Hydraulic Disc Brakes - Anyone Change 'Mineral Oil' With Brake Pads?

[mail_e36]

Friends,

I have 3,000 miles on my 85-pound ebike with Tekro Hydraulic Disc Brakes.

I'm on the third set of disc brakes, installed professionally at a LBS, but have never drained/refilled the 'mineral oil'.

The LBS bike mechanic (not focused on ebikes) said they don't generally get involved with draining/refilling the mineral oil.

How would we know if it's necessary to do this?

BTW, according to the web, ‘Mineral Oil’ is a vague and unregulated term that doesn’t refer to one specific fluid.

Does anyone actually have their 'Mineral Oil' actually changed when getting new brake pads?

Thanks!

 

[fooferdoggie]

no and even then you don't change it out. you bleed them pushing the old oil out but usually not all of it. but you only do it when you start getting mushy brakes usually you can go years between having to bleed them unless you screw something up.

 

[Bicyclista]

My LBS bled and replenished my Magura hydraulic disc brakes. Strange that your LBS won't get involved with this aspect of bike service. Maybe find a better LBS. You know it's time to bleed and replinish when your brakes feel mushy and there is excessive travel of your brake levers.

 

[fooferdoggie]

I was my own worst enemy to my brakes till I got a handle on it. The last time I had to bleed one was when I removed the pads then I peddled so I could shift to the smallest cog to take the wheel off and squeeze the lever to stop the wheel. oopsy.

 

[Gionnirocket]

I wouldn't fix what ain't broke.
Depending on how much you overheat them will determine how often it needs to be changed.
When the system is full but the brakes feel mushy less responsive is when I would change the fluid.

You buy mineral oil specific for bicycle brakes...

Amazon.com : bicycle mineral oil brake fluid

Not at the CVS

 

[Mr. Coffee]

Note that what kind of brake fluid you need will depend on the brakes.

https://www.bikeradar.com/advice/buyers-guides/brake-fluid-mineral-oil-vs-dot

Having said all that, some mountain bikers have used baby oil as brake fluid and relatively few of them have died in horrible crashes caused by brake failure. Also, a lot of the brake fluids sold at bike shops will irritate your skin (wear rubber gloves when working on your brakes), can dissolve some plastic parts of your bike, and can trash your paint. So be damned careful with that stuff.

 

[Gionnirocket]

Note that what kind of brake fluid you need will depend on the brakes.

https://www.bikeradar.com/advice/buyers-guides/brake-fluid-mineral-oil-vs-dot

Having said all that, some mountain bikers have used baby oil as brake fluid and relatively few of them have died in horrible crashes caused by brake failure. Also, a lot of the brake fluids sold at bike shops will irritate your skin (wear rubber gloves when working on your brakes), can dissolve some plastic parts of your bike, and can trash your paint. So be damned careful with that stuff.

That's mostly in reference to the DOT.. and why I would avoid brake systems using it as it's unnecessary.

 

[PCeBiker]

You buy mineral oil specific for bicycle brakes...


Not at the CVS

View attachment 190683

Having said all that, some mountain bikers have used baby oil as brake fluid and relatively few of them have died in horrible crashes caused by brake failure.

I was considering using this stuff so my brakes would smell like a baby's ass,..

Then I found out that mineral oil for brakes is more refined and less viscous.

With the oil more like water, the brake lever feels more responsive and it's also better able to deal with more heat without turning brown or burning, which can cause brake fade.

But as @Mr. Coffee stated, it's not that big a deal.
If your stuck and can only find Baby Oil, it will do until you can flush it out and replace it with proper brake oil.



Using DOT fluid on a mineral oil brake is a Big NO-NO Though.

DOT brake fluid can wreck brake piston seals and the seals on the brake lever plunger if the seals aren't made to deal with regular corrosive brake fluid.

 

[PCeBiker]

I was my own worst enemy to my brakes till I got a handle on it. The last time I had to bleed one was when I removed the pads then I peddled so I could shift to the smallest cog to take the wheel off and squeeze the lever to stop the wheel. oopsy.

I just did the same thing a couple of weeks ago, but I didn't lose any fluid,..

I had forgotten that I had removed the pads and must have hit the lever half a dozen times.

When I finally noticed, both pistons were touching the rotor but neither one blew out?

So I pumped the lever to see what was going on, and the one piston was pushing harder, and bent the rotor a smidgen against the opening in the caliper, then it would bend back and push the piston back in.

I figure that the caliper was designed that way on purpose so that people like me don't blow their pistons out even when they are trying to.

 

[Mr. Coffee]

That's mostly in reference to the DOT.. and why I would avoid brake systems using it as it's unnecessary.

The justification for DOT fluid is that your brakes will still work and work much better when the brake fluid is contaminated with water. At least in theory.

Some of the mineral oil fluids sold at bike shops also are not great for you or other parts of your bike, so wouldn't assume that just because it is mineral oil everything is going to be fine.

 

[Gionnirocket]

The justification for DOT fluid is that your brakes will still work and work much better when the brake fluid is contaminated with water. At least in theory.

Some of the mineral oil fluids sold at bike shops also are not great for you or other parts of your bike, so wouldn't assume that just because it is mineral oil everything is going to be fine.

I guess moisture can enter any closed system... But I don't think the chance is anything to worry about here.
And sure a company can have additives to make even mineral oil corrosive... but again I'm not too worried.
Just saying.. given the choice I would choose mineral oil over DOT most days and since today is Sunday... I'll double down.

 

[PCeBiker]

Some of the mineral oil fluids sold at bike shops also are not great for you or other parts of your bike, so wouldn't assume that just because it is mineral oil everything is going to be fine.

I can see that with toxic additives or something.

And any contamination on the brake pad or rotors is bad.
Contaminated brake pads may have to be replaced.

And just an FYI to everyone, ..
If your brakes are squealing, spraying them down with WD-40 IS NOT a good idea.

 

[PCeBiker]

I was my own worst enemy to my brakes till I got a handle on it. The last time I had to bleed one ,..

The first time I went to lever bleed my calipers, I bumped the damn funnel and broke it off, spilling mineral oil down onto my caliper and rotor.

I bought a new funnel, so I'm ready to make another big mess.

 

[smorgasbord]

I second the recommendation to get a new bike shop. Brake bleeding/fluid change is a standard maintenance item that any partially decent bike shop should be able to handle.

As for when to change, Shimano says when the brakes feel spongy or the fluid color has changed. Unfortunately, to see the fluid color, you've got to open up the system, which itself leads to potential for contamination.

As for DOT versus mineral oil, you gotta stick with what the manufacturer recommends. SRAM is the main company that uses DOT brake fluid. I love SRAM stuff, but hate that for brakes, and actually pulled SRAM brakes off a new bike to put Shimanos on because of that. Bike brakes don't need DOT brake fluid's properties, IMO, and mineral oil is so much easier to deal with (and actually absorbs less moisture). It just doesn't have the heat properties of DOT fluid, but unless you're a down-hiller you don't need that anyway.

 

[DDBB]

If you fill the reservoirs with water you never have to worry about water contamination