 

[Pale Rider]

Water is not a good idea for two reasons I can think of offhand.

1) Boiling point does matter. It is relatively easy to boil your brakes on a bike, especially what you call push bikes which I'll take to be entry-level bikes not intended for racing. The discs are small and thin and store very little heat. Likewise the calipers. Thus the system heats up very quickly, especially with novices who like to drag their back brake down inclines. 200m on a steep incline with only one brake doing the stopping quickly boils the brake. An experienced rider will alternate brakes and get up to a higher speed where airflow cools the brakes. Novices do the opposite. The moment brakes boil it is asif they are switched off. Onset is sudden and precipitous and if you are not skilled in dealing with it, you're toast.
2) Water corrodes the uncoated aluminium/magnesium master and slave cylinders very, very quickly. The slightest bit of pitting in those renders the brake useless.

Hydraulic brakes are just about standard on most mountain bikes nowadays, not because they are better ( @Yellow Tim is absolutely right here) but because users perceive them as better and they're fitted as a marketing, not engineering decision. I concede that water works - just about any fluid will "work" but working and suitable are not the same. Let me put it this way. If a bike mechanic has to go to court because his customer's brakes failed and he had filled it with water. Will he have a case?
In other words, did he do a sensible thing?

Your point two is the main point against water - it promotes corrosion.

If you think about it, the boiling heat just isn't there, which is why the trails aren't littered with crashed'n'boiled Royal Blood mountain bikers.

Brake hard and the disc rotor will get very hot to the touch.

The calliper? Only warm.

Grasp the brake pipe at any point and, even after heavy braking, it will be at ambient temperature.

Compressing the fluid will produce heat, but nowhere near enough to boil water - the Royal Blood has a safety margin at 120C, it is German after all.

The higher boiling points - 200C and above - may come into play in motorsports applications, but for a bicycle they are no more than oil company marketing puff.

 

[Profpointy]

.....

Compressing the fluid will produce heat, but nowhere near enough to boil water - the Royal Blood has a safety margin at 120C, it is German after all.

......

Umm, "compressing the fluid"? I'd like to see you compressing water by pressing the lever !

(well, pedantically for a physicist it compress by a gnat's crotchet, but that's zero in engineering terms)

 

[Klassikbike]

Water is a no go!
There are some differences between Maguras Royal Blood and Shimano Mineral Oil, cant tell about most but one of the differences is the different level of viscosity.
Shimano clearly state that they should not be mixed with Maguras Mineral Oil.

 

[Yellow Saddle]

Water is a no go!
There are some differences between Maguras Royal Blood and Shimano Mineral Oil, cant tell about most but one of the differences is the different level of viscosity.
Shimano clearly state that they should not be mixed with Maguras Mineral Oil.

Where does Shimano state that? On the bottle?

 

[Klassikbike]

Dont remember exactly but it was a small piece of paper, I guess it came with the brakes. It stated do not mix with Dot4, Dot5, Magura Royal Blood mineral oil...

 

[Yellow Saddle]

Dont remember exactly but it was a small piece of paper, I guess it came with the brakes. It stated do not mix with Dot4, Dot5, Magura Royal Blood mineral oil...

All Shimano's product manuals and brochures are online at http://techdocs.shimano.com/techdocs/index.jsp and I can find no reference to any Magura mention in any of those brochures. This is what I do find:

The problem with mineral oil is its nomenclature. Mineral simply means "from the earth" and technically any oil that's derived from fossil carbon and fractionated in a refinery distillation column is mineral oil. It could be refined to be thick or thin. It could even be made from gas or from coal. Your car engine has mineral oil in the sump and pharmacies sell a refined mineral oil for babies' bottoms. It is all mineral oil, but not the same thing.

Shimano's disclaimer is there to ensure that you don't use baby oil or car oil. And obviously the company doesn't want to punt the opposition's product or take responsibility for it, hence the disclaimer. This is also why the various mineral oil brake manufacturers colour their oils so vividly, for instant recognition. However, any good quality mineral oil with the right additives, viscosity, heat range and additives will do the job. But putting all that information in a brochure is looking for trouble.

That doesn't mean we should slavishly follow manufacturer rules. The informed user will, for a variety of reasons, substitute one product for another, based on knowledge and understanding and experience. Such a user will of course also assume the risks, if any, associated with such substitution.

Thus, what are the big risks with substituting fluids in brakes with non-OEM fluids?

1) Mixing DOT with oil. The rubbers will swell, go soft and the piston will jam because of the huge sticky rubber seal on it.
2) Mixing incompatible DOT fluids. Ditto rubber problem.
3) Substituting DOT 5 for DOT 3x/4X or 5.1 - Water in the system, omnipresent in DOT fluid will pool in the caliper and possibly boil and cause vapour lock.
4) Substituting OEM mineral oil with "mineral oil" In appropriate additives could damage the rubbers and, the boiling point could be too low for the brake's design. Vapour lock.
5) Mixing mineral oils from different manufacturers. Reactions amongst additives could create by-products that jam the system or even damage seals.

Once you understand these consequences you could safely go ahead and experiment. One sensible substitute would be to, as the thread started, put Shimano oil in a Magura system. Obviously it would make sense to not just top up, but completely flush and replace. Another sensible substitute would be to use Castrol LHM in Shimano or Magure brake systems since this product meets all the specifications and requirements listed above.

The long-winded point I make is that you don't have to follow rules slavishly if you understand the issues.

To get back to the OP's question and summarise. Shimano fluid will NOT damage a Magura system. Further, seal damage manifests as swollen rubber that will not leak but actually increase its sealing ability. Swollen rubber will also manifest as a lever that will not move, the swollen piston rubber will jam in the master cylinder. Therefore, the leak is not due to the fluid but due to some other fault.

 

[wam68]

Nope. Royal blood is mineral oil and will NOT damage seals made for mineral oil. Fox Float fluid, likewise. It is a mineral oil and does no damage to the buna O-rings in fox or Rox forks.

I am yet to see a fluid that makes rubber crack. If you apply the wrong fluid to the wrong rubber, all you see is a swelling of the rubber and eventually it turns soft and sticky. It does not crack. It doesn't warp either. Once the rubber has swollen and gone jelly-like, you can physically warp it but it slowly returns to its default form. I've attached a photo of a various brake components dunked into the wrong fluid i.e. mineral oil in DOT and vice versa. Note how they all swell up, but never crack or warp. The first photo is Hope (DOT) dunked in mineral oil. The second is, I think Hayes (DOT) in mineral oil and the third is Tektro (Mineral oil) dunked in DOT. I would love to see evidence of cracking or warping. Please post such photos.

Finally, only DOT fluid damages paintwork. The mineral oils do absolutely nothing to paint.

View attachment 63242 View attachment 63243 View attachment 63244

That was an outstanding explanation. Well laid out and very impressive. I knew there was a reason I joined this forum. Thanks