Brake pads

[davidc83]

I changed my brake pads last night due to squelling from my front brakes when I applied them. Even though I had it serviced 3 weeks ago for preparation for the Franklin meet, the service department didnt catch I was needing new pads (whole nother story-wont be going back there after I get my next 'free' service)

2006 Suzuki gz250. 7000 miles, mostly Interstate and country roads riding. Very little stop and go city riding.

One pad was completely worn down (piston side) while the off-piston side had no wear ( I am going to save it) at all.

Question for you wrench monkeys: Is this normal wear for the gz? I would think so since it only has one piston caliber.

I know when you press the hand brake, the piston pushes against the pad to press against the rotor.

Question: What causes the tension/piston to return to 'home' position, that is, not pressing against the pad to the rotor, when you release the hand lever.

I did notice the first time i installed the pads, I couldnt get the caliber on the rotor due to the piston was not completely in (didnt touch the hand lever after removal of the caliber). I then removed the new pads, used Channel Lock to squeeze the piston in some, and installed the pads. Placed caliber on the rotor, bolted everything down, squeezed the handle a couple of times to get the piston back to 'home' (feel pressure when hand level squeezed). I have inspected the bike and there are no brake leaks anywere in the line or caliber/reservoir.
Does all this sound normal?
Sorry for the tech questions, I have never been much of a wrench monkey, but I am trying to learn.

P.S. Not quite as easy as the service manual made it out to be but very close. Not bad. Did the job in 20 minutes, including removing the pads and squeezing the piston in; basically installed pads twice into the caliber. Still start to finish-20 minutes.

[Quimrider]

Question 1:
I'm not familiar with the GZ250's brakes yet, but from my experience with other vehicles it is not uncommon for single piston caliper disk brakes to have uneven wear between the pads. However if it is as you say one completely gone and the other hardly worn at all, your caliper may have seized. This happend to me on my car. There are usually two bolts or shafts that each half of the caliper can slide on to squeeze the pads on both sides of the brake using just the one cylinder. If by corrosion or other means the caliper halves no longer can slide on these shafts only the one brake pad gets used up. Usually when this happens a mechanic will tell you that you need a new caliper because the labor to fix your existing caliper would be more expensive.
I'll be working on my front brakes sometime within the next few weeks. I'll keep my camera handy and I may be of more help then.

Question 2:
To my knowledge, there really isn't anything that pushes the pad back from the rotor. Disk brakes usually always have a small bit of drag to them. It's as simple as when you release the brake lever you release the hydraulic pressure on the pad.

There is some good information on brakes in the how to section: http://www.gz250bike.com/viewtopic.php?t=100

[Badbob]

Originally Posted by davidc83

Question: What causes the tension/piston to return to 'home' position, that is, not pressing against the pad to the rotor, when you release the hand lever.

Nothing. When the pressure is removed the pads remain where they are lightly skimming the disk. This helpskeeps debris and water off the disk.

Originally Posted by davidc83

Question for you wrench monkeys: Is this normal wear for the gz?

Yes and no. Its normal for the wear to be uneven Its not normal for one to wear out and the other to not wear at all.

You may also notice thet the leading edge of the pad wears a little more than the trailing edge. Some people switch there pads around trying to get even wear. Since the pads wear to fit the caliper, it seems like this would reduce the braking. I don't do this!

Originally Posted by davidc83

I couldnt get the caliber on the rotor due to the piston was not completely in (didnt touch the hand lever after removal of the caliber).

The pads are new and thicker so after you install them the gap is narrower. You will almost always have to push the piston back in when new pads are installed. They make tools to do this with but a large c-clamp with padded jaws will do.

As you discovered hydraulic systems do not like to go backwards. When you squeeze the brake lever you put pressure on a small piston and that pressure is felt equally all over the system. If the caliper piston is four times as big it squeezes four times as hard on the brake pad so ten pounds of pressure on the master cylinder end equates to 40 pounds on the caliper piston but move it 1/4 ov the distance. When you go in the opposite direction it divides instead of multiplying. If it takes 10 psi to move the master cylinder piston back we have to apply forty pounds of pressure to the caliper piston to get pistons to move back enough for you to get the pads in and the caliper reinstalled. Note that although it may seem like it does, brake fluid does not compress. Moving the small master cylinder piston a lot causes the larger caliper piston to move a tiny bit. And there yo have it, hydraulics in a nut shell.

I just put a clamp on there and push the caliper piston back in all the way because I know its gong to give me problems.

Oddly enough I have never worn out any brake pads. As you have I always check them before heading out on a trip and every time but this one they were almost worn down to the bottom of the groove so I went ahead and changed them. This time I had other problems.

And just for grins the caliper IPB:

[xt477]

Check the guide pins. (#6 and #8 on the diagram) If they are frozen the caliper can only push on the piston side. I was told that Suzuki is bad about not lubing them from the factory causing them top freeze up. With the caliper off you should be able to slide the caliper back and forth on them easily. With every brake job you should lube with non petrol based grease or replace them.

[Badbob]

You can get grease for brake calipers at any auto parts store real cheap.

Now you have me curious. I'm going to have to pull mine and check them.

[5th_bike]

Originally Posted by xt477

Check the guide pins. (#6 and #8 on the diagram) If they are frozen the caliper can only push on the piston side. I was told that Suzuki is bad about not lubing them from the factory causing them top freeze up. With the caliper off you should be able to slide the caliper back and forth on them easily. With every brake job you should lube with non petrol based grease or replace them.

Aha, I was wondering why my brake pads had worn unevenly.
I will silicone grease the boots and pins, and let you know how it goes.

[blaine]

Originally Posted by 5th_bike

Aha, I was wondering why my brake pads had worn unevenly.
I will silicone grease the boots and pins, and let you know how it goes.

With everything working properly the pad on the piston side will always wear more than the one on the outside.

[5th_bike]

Well mine were worn diagonally, here is what was left:

piston side, leading edge: 2 mm
piston side, trailing edge: 3 mm
other side, leading edge: 1 mm
other side, trailing edge: 0 mm (bare metal)

The latter causing a kind of grinding sound when braking :whistle:

Thanks to the posts above we now know where to look for a fix. I'll let you know how it goes.

[5th_bike]

When putting new brake pads on yesterday, I noticed the old ones had worn unevenly (previous post).
Also, with the new brake pads, there was quite a drag from the front brake, more than you would expect.

Looking for a solution, I found Badbob's and xt477's posts above.

This morning I found that the caliper could be moved but it was quite stiff.

I pulled the pins out of the boots and indeed, no grease whatsoever, just some dirt.
Cleaned them, put silicone grease on them, and it's working great now :2tup:

And the drag is now minimal.
I hope these pads will last longer than the 6,800 miles for the old ones.

PS (edit) Thanks Sarris for the tip to drain the brake fluid while pushing the piston back.

[Easy Rider]

Originally Posted by 5th_bike

PS (edit) Thanks Sarris for the tip to drain the brake fluid while pushing the piston back.

A little experience is often worth a LOT. Those pistons move MUCH easier if you vent a bit of the pressure.

Just a note on the silicone grease: Silicone in all forms, tends to spread out as thin as it can (sometimes called "migration"). Just need to be sure there isn't too much on there, such that it could "migrate" over to the pads or the rotor.