Rear brake4 pistons caliper Upgrade

[didie92]

Hello everyone, I'd like to install 4-piston calipers on the rear of my car. l've seen that it's possible to fit rear brake calipers from an M3 F80, but those only have 2 pistons. Has anyone already installed 4-piston calipers on the rear? And which model did they use? Also, what is the bolt pattern of the caliper bracket on an M3 F80 or E92, which should be the same?

[Brandoch]

Originally Posted by didie92

Hello everyone, I'd like to install 4-piston calipers on the rear of my car. l've seen that it's possible to fit rear brake calipers from an M3 F80, but those only have 2 pistons. Has anyone already installed 4-piston calipers on the rear? And which model did they use? Also, what is the bolt pattern of the caliper bracket on an M3 F80 or E92, which should be the same?

Why? The rears do not need that much.
Do you track?

[M43ver]

What are you running on the front? The f8x Blue brake setup is a nice upgrade for the e9x M3. A two-piston rear caliper is all you need when paired with the four-piston front caliper. The 380 and 370 mm rotors are a nice step up from the e9x M3 370 and 350 mm rotors. Your other option would be the f87 M2C brake setup but that requires 19” diameter wheels unless you buy a custom front caliper mounting bracket that uses a Girodisc 380 mm rotors. This setup gives you six-piston and four-piston calipers. Replacement parts are more expensive than the f8x Blue brake setup and it’s all you need unless you’re heavily into tracking your car.

[Redd]

Most aftermarket big brake kits have 4 pot rears.

[didie92]

Yes, I use the car on the track. At the front, I currently have 6-piston Brembo calipers with custom adapter spacers, and I've read that using only 2 pistons at the rear can cause an imbalance in braking. Since I already have front calipers, I don't need a complete brake kit.

[didie92]

I forgot to mention that I have 380mm front and 370mm rear discs that came from an M3 F8X, so I would need 4-piston calipers that would be compatible with this setup.

[maddmatth]

Originally Posted by didie92

Yes, I use the car on the track. At the front, I currently have 6-piston Brembo calipers with custom adapter spacers, and I've read that using only 2 pistons at the rear can cause an imbalance in braking. Since I already have front calipers, I don't need a complete brake kit.

Hmm that's not right. It's not the number of pistons that determine brake force. It's more complex than that. But you'll be fine with the stock rears. The F80 rears will add a nice cosmetic upgrade though.

I track my car with F80 brakes front and rear. Fronts get super hot while the rears only get warm, so even those are more than the car needs back there. Anything bigger is just unnecessary weight I think.

[Spectre]

Originally Posted by maddmatth

Hmm that's not right. It's not the number of pistons that determine brake force. It's more complex than that. But you'll be fine with the stock rears. The F80 rears will add a nice cosmetic upgrade though.

I track my car with F80 brakes front and rear. Fronts get super hot while the rears only get warm, so even those are more than the car needs back there. Anything bigger is just unnecessary weight I think.

I second this, I have 6 piston brembo front with F8x m3/m4 front 380mm rotor and F8x m3/m4 2 piston rear calipers with 370mm. brake bias is 1% rearward from stock and pedal feel is great.

There are multiple factors that affect bias. you can use this tool to help you:
actor
https://www.tceperformanceproducts.com/bias-calculator/

[M43ver]

Originally Posted by didie92

Yes, I use the car on the track. At the front, I currently have 6-piston Brembo calipers with custom adapter spacers, and I've read that using only 2 pistons at the rear can cause an imbalance in braking. Since I already have front calipers, I don't need a complete brake kit.

You’re currently running the stock single-piston sliding caliper? What are the piston sizes or total piston area of your Brembo six-piston caliper? The f8x blue two-piston fixed caliper piston area is ~7% smaller than stock rear but the f8x gray/gold four-piston fixed caliper piston area is ~25% smaller than stock rear. So the f8x blue two-piston fixed caliper is a much better match to the stock rear sliding caliper. Whoever told you the two-piston caliper can cause a rear brake imbalance (too much forward or rearward brake bias shift?) doesn’t know what they are talking about. It’s the much smaller piston area of the f8x gray/gold four-piston caliper that could result in a brake imbalance (large forward shift in brake bias) as well as a potentially much stiffer and shorter travel brake pedal relative to the stock rear brake setup.

