I wanted to do a brake upgrade on my X3 using other OEM BMW parts and found, after some experimentation, that the last two generations of X5 brakes will work with a relatively simple spacer setup to allow the correct lateral offset.
I fabbed up some prototype spacers and sourced some proper bolts to accommodate the setup.
I'd purchased a refurbished set of E70 X5M calipers, only to find they didn't clear my 19" wheels. A lucky F10 5-Series owner ended up buying them from me.
Rather than buy new wheels and tires, I ended up with a set of F15 X5 50i two-piston calipers from the junkyard for $120 for the pair. Fifty bucks later, they were fully rebuilt with new seals, boots and paint. So, $170 for the pair of 50i calipers and my DIY time! I bought some new EBC X5 50i 365x36 rotors, along with YellowStuff pads, sold together as a kit, EBC part number S13KF1645, for $225. I added in some ECS braided stainless lines for $75. Note that the X3 brake lines and pad sensor work without issue on the X5 calipers.
The heat shield required a little trimming to clear either of the 50i or X5M calipers. Here's the uncut OEM shield.
Here it is after a little trimming with my Wiss shears.
Here are the little pie slice pieces I cut away.
An inside view for fun. Oops, I forgot to put the dust caps on the sliders in this pic! They're on there now.
Here's what they ended up looking like. Pardon the dust and filth!
After $30 in brake fluid, I'm all in at around $500 for a nice big brake setup worthy of my PS2 powered X3!
In case someone else wants to do the same, I had a batch of spacers custom milled from 304 stainless steel, with proper length grade 10.9 OEM quality bolts and sweet Nord-Lock safety washers. Check out my for sale thread and PM me if you want some.
X3/X4 to X5/X6 brake upgrade adapter kit
