Z4M calipers on 3.0si

[belcom]

My M Coupe got Brembo all around last year so I have Z4M calipers with SS lines kicking around. Just got new SHW Performance pin drive rotors for the Si and started thinking... what if...

So I did a dry fit and it ended up working out. I had to use the Si bracket and clip as the Z4M bracket does not fit and the clip is a bit different size as well. Otherwise Z4M caliper drops in like it belongs there. 3.0si uses exact same brake pad shape so I am reusing the brake pads which were basically new. SS lines are the same size/length. The rotor is the stock Si size 325x25mm. Z4M caliper has a 60mm piston vs 57mm of the Si. This is basically 11% bigger area.

Initial test drive done, everything works. Pedal a bit soft for now but I did not bleed or installed the SS lines in the rear yet. And I want to bleed the fronts a bit more as well as do some more break-in runs before coming to any conclusions. Fingers crossed this fully works out.

Update: I took it out again today once everything has cooled down overnight and confirm that pedal feels nice and solid now.

[belcom]

Pics

[maupineda]

pedal will be a bit softer since you upped the piston size. will it work, yes, but will be different.

I did this on a 130i, where I installed 335i calipers and pedal became slightly softer.

On my M Coupe, i put 135i calipers, which reduce piston area size, and pedal went firmer, not necessarily better for performance, but better for feel, clamping force actually goes negative.

In your case, despite the softer pedal, you will have more bite.

[dre99gsx]

I have played around with that concept for quite some time. Do yourself a favor and get the Z4M master cylinder. This way, you can use the larger front piston and get back to a better brake bias (and firmer pedal).

For the rears, the 135i calipers/pads + Z4M rear rotors are a direct swap (with two washers in between) and get you closer to Z4M brake bias.

[belcom]

Appreciate your inputs dudes. I have observed that on the second day after break in, pedal has become much better and way less soft (practically normal) than the first time I went for a spin right after the install was finished. At the same time I felt that the pads were not fully bedded yet as the initial bite was just not there yet. Fast forward couple days later, I went out again and it feels like the bite is coming back to normal and pedal is still good and firm.

I think it is characteristic of these pads I am using. Kinda remember it was sort of similar experience when I put them on with the old rotors. After the initial bed in procedure it took some driving for them to fully bed in and deposit material onto the rotor and feel normal. Pads in question are Cool Carbon S/T+ front and S/T rear. As a matter of fact, just read a bunch of forum threads/discussions and someone had mentioned they require around 400km driven to properly bed in. Looks like I got some driving to do

Andre, I did read your threads on the brake upgrades. Not sure if all of it. But the last one I went over was where you had developed a custom bracket for Willwood calipers. Very cool! Care to share the design file? lol

I don't recall a thread talking about 135i rears though. I do have my old rear Z4M rotors which I could use and test with. What about hand brake? I am assuming still requires welding another set of shoes on top of the old ones to accommodate the larger inside diameter of the Z4M rotor hat?

But ultimately guys, this car is not for racing but rather street curve carving top off type of experiences. I was just messing around with the parts I have kicking around. Thought it would be cool to do the "upgrade" with M calipers and SS lines. Fluid in this car has been neglected so bad that when I siphoned it out of the brake reservoir it looked like coca cola colour. Yeah, it was that bad lol. Frankly I still have this dark crap in the rear lines/calipers that I need to bleed. Been feeling lazy last couple of days. Even though its most likely a great idea to upgrade the master, I will not be going this far. Its good enough for now. I might still mess around with the rears and 135i calipers and all, we shall see. But for now car stops really well, pedal feels good and all in all the car drives great for what it is and what its used for.

[dre99gsx]

Ah yes, to use the Z4M rotor on Z4 3.0si (rear), I just cut/welded another set of drum pads on top of the 3.0si pads to make up the diameter difference. Working great till this day.

You don't need custom brackets for the 135i rear calipers, just spacers you can order online from Amazon/Ebay.

Wilwood caliper bracket I have available as a cad file but you would still need to drill/tap, source the bracket studs/nuts, etc from Wilwood.

Yeah, if it's just for street, you should be in good shape! But definitely look into going Z4M rotors in the rear to complete the 'look'.

[Willy Sea]

Down here in the colonies we fitted the 4M drilled rotors at 345mm, and E90 M3 calipers. It all worked, although we had to take a bit off the calipes so the Apex Arc8's in 18" fitted.

[belcom]

Originally Posted by Willy Sea

Down here in the colonies we fitted the 4M drilled rotors at 345mm, and E90 M3 calipers. It all worked, although we had to take a bit off the calipes so the Apex Arc8's in 18" fitted.

Just to be clear we are talking regular Z4, say 3.0si or 3.0i? 345x28mm front rotor + e92/e90 M3 caliper bolts right up with zero modifications except a bit was shaved to accommodate an apex wheel barrel? And everything is centered and spaced proper? And how's the pad engagement? Does the pad stay within the surface or sweeps perfectly or overhangs a bit?