Topic: Brake Caliper Piston Identification Mystery

[M Schepis]

Decided to overhaul the front brakes on my 1976 K6 . In pulling the piston something unexpected popped out and has me stumped. I was expecting a hollow piston with a seat pad. Instead I found a solid piston and no seat pad. Any ideas.
Thanks in advance

[bryanj]

Looks like it might be a stainless replacement

[Kelly E]

I've installed quite a few stainless steel caliper pistons and I've never seen a solid one before.

[M Schepis]

Yes, exactly. I measured the length and it corresponds to the hollow (piston) one, this create a problem because without the spacer (#17 above) thickness I think the caliper placement will be off center or at least the piston side friction pad.

[jonda500]

I used solid stainless steel pistons in all three of my bikes (cheapest option at the time) - they are exactly the same size as the original hollow ones so I assembled the parts exactly as they were and had no problems?
I have never seen hollow stainless pistons - they must be hard to make and expensive?
John

[M Schepis]

ok, I agree they are the same size but did you use the spacer that the hollow ones use ? if not, there would be a difference in the assembled length due to that omission of that spacer  (#17 "Seat Pad") ?

[jonda500]

I did put the nylon ring in - but the assembled length shouldn't matter as it depends how worn out the brake pads are and the piston simply sits further out?
John

[M Schepis]

What nylon ring are you referring to?

[Shtonecb500]

I think the nylon ring he is talking about applies to 500/550 brake pads, as for the solid 750 piston I have also used them and they were in there alone.

[M Schepis]

Thank you, I have been looking at this closely and have come to some understanding that might help others, especially with poor braking. The bikes that use this swinging cantilever style bracket for the brake caliper misaligns the actual caliper and pads with the face of the disc. The degree depending on level of wear of the pads. I noticed that the external pad mounts in the housing making contact on a high point on the pad backing plate. This allows the pad to self align and correct any misalignment with the disk. Normally, a caliper using a hollow piston would include a spacer (#17 pictured above) which incidentally has a convex face that contacts pad backing. This allows the piston side pad to self align against the disc surface as well. Not, using the spacer eliminates this effect and may cause partial contact of at least one pad during braking, reducing stopping power.
Just my thought if I'm totally out to lunch on this, please politely enlighten me.

[bryanj]

Nice idea but the pad in the piston side is always too tight a fit(usually have to remove paint round edge) to be able to self align with disc

[Don R]

 It seems that we are finding different parts inside our calipers. Domed spacers, plastic washers and nothing at all. It's been a few years since they were new and I'd guess nearly all of our calipers have been taken apart and freshened by now.

[bryanj]

They all had the nylon washer from the factory but it was like the steel washer between filter and spring, got lost first time taken apart

[M Schepis]

What is the "Nylon washer" that is being referred to ? Part #17 (45151300000) above appears to be metal in all references I've found in my search to buy one. If indeed they were once nylon it would be much easier to fabricate, but I would think heat from braking would affect it?
If anyone has a spare or can provide me the measurements of this part I would greatly appreciate it.

[bryanj]

Its not shown on that pic and from memory only came with a genuine Honda pad, note Honda pads were sold seperately not as a pair!

[M Schepis]

So that was in addition to the metal domed pad #17?

[bryanj]

Yes