Road trip coming up so had a look at the brake pads. The wear is uneven and some still have life but I'm thinking to replace them. I question the uneven wear. Possibly a rotor issue?

Looks like one piston is applying the most pressure and wearing one of the four pads faster than the others. I'd say a good cleaning is in order. Possibly the caliper piston behind the worn pad or it's bore is corroded and the pad is dragging when the others only 'kiss' the rotor as they should,

^^^ Right on the $$. It's not the rotors. It's you! You should have cleaned and inspected those a long time ago. Time to get the tooth brush and the W40 out. Soapy water or simple green should work pretty good as well.
Oh and I would replace the pads, hopefully you don't have to do a rebuild.

click here

* Last updated by: dragking on 6/1/2014 @ 7:23 PM *

looks like the top right one in the pic is GONE! Good thing you checked when you did. I used brake parts cleaner on mine and that was all but I can see no harm in using WD if the pads are out. There is a technique to cleaning the pistons. If you can work the brake lever gently and get them to come out, then press them back with your fingers, that should free up any that might be stuck. Be careful, if you apply the brake without the rotor to clamp down on, the pistons will fall right outof the caliper (so I heard)...stick a piece of soft wood between them...IDK how far they will come out before they fall out. Work them back and forth and that should free them up. You can also floss them with a piece of twine to remove any dust buildup that might be making them stick.

The pistons are lubed by the brake fluid. I'm not so sure if using water or WD on them while you work them in and out will introduce a trace of contamination into your brake fluid. I guess I'd avoid it and work them dry after you give everything a good cleaning.

This is all just stuff I am recalling from previous threads and conversations. Hopefully Hub will come along to right me if I'm wrong on this...or anyone else.

As long as he holds them like pictured and don't push them out too much (had one of my nissin pistons fall out ) he should be ok. Brake Fluid is really sensitive so anything foreign would ruin it anyways, whether it's soapy water or WD40. If you're apprehensive just put some on a toothbrush instead of spraying directly but in my opinion if brake fluid is not leaking pass the pistons, you should be fine. Maybe try brake cleaner first but whatever you use it's going to require some aggressive brushing. If you check on youtube, Dave Moss advise to let them soak in simple green (when they are really bad) but says not so long that you damage the piston. I wish I knew what it meant by "not too long".

I would use really warm soapy water and rinse thoroughly with warm clear water and see what it looks like. If they are still acting up after that get the brake cleaner or up the ante as you see fit. I clean mine every 3-4 months or so and if I've ridden in the rain several times. Post a pic once you get them cleaned up.

Thanks for all the input. I will definitely watch this more closely in the future. I'll post back once I get things cleaned up.

There is a technique to cleaning the pistons. If you can work the brake lever gently and get them to come out, then press them back with your fingers, that should free up any that might be stuck. Be careful, if you apply the brake without the rotor to clamp down on, the pistons will fall right outof the caliper (so I heard)...stick a piece of soft wood between them...IDK how far they will come out before they fall out.

just to clarify for anyone reading, it's okay to press the pistons in with finger but I wouldn'y recommend holding your fingers in there if you apply the brake. Use a chunk of wood.

I ended up using the simple green, a toothbrush, some patience, and all the pistons are moving well now. Question remains, the brake reservoir is now at the top line. I think I read somewhere that it can expand in heat. Is it recommended to remove some to keep in the middle after putting in new pads?

Is it recommended to remove some to keep in the middle after putting in new pads?

Absolutely! It is normal to have the brake fluid level go up in the rez after changing pads. The pistons are pushed in farther to fit the new pads which are an eight inch or more thicker than the worn ones. That fluid gets pushed back up the system.

Any time the brake fluid level is above the HIGH mark, there is a chance that the brake could lock (or i suppose drag real hard). The fluid expands with heat from using the brake and this creates pressure in the system. If the fluid is too high when cold, it can run out of space when it expands and push the pistons outward, applying the brake, in effect. I believe the rubber baffle in the rez is sort of a safety buffer for this situation. Yours is probably popped up out of shape if you've used the brake. Definitely remove the cap and have some rags under the rez because there may be a few drops waiting to drip on your plastic (especially if you were working the pistons in and out). wick the extra fluid up with clean paper towel or a clean squeeze bottle until the fluid touches JUST BELOW the top line.

Reform your baffle if necessary and close it up. Wash the whole area down with water. Make sure the cap is TIGHT/service manual specs. I had mine leak and spit some drops on my multifunc meter and ram air covers. It left etched spots. Polished out but what a PITA for a small thing like not tightening the cap properly. The cap retainer is just a failsafe. It doesn't do anything to keep the cap from coming loose. ...but use LokTight on the retainer screw cuz it vibes out pretty easy...I lost mine once.

