135i Calipers Fitted to Z4M

[Mangozac]

Prompted by the recent thread discussing some brake options, I figured I should share my recently completed front brake upgrade.

I did a lot of testing with many different Brembo front calipers, testing blue calipers from an F82 M4 and F20 M140i. The M4 calipers can be made to work on E46 M3s, so the expectation was that they would work with the Z4M but alas the slight difference in steering knuckle meant it wouldn't work. The M140i calipers can be made to fit but would need a significant spacer so that the wheel spokes will clear the caliper.

In the end, I saw how nicely the E82 135i Brembo 6 piston calipers worked on another member's car and decided to stop giving myself headaches and go down the tried and tested route

I'm running the 6 piston Brembo fronts on the stock CSL rotors and the stock rear brake setup. Based purely on piston sizing calculations this will have adjusted the bias backwards slightly, however accounting for a more aggressive pad in the front I feel that there's no significant difference in the bias.

I had the new calipers and the stock rear calipers both painted a metallic blue, similar to the M4/M140i calipers, then M decals added and a clear coat. All high temp paint. At first I was unsure about drawing attention to the small real calipers, but justified it due to the fact that the F10 M5 has a similar setup: big, 6 piston calipers up front and little single pistons at the back.

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He best thing is that a new caliper bracket isn't even necessary! They bolt straight up to the knuckle with some 8mm spacers and longer mounting bolts (the mounting bolts from the 135i are perfect). The spacers are basically M12 washers 8mm thick and 32mm diameter - I machined mine from some 304 grade stainless round bar. I also fitted some braided steel brake lines to the front calipers while I was at it

How do they perform? Well I haven't had a chance to give them a workout with a hard drive yet, but for day to day driving they feel fantastic! The pedal feel is improved but also still very "BMW factory" feeling, if that makes any sense. Still very linear.

I am familiar of reports of the ceramic part of the pistons fracturing on these calipers but in the very few cases I've heard of it has been restricted to cars under heavy track use. I'm not concerned, but worst case they need rebuilding one day.

I'll have a better idea/confirmation of the performance in heavy use in a couple of weeks but so far is proving to be a very satisfying upgrade. They look amazing and give the Z4M a more modern feel.

[Bing]

They look great

I also like how they are slimmer than OEM - not just for the looks, but the wheel cleaning

[Mangozac]

They look great

I also like how they are slimmer than OEM - not just for the looks, but the wheel cleaning

Cheers Bing!

Indeed, cleaning that part of the wheel where the stock caliper was located was impossible. Truthfully, I've not done a proper wheel clean (with the "wheel wooly") since fitting the calipers but I do expect it to be a little easier. Of course, now I have to keep the calipers clean too though

[BMWZ4MC]

Looks great I’m looking forward to hearing how they perform during a proper workout in a week or two.

[flimper]

but the wheel cleaning

+1

[abar121]

Looking good.

For me, a brake upgrade has to including replacing the stock disks, to get rid of the grumbling, noisy operation when used hard. They are awful!

A set of PF disks and pads on stock calipers is a great setup for road and reasonable trackday use.

[tomscott]

Looks awesome!

What are these like in terms of piston surface area and pedal feel? They a bigger calliper but small area right? Reading from the other thread.

[Mangozac]

Looks great I’m looking forward to hearing how they perform during a proper workout in a week or two.

Thanks mate, I'll be sure to report back!

For me, a brake upgrade has to including replacing the stock disks, to get rid of the grumbling, noisy operation when used hard. They are awful!

A set of PF disks and pads on stock calipers is a great setup for road and reasonable trackday use.

This is the first time I've ever hear anybody complain about discs making grumbling, noisy sounds!

What are these like in terms of piston surface area and pedal feel? They a bigger calliper but small area right? Reading from the other thread.

Correct, although the caliper is bigger and there are 3 pairs of pistons, the overall piston bore area is slightly less than stock, meaning that the bias will shift rearward. My calculations put it at 54.5% front bias (vs 58% stock). Like I said though, this is corrected somewhat by using a more aggressive compound on the front.

Thee pedal feel is fantastic. There is ever so slightly less pedal travel vs stock but as it's still extremely linear I feel that this is in no way detrimental. I certainly didn't have to adjust to the new braking feel or anything.

[Bmmeupscotty]

Looks Great, Good job

[TomK]

What are these like in terms of piston surface area and pedal feel? They a bigger calliper but small area right? Reading from the other thread.

Correct, although the caliper is bigger and there are 3 pairs of pistons, the overall piston bore area is slightly less than stock, meaning that the bias will shift rearward. My calculations put it at 54.5% front bias (vs 58% stock). Like I said though, this is corrected somewhat by using a more aggressive compound on the front.

Nice! I found them to be a great improvement in feel over the stock setup. When I was running them I also used the boxster s rear calipers which can be picked up for not a lot and brackets are readily available for them. That puts the balance back close to stock, 59% ish.
Useful chart here, though I'm not certain that our master cylinder is the same as the later m3s using the mk60.
https://thebuildjournal.com/tech-guides ... rt-e46-m3/

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[hopz121]

You have any pictures showing spacers etc?

Interested to see how you mounted them with the spacers.

[Mangozac]

Nice! I found them to be a great improvement in feel over the stock setup. When I was running them I also used the boxster s rear calipers which can be picked up for not a lot and brackets are readily available for them. That puts the balance back close to stock, 59% ish.
Useful chart here, though I'm not certain that our master cylinder is the same as the later m3s using the mk60.
https://thebuildjournal.com/tech-guides ... rt-e46-m3/
E46-M3-MK60-Master-Cylinder.jpg

Indeed, I'm very familiar with that table and have my own spreadsheets I used for calculating Z4M braking options

The Z4M master cylinder is the same as Mk60 M3 and CSL: https://www.realoem.com/bmw/enUS/part?i ... 4317838638

There are a few options for the rears and I would have looked at them but honestly for the driving I do I don't believe there's any need to upgrade them. Knowledgeable people I've discussed it with agree.

You have any pictures showing spacers etc?

Interested to see how you mounted them with the spacers.

Unfortunately I didn't think to take any photos of the actual mounting. Here's what the spacers look like though. They simply sit between the knuckle and the caliper bracket.

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[buzyg]

They look great. Will watch this space for howchey perform when pushed.

[bradz]

Good setup I have been running these on my Z4M for a couple of years, With the boxter rears as TomK.

If you use them on track, Fit the stoptech pistons as the stock ones have a ceramic top. (They disintegrate, well documented.)

[Mangozac]

If you use them on track, Fit the stoptech pistons as the stock ones have a ceramic top. (They disintegrate, well documented.)

The gold calipers look great on black!

I wasn't aware of the replacement Stoptedh pistons! Do they still have a ceramic ring (I understand it's purpose is to insulate the brake fluid from the high temperature of the pad)? How much did a set cost?