911 M front caliper piston sizes, Same as 914-4 caliper pistons? Options

[phantom914]

I know that the M calipers allow the use of a vented rotor, but are the piston sizes any different than the 914-4 caliper? (speaking of front calipers)


Andrew

[davep]

914 front are 42mm, 911 front are 48mm. I believe that the 911 front vented have caliper spacers between the housing halves. Some early 911 were non-vented and of course did not have the spacers. I do have the spacers required to convert the 914/4 calipers, but you might be better off just getting the 911 caliper.

[phantom914]

Thanks.

Wow, 48 versus 42. That's a 30% change in area. It would probably be better to use the 19mm master cylinder with the M caliper.


Do you know the piston size for rear 914-4 and M calipers?


Andrew

[davep]

I have discussed this at length in other threads on brakes.

The 914 rear is 33mm, the 914/6 rear and 911 up to about 77 were 38mm. Later 911 got the 42mm rears.
The 911 rear and the 914 front are very similar since they are all "M" type parts.
The 911 front is a larger casting than the 914 part, but they will interchange. The 911"S", 911"A" and the 911"M" calipers all had 48mm pistons. The "A" and the "S" had bigger pads than the "M". One could almost say the designations were more in reference to the pad sizes than the caliper sizes.

The 914 and 911 fronts had different piston sizes but the same pads.

[phantom914]

Thanks.

I have discussed this at length in other threads on brakes.

Sorry. I should have just done a search.


Andrew

[davep]

No need to be sorry. I just know that there have been four or more threads on the basic subject in the past few months. I am very aware of it because of my strong interest in brakes. I've leaving now to pick up the parts from the machine shop for the 914/4 rear vented rotor conversion. I'll take a brave pill and sit down before he tells me the cost.