The Ultimate A -vs- S -vs- M Caliper Thread
 

As if I wasn't having enough problems with my alternator this week, I start in on the brakes tonight, and now I want a definitive answer and also to collect the info for those that will need it.

I performed searches, but there seems to be conflicting info here, so lets settle this once and for all!

S-calipers: Alloy..easy right! Non-magnetic..hardline connecting both sides of the caliper..

Like this:

http://forums.pelicanparts.com/uploads/s-caliper.JPG

M-calipers: steel, 3.0 inches between the mounting bolts, 62 MM pad width (2.44)

Sorry, not picture, but there is one on Bill V's webpage, perhaps he will chime in and post the picture.

A-calipers: steel, 3.5 inches between mounting bolts, 73 MM pad width (2.83 inches)

Like this:

http://forums.pelicanparts.com/uploads/M-caliper.JPG

As far as I can gather, there were varying widths to the calipers too! So confusing, right? Bill V's webpage is excellent for brake information. Check it out (Bill, I hope you don't mind.)

http://forums.pelicanparts.com/great-lakes-us-il-mi-mn-oh-wi/109106-chicagoland-quigs.html#post794876

So, if I'm right, then the pads that I ordered today with fast delivery..sorry Wayne, Pelican did not have any in stock...from the other PP store won't work? Dang it all to H...this is a bad week! I checked and checked, and even had the phone guy check at PP, but until I got the wheel off to measure..I thought I had M calipers, but as it turns out I have A calipers! SO I'll have to fix this in the morning. Good thing is I have more pad surface, bad..I have to spend more money!

So anyone need M caliper Ferodos? :( mofo world is so cruel to me!

Now! Please, Bill, Warren, JW..all you more knowledgeable guys, post here and lets prevent this from happening again (esp. for lazy, unorganized boneheads like me).

A/front/3.5/10mm pad

S/front/3.5/13mm pad

M/rear

One more thing, the casting numbers on my calipers are 282 on the outside halves of both left and right calipers, but the inside casting number for the passenger side is 21 while the driver's side casting inner is 22.

Edit: I should clarify that I my car (as do all 69-83 911's, right?) have M calipers in rear.

That's fine for the rear, but I thought my front calipers were M's as well! Doh! They are A calipers!

Front calipers can be A, S, or M on the 69-83 cars.

Thanks, Ron. You want to fly out and help me this week? Free room and board. :D