Upgrade "M" calipers with BMW 320i calipers?

[jameshtaylor]

Ran across this interesting Pelican thread while pursuing an upgrade involving swapping my "M" calipers for "A's", with 84-89 struts and rotors. Anybody swapped an M caliper for one from a BMW? Awfully cheap, and gets you everything you get from the Carrera swap except the 20% thicker rotors.

http://www.pelicanparts.com/techarti...W_calipers.htm

[M491]

I have actually done this. It's basically a direct swap, very easy to do and makes a big diffference in braking. There should be no problems with the master cylinder, and the bolt spacing is the same (3 inches). The only issue is that, if you have vented rotors, you have to make sure to get the type of calipers with the spacers in the middle, which makes the slot broad enough to accept the thicker, vented rotors. Most of these calipers that I've seen will work on non-vented rotors only because they were used with thinner (nonvented?) rotors and do not have the necessary spacers.

[Neunelfer]

That thread is about swaping 914 calipers with 43mm pistons with BMW calipers with 48mm pistons. 914 Calipers are not M-Calipers

Odd to put a 48mm piston ATE caliper in place of another 48mm pison ATE caliper (M-Caliper)

I am against that mod on a 914. This is not what I call an "upgrade". You're working with the same solid rotor you would have with the stock pistons. You're simply heating it up and warping it faster (if you're doing any type of performance driving). A stock 914 disc brake system, as simple as it may seem, is enough to throw your passenger through the windshield given the fact the system is in proper operating condition and has great pads. A simple 911 braking system is the same. A set of Porterfield P4S pads is much cheaper and much less labor intensive than mis-matching your brakes and components.

Most people who think they are upgrading and feeling big differences went from a $hitty old worn, sticking 914 or 911 system to a new BMW system. We've done a "lot" of testing and asking professional drivers and the fact is, there has been no brake fade ever with one exception -- Serious Road Racing.

That being said... there are some BMW 5-Series calipers which would effectively give you the same pad size as the S-Caliper/A-Caliper (they all use the 48mm pistons BTW) and mount on a 3" mount. It would be the same as the A-Caliper/3.5" strut swap (SC system with the 20mm rotor). This may be what M491 is referring to.

James, are you road racing your 911?

With struts and calipers so readily available... I think swaping a 3.5" strut assembly is the best bet, that's my $0.04 worth.

[M491]

Yeah, that's what I was referring to. Sorry for the confusion.

[jameshtaylor]

So its a 5 series BMW which might offer an ATE A or S size pad in a caliper with 3" centers, not the 320i?
I'm probably headed toward the Carrera strut and caliper mod, not this one, but I found it an interesting and possibly very inexpensive option.

[M491]

Wait a moment... I thought there was also a pre-1974 BMW 320 Ate front caliper that had bigger pads and a 3" on center bolt spacing that worked well on the 1969-73 911. Were these actually 5 series calipers? I believe it would make sense that these calipers, for the simple fact that they would lay a bigger friction patch on the rotors, would be an upgrade over the smaller M calipers (1969-73 911). Maybe I'm wrong... Dunno. Anyone know more about this?