* Last updated by: Rook on 6/7/2014 @ 5:11 PM *

If the fluid level went up but is still below the upper line, you should be safe but I think its best to have the level touching the bottom of the upper line. The air in the rez could potentially be a source of condensation or air bubbles that should be kept out of the system.

Good job T! I didn't know you were going to be able to get them that clean! Did you clean the rotor as well? Not that you need it anymore but I think I this video is a little better.
CLICK HERE .
In the video Dave Moss says to do it monthly if your bike is a daily commuter. I'm going to do it every 3000 miles with my oil change instead of going by the 3-4 months period since I ride more during this time of the year.
Most people use soapy water because it lubricates the piston according to Dave but you clearly needed more. Anyways, I'm glad you got things to tip toe shape. Enjoy the trip.

* Last updated by: dragking on 6/7/2014 @ 6:00 PM *

Upper right is still a concern. That says, debris under the quad-ring is dragging piston, which drags the disc, which causes the one pad to wear more than the others.
I'd say the same common sense with the coolant temp applies. You see cars needing pad/piston/cleaning every so often? Do you see the shop/owner's manual suggesting one clean the caliper at said m/k? They [cars] go thru more or less the same air as you. More rain, mud, shit and if that wheel spins free, no drag, where is this in the automotive shop manual where it is that critical for safety?

Moss is in a different environment and I don't think brake dust has caused brake failure if say you don't clean the car's calipers with geenmeanie and a brush. The cause is more not changing the fluids as per manual or sooner.

Right now, your bet is to inspect that pad vs. the other 3. Or if it drags now, meaning, pump the brakes up, run the wheel off the ground with a good spin. Where are we at if we just push back that one pad; stick a feeler gauge up between the pad and disc; pump the brakes; remove the feeler [even the drag out will tell]; then spin the wheel. Was there less drag? More counts to the same spin?

Pump the brakes up; no feeler this time. How many spins could you count? Which means, you'd have to shim each pad on the other disc or pull caliper and place the old pads in between so you are focused on the one pad that drags.

Then, bleed brakes and I doubt that will help, but it's all a crap shoot sans a full rebuild with new rubber and clean quad-grooves in the caliper.

As stated, you are just swishing the same swallow of water between you cheeks you go pushing that gulp to one side of the mouth or the other is the same idea with the filling of the master's level lines.

1. If you remove the cap, look at the penultimate grooves [call them] up the threads. This keeps 14.7 psi constant no matter the level drops or the oil warms and expands, it will collapse that diaphragm, but if...

2... If say you filled more oil in the master, pushed the pads back up and did not compensate for it, then yes, my guess is it collapses the air pocket if not out thru the grooves of the threads.

3. So, with pistons all the way home, the oil is at the highest level at the master's line. See how there is no way to collapse the diaphragm once you see you squeezed the air out of it installing the diaphragm into that level, right? Overfill, watch out opening the cap. Make sense how/where the oil went, when you brush your teef wit pep sea dent.

Hub:

What / where is this "quad ring" you speak of?

Thanks...

Tetrec whens the last time you flushed the old fluid out and replaced with new? I do mine once a year, ez cheap job.

Last change of brake fluid was about 20,000km at the dealer so will do again soon. The manual is every 24,000km. Before I remounted the caliper all the pistons were moving at the same rate which was better than before the cleaning. The fluid level in the reservoir is where it should be now just below the upper line, and after taking it out yesterday all feels good. Thanks to all for the help with this.

IMO, fluid change isn't really a every X number of miles, its more of a if there's air in the system, or the fluid starts looking bad (darker colour/dirty). I think I've been changing mine every year as well, I find the clutch fluid tends to get crap in it way quicker than the brakes.

Don't forget that the fluid absorbs water which can lead to decomposing rubber lines and rusting metal parts.

Don't forget that the fluid absorbs water which can lead to decomposing rubber lines and rusting metal parts.

When oil boils, what is inside the bubble? Water.
What is heavier, oil or water? Water.
What crystallizes under the rubber and raises the rubber up on the piston and locks it? Water.
What is that crystallization mixed with as both water reacts on certain metals? Aluminum.
What is stable in water as in we find some ww2 boat sunk with cargo like jeep tires still intact? Rubber.
What is most likely to swell rubber if you want some cleanass aluminum? Vinegar.