Hi, do the AP Racing big front brakes for the E36 M3 maintain the factory brake balance? Or are they like some tuner brakes that make the brakes more front-biased and lengthen stopping distances?

TIA

Nobody has experience with these brakes?

I use them...not sure if they maintain the factory bias. I had trouble running them with the stock 325is boosted brake system. I have since switched over to an unboosted setup w/ tilton master cylinders and bias adjustment

I run 6 pot APs up front along with AP rear brakes - stock M3 master cyl and no bias adjustment. I am completely happy with it.

Vince

I run 6 pot APs up front along with AP rear brakes - stock M3 master cyl and no bias adjustment. I am completely happy with it.
Vince

Jack M. ran the 6 piston APs also in his C-mod car along with the AP 4-piston rear calipers (stock rotors in the rear). Same setup that Chuck Stickley uses as well I believe.

-Carlos.

Turn off the ABS, and you'll see the BIAS is totally off with these calipers.

Do you mean if the stock rear brakes are retained, or even with their 4-piston rears?

but I like the ABS :)

Do you mean if the stock rear brakes are retained, or even with their 4-piston rears?

With the stock rear brakes the BIAS is WAY OFF...

If you use these brakes, they are "ok" with ABS, they stop well, don't fade and have plenty of braking power BUT PEDAL FEEL IS TERRIBLE unless you go to dual masters with a balance bar.

Why do you need big brakes anyways? The 6 pot APs are awesome hardware but a bit of a pain. Few 17" wheels will with them, and bias out of the box is not good....

If you want better pedal feel, get dual masters first or get something that will work with the stock master cylinder.

With the dual masters and ABS, the setup however is AWESOME....does not get any better than that....

I don't need them but the car I bought came with them. I'm considering downgrading.

There's more to bias than piston area...you failed to consider rotor diameter. Larger rotor diameter results in longer torque arms, i.e. it takes less clamping force to create the same stopping force.

You're absolutely right, I completely forgot about radius. I have to go measure it.

There's more to bias than piston area...you failed to consider rotor diameter. Larger rotor diameter results in longer torque arms, i.e. it takes less clamping force to create the same stopping force.

Touche. But are you accounting for a larger rotor in the rear?

Here are the numbers:

stock AP 6 pot
piston area 27.1 25.1 cm^2
est torq arm 5" 5.75" (eyeballed with tape measure)

net gain increase of AP 6 pot is ~6.5% over stock.

PS Why do you say pedal feel is terrible with the AP 6pots? I have them and the feel is terrific, better than a stocker I remember as feeling.

Here are the numbers:

stock AP 6 pot
piston area 27.1 25.1 cm^2
est torq arm 5" 5.75" (eyeballed with tape measure)

net gain increase of AP 6 pot is ~6.5% over stock.

I made a little spreadsheet years ago to figure out what size pistons to get for some brakes I was spec'ing. I still have it and I can just plug in the numbers to get a better estimate.

Is the stock caliper a single piston that's 27.1 cm2?

Is the "25.1" for the AP 6 pot for all 3 pistons on one side of the caliper?

Yes and yes.

PS Why do you say pedal feel is terrible with the AP 6pots? I have them and the feel is terrific, better than a stocker I remember as feeling.

Total dead spot when you first hit the brakes...absolutely no feel at all...maybe if you have the rear caliper setup it matches up better, but with the stock master and stock rears its not very good at all.

Do you mean the first inch or so is soft, and brakes the car somewhat, before you hit the firm spot?

Need different size master cylinders if you want different pedal feel, and size the caliper pistons accordingly. Firmer pedal go up a click on MC size.

Are the pistons in those AP's changable for different sizes?

With the dual masters and ABS, the setup however is AWESOME....does not get any better than that....

QFT :alright

PS Why do you say pedal feel is terrible with the AP 6pots? I have them and the feel is terrific, better than a stocker I remember as feeling.

Give them some time, when mine were first installed they were great. Over time I believe they overpowered the rest of the system and progressively got worse to the point that I would have to double-pump the brakes to get them to bite....got a bit hairy there a few times :devillook

Then I switched to the system that Like2short was talking about and it is "braking nirvana" :cool

Yes and yes.

That's the problem right there, unless something is escaping me. With the oem caliper, you're pushing fluid on 27.1 cm2, while with the 6 pot, you're pushing fluid on 25.1 X 2 or 50.2 cm2.


Steve, are there actually calipers that have interchangable pistons? How's that done? Some type of sleeves?

Hmm, the feel on mine is excellent.

Another Drew, with the 6pot it's only 25.1 cm^2, not 50.2. No x2 factor. A single piston design is like having a floating caliper with a piston on either side. Thought experiment: take a floating caliper design with a piston on either side. If one piston gets frozen to the caliper, the braking force remains the same, and doesn't halve. The only difference is that the caliper begins to move with piston motion instead of staying put.


That aside, I think having smaller pistons but a bigger radius (like with the AP's), I think would yield a firmer pedal for a given braking force.

///M3Matt, I thought about what you typed, and I think you had a master cylinder problem, not an issue with the AP's.