Lost back brakes

Tore the original master cylinder apart ,the piston was semi-frozen had knock it out with a punch.There was a bit of corrosion under the dust seal.Also the front of the piston had oxidation on it .pretty sure that was what making it stuck .Used 1’000 grit wet and dry to clean the oxidation off of the piston.I reassembled the unit and put fluid in,seemed to work ok.I’ll source a rebuild kit and have in stock.

1K9 said:

Has anyone tried to replace the front rotors buttons? A set of new EBC rotors is $200 but, I wonder if I can rebuild the originals for $50.

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????
R U TALKING ABOUT removing THE CAPS THAT COVER THE ROTOR BOLTS? (sorry caps)

TURBO200R4 said:

????
R U TALKING ABOUT removing THE CAPS THAT COVER THE ROTOR BOLTS? (sorry caps)

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No, Im talking about the "buttons" that fix the friction portion of the rotors to the carrier that fixes it to the bike. One would need 20 of these. They are expensive. Is this the component that fails when the discs develop play?

barbagris said:

If the buttons are worn - then usually the carrier and maybe the rotor have worn too.

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The disc gets scuffs the moment you take a pad to it. That's why new discs have to be bedded with new pads. The metal disc will wear but if run clean with good pads, they should last the life of the bike. (Unless you race). Is it said that repeated cycles of high heat accelerates their ware.

I wonder, where does the connection fails, the machined edges of the rotor or carrier or the weakest like, the button. BTW are the R3 rotors floating or semi floating and what is the difference between the two.

1olbull said:

Might also consider reverse bleeding.
Works well for me and much easier eliminating air in system.

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Borrow your wife's vibrator and shock the bubbles out. Works for the front lines. I used my Sonicare for that It works, your just have to be patient and persistent. The air will work itself out into the reservoir on the handlebars.

idk said:

Use some tyre levers, or similar, to pry the pads apart, then pump them back again with the brake lever. Repeat on other side. All will be good and hard again.

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That's what happens when you pry brakes open with the pads on. Take the pads off or better yet, take the calipers off the bike and give them a thorough cleaning. You might even remove the pistons and lube the seals, then exercise them. Better yet, replace the seals $65 and install Speed Bleeders.

Get a new set of pads and bed them in slow. If the surfaces of your rotors look like a vinyl record, you might be thinking of new rotors.

Compared to the cost of making the bike accelerate faster, making the bike decelerate better is cheap. Plus you can do it yourself.

The discs are very much SEMI. These use the buttons merely to thermally isolate the carrier from the rotor. The disc (when cold) is basically as good as solid. If it's not - then it is toast. It'll be the carrier that's worn sacrificially if anything has.

Fully Floating are designed with auto alignment in mind - these will exhibit lateral motion as they warm and are usually identifiable by having springs on each button. They will usually be SUBSTANTIALLY more expensive. Usually race grade Ductile Iron Rotors : because race riders don't care about a little surface rust. Even so don't expect much more than 0.25mm lateral play (each side of centre).

Most discs are now Laser or Water Jet cut, not machined.

The issue is NOT machining - It is the ingress of dirt/dust into the surface interfaces under circumstances of rotor thermal expansion - but maybe in cooler weather (this means the carrier may also slightly contract). Imagine if it was fine carborundum powder). It's a pressure grind medium.

The addition of any lubricant to the buttons that can get sticky and hold dust etc - is a simply going to exacerbate the issue. Lubricating the buttons on semi-floaters will not make them float.

Nothing on this earth would induce me to piss about with discs on a half tonne 2 wheeler. Fit new and be blowed. And I'd hunt for fully floating ones.

if it was me i would just replace rotors. i would guess that the buttons hard metal

TURBO200R4 said:

if it was me i would just replace rotors. i would guess that the buttons hard metal

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That's what I did.



The button washers on these are "wavy" instead of flat. They are less than 1/2 the weight of the original.

for a few pennies more u could have had a complete rotor without all the holes