Topic: Why?? - Brake piston CB 750

[Lars]

This is my first CB 750 K4. After struggling to get brake caliper A and B apart due to a bad bolt, I finally succeeded, but only after cutting caliper B to pieces so I could get a good grip on the bolt.

After getting the piston out, I was wondering of the construction of it. Why is the piston made hollow and with a lid? To have less weight and move more freely back? I am going to mount the piston back on today, anything in particular I should pay attention to? The lid? The lid's contact on the backside of the pad - any grease. I am familiar with the CB 550's and CB 350 F's, but on this one I find it wise to ask before reassembly.

Lars

[Alan F.]

Hi-temperature grease on the out facing side of the piston, the side of the lid that contacts the piston, the face of the lid, and the back of the brake pad that contacts the lid.  This can help reduce squeal.

don't get any on your brake pads.  Regular grease won't do, this had to be the super hi-temp stuff.
I'm not sure if it's available as 'brake parts assembly lube' or not.   Anyone?

[Lars]

OK, thanks, I have the caliper grease.

Do you know why the piston is constructed hollow and with a lid?? Anyone??

[Steve_K]

I would guess that if it was solid the oring would have more problems pulling back.  I made a stainless steel piston and I did not make it hollow.  It was quite heavy compared to the stock.  I next made one hollowed out without a lid over the opening.  Much lighter.   Someone on  the forum makes pistons out delrin or some other plastic material.
Someone else may have thoughts on it too
Steve

[Duke McDukiedook]

Read This

[Lars]

Thanks for the link, usefule reading.

Had a comment yesterday from my friend Ellis Holman regarding why the piston is hollow, here you go:

"Piston is hollow to reduce the amount of heat transferred from the pad to the brake fluid. This is meant to help reduce the tendency of the brake fluid to boil. When the brake fluid boils, brake fading is experienced."

So now we know