[didie92]

Okay, thank you all very much for all these explanations. So I'll look for F8x brakes then.

[KawBoy]

[M43ver]

Originally Posted by didie92

Okay, thank you all very much for all these explanations. So I'll look for F8x brakes then.

I wouldn’t be surprised if the Brembo caliper you are currently using has a piston area that’s close to the 2NH gray/gold front caliper. The 2NH six & four piston calipers with 400 mm and 380 mm rotors, respectively has a 69% forward brake bias vs. stock e9x M brake setup forward bias of 64%. The f8x complete blue calipers brake bias is 63% forward. Both f8x blue and gray/gold brake setups can be used on the e9x M3 but the f8x blue brake setup is very close to the e9x M3 stock sliding caliper brake setup. For the f8x gray/gold setup, you can use a more aggressive rear brake pad to increase the rear brake torque and pull the bias more rearward.

[KawBoy]

[Tristan1980]

I've just done front and rear caliper conversions on my E92 M3 using Freaky Parts adapters.
I've used a Brembo 6 pot fronts and Brembo 4 pot rears (off an Alfa Romeo Quadrifoglio).
For reference, I use F80 front discs (380x30mm) and the standard E90 rear discs (350x24mm). I use homemade pad spacers in all calipers.

Regarding the rear 4 pots, everything fits and works fine, but there is 1 significant drawback - which is pad availability. And to be honest, it's something I wish I had considered before fitting!

Not many aftermarket brake pad brands make pads to fit them. Your choices are either crap random ones; Bremo's own pads which are lack lustre to say the least; some super basic Pagid ones; so the only compatible performance related pads I can find are EBC in either Blue or Yellowstuff - and I'm not a huge fan of either based on previous experience in other cars

[SalimM3]

Originally Posted by Tristan1980

I've just done front and rear caliper conversions on my E92 M3 using Freaky Parts adapters.
I've used a Brembo 6 pot fronts and Brembo 4 pot rears (off an Alfa Romeo Quadrifoglio).
For reference, I use F80 front discs (380x30mm) and the standard E90 rear discs (350x24mm). I use homemade pad spacers in all calipers.

Regarding the rear 4 pots, everything fits and works fine, but there is 1 significant drawback - which is pad availability. And to be honest, it's something I wish I had considered before fitting!

Not many aftermarket brake pad brands make pads to fit them. Your choices are either crap random ones; Bremo's own pads which are lack lustre to say the least; some super basic Pagid ones; so the only compatible performance related pads I can find are EBC in either Blue or Yellowstuff - and I'm not a huge fan of either based on previous experience in other cars

Can you provide some pics and info on your home made pad spacers? I want to make some on my upcoming c63 amg front 6 piston calipers also. Thanks!

[M3SQRD]

Originally Posted by Tristan1980

I've just done front and rear caliper conversions on my E92 M3 using Freaky Parts adapters.
I've used a Brembo 6 pot fronts and Brembo 4 pot rears (off an Alfa Romeo Quadrifoglio).
For reference, I use F80 front discs (380x30mm) and the standard E90 rear discs (350x24mm). I use homemade pad spacers in all calipers.

Regarding the rear 4 pots, everything fits and works fine, but there is 1 significant drawback - which is pad availability. And to be honest, it's something I wish I had considered before fitting!

Not many aftermarket brake pad brands make pads to fit them. Your choices are either crap random ones; Bremo's own pads which are lack lustre to say the least; some super basic Pagid ones; so the only compatible performance related pads I can find are EBC in either Blue or Yellowstuff - and I'm not a huge fan of either based on previous experience in other cars

Cobalt, Carbotech and G-Loc will make custom pads in any of their race compounds if you send them a used set of brake pad backing plates and tell them the overall pad thickness.

