Stuck front brakes

[SiskoWarrior]

Hi All

I have a 2011 125cc PCX and a few weeks ago did a bit of maintenance on the brakes. I was not happy with the front brakes performance as I could feel that it was jerky when I applied it. So I got a bit of sand paper, removed the pads and cleaned them thoroughly and sanded them and the rotor gently. I also cleaned the pistons and the callipers with warm soapy water and an old toothbrush.

After putting everything back together and running in the brakes I noticed the discolouring on the rotor and when I touched it I almost got burned! It appears that the pistons are not retracting and the pads are constantly touching the rotor.

To remedy the issue I got some rubber lube and lubed the pistons. This seem to helped a little but the pads are still touching the rotor and blocking the wheel.

Now I'm thinking that I may have introduced some air into the system and that's why the pistons are not retracting. When applying the front break the lever feels a little "bouncy" and soft, like it was compacting air. I can't remember if it was like this before the cleaning though. Any idea what else could cause this?

I most likely will bleed the system this weekend (front brakes only) just wanted to hear a different opinion. Also, any advice on bleeding the front breaks?

Thanks

PS: Thanks for all the advice on the forum, they helped a lot!

[Alibally]

Try pushing the pistons right back in the caliper then pump up the brakes to reset the piston. If the seal on the piston is distorted it might cause the problem. There is always the possibility the caliper is seized .

[SiskoWarrior]

The pistons move freely and I did push them back. When the pads are off and I apply the brake they come out and when I release the lever I can see them moving back in a little bit. It's like there is not enough force to pull them back in the caliper.

[gn2]

The caliper has all the pistons on one side.
This design of caliper is known as a "sliding" caliper, the two halves of which are able to move towards each other on a pair of pins.
It is usually these pins which cause bike caliper sticks and seizures.
To fix the problem unbolt the caliper from the fork leg, slide it off the disc and have a look for how to separate the two halves.
Clean up the sliding pins and any mating faces then apply copper grease and reassemble.

[SiskoWarrior]

That makes sense. I remember cleaning the pins as they were pretty dirty too and have not applied any grease afterwards. Will give this a go in the next few days and report back.

Thanks very much!