Complete front caliper service
Front Caliper Service
Many folks have posted here with a Varity of front brake problems. Many of which are attributable to the lack of proper maintenance. Here’s how you can always have a brake like when your bike was new.
A short list of the problems and the causes.
Soft lever or lever goes to the bar.
The usual cause is the pistons are pushed too far back into the caliper by a flexing a warped, coned, disc. Using up too much piston travel before the disc is pinched.
Juddering in sync with wheel rotation.
The disc is worn, and its thickness varies. This causes the caliper to “sink” into the thin part and when the thick part comes around, it gets wedged into a smaller space causing a tightening of the brake. Then the tight spot passes through and it like the brake is released. Then repeat, repeat.
Cupped, coned, or warped disc.
Unfortunately this is a common problem with EX’s the cause is the disc is stretched in the center due to being rigidly bolted to the wheel. The huge force of braking is transmitted to the wheel through the webbed center of the disc which gets stretched and becomes larger than the space it occupies in the center of the disc. This causes the center to push to the side trying to find room for itself. Resulting is a cone shaped disc.
Soft lever 2
The caliper has pistons only on one side, so as the pads wear the caliper must shift sideways apply even pressure on both sides of the disc. To allow this the caliper floats on two pins. If these pins get dry (no grease) dirty or bent. The caliper won’t center itself and bends the disc to wherever it is. This take up lever travel and when released pushes the pistons further back than necessary. If not fixed will eventually destroy the disc (warp it).
Ok how to prevent all of the above.
When new pad time comes around, resist the temptation to just pop in new one and go. Every time you must do these things.
Remove caliper disassemble and clean it.
Clean and re grease the sliding pins.
Polish the caliper pistons to remove dirt. If you just push the pistons back into the caliper leaks will result. Or binding.
Tools required: 12 mm socket, 8mm open end wrench, 3” or bigger C clamp, a supply of new bake fluid. Wire brush and or steel wool.
Remove the caliper from the fork leg but leave the brake line on.
Remove the old pads and the mounting frame (the sliding pins)
Remove the cover from the Master Cylinder on the Handel bar.
Attach the C clamp to one of the pistons but don’t squeeze it. Pump the lever on the bar slowly to push out the other piston almost all the way. Put the C clamp on that piston and push out the other one.
Remove both pistons by hand.
Remove all the rubber part from the caliper, the seals are in the grooves in the caliper and dull pointed thingy will get them out easy.
Disconnect the caliper from the brake line.
Soak all the rubber parts in new clean brake fluid ONLY!!!!! Rub them with you fingers till as clean as new.
The caliper can be cleaned with a wire brush or even a Moto tool for the internal grooves, NOW’s the time to paint it if you wish.
Polish the pistons till they are smooth and shinny. They are chrome plated. If any of the plating is chipped or damaged below the dust cap groove. Replace it.
The master cylinder is the subject of another write up and we’ll assume it in good working order here.
If you suspect your disc is bad, your bets bet is to replace it with an after market one fro EBC or Galpher.
Don’t remove the disc unless you intend to replace it. It will assume a new shape if it is stressed and will not be flat again. You can try to check its condition by placing a straight edge across the face of the pad swept area looking for any distortion.
Take the nice clean rubber seals and install them into the caliper then the Dust covers.
Wet all the rubber with new clean brake fluid and partially fill the caliper with new fluid.
Push the pistons though the dust seals and into the caliper body until the dust covers snap into the grooves.
Fill the MC with new fluid and pump the lever while holding the Line above the MC till clean fluid flows.
Connect the line to the caliper while holding it above the MC.
Pump the lever with the bleeder valve open till fluid flow from the bleeder. Hold the caliper so that the bleeder is the highest point.
Close the bleeder and pump more fluid into the caliper but don’t push the pistons all the way out.
Then squeeze the pistons all the way back in and install the new pads.
Re grease the slider pins and assemble the dust seals and re mount the caliper on the forks but leave the bolts loose.
Now clamp the caliper to the disc with the brake lever.
Look at the space between the fork lugs and the caliper, clamp and release a few times as you tighten the bolts by hand. It one lug touches much before the other the odds are you mounting bracket is bent. You can straighten it. After you get it the best you can. Some shim washers made from alum can stock can be fitted to the loose side.
What we are doing here is trying to mina muse the bedd in time and gets the best pad life.
Ok with everything tight you should be through, Notice we don’t need to bleed the brakes, but if you screwed up in any of the above steps, you might do that here.
Care full to Bedd in the new pads gently. Too much pressure too soon will burn the pad material as only a small area will be gripping at first. You also won’t have full braking power till the pads are fully familiar with the disc.
Good luck Ride Hard.
I hate PMs if you want to contact me, find my email address.Look in the for sale section.