[bguild]

Guys,

I'm doing a retrofit over in the SRX forum, and I'm wondering if anyone would be kind enough to confirm a few things for me.

1) On the CTSV the front calipers mount forward of the axle (this seems like a no brainer "Yes" but just for my confirm)

2) The front calipers mount such that the smaller 40mm piston is on top. So, if the rotor were a clock, the caliper itself is situated from like the 9pm-11 position, oriented so the smaller 40mm piston is around 11pm, and the larger 44mm piston is around 9pm. See first pic.

3) Is your inlet/banjo port on the mounted caliper positioned toward the bottom or top of the rotor? See attached pic showing what I think may be correct where the inlet is at the bottom if they are mounted correctly.

I'm basically going nuts here, one of the mechanics at my dealer swears I have these mounted wrong... ugh.

Thanks for any help!

 

[darkman]

On my 2005 CTS-V the front calipers mount rear of the front axle. On both sides the bleeders face up (skyward) and the inlets are on the bottom (ground side) of the caliper.

Stated differently, my passenger side wheel looks like the first picture in your post, which I believe (?) is your driver's side. The left and right calipers have different part numbers 89047727 and 89047726 for the left (driver's) side and right (passenger) side, respectively.

 

[bguild]

Damn, I didnt know they mounted rear of the axle. That makes comparing my scenario rather difficult because on the SRX, they mount front of the axle.

Thanks for the info on the blenders and inlet.

The last part I am trying to figure out is the positioning of the small vs large pistons.

I was told the small piston should be on top because that piston is on the "leading edge of the pad". This is currently how I have them mounted. Supposedly, doing it this way prevents "taper wear" of the pads.

I think given how they are mounted rear of the axle on the CTSV, your small piston would be at the 9pm position vs the 11pm position? Can anyone confirm?

 

[darkman]

https://haynes.com/en-us/tips-tutorials/understanding-different-types-brake-calipers seems to confirm that the small piston should encounter the disc first during rotation. I don't know which is piston is where on my calipers, But I do know that on both sides of the car, the inlet side of the caliper is encountering the disc first during rotation.

Assuming the first picture in your original post is the driver's side, and assuming you have one left side caliper and one right side caliper- I think your calipers need to be swapped, such that the inlet side encounters the disc first during normal (forward) rotation.

 

[AAIIIC]

This link has some good diagrams to add to what is said at the link darkman posted - https://www.quora.com/Why-do-BMW-brake-calipers-have-multiple-pistons-that-are-different-sizes-in-the-same-caliper. Just look at the first response to the question.

I'm not sure how big of a concern the pad tapering really is. There are some OEM 4-piston calipers out there that use pistons that are all the same size; my Subaru, for example, has 4-pots with pistons all the same size and I've never encountered pad taper, even in track use. Admittedly, that's a smaller caliper, with a smaller pad, which means they're less susceptible to the effect that staggered piston bores is intended to compensate for, so that could be why I haven't seen any taper. But anyway...

I've never done it, but AFAIK the Brembo caliper bodies are designed to be modular. I think you should be able to trade the position of the balance tube and the bleeders, and then swap your calipers so that the pistons will be staggered the way they're supposed to be. If I'm visualizing properly,that would also flip the inlet to the calipers (where the brake hose connects), which would make it match the way it is on the CTS-Vs.