914 calipers 4 and 6?

[InGearguy]

I thought these were from my 70 914/6 but it appears now perhaps a set of rear calipers from a 4 cyl and larger calipers from the front 6 cyl? Any help to clear up the confusion? Thanks in advance.

Happy Motoring,

Alan

[Dave at Pelican Parts]

The only practical difference between the -4 and -6 rear calipers is the piston diameter. The -6 pistons are slightly larger than the -4 ones, but I do not remember the numbers.

Most 911 front calipers are designed to go over vented rotors, which are much thicker than the solid rotors that the 914-4 came with. The 914-6 used 1969 911T front brakes, which were vented. Quite a few other 911s used the "M" front caliper, which is the same as the 914-6.

It looks like those front calipers are wide enough for vented rotors. They don't look like the aluminum "S" calipers, so they are either early "M" calipers or later "A" calipers. Measure the mounting bolt spacing, the M calipers are 3" (on center) while the A calipers have 3.5" spacing.

It is possible that they are from some other vehicle; I am not good enough to tell them apart on sight.

Eric at PMB Performance in Utah is probably the best single person with 914 brakes that I know of. He would be able to tell you. He would also be able to rebuild those rear calipers--and judging by the uneven brake pad wear on those, they need it.

--DD

[J2Hanson]

I believe the front ones are off a 6 cylinder car. The vented rotor version has a spacer between the halves. The rears are definitely for a solid rotor.
John

[mepstein]

The rear are 4's

[Dave at Pelican Parts]

How can you tell?

--DD

[djpateman]

Easy to tell the difference. Look at the top side view and note the casting differences. The 914/4 has a "backbone" that the 914/6 does not have. Also the 914/6 is as wide as the M front calipers since it takes the larger M pads as do the fronts.

[Dave at Pelican Parts]

Thanks! It could be handy to be able to tell.

--DD

[mepstein]

Originally Posted by djpateman

Easy to tell the difference. Look at the top side view and note the casting differences. The 914/4 has a "backbone" that the 914/6 does not have. Also the 914/6 is as wide as the M front calipers since it takes the larger M pads as do the fronts.

Eggzactly - The 4's have a bump the 6's are smooth.
If you go onto pmbperformance website you can see each model porsche caliper identified properly.

[Scott Walshaw]

Thought these pics from my recent post would add some additional info...fronts are "S" aluminum calipers and the rears + rotors were NOS 914-6 GT brakes...note spacer and vented rear rotors (+ larger pads)...

[Eric_Shea]

Late to the party but, the original poster has late model 914-4 rears and 911 rear M-Calipers not 914-6 front calipers.

Also, the difference between the -4 and the -6 calipers is more than just the piston. The basic caliper is the same as a rear 911 with 38mm pistons and the pads are larger FMSI D31 size. In fact, the nose section of the caliper is the same. If you look closely at the 911 version, you'll see a ring in the casting where they cut the adjuster hole. It obviously have the integrated handbrake and yup, the easiest way to tell the difference in pictures is that spine which is smooth.

Also... The fasteners have been installed backward in the 911 rear calipers shown above.