BMW calipers explained

[sammygon1]

OK, I promised a post about my BMW caliper upgrade awhile ago.
Here it is:

I wanted vented rotors on my '69 912-6 so I did some searching and became interested in the BMW caliper mod. The calipers are from a EDIT: '77 BMW E21.

The main reason I chose the BMW calipers is because I'm a poor grad student and didn't want to shell out the cash to upgrade my struts to the 3.5 inchers.

The mod was simple. The calipers bolted right on to the 3" ears. The only thing I had to do was bend new hard brake lines for the calipers.

The benefits:
I now have vented rotors.
The calipers use roughly the same size pads as the aluminum S calipers but don't flex like S calipers are said to and I didn't have to upgrade to 3.5" struts.
They were cheap, I picked up the calipers for $100.00 from a local wrecking yard.

Pics:


The ATE BMW calipers look almost the same as the Porsche ATE calipers.



Pic of new hard brake line. Only took about 5 minutes to bend with a standard tubing bender. Yes I know I need new sway bar bushings.

Overall, I'm very happy with the mod. I recommend this to anyone who wants larger brake pads and wants to run vented rotors but doesn't want to switch to 3.5" struts.
-Sam

[Dixie]

Looks good!

[evill]

I did that exact swap on my 914 years ago. The performance was great.

1 caveat - The top edge of the pads overhang the rotor a slight amount. As the pad wears the outer diameter of the rotor will embed it self into the pad. The pad will eventually rub on the edge of the rotor by the vent holes. This will cause the brakes to get grabby and possibly pull to one side or the other. When I discovered this, I simply chamfered the top edge of the pads where this overhang occurred. It solved the problem.

Ed

[Early_S_Man]

Sam,

What is the diameter of the pistons in those BMW calipers, and what model[s] BMW are they from?

[sammygon1]

Originally posted by evill
I did that exact swap on my 914 years ago. The performance was great.

1 caveat - The top edge of the pads overhang the rotor a slight amount. As the pad wears the outer diameter of the rotor will embed it self into the pad. The pad will eventually rub on the edge of the rotor by the vent holes. This will cause the brakes to get grabby and possibly pull to one side or the other. When I discovered this, I simply chamfered the top edge of the pads where this overhang occurred. It solved the problem.

Ed

I didn't notice this on my install but will keep an eye on it. Thanks for the heads up. Did you use BMW brake pads or S pads with the calipers?

[sammygon1]

Originally posted by Early_S_Man
Sam,

What is the diameter of the pistons in those BMW calipers, and what model[s] BMW are they from?

Warren,
The diameter of the pistons is the same as the original M calipers. Using Bill Verburg's brake page the M calipers are 48mm. So no real gains there but the bias remains the same.

The calipers came off a EDIT: '77 BMW E21. This was the only year that used vented rotors.

[makaio]

Sam, the 77'-83' 3 series BMW's are actually E21's not E30's. Just wanted to point out if anyone is going parts hunting in the local wrecking yard.

[sammygon1]

Matt,
You are right, my mistake. It's the E21 model not the E30 model.
Thanks,
Sam

I edited my posts to state E21 for clarity.

[evill]

Originally posted by sammygon1
I didn't notice this on my install but will keep an eye on it. Thanks for the heads up. Did you use BMW brake pads or S pads with the calipers?

Sam, I used the S pads on mine. The overhang is slight and hard to notice. After you have some miles on them, pop a pad out and look at the wear pattern. There may be a narrow arc cut in along the top edge of the pad if the overhang is the same as it was on my car.

Ed

[sammygon1]

Ed,
I used the BMW pads on mine so hopefully there wont be any overhang but I'll have to keep an eye on it.
Thanks,
Sam

[chris68912]

what brake rotor did you use?