Brake Caliper Overhaul

[basadia]

My 02 Ex Police bike is about to get the front brakes overhauled, I have found the front brakes to be a bit soft of late and I really need to pull hard on the front brake lever to get any stopping power. I am looking pulling the calipers apart to give them a clean out. I will be putting on fresh disk rotors, a master cylinder kit and new metal gear pads.

I am hoping that with some work the front brakes will give me much better stopping power. Anyone else noticed that their front brakes are not what they want?

[Brock]

The cause is probably glazed  pads and rotors. Give the rotors a good rub with coarse scotchbrite to remove the shine, and it will help bed the new pads.

[Biggles]

The cause is probably glazed  pads and rotors. Give the rotors a good rub with coarse scotchbrite to remove the shine, and it will help bed the new pads.

That tip from Brock will save you buying new rotors, unless the old rotors are under-spec.  The minimum thickness is stamped on the rotor, so you can check it with a micrometer.

[basadia]

I had the rotors skimmed about 12 months ago and they were at their minimum usable thickness. I sourced a new aftermarket set from EBay. Overhaul is now done, very happy about the results as the brake efficiency has improved with less pressure on the brake lever.
Issues I had were:
1. I Could not get the retaining circlip off the brake master cylinder, I had to grind down the tips of the circlip pliers I purchased as they would not fit in the holes. The first set I bought had a right angle but would not reach into the circlip.  I was also unable to get a hone small enough as the master cylinder was 15 mm in diameter and the smallest one I could get from the auto shops was 19 mm. I ended up using a piece of dowel and some emery paper to roughen up the cylinder to help the new seals to seal.
2. One of the pistons in the right side caliper would not come out. The manual suggests using compressed air and G clamp on the moving piston, I did this and was still unable to remove the piston. I ended up reinstalling the caliper without getting the piston out. Next time I change the front tyre I will use the hydraulic pressure of the master cylinder to push out the piston. I buffed up all the pistons I could get out with the wire buff on my grinder and cleaned all the gunk from inside the calipers.
3. Break bleeding  took ages as I had trouble getting all the air out. I bought a car break bleeding kit a while ago and this came in very handy, if I did not have it I don't think I could have got the job done.

I would suggest if your brakes are getting hard a good clean will make a big difference.

[STeveo]

An old time trick is to find a bolt of the right thread for the hole where the line screws in, drill hole through bolt and tap to fit a grease nipple, use hand pump grease gun to push out the piston. Old style lever types can get up to 2000psi, so if they cannot move the stuck piston get another caliper.

Would suggest to you that you go back and fix that stuck piston as only having one moving will not be as effective as two, and will wear the pads at an angle.

 

[basadia]

I did an oil change today so while I was waiting for the oil to drain I dropped the calliper off and clamped the moving piston, the other one was not frozen but very tight. A couple of pumps on the brakes the piston popped and man was it covered in gunk, I buffed it up and put it back in. Man that brake fluid gets everywhere, it took me ages to get the air out of the lines this time. I bled the luntil no air came out but still could not get a good brake pressure. What I ended up doing was to pump the brake every half hour and I would get a couple of bubbles of air from the master cylinder. After a couple of hours the brake came back, frustrating when I could get no more air from the bleeders.
I have seen a vacuum assisted bleeder but for the amount of times I work on the brakes probably not worth spending money on though.

[STeveo]

Last time I had mine apart to fit the braided lines I had to push the pistons back into the callipers, thereby forcing the fluid back up the lines to get the last bit of air out of the master cylinder.

 

[Sailor Sid]

Just try tying the brake lever back to the bars and leaving overnight. Should allow any bubbles to migrate to the master cylinder
Sailor Sid

[Nigel]

Just try tying the brake lever back to the bars and leaving overnight. Should allow any bubbles to migrate to the master cylinder
Sailor Sid

Yes I have used that trick with a few cars and worked a treat. Must leave overnight though, with pedal/handle depressed, brings any air back  to the master cylinder.

Nigel