Brake Rotor Question

look585 · 12-17-2023, 10:51 AM

OK.

I have a CS red calipers.

Assuming that the fronts are 400mm. Ordered some Giros accordingly. It is advertised as using several color calipers including red.

The rears on the site are advertised as 400 mm as well. I thought they were 380mm?

Are the rears 400mm as well?

Thank you.

medphysdave · 12-17-2023, 02:34 PM

Quote:

Originally Posted by look585

OK.

I have a CS red calipers.

Assuming that the fronts are 400mm. Ordered some Giros accordingly. It is advertised as using several color calipers including red.

The rears on the site are advertised as 400 mm as well. I thought they were 380mm?

Are the rears 400mm as well?

Thank you.

Rears are not 400mm. I believe you are correct that they are 380.

///MPhatic · 12-17-2023, 05:12 PM

Rears are definitely 380, and different from the blue brake front 380.

look585 · 12-17-2023, 05:27 PM

Ok thanks guys I’ll call them tomorrow to clarify

look585 · 12-18-2023, 11:40 AM

Didn’t doubt you guys as I’m replacing these for floating rotors

380 mm

Thanks again

look585 · 12-18-2023, 02:23 PM

Can anyone confirm these are the correct part number Manufacturer Part Number
A2-220 for the rears

GiroDisc

///MPhatic · 12-18-2023, 05:29 PM

I always use Getbmwparts for the best prices and OE part numbers. Not sure about the GiroDisc number.

look585 · 12-20-2023, 04:36 PM

Done

https://girodisc.com/bmw-f8x-m2-m3-m...m-rear-rotors/

BMW F8X M2, M3, M4 380mm Rear Rotors
SKU: A2-220

Other sites have it advertised as 400mm even though it's not.

Ordered.

look585 · 12-27-2023, 09:19 PM

The rears on. The fronts coming.

Just getting her ready for the track.

Sorry about the pics.

Westersund · 12-28-2023, 03:08 AM

How did the bell look like on the inside? Is there a pressed in metal ring for the emergency brake like the OEM discs?

///MPhatic · 12-28-2023, 08:56 AM

Quote:

Originally Posted by look585

The rears on. The fronts coming.

Just getting her ready for the track.

Sorry about the pics.

It looks like you did a nice, clean job.

look585 · 12-29-2023, 07:30 AM

Quote:

Originally Posted by Westersund

How did the bell look like on the inside? Is there a pressed in metal ring for the emergency brake like the OEM discs?

No steel ring.

Quote:

Originally Posted by ///MPhatic

It looks like you did a nice, clean job.

Thank you, it's appreciated.

///MPhatic · 12-29-2023, 08:10 AM

Quote:

Originally Posted by look585

No steel ring.

How does the e-brake work?

Westersund · 12-29-2023, 05:34 PM

Quote:

Originally Posted by look585

No steel ring.

Feels like the brake shoes will eat through the aluminium bell quite fast if there's no steel ring, no emergency brake turns for you mister.

F87source · 12-29-2023, 05:41 PM

Quote:

Originally Posted by Westersund

Feels like the brake shoes will eat through the aluminium bell quite fast if there's no steel ring, no emergency brake turns for you mister.

Really interesting how the girodisks don't have a rear bell for the emergency brake.

My 034 motorsport rotors had a separate steel bell that was removeable and replaceable if needed. It was held on via the lug bolts and rotor bolts.

look585 · 12-30-2023, 12:14 AM

Regarding the steel ring. Whether the shoes are squeezing against steel or aluminum it really makes no difference. It's not like the shoes are doing anything to slow the car down like the rotors on a consistent basis.

It's the E-Brake, is either off or on.

Debate welcome.

medphysdave · 12-30-2023, 12:16 AM

I don't think it matters as long as the hat is machined so there is contact. I agree with you. Not much wear going to happen unless you're using the brake frequently while driving.

look585 · 12-30-2023, 10:37 AM

I'm thinking the steel is there for a reason. Maybe to stop the deformity of the alum hat. when the ebrake is applied.

I'll be sure not to apply after some hot laps

HP Autosport · 01-06-2024, 01:52 PM

If anyone is interested in Girodisc or Paragon two-piece rotors, don't hesitate to reach out to us with any questions you might have or for quotes.

M3SQRD · 01-14-2024, 12:51 PM

Quote:

Originally Posted by look585

I'm thinking the steel is there for a reason. Maybe to stop the deformity of the alum hat. when the ebrake is applied.

I'll be sure not to apply after some hot laps

Coefficient of friction between steel on steel (assume metallic brake shoes) is 0.80.

Coefficient of friction between Aluminum and Steel is 0.61.

So the difference between an Aluminum and steel brake drum is you have to pull the handbrake farther to get the same parking brake holding torque. Deformation differences are negligible.

