Dictatorsaurus

My 2019 Revolt Advanced has the original mineral fluid in the Ultegra brakes. The brakes feel fine and no mush. Do I still need to replace the fluid even if the brakes feel fine?

Koyote

If it ain’t broke, don’t fix it.

Lombard

^^^This.^^^ My original brake mineral oil in my gravel bike lasted 5 years and 6000 miles. My first warning the oil needed to be changed was that lever travel increased on one of my levers. As it turned out, one of the shifters went south shortly after. That made the decision easy - replaced shifters and bleed with new oil.

Koyote

My hydro brakes are four years old, 15k miles. They've never been opened up. Mineral oil is NOT hygroscopic, meaning that it does not absorb water. No need to touch it if everything is working properly.

Lombard

So IOW, if you had SRAM brakes that use DOT fluid, you would need to change more often?

So if no contaminants got into my Shimano brakes, what could have caused the increased lever travel?

Dictatorsaurus

Some air gets in through the seals over time.

Lombard

That's what I suspected. And possibly a little dirt too.

Kontact 

Definitely.

Koyote

Yup.

How worn are your pads and rotors? Theoretically, hydro brakes should self-adjust for such wear, but - in my experience - when pads get towards their minimum thickness, lever travel increases.

Lombard

As a matter of fact, yes, the rear pad was worn and needed to be replaced.

dsbrantjr

Mineral oil is already millions of years old, it should last indefinitely.
I was amused the other day when I saw a box of table salt with an expiration date. I am having trouble imagining how, exactly, salt can go bad.

Russ Roth

I was on the don't worry about it bandwagon till this fall/winter. The wife's bike never seemed from new to have the stopping power it needed and I like my maguras which always felt spot on. But on a trip to a local trail I ripped the front hose out with a local tree, one replacement and bleed later I noticed that the front brake felt more locked on, the lever didn't pull as far and everything felt stiffer. I didn't like the difference between the two and so I bled the rear, the fluid was more grey than blue, the lever hit faster and stronger and the difference was surprisingly noticeable. Over the 6 years I had the bike the change in the braking was so slow I didn't notice how bad it had gotten since it still worked so good.
Also bled the MT-200 shimano brakes on my wife's 2 year old bike and the difference was night and day, I suspect the brakes are minimally bled after being installed at the factory so everything feels good enough.

Lombard

LOL! Point taken. Though that doesn't mean that contaminants can't get into the oil.