The biggest issues with your brake setup are they use stock f8x and e9x M rotors; i.e., you haven’t addressed the weak link in the stock brake setup because there’s no increase in thermal capacity like you get with 380x36 and 365/355x32 true two-piece floating rotors with a 72 vane count. Stock rotors means your braking distances continue to increase with each braking event which doesn’t happen with rotors with increased thermal mass and improved cooling.

[Tristan1980]

Ok quite a few things to reply to.
Firstly, this is an ongoing project for a car I have currently owned for 4 months, so please cut me some slack with how tatty this all looks! I'll address aesthetics later...

So, the pad spacers - Freaky Parts said I shouldn't actually need pad spacers, but I did just to be sure - and to not over stretch the pistons when I use every mm of pad, haha!
So the Alfa calipers should be used with a 28mm width disc. Mine are the factory E92 M3 rear discs which are 24mm wide. I just made some 2mm packers out of sheet steel. It isn't pretty, it's just temporary. So one either side of the disc =4mm, added to the disc of 24mm makes 28mm total. Unfortunately I didn't take any pics of them off the car, but you can see in the pics below when inside the calliper.
The plan in the future is to find a 350x28mm disc that fits, which will address what M3 SQRD is saying - that it's the thermal capacity which is also important.

Likewise with the fronts, I've fitted calipers off a G80 M3, which should take a 380x36mm disc, but just in the short term I'm using 380x30mm discs of an F80 M3, with 3mm each side of pad spacers - this is entirely because it happens to be what I had laying around from other cars.

The biggest reason for doing it all this way is firstly cost and secondly, like I say, I already had the front discs around and I'm still using the factory-fit rear discs. So all I had to buy was callipers and adapters.
In the short term I even reused the brake pads which came with both pairs of used callipers (death wish?). So I've so far spent £1040 in total on this kit (including braided hoses and fancy fluid).
All the calipers are from eBay from wrecked cars. The fronts were a particular bargain of £425 from eBay that came with 90% new pads. Sweet!

[M3SQRD]

The g8x 380x36 mm rotor will most likely have a different rotor centerline offset distance from the rotor mounting face (i.e., the hat offset) from the thinner f8x front 380x30 mm rotor centerline (hat) offset mounting distance.

[Tristan1980]

Originally Posted by M3SQRD

The g8x 380x36 mm rotor will most likely have a different rotor centerline offset distance from the rotor mounting face (i.e., the hat offset) from the thinner f8x front 380x30 mm rotor centerline (hat) offset mounting distance.

Yes - and it has a different BCD too.
However, EBC can apparently make a disc that will work, ie a bell that fits E92 BCD hub, with the offset of a G80 and the wider disc of a G80.

It's a work in progress...
For now, I'm happy using an F80 disc with 2x3mm pad spacers.
It has much improved power and feel, just only minimal increased thermal capacity

[M3SQRD]

Originally Posted by Tristan1980

Yes - and it has a different BCD too.
However, EBC can apparently make a disc that will work, ie a bell that fits E92 BCD hub, with the offset of a G80 and the wider disc of a G80.

It's a work in progress...
For now, I'm happy using an F80 disc with 2x3mm pad spacers.
It has much improved power and feel, just only minimal increased thermal capacity

Another option is Coleman Racing who makes custom rotors and hats at very reasonable prices.

Track/S may be another option for creating a custom hat with the correct PCD (pitch center diameter) for GiroDisc or Paragon g8x 380x36 mm rotors.

What are pad spacers? The 380x30 mm rotors aren’t centered in the calipers so pad shims/spacers of different thickness are being used to center the pads on the rotors?

[Tristan1980]

Cool. Thanks for the suggestions.

The spacers I'm using are between the pad and pistons. They're to compensate for using a thinner disc than the calliper is designed for. Without them, I'm worried that as the pads wear, the pistons will eventually poke out beyond where they're supposed to.
The discs are central in the calliper