12-17-2023, 10:51 AM	#1
look585 Lieutenant 311 Rep 477 Posts Drives: M2CS Join Date: Oct 2008 Location: Los Angeles iTrader: (0) Garage List 2020 BMW M2 CS [10.00]	Brake Rotor Question OK. I have a CS red calipers. Assuming that the fronts are 400mm. Ordered some Giros accordingly. It is advertised as using several color calipers including red. The rears on the site are advertised as 400 mm as well. I thought they were 380mm? Are the rears 400mm as well? Thank you.
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12-17-2023, 05:12 PM	#3
///MPhatic The Seeker 13856 Rep 3,317 Posts Drives: OG M2 • Exige Join Date: Aug 2008 Location: USA iTrader: (2)	Rears are definitely 380, and different from the blue brake front 380.
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12-17-2023, 05:27 PM	#4
look585 Lieutenant 311 Rep 477 Posts Drives: M2CS Join Date: Oct 2008 Location: Los Angeles iTrader: (0) Garage List 2020 BMW M2 CS [10.00]	Ok thanks guys I’ll call them tomorrow to clarify
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12-18-2023, 11:40 AM	#5
look585 Lieutenant 311 Rep 477 Posts Drives: M2CS Join Date: Oct 2008 Location: Los Angeles iTrader: (0) Garage List 2020 BMW M2 CS [10.00]	Didn’t doubt you guys as I’m replacing these for floating rotors 380 mm Thanks again Attached Images Last edited by look585; 12-18-2023 at 02:21 PM..
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12-18-2023, 02:23 PM	#6
look585 Lieutenant 311 Rep 477 Posts Drives: M2CS Join Date: Oct 2008 Location: Los Angeles iTrader: (0) Garage List 2020 BMW M2 CS [10.00]	Can anyone confirm these are the correct part number Manufacturer Part Number A2-220 for the rears GiroDisc
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12-18-2023, 05:29 PM	#7
///MPhatic The Seeker 13856 Rep 3,317 Posts Drives: OG M2 • Exige Join Date: Aug 2008 Location: USA iTrader: (2)	I always use Getbmwparts for the best prices and OE part numbers. Not sure about the GiroDisc number. Attached Images
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12-20-2023, 04:36 PM	#8
look585 Lieutenant 311 Rep 477 Posts Drives: M2CS Join Date: Oct 2008 Location: Los Angeles iTrader: (0) Garage List 2020 BMW M2 CS [10.00]	Done https://girodisc.com/bmw-f8x-m2-m3-m...m-rear-rotors/ BMW F8X M2, M3, M4 380mm Rear Rotors SKU: A2-220 Other sites have it advertised as 400mm even though it's not. Ordered.
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12-27-2023, 09:19 PM	#9
look585 Lieutenant 311 Rep 477 Posts Drives: M2CS Join Date: Oct 2008 Location: Los Angeles iTrader: (0) Garage List 2020 BMW M2 CS [10.00]	The rears on. The fronts coming. Just getting her ready for the track. Sorry about the pics. Attached Images
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12-28-2023, 03:08 AM	#10
Westersund Captain 496 Rep 874 Posts Drives: BMW Join Date: Nov 2011 Location: Hallstahammar iTrader: (1)	How did the bell look like on the inside? Is there a pressed in metal ring for the emergency brake like the OEM discs? __________________ BMW M2 LCI -18 \| BMW 520DA Touring M-Sport -12 \| BMW Z4 M Coupe -06 \| BMW M3 -02 \| BMW Z3 Coupe -99 \| BMW 740i/6 -96 \| BMW M5 3.8 -92 \| BMW M535i -87
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12-30-2023, 12:14 AM	#16
look585 Lieutenant 311 Rep 477 Posts Drives: M2CS Join Date: Oct 2008 Location: Los Angeles iTrader: (0) Garage List 2020 BMW M2 CS [10.00]	Regarding the steel ring. Whether the shoes are squeezing against steel or aluminum it really makes no difference. It's not like the shoes are doing anything to slow the car down like the rotors on a consistent basis. It's the E-Brake, is either off or on. Debate welcome.
	Appreciate 0 Quote

12-30-2023, 12:16 AM	#17
medphysdave Brigadier General 4556 Rep 4,668 Posts Drives: M2 CS \| 85 of 592 Join Date: Apr 2015 Location: Charlotte, NC iTrader: (3)	I don't think it matters as long as the hat is machined so there is contact. I agree with you. Not much wear going to happen unless you're using the brake frequently while driving.
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12-30-2023, 10:37 AM	#18
look585 Lieutenant 311 Rep 477 Posts Drives: M2CS Join Date: Oct 2008 Location: Los Angeles iTrader: (0) Garage List 2020 BMW M2 CS [10.00]	I'm thinking the steel is there for a reason. Maybe to stop the deformity of the alum hat. when the ebrake is applied. I'll be sure not to apply after some hot laps
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01-06-2024, 01:52 PM	#19
HP Autosport BimmerPost Supporting Vendor 3842 Rep 54,352 Posts Drives: F80 M3 Join Date: Mar 2007 Location: Santa Barbara, AP, Brembo, GIAC, Koni, Ohlins, Performance Friction, www.hpautosport.com iTrader: (36)	If anyone is interested in Girodisc or Paragon two-piece rotors, don't hesitate to reach out to us with any questions you might have or for quotes.
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