Adapting M3 AP's to fit the Z4M

[Fishy Dave]

As I posted in another thread I picked up a nice used set of AP front and rear calipers, front discs and Pagid RS29 pads for a good price last month. These were from an E46 M3 being rebuilt for racing at Geoff Steel (one make series requiring yellow bird brakes). Having spent an enjoyable few hours browsing old threads on here I knew that the rear brakes would fit perfectly but the M3 kit differs from the Z4M by having different brackets and disc bells. To get the M3 fronts to fit I would need to either replace the brackets or space them out by 2mm and have to buy new bells (disc centres).
I contacted a gentleman who races with us (CSCC) who is an engineer for AP and he suggested another alternative to replacing the bells (currently out of stock and £500), that is to add a 2mm spacer between the disc bell and the hub. Assuming I have a pair machined in 2mm alloy or steel and longer wheel nuts could this be a good solution both for myself and anyone else looking for AP's in the future? Without having the car in front of me how do the front discs locate onto the hub?

Thanks, Dave

 

[Fishy Dave]

Answering my own question, it looks like the standard front discs sit on three pegs and then the discs are held with two torx bolts. The 2mm spacer would require longer torx bolts and would also mean that the pegs wouldn't reach so far into the disc centre? Problem?

 

[Mister T]

Should work fine, you'd also need a 2mm shim for the caliper mounting bracket.

 

[gwatson]

You don't need the 2x torx bolts, it just makes it easier to take the wheel off and on, keeps everything aligned.

You shouldn't need longer wheel bolts with just 2mm difference. You'll still get 6+ full turns...

 

[Fishy Dave]

Thanks both, will report back when I have had shims made and go to fit them.

 

[Anonymous]

Ps as such nice brakes I'd get them cleaned and painted up first

 

[srhutch]

Should work fine, you'd also need a 2mm shim for the caliper mounting bracket.

If you did that it negates the 2mm one on the disk so would be a net result of zero.

 

[Fishy Dave]

Pretty sure you need both? : ) I've found a local engineering company to make me a pair of spacers to fit between the hub and disc centre, I can then experiment with washers as needed to ensure the caliper is centred around the disc.

 

[srhutch]

Pretty sure you need both? : ) I've found a local engineering company to make me a pair of spacers to fit between the hub and disc centre, I can then experiment with washers as needed to ensure the caliper is centred around the disc.

So you need to move the disc and caliper out by 2mm?

 

[Fishy Dave]

Yes, that seems to be the case from what I've read on here.

 

[Mister T]

Should work fine, you'd also need a 2mm shim for the caliper mounting bracket.

If you did that it negates the 2mm one on the disk so would be a net result of zero.

I believe it's an issue with clearance, so both disk + caliper need to be moved outwards.

 

[simonlpearce]

IIRC the reason for moving everything out by 2mm is due to how close the disc sits to the control arm which would cause rubbing issues. So i believe everything does have to move out by 2mm.

 

[BMWZ4MC]

That's certainly the case with the Alcon kit for the E46 M3 CSL - the disc fouls the track rod end.

 

[Fishy Dave]

The spacers have been beautifully made by http://www.turnertech.co.uk/ at a total cost of £60 which I didn't think was bad. I gave them a quick coat of zinc primer and am ready to fit them in a few days time, exciting.

 

[srhutch]

Makes sense, I was thinking it was an alignment issue.

 

[jpeeters]

Which part number are the front calipers? I'm also getting my hands on a used M3 set (from the E92 M3, before they made a specific one for this platform). Is it CP5575?

Very interested to see if our approach works. I'm quoted > 1000 gbp for brackets and bells to convert my set into a z4m kit, with a long lead time.

 

[Fishy Dave]

Hello,

Yes, CP5575-802(S4) is printed on one of the calipers. I'm going to fit them in a couple of days and will report back. I almost had a second set of spacers made up in case someone else wanted to follow the same path.

 

[jpeeters]

Great! I'll keen an eye on your progress. If everything fits I'll order a set of spacers. We'll work something out

 

[TomK]

Dave, good thinking with the spacer, that should work fine. FWIW with the Z4M specific bell I ended up having to shim the bracket 3.5mm IIRC,.

Which part number are the front calipers? I'm also getting my hands on a used M3 set (from the E92 M3, before they made a specific one for this platform). Is it CP5575? Very interested to see if our approach works. I'm quoted > 1000 gbp for brackets and bells to convert my set into a z4m kit, with a long lead time.

Yes 5575 is the caliper you want, however I'm almost certain you'll need new brackets and bells (and possibly discs) if you buy an E92 M3 kit intending to use it on these cars. An E92 M3 kit will not fit an E46 M3 (which the Z4M is almost identical to). Apologies if I'm teaching you to suck eggs.

 

[Fishy Dave]

I spent an enjoyable afternoon and early evening fitting everything in my friends workshop (all four calipers and front discs). Lighting not great for my camera phone, you can tell I live down muddy lanes too

Spacers fitted well, pic shows the back plate trimmed at the bottom to accommodate the larger caliper.

As others have reported, the clearances are very tight when using the standard 18" M wheels, hence relocating the wheel weights.

The disc back plates require bending such that they are touching the steering arm and bottom joint. Removing the two lower bolts that hold the back plate on, use a pry bar behind and bend the back plate in, insert the two small bolts back in.

Even after bending there is little space.

Comparisons

You know what the standard set up looks like

Fronts fitted

Tight enough clearance?!

I didn't worry about taking any photos of the rears, which are really straightforward by comparison. Just trim the backplates top and bottom.

Really good 20 mile drive home, no rubbing at all despite some vigorous braking and cornering. I'm very impressed so far, not a squeak from the Pagids and the pedal feel is better than standard. Yes, there is certainly greater performance when pressing the pedal firmly, but there is no grabbing/sharpness for example when heel and toeing (unlike the standard set up which gave strong performance but felt too assisted and sharp). I will report back after the next trackday, but so far I'm pleased with the M3 set up and spacers.

Cheers, Dave