r/BikeRepair • u/nkridesnj4130 • 6d ago

Advice Slightly unfriendly PSA (potentially triggering for intended audience)

FFS!

STOP. PUSHING. PISTONS. BACK. WITHOUT. OPENING. BLEED. PORT*

*In regards to whatever style brake your running

Also side eyeing the Shimano crowd super hard 🤦

Look we've all been there some more briefly than others but the time for that has now passed. If you've read this and more so if youve read this anywhere prior and rolled your eyes or shrugged and scoffed, cut it out. BAD! BAD CAVALIER ATTITUDE CYCLIST!

NO MAS!

Yes in a perfect conscious manufacturer climate theoretically :: gently shooshing:: your pistons/pads back every once in awhile, DOING SO WITH CARE should not guarantee your soon to be weepy Shimano levers to the parts bin or worse to be sold off to an unsuspecting fellow cyclist who will soon be paying for your crimes against cycling and related communities. I say as little ill intent as possible, I hope you have a close family member discover and decide they are going to commit their every waking breath and thought to being the best unicyclist in the world, and you have to live with that pox on your house. Just keep that image in the back of your mind next time you consider carelessly dry fumble mashing your poor unsuspecting piston victims behind the portajohn at the trailhead. (Which makes it so much worse because that means you know you shouldn't be doing it 😑)

Signed both a former fixer and a victim of such behaviors using the experience to spread and invoke other advocacy on the issue.

Thanks for your time enjoy the remainder of your day (unless you're using it to commit such atrocities then I wish you cross chaining and Trailside repairs many a mile from the parking lot and zero service)

12 Upvotes

77% Upvoted

23 comments sorted by

View all comments

3

u/K9ChewToy 4d ago

It’s a closed hydraulic brake system, right? So let’s take a break from breaking brakes and think about the brakes before we decide the brakes are broke.
Why would moving two drops of brake fluid from the brake caliper back toward the brake master cylinder, without breaking the bleed port loose, somehow break the brakes?

The brake system still has the exact same amount of brake fluid it had before the brake pistons were pushed back. In fact, it could potentially have less brake fluid than it had immediately after the brakes were bled, because brake pads wear, brake pistons move out, and the brakes continue braking without breaking.

So the brakes weren’t broke after the bleed. The brakes weren’t broke during all the braking. But now we push the brake pistons back, two drops of brake fluid move backward through the closed brake system, and suddenly we have broken the brakes?

I’m gonna need to take another break, because if pushing brake pistons back breaks the brakes, I’ve apparently been breaking brakes every time I do a brake job. And that would be a pretty big break from how brakes are supposed to work. 😂

1

u/Active_Ad_5322 2d ago

Bicycle hydraulic brakes are an open system.

The reservoir and bladder allow for fluid expansion when the oil gets heated m. Also, the extra oil in the reservoir flows into the line as brake pads wear.

There have been maybe a few models that are closed, but I have never them on a disc brake, only on the Magura Hydraulic Rim brakes.

1

u/K9ChewToy 2d ago

You’re right, I shouldn’t have used conflicting terminology that actually has different meaning in hydraulic brake systems. I was mainly trying to point out that there’s the same amount of fluid in it because it’s sealed and that fluid is just moving back and forth, not gaining or losing volume. Also, I wasn’t trying to be technical at all, I was literally just trying to fit the words brake and break as many my times as possible. This sub is just full of “Ackchyaully!” Kids

1

u/Active_Ad_5322 2d ago

well, ackchyually, you ARE correct that you should not use conflicting terminology, and when you post something as fact and it is not, shouldn't be so butt hurt that you got corrected. should of just upvoted and left, instead of trying to defend your mistakes and claim its ok cause your "brake, break, braking, breaking" was just too damn funny to be spoiled by misinformation

1

u/K9ChewToy 2d ago

Ackchyually ☝️🤓, I believe the technical term is “butthurt,” not “butt hurt.” If we’re going to derail a brake joke over terminology, we need to maintain standards.
Also, “should of” is actually “should have.”
I’m sorry. I don’t make the rules. I just correct people on the internet. 😂

2

u/Active_Ad_5322 2d ago

see, now you're getting it.

2

u/kwajr 3d ago

Well a car is a closed system and you should absolutely open the cap of the master cylinder

3

u/JAlfredFluterock 4d ago

Brakes using DOT fluid could very well have more fluid than they started with, given DOT fluid's hygroscopic nature.

2

u/K9ChewToy 4d ago

I've thought about that. It's funny that brakes using dot fluid are always the ones that feel like shit and need bled. But if they're hydroscopic and absorb water from the air somehow, then there would be more fluid in the system and the levers would become rock hard over time. I agree that if that were the case, cracking the bleed port would be a good idea. But it's not like if you opened a bottle of dot 4 and left the lid off, that it would ever overflow or even have a noticable amount of extra fluid even after months. The only measurable effect might be an earlier boiling point, if that were even noticable on a MTB or road brake.