F8x M4/M3 Brake Caliper/Rotor Retrofit Guide to E9x M3 - Using OEM Parts

[tdott]

I've been getting a lot of questions about my F8x M4/M3 brake upgrade, so I thought I'd give an overview on how it is done and what parts are required. This is not meant to be a step by step DIY but a guide on how it's done since it's really pretty simple with the right parts.

They can also be done using F8x CCB setup or M2 Comp parts as well.

Part list:

• F8x Calipers and Rotors/Pads
• F8x Spindles
  Right: 31212284002
  Left: 31212284001
• 4x M12 Flat washers, ideally around 2mm thickness.
• F8x dust shields or you can cut trim the e9x ones.
  (also not a bad time to do brake ducting with a custom backing plate if you wanted to go that route)
  Wheel bearing bolts (one time use)
• 31206783065 - M12X1.5X45 - (x8 - 4 per wheel bearing)
  These bolts are required because the f8x carrier has a ball seat vs e9x which is flat
  These are not the ones from an f8x since the f8x wheel bearings are a different thread pitch, I ordered these ones new from FCP Euro.
• New Brake lines are recommended, I went with E9x M3 Stainless stain lines from FCP Euro

Finally, you need to decide how to handle the ABS sensors. Since the F8x sensor location is slightly different requiring you to change the orientation of the E9x ones to read correctly.
Some have cut the e9x ones and created a holder out of metal.
Using the abs live obd2 reader, I was able to get the sensor to read correctly in this position (cut portion facing towards the outside center of the hub)
Eventually I bought 2 F8x sensors and spliced them into the E9x connectors and they worked perfectly and I was happier with that solution but both will work.



Full Install notes are on my blog, not meant to be step by step but will give you a guide, it's fairly straight forward but I do include a few tips.

https://www.tdott.me/2020/04/project...on-e92-m3.html

[terra]

Huh that's pretty cool, never realized the F8x spindles fit the E9x. Any changes to your alignment?

[IamFODI]

Huh that's pretty cool, never realized the F8x spindles fit the E9x. Any changes to your alignment?

His blog lists ride height and camber. Though I also wonder about other aspects of suspension geometry. Would be cool to have measurements or software modeling. This could be a suspension mod, too. :]

[tdott]

Huh that's pretty cool, never realized the F8x spindles fit the E9x. Any changes to your alignment?

All dimensions are the same, except for about 4mm more height and some additional camber built into the spindles.
Another guy had done all the measurements, this is one picture to show how he measured both spindles to ensure the mount points were the same.




With coilovers and camber plates, those changes didn't matter to me as I was able to do an alignment after and set it where I wanted it.

Whats also impressive is that the F8x wheel bearing can be used, they are interchangable. I used the e9x wheel bearing, but the f80 wheel bearing could be a future upgrade. It just means the lug nuts/studs will need to change to M14.
The f8x hubs have more machining to reduce weight.

[IamFODI]

Are F8x spindles lighter?

Also, has anyone done the math to assess brake bias?

[terra]

Quick napkin math: F8x: Fronts are 4 x 40mm piston with 380mm rotors, rears are 2 x 44mm piston with 370mm rotors. That makes the ratio about 1.69:1 or about 62.9/37.1

E9x: Fronts are 60mm with 360mm rotors, rears are 46mm with 350mm rotors. Results in 1.75:1 or 63.6/36.4

I think that's close enough to be fine. Doubly so when you consider the cars are similar in size, weight, weight balance, etc.

[SUPREM3]

Curious if you have had these on track and whether or not a difference can be felt.

[tdott]

Curious if you have had these on track and whether or not a difference can be felt.

Yes, definitely can be felt on the track. High speed heavy braking feels more stable due to the fixed caliper compared to the stock floating calipers. I got to do a track day at PBIR before things closed down. I wasn't a huge fan of the cheap PowerStop track day pads I was trying out compared to the Hawk DTC70 pads I had with the stock calipers, but I guess you get what you pay for. If I could do it again i'd skip the powerstop pads and go with something better but all other options were 3-4x the price which is why I thought i'd give them a try.

With stock brakes and DTC70 pads the car would dance around alot on the track under heavy high-speed braking.

[M Coupe]

Nice writeup homie! Does anyone know if the 380mm setup will fit under monoblock (one-piece) 18" wheels? Modular wheels generally have less clearance so I'm wondering if an 18" monoblock will clear radially (between caliper outer body and wheel barrel) with room to spare.

[tdott]

Nice writeup homie! Does anyone know if the 380mm setup will fit under monoblock (one-piece) 18" wheels? Modular wheels generally have less clearance so I'm wondering if an 18" monoblock will clear radially (between caliper outer body and wheel barrel) with room to spare.

It depends on the wheel and barrel design.

Apex Arc8 does not clear but EC7 and others do. So it will depend.

[IND-Distribution]

Thanks for sharing! We have been offering the F8x hub retrofit kit for E9x M3 and E82 1M, but addressing the brakes is one of the car's only shortcomings in stock form.

[SYT_Shadow]

Thanks for sharing! We have been offering the F8x hub retrofit kit for E9x M3 and E82 1M, but addressing the brakes is one of the car's only shortcomings in stock