Aftermarket Rear Discs

[stopintime]

Overfilled reservoir?

[koko64]

That can cause problems for sure.

[ducpainter]

I reckon the fatter rotor results in more drag or exacerbates any condition that results in drag which heats up the fluid and robs free play. After a ride and the disc is hot, freeplay has been halved. Once it coools off, the freeplay returns. That is what I observe even if there is generous freeplay to begin with.
So when cold, you are correct, I just think the thicker disc exaggerates the known issues which eats up freeplay as the fluid heats up.

Right...reduced freeplay is the result of sticky pistons, not the thicker rotor.

You might very well have the same symptoms from anything that puts those pistons somewhere else in the bore, like if you threw in a set of worn pads.

[koko64]

I get you, and that makes total sense, but I'm seeing it at it's worst with new pads and thicker than oem rotors.

[Howie]

Both are putting the pistons further into the gunky area of the bore.  Mostly the new pads.  Imagine what must be lurking after 154K km.  When I change pads I open the bleeder so I push the worst of the brake fluid out of the caliper.

[stopintime]

...............  Imagine what must be lurking after 154K km.  ....

I have changed the fluid along the way, but I'll see/photo what it looks like 

[Speeddog]

Hadn't thought of that as an upgrade. Easy bolt on?

This is the one I got.
Likely a Brembo 20.B852.30.




Unfortunately, it's visually identical to a 32mm bore unit, as far as I've seen, so you'll have to get a measurement confirmation from a used parts seller.

Same bolt pattern at the mount.

Side mount bleeder and banjo bolt, way better than top mount IMO.
So you'll need to alter the hose if you're converting a Monster.

You can run banjo or bleeder in either hole, so you could put one on .... an old Triumph, left side

[koko64]

Thanks. That's a good option

[Howie]

I have changed the fluid along the way, but I'll see/photo what it looks like 

Since it is your bike I have no doubt the fluid id nice and amber.  Gunk still accumulates in the cylinder over time.

[stopintime]

In my rebuild kit I (probably) had two small (guess 7-8 mm) brown O-rings. Also two new bleed nipples and two bronze washers...  I now only have one brown O-ring. Are they for the bleed nipples?

30/34 '996' calipers.