[Marc R]

Super interesting thread to read, i have only one question tbh: Which M specific calipers fit without adjustment? (M/Y and Model)

[Th3Walrus]

X5M 2020+

https://x3.xbimmers.com/forums/showthread.php?t=1858189

https://x3.xbimmers.com/forums/showthread.php?t=1999560

[Dasky_spas]

But in terms of brake bias, at what point (%) does the greater rear brake transition start to become noticeable during track use ( aggressive braking, high speed trail braking)?

In my application, Triton Motorsports has a kit: matching ap style rear 4 pot caliper on a slightly larger than oem rear rotor. The front is a 4 piston, so nearly equal rotor sizes, both 4 piston but front pads are significantly bigger. I imagine on large, heavy vehicles, there will always be an excessive amount of front bias but logically that wight swings both ways and its the high speed trail braking that would make me nervous in these kinds of situations.

[Bimma360]

Originally Posted by Dasky_spas

But in terms of brake bias, at what point (%) does the greater rear brake transition start to become noticeable during track use ( aggressive braking, high speed trail braking)?

In my application, Triton Motorsports has a kit: matching ap style rear 4 pot caliper on a slightly larger than oem rear rotor. The front is a 4 piston, so nearly equal rotor sizes, both 4 piston but front pads are significantly bigger. I imagine on large, heavy vehicles, there will always be an excessive amount of front bias but logically that wight swings both ways and its the high speed trail braking that would make me nervous in these kinds of situations.

Hey I started another thread that has some charts that shows this info in a little bit more detail.

https://x3.xbimmers.com/forums/showthread.php?t=2072977

I don't think there is a standardized threshold of a % shift. Unfortunately, it's probably car to car specific. The caliper piston area and the effective radius of the brake rotors will determine the bias %. Fun fact a 3200lb e36 M3 has a bigger front piston area and smaller rear piston area compared to the X3M. This calculator isn't really meant to compare different cars against each other, but generally the X3M is less front biased than a smaller E36 M3. I thought that was interesting.

For me personally, I would be a little more cautious moving the X3M's bias more towards the rear. I'd love to get the caliper piston diameters and the pad height on the X3M Brembo GT kit, to see how they handled the brake bias. My hunch is that the kit actually increases front bias. If that's the case, I am not sure how that makes me feel about increasing rear bias instead.