I've just got my late ('76) front brake calipers back from being rebuilt but I don't know which is the left (drivers) side and which is the right (passenger) side.
I can see a difference in that one of the bleed screws is recessed, does this go to the top or the bottom?
Picture attached.
Please can all respondents agree, I don't need anymore confusion!
Click to view attachment
Full Version: Front Brake Caliper Identification
Calipers were designed to be interchangeable. The secret is the direction of the pistons in the caliper, 20 degree angle goes to top. Pistons should have clip retainer. It always goes to the top
@flatsix
This is the piston orientation. If not installed correctly the piston tops will wear at an angle.
This is the piston orientation. If not installed correctly the piston tops will wear at an angle.
It appears as if those were rebuilt using the incorrect pistons. As the posters above me have pointed out, the pistons should have a cutout over about 30% of the face that is designed to reduce leading edge bit of the pad to prevent noise.
The pistons that your calipers have appear to be flat, with no cutout.
The OEM pistons used an anti-knockback mechanism along with a pin in the caliper casting to pre-load the pads a tad bit against the rotor. These are not available anymore and if a piston needs to be replaced due to rust or pitting, a cup type piston is typically used and the pin removed from the caliper....these work just fine as long as the wheel bearings are adjusted correctly.
Here's what the correct replacement should look like.
https://www.ebay.com/itm/284791766992
If your pistons are flat (looks like it from the picture, but they might be oriented wrong and hidden)...they'll still work OK, but you may have some noise.
The pistons that your calipers have appear to be flat, with no cutout.
The OEM pistons used an anti-knockback mechanism along with a pin in the caliper casting to pre-load the pads a tad bit against the rotor. These are not available anymore and if a piston needs to be replaced due to rust or pitting, a cup type piston is typically used and the pin removed from the caliper....these work just fine as long as the wheel bearings are adjusted correctly.
Here's what the correct replacement should look like.
https://www.ebay.com/itm/284791766992
If your pistons are flat (looks like it from the picture, but they might be oriented wrong and hidden)...they'll still work OK, but you may have some noise.
Wrong pistons. Cheap Chinese seal kits (original ATE kits don't have the dust boot clips on the outside, they're integrated in the dust boot).
Pistons should have the knockback mechanisms in them that "knock" the piston "back" out toward the rotor. This keeps a higher pedal. The cup style pistons are for "booster circuit" cars. Boosters keep a residual 2-3 psi on the system hence not needing the "knockback" mechanism.
Regarding the seal kits; your dust boots should fall apart within the first year. Sorry to be a Danny Downer, that's just what you get with cheap rebuilds.
To answer your original question; we treat the recessed bleeder as the top bleeder and align our pistons accordingly (your pistons are, at best, aligned improperly). That would mean the caliper on the left is the right side caliper and the caliper on the right is the left side. As mentioned, they can be universal but the pistons should be positioned properly. If you use those, it's probably best to blow the pistons out and position them properly. The image Bruce posted above is one I added the green line on to show people how to orient the pistons properly without a fancy tool. Pay attention to the notch in the piston and the line representing the meridian line of the pad cavity. While you're at it... trust me, get the proper ATE seal kits. They're around $24.00 each and it will be money well spent. The cheap ones do not have anti-ozonates in the rubber and they will crack, fail and disintegrate in a few short "months".
I'll let 30 post copy-cat guy who uses cheap Chinese seal kits and Home Depot fasteners weigh in below...
Pistons should have the knockback mechanisms in them that "knock" the piston "back" out toward the rotor. This keeps a higher pedal. The cup style pistons are for "booster circuit" cars. Boosters keep a residual 2-3 psi on the system hence not needing the "knockback" mechanism.
Regarding the seal kits; your dust boots should fall apart within the first year. Sorry to be a Danny Downer, that's just what you get with cheap rebuilds.
To answer your original question; we treat the recessed bleeder as the top bleeder and align our pistons accordingly (your pistons are, at best, aligned improperly). That would mean the caliper on the left is the right side caliper and the caliper on the right is the left side. As mentioned, they can be universal but the pistons should be positioned properly. If you use those, it's probably best to blow the pistons out and position them properly. The image Bruce posted above is one I added the green line on to show people how to orient the pistons properly without a fancy tool. Pay attention to the notch in the piston and the line representing the meridian line of the pad cavity. While you're at it... trust me, get the proper ATE seal kits. They're around $24.00 each and it will be money well spent. The cheap ones do not have anti-ozonates in the rubber and they will crack, fail and disintegrate in a few short "months".
I'll let 30 post copy-cat guy who uses cheap Chinese seal kits and Home Depot fasteners weigh in below...
QUOTE(Eric_Shea @ May 2 2022, 07:12 PM) 
Wrong pistons. Cheap Chinese seal kits (original ATE kits don't have the dust boot clips on the outside, they're integrated in the dust boot).
Pistons should have the knockback mechanisms in them that "knock" the piston "back" out toward the rotor. This keeps a higher pedal. The cup style pistons are for "booster circuit" cars. Boosters keep a residual 2-3 psi on the system hence not needing the "knockback" mechanism.
Regarding the seal kits; your dust boots should fall apart within the first year. Sorry to be a Danny Downer, that's just what you get with cheap rebuilds.
To answer your original question; we treat the recessed bleeder as the top bleeder and align our pistons accordingly (your pistons are, at best, aligned improperly). That would mean the caliper on the left is the right side caliper and the caliper on the right is the left side. As mentioned, they can be universal but the pistons should be positioned properly. If you use those, it's probably best to blow the pistons out and position them properly. The image Bruce posted above is one I added the green line on to show people how to orient the pistons properly without a fancy tool. Pay attention to the notch in the piston and the line representing the meridian line of the pad cavity. While you're at it... trust me, get the proper ATE seal kits. They're around $24.00 each and it will be money well spent. The cheap ones do not have anti-ozonates in the rubber and they will crack, fail and disintegrate in a few short "months".
2-3 PSI will accomplish nothing...normal cup pistons work fine in any caliper if the wheel bearings are adjusted correctly. The 42mm piston has 2.14 sq/in of surface area. Do you think 6lbs of force will push the piston through the seal? no...it won't.
As far as the boots lasting less than a year? Gotta call BS on that. I tear apart calipers all the time (did a set a few weeks ago that I installed on MY 914 20 years ago that were rebuilt with aftermarket kits 20 years ago and the boots were in fine shape. New owner broke a bleeder, which is the only reason they came back off the car.) where the boots are in fine shape. Many of these boots are made in china.
The boots on the late calipers pictured above are simply the early boots, not the late boots, so they'll likely pop right off the caliper if the pads approach "worn out" because they don't have the bellows to allow the pistons to extend as far as the late pistons need to between new and worn out pads. Realistically, nobody is putting 15K miles a year on their 914 anymore I don't think...so they'll likely never wear out a set of pads anywhere close to the halfway point (unless they're on the track)...so those boots will probably be just fine, even though they're not "correct".
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