Posted By: 68HemiB
Poll for brake guys - NOS caliper opinion UPDATE/photos - 05/09/09 03:45 AM
Intelligent people can disagree.
My buddy and I do not share the same opinion on a pair of NOS F body calipers. The calipers are obviously unused, and the brake inlet is still capped. Take the cap off, and all looks pristine down the hole. There is some shelf rash and very light surface rusting. Dust boots are soft and intact. Nothing scary in the visual inspection.
The problem? Neither piston will budge upon application of compressed air with a rubber-tipped snozzle.
Person A: This is not good. These calipers are stuck. 2.75 inch piston diameter means 6 square inches of surface area (Pi are ROUND, Cornbread are square), which at 120psi air pressure means they won't budge with over 700 pounds of force. We need to get them apart, inspect them, and likely rebuild them.
Person B: Nice math, Archimedes. So how do you suggest we get the pistons UNstuck?
Person A: Well, as any professional knows, you hook them up to the vehicle's brake lines, bleed them, and then use the M.C.'s pressure advantange to get them pumped out.
Person B: So, we'll go to the trouble of doing all that, without even seeing if, once they get unstuck, they even hold pressure? Why don't we just do all that, but see if they hold pressure, can be pushed back, etc., BEFORE we tear them down.
Person A: But they're STUCK now. That means there's something wrong.
Person B: But if they free up, and don't leak...?
Person A: They are a problem waiting to happen.
Are you person A or B in this case?
My buddy and I do not share the same opinion on a pair of NOS F body calipers. The calipers are obviously unused, and the brake inlet is still capped. Take the cap off, and all looks pristine down the hole. There is some shelf rash and very light surface rusting. Dust boots are soft and intact. Nothing scary in the visual inspection.
The problem? Neither piston will budge upon application of compressed air with a rubber-tipped snozzle.
Person A: This is not good. These calipers are stuck. 2.75 inch piston diameter means 6 square inches of surface area (Pi are ROUND, Cornbread are square), which at 120psi air pressure means they won't budge with over 700 pounds of force. We need to get them apart, inspect them, and likely rebuild them.
Person B: Nice math, Archimedes. So how do you suggest we get the pistons UNstuck?
Person A: Well, as any professional knows, you hook them up to the vehicle's brake lines, bleed them, and then use the M.C.'s pressure advantange to get them pumped out.
Person B: So, we'll go to the trouble of doing all that, without even seeing if, once they get unstuck, they even hold pressure? Why don't we just do all that, but see if they hold pressure, can be pushed back, etc., BEFORE we tear them down.
Person A: But they're STUCK now. That means there's something wrong.
Person B: But if they free up, and don't leak...?
Person A: They are a problem waiting to happen.
Are you person A or B in this case?
They will most likely be pitted to a point that no ammount of clean-up will save them. Cores got my vote. They're a dime a dozen!
But your caliper knowledge is better.. 
FWIW Glad the calipers looked good, sorry I wasted your time 
