General Brake question about pins that caliper floats on

One of the pins has a plastic sleeve, I don't understand the reason for this. On mine (1982 GPZ550) the grease lost all the oil, I assume baked away from heat, and ended up expanding which prevents the caliper from sliding back out after the brakes are released.
The other pin which is just metal, no sleeve, is fine. Seems to me whatever reason the one has a sleeve is also a problem, plastic is a good insulator preventing heat transfer.
Anybody replace the sleeved pin with plain metal? Seems to me this would be more reliable, although not understanding the purpose of the sleeve, maybe there is a good reason for it.
The problem is, once brakes are applied, caliper slides in but fails to slide back out since the plastic sleeve binds. Sure a new sleeve will be the ticket, but if it happened once ... it might very well happen again.
Anybody have experience with this?

Are you asking about the sleeve, reference number 92028?

www.partzilla.com/catalog/kawasaki/motor...-kz550-h1/rear-brake

Does the sleeve slide easily by itself, in the bracket?
I do not think that grease could cause the sleeve to swell. If the grease is all dried up, it may have left behind some residue that is causing the binding. Both pins and the pin bores in the bracket should be very clean and lightly greased with genuine brake caliper grease.

The sleeve is designed to cause drag inside the pin bore to sorta "anchor" the rear (upstream edge) of the piston. This allows the downstream edge of the piston and pads to grab first. (The disk is the "stream".) This prevents chatter and squeal.

You have to use a silicone grease designed for brake use to prevent a reaction with the rubber. I usually use SIL Glyde.

The FSM calls for PBC grease: Poly Butyl Cuprysil grease.

I use heavy black moly caliper grease. It's designed to withstand high temperatures.

I believe that sleeve - which is usually made out of rubber on most vehicles - is there as an anti-vibration device. Since there is a little clearance in the pins, without it the two sides of the caliper can rattle against each other.

I have heard of them swelling and binding, but never seen it myself. Some people just remove them. My KZ still has them as they were not binding. The way I see it, if it's to prevent vibration, enough think grease should stop them from vibrating too, and prevent corrosion at the same time.

Like Nessism, I've always used moly grease for the brake pins.

TexasKZ wrote: Are you asking about the sleeve, reference number 92028?

www.partzilla.com/catalog/kawasaki/motor...-kz550-h1/rear-brake

Does the sleeve slide easily by itself, in the bracket?
I do not think that grease could cause the sleeve to swell. If the grease is all dried up, it may have left behind some residue that is causing the binding. Both pins and the pin bores in the bracket should be very clean and lightly greased with genuine brake caliper grease.

Yes, that's the part.
I didn't say the grease caused the swell, lack of lubricant IMO did (I just retired after 44 years as a mechanical engineer, fault analysis is part of the job).
The only thing left of the grease is the "wax" the oil rides in a grease.
The plastic is expanded, I suppose it is possible a grease incompatible with the polymer in the plastic caused it to swell, but it sure looks like excessive heat to me.
The grease in the other pin looks brand new. The difference between the two is that metal to metal is a much better conductor of heat than metal to plastic.
Once the oil in the grease was gone, the "wax" is not a good lubricant, it is only there as a carrier for the oil.
So once the oil is gone the "wax' only exasperates the heat problem. Heat by itself can cause expansion of the polymer. There isn't much room for expansion, once it does the caliper doesn't move in and out as it should, which is exactly the problem I was experiencing.

loudhvx wrote: The sleeve is designed to cause drag inside the pin bore to sorta "anchor" the rear (upstream edge) of the piston. This allows the downstream edge of the piston and pads to grab first. (The disk is the "stream".) This prevents chatter and squeal.

You have to use a silicone grease designed for brake use to prevent a reaction with the rubber. I usually use SIL Glyde.

The FSM calls for PBC grease: Poly Butyl Cuprysil grease.

I'm glad you said upstream, because rear isn't quite right, it's really the lower (although yes, also rear most) and consequently the leading edge, or upstream part of the pad contacting the disk.
Just as an experiment I'm going to toss the plastic since it is no good anyway and check out how it operates without it.
If it doesn't chatter, I'll just use the sleeveless pin.
Being that I used the same grease in the other two calipers and it also appears the oil is close to dissapearing, while the "wax" remains, I am going to stick with heat as the culprit, not incompatible grease. Or maybe it was just crappy grease, lol, supposedly it was a high temperature moly for wheel bearings