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Proper brake fluid level when pistons are pushed in?

Bavarian3

Bavarian3

New member
Joined
Jun 18, 2007
Location
SF
Moto(s)
07' 600rr track
Name
Charles
I am trying to fix a brake drag issue. Yesterday I took the pads out and push the pistons all the way into their bores. As expected the fluid goes up into the reservoir.

My question is if it's normal for it to overfill at this point, and what the fluid level should be when the pistons are all the way in?

Mine overflowed a bit and now i'm curious if I should take more out or leave it. Thus leaving it at a low level in the reservoir when the pistons are actually engaged.
 
you're over thinking this.

the mark on the reservoir indicates what the level should be with the pistons in whatever position puts the brake pads in the right spot to contact the rotor.

there is a range indicated because as you've seen, more fluid is needed as the pistons "home" position is farther out as the pads wear down.

if your pads are being replaced due to the old ones being worn out, you'll likely have to remove some fluid... but you're going to bleed the brakes anyway right?

disk brakes drag just a little itty bitty bit all the time. i'd start with making sure the things that are supposed to slide freely are doing so including the pads within the caliper and the caliper pins if applicable (you probably have radial brakes in front so wouldn't be applicable there.)
 
The level is not set with the pistons pushed all the way in, it's set with new pads seated lightly on the rotors so they rub slightly. Easily done by simply squeezing the lever a few times to seat the pads and then checking fluid level.

Sometimes people will either add fluid as the pads wear and the level drops, or they'll change fluid but not change worn pads and then top off to the top mark on the reservoir. If either of these things have been done, know that you'll be needing to remove some fluid if new pads are then installed. Watch the reservoir as you're pushing the pistons in to make room for the new pads and remove fluid as necessary.

That's it.
 
auntiebling said:
you're over thinking this.

the mark on the reservoir indicates what the level should be with the pistons in whatever position puts the brake pads in the right spot to contact the rotor.

there is a range indicated because as you've seen, more fluid is needed as the pistons "home" position is farther out as the pads wear down.

if your pads are being replaced due to the old ones being worn out, you'll likely have to remove some fluid... but you're going to bleed the brakes anyway right?

disk brakes drag just a little itty bitty bit all the time. i'd start with making sure the things that are supposed to slide freely are doing so including the pads within the caliper and the caliper pins if applicable (you probably have radial brakes in front so wouldn't be applicable there.)
Click to expand...

ST Guy said:
The level is not set with the pistons pushed all the way in, it's set with new pads seated lightly on the rotors so they rub slightly. Easily done by simply squeezing the lever a few times to seat the pads and then checking fluid level.

Sometimes people will either add fluid as the pads wear and the level drops, or they'll change fluid but not change worn pads and then top off to the top mark on the reservoir. If either of these things have been done, know that you'll be needing to remove some fluid if new pads are then installed. Watch the reservoir as you're pushing the pistons in to make room for the new pads and remove fluid as necessary.

That's it.
Click to expand...

Thanks guys makes sense.

My brake drag issue is more significant than a light drag which i realize is normal. It has to do with removing and reinstalling the forks. After more research I learned about the process of aligning the forks and pads properly so hopefully I'll have it sorted.

The bike is unfortunately only a track bike so it's hard to know if they need to bed themselves in a bit to settle. The pad's already have 1-2 trackdays on em.

I also cleaned the shit out of the pistons, greased up all the pins etc. It seems like the pads didn't want to retract. We'll see what I end up with tonight.
 
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They don't really retract, it's more like they loosen their grip a bit. That's why they still rub.
 
make sure the pistons are clean. @ the track we do this several times a weekend. we remove the pads & pump the brake a couple times to expose most of the pistons surface, then we use simple green & a tooth bush to clean them, rinse with water, dry with compressed air & then gentle push the pistons in by hand & install the pads & then a quick bleed. it greatly reduces drag.
 
elskipador said:
make sure the pistons are clean. @ the track we do this several times a weekend. we remove the pads & pump the brake a couple times to expose most of the pistons surface, then we use simple green & a tooth bush to clean them, rinse with water, dry with compressed air & then gentle push the pistons in by hand & install the pads & then a quick bleed. it greatly reduces drag.
Click to expand...

Yup I cleaned em very well.

I'm starting to think my rotors are warped.

Just curious why you bleed them afterwards? If the piston doesn't come out no air should go in right?
 
its just good practice & @ our level of competion you don't half ass it.
 
elskipador said:
make sure the pistons are clean. @ the track we do this several times a weekend. we remove the pads & pump the brake a couple times to expose most of the pistons surface, then we use simple green & a tooth bush to clean them, rinse with water, dry with compressed air & then gentle push the pistons in by hand & install the pads & then a quick bleed. it greatly reduces drag.
Click to expand...

On some caliper designs I discovered that even doing this, you cannot fully clean the entire piston circumference; parts of the caliper body proper still get in the way. I've had to remove the piston(s) in question entirely to really get at every dirty bit...sometimes simply rotating them in the bores is impossible due to seal friction. Ex. I recently cleaned up a set of late-model CBR1000RR monoblock calipers, but fortunately I have an air compressor which made popping them out a doddle. :thumbup
 
Hooli said:
On some caliper designs I discovered that even doing this, you cannot fully clean the entire piston circumference; parts of the caliper body proper still get in the way. I've had to remove the piston(s) in question entirely to really get at every dirty bit...sometimes simply rotating them in the bores is impossible due to seal friction. Ex. I recently cleaned up a set of late-model CBR1000RR monoblock calipers, but fortunately I have an air compressor which made popping them out a doddle. :thumbup
Click to expand...
if you do it a couple times, several weekends a year, you can rotate the pistons pretty easily :teeth
 
these help w/ rotating

7224975.jpg
 
elskipador said:
if you do it a couple times, several weekends a year, you can rotate the pistons pretty easily :teeth
Click to expand...

Good tip on that tool Robert, I'll look into it. :thumbup

Shawn, I bought the calipers used. They were evidently quite neglected...some of the pistons show slight scarring, as if the previous owner used pliers on them. :wtf
 
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Maybe you need to rebuild your calipers with new seals and a real good polish on those pisons. Try and avoid jamming dirty Pistons inside the caliper.

Note that the seals themselves supposedly contribute to pull back on the Pistons, which is part of the drag equation. I have been told that 3 rotations is a good target.
 
DefyInertia said:
Maybe you need to rebuild your calipers with new seals and a real good polish on those pisons. Try and avoid jamming dirty Pistons inside the caliper.

Note that the seals themselves supposedly contribute to pull back on the Pistons, which is part of the drag equation. I have been told that 3 rotations is a good target.
Click to expand...

yikes. im getting like.... half to one rotation?
 
stangmx13 said:
these help w/ rotating

7224975.jpg
Click to expand...
i have a set of snap-on fuel line pliers that work well, but admittedly, i'm using them in reverse.

Hooli said:
Shawn, I bought the calipers used. They were evidently quite neglected...some of the pistons show slight scarring, as if the previous owner used pliers on them. :wtf
Click to expand...
& the truth comes out, lol. scotch-brite for TMFW!

Bavarian3 said:
yikes. im getting like.... half to one rotation?
Click to expand...
thats really not that bad, for just realizing you may have a problem. keep cleaning & rotating & it may get better.
 
elskipador said:
i have a set of snap-on fuel line pliers that work well, but admittedly, i'm using them in reverse.


& the truth comes out, lol. scotch-brite for TMFW!


thats really not that bad, for just realizing you may have a problem. keep cleaning & rotating & it may get better.
Click to expand...


any opinion on using this methods to align the forks? (you can skip to about 7mins in)
https://www.youtube.com/watch?v=6KDolPU-7KM

then this to align the pads?
http://www.ehow.com/how_7820564_fix-brake-rubbing-wheel-motorcycle.html
 
Bavarian3 said:
yikes. im getting like.... half to one rotation?
Click to expand...

Front or rear wheel? That's about all I get and the front will be different from the rear regardless because other things help determine how much it will rotate. Bearings are different front and rear. Chain and output shaft adds drag. Bearing seals will drag to different degrees. Speedometer drive will add drag. Etc., etc.
 
ST Guy said:
Front or rear wheel? That's about all I get and the front will be different from the rear regardless because other things help determine how much it will rotate. Bearings are different front and rear. Chain and output shaft adds drag. Bearing seals will drag to different degrees. Speedometer drive will add drag. Etc., etc.
Click to expand...

front.

i should point out the wheel/pad even dragged quite a bit after putting the calipers back on, BEFORE squeezing the lever at all. this was after pushing the pistons all the way back in.

the guy in that video i posted has the same bike as me and shows what kind of rotation is proper. maybe vesrah pads are just thicker? i don't know
 
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