what's the difference between "S" & "M" calipers
 

hello, pelicanites. pardon my ignorance. i would like to know the difference between the two calipers. what gives? how come it cost more to maintain and replacement for "S" than "M"? is it just by wideness or aluminum? please enlighten me with your knowledge. thank you.

I believe the "S" is made from Al and the "M" is steel. And the "S" has larger pads. So they are quite different. Do a search here for more details.

The "S" is thus lightweight but some say they flex more and have not the same crisp feeling compared to the Carrera callipers.

Cheers,
Ingo

S are 1 piece aluminum calipers used on the front of sport 911s in the late '60s and early 70's. 3.5" axial mounts, 2x48mm pistons
http://forums.pelicanparts.com/uploa...1183483234.jpg
A are 2 piece iron w/ a spacer between the halfs, they replaced the S calipers in '76, same size pad as S(some versions are thinner), same 3.5" axial mounts, 2x48mm pistons
A on left, M on right
http://forums.pelicanparts.com/uploa...1183483389.jpg
M are iron 2 piece w/ spacer between the halfs, used on the back of all 911 '69 - '83, 2x38mm pistons

From '84 -89 the spacers on the A&M were widened by 4mm to make wide A&M and the wide M pistons grew to 2x42mm

There were also several other versions of the M variously used on front and back often w/ thinner rotors and also an L.

thank you both for the information. although, i did search over here. i didn't really find the answer. thanks for the pics.