Renix to HO front axle, do i need a HO master cyl?

I just switched over from my 87 30 non disco to a 92 30 with abs and the larger u-joints. I ditched the abs switch and bought 92 rotors, pads and took the calipers from the junkyard with the axel. The calipers will not fully close on the rotor. Do i need to convert to a newer master cylinder? i'm thinking the newer master may have a bigger valve in it to pump more fluid to create more pressure to push the piston out.

Gah. I have to figure out where the Hell my spreadsheet on brake parts went before I can dig into this, but my first impression would be No, you don't need to swap anything. I know there was a change in the rotors, and the calipers (I think) changed as well - but they used a similar bore size.

If you're using JY calipers, did you inspect them thoroughly? It's possible, for instance, that there may be a "rust band" that is blocking the piston from extending fully. No trouble with swapping the axle proper - but I tend to use "new remans" or new parts entirely when swapping out brakes hydraulics, just because I'm cranky that way and tend to think of brakes as fairly important...

Oh - and it's not a "valve" that moves fluid - a valve controls the flow of fluid (can be used to meter fluid flow volume, or cut it off entirely.) The critical factor in moving fluid in hydraulic systems is the size of the piston (volume) and force applied (pressure.) Just to let you know...

The axle and calipers are from an xj. The rotors, calipers and brake pads were different per newer application. I did not inspect the piston bore for a rust band. I was able to push the piston back no problem when installing the pad, I assumed it was fine from that. I did check on part #'s for the two masters and they were different. I'll check the caliper bore tonight.
Oh and thanks for the term. lesson john. I always walk away with some usefull piece of tid bit after reading your comments.

Year should not matter, something is wrong with your caliper(s).

I have a 92, with 87 knuckles and calipers, 92 housing and 2000 rotors and hubs. Everything is peachy.

The only thing that changed through the years is the thickness of the hub and hat depth on the rotor (so those two have to match year) and the caliper mount (caliper+knuckle has to match year).

-Cal

sweet thanks cal