Source for caliper pistons??

[Dirtcrasher]

Any updates on sourced parts??

In measuring an 85 front and an 85&86 rear.. The front 250r pistons are .001" less than the rears in diameter. The difference must be due to the expansion if the steel being greater. Aside from the parking post the rear pistons are almost .035" shorter in height.

Why not just use the front phelonics in the rear, shave them down .035" and enjoy the weight savings..

Long read but hopefully helpful...

I wonder if the measurement difference your getting is just because steel is harder than phenolic and the micrometer tip just bites in a bit more, or did you use calipers? There very well could be some thermal expansion going on with that material. How did you come up with a .035 difference for the rear?? Did you mean .039 or 1MM?? Doesn't matter, just trying to be on the same page as everyone. Anyway, it's always hard to hold any type of plastics in a lathe and I don't have a phenolic piston in front of me but I believe the phenolics are solid with a short relief in one side but it's not like the "bucket" of a steel caliper. A bucket you could hold the inside on a lathe and turn off 1mm or whatever the spec is, but a Phenolic, being a harder type of plastic that flexes far more, there would be no way to hold one and take off that whatever >1mm dimension and half and half always sucks.

I don't know of any Delrin being used by Honda in their calipers but some other manufacturer may have used it. Although, It has self lubricating properties which means it has absorbed oil and gives it up when it gets warm, hence why Delrin is considered "self lubricating", so brake fluid wouldn't be too friendly with it. But the material I priced, and that was with me being aware that I'd try to lose less than 4mm's when cutting them off to length after machining, was still expensive.

The dudes selling the rebuild kits must be using K + L or a similar Japan or Taiwan vendor because it's a good kit, or it seems to be. The rubber stuff and the bolts/pins are very Japan looking rather than China, but I could be wrong there too!!?? The new calipers and masters that are cheap are definitely China, we all know that buy now but someone is buying 18$ front master cylinders - crazy... Unless you see "Nissan" avoid whatever they try to sell you for a replacement, it's better to rebuild your OEM stuff. Most of our OEM stuff is bad because any of us hoarders - we don't always use all of them and or the parts all year round, or they sat for many many years, but what I'm saying is that often none of the metal parts are out of spec, the OEM stuff typically needs a total tear down and rebuild with all new rubber stuff, pins and bores cleaned up, caliper painted or coated, new bleeder and cap, and they're like new. I think I mentioned I bought a China caliper for 40$ just to see the guts. They seemed to be a drawn cup steel piston that was then coated but the diameter was weird, not .001 either, more like .05 or half of on mm different diameter. The China brake castings are very rough, there is no secondary operation to ensure the castings are clean. They blast that casting out quickly, they must cut half the operations out of the fine tuning and finish. The amount of cast aluminum barely hanging on was quite a bit, the finish on every piece is rougher, less round, poorer tolerances, misaligned and I doubt the steel and aluminum were quality metals either.

The pistons on Ebay (2) for 49.99 must also be from K + L , Parts Unlimited or somewhere similar, IDK what those guys pay. If we aren't dealers we may still have to pay quite a bit ourselves even if we could use them. I'd turn them on a lathe but I'd need exact sizes, thermal expansion rates (unless we figure out whether that matters) and a much longer piece of material that's much more expensive. I think I priced it off of an 8" or 12" piece and I could not make them inexpensively.

Anyhow, I look at valve buckets and there cost and I say to myself that they aren't made too much different than a brake caliper piston!! Who knows...

[Allstock]

Were these oem pistons or did someone make them? Are you sure they were Delrin and not Phelonic? The Phelonic can appear to be a hard plastic. It is what was used on the oem 85 fronts.

As for measuring I used a micrometer. I measured 2 sets of rear steel pistons and 1 set of front phelonics (oem 1985). The difference of .035" was measured with a caliper as it is greater than the one inch limitation of the micrometer I have on hand. I wasn't concerned with exact accuracy on that measurement anyway because that difference was in the height it would not be an issue except for pad and rotor thickness as to whether or not the piston could sit in the caliper deep enough to allow the pads sufficient gap for the rotor without dragging. In addition, it can be shaved down (insert side) without precision (except for enough to cause side loading in the bore) as it has no bearing on the precision of the O.D. that the seal rides on.

[oldskool83]

like i said, i use trx450r ones, yes they are phenolic and about never wear out. A lot of old XR ones are the same. Go on partzilla.com look up the part number, find the machine go buy what you need.