I'm in the process of putting 911 brakes up front.
I have 2 sets of calipers and noticed one at has a wider space between the 2 caliper halves than the other set.

Are there different thicknesses of rotors or what is the purpose and how do I know which one to use?
Just test fit and use prices of elimination I suppose?

What rotors are you using? vented or not?

Easiest way is to ask Eric at PMBPerformance.

OR
Stick pads in there, use clamps to push the pads all the way open...measure between pads.
Do both calipers
do both rotor types.

Rich

I'll be using vented rotors.

Guess I will mock up the assembly

No expert here, but I believe, pre 78 are 24mm and post 77 26mm, but not exactly sure. But I am sure the earlier rotors were a bit thinner.

I am pretty sure your set up is a 74’ Bilstein, with A calipers. Then the other set is a wide A. Again, hopefully some more people chime in.

Early is 20mm, Carrera is 24mm

I knew someone knew the deal!! Ha!

Do those calipers have the same spacing - 3” or 3.5”
What front hubs are you using?
Eric is the one to ask regarding all the compatibility.

All 3.5”
Maybe Jeff will chime in…..not sure if he has different parts from what I had sold him.

Nope still same parts you sold me!
Getting closer to putting out all together!

So 7.2mm spacer = 24mm gap in caliper for rotor
11.2mm spacer= 27.5mm gap in caliper for rotor

My rotor thickness measures just over 20mm.

There aren't different hat heights on the rotor are there?

Next question
Should this inner bearing slide on or does it need to be driven on slightly?

another question
the spacers between the caliper halves, should those stay matched to the calipers or can they switched?

If caliper #1 was a wide and caliper #2 is normal is it ok to swap the spacers and make caliper #2 the wide one?

Bearings just drop into the hub.

Spacers can be switched to at least some extent. For example, I gave Eric a rear M caliper and a 914-6 caliper. He used the spacer and hardware from the M caliper to remake the six caliper into a 914-6GT caliper. But again, I would go to Eric for exact specs.

One more 911 caliper question.

Are there rights and lefts on the front Wide A calipers?or are they interchangeable?

I would assume in order to get the bleeder on the top when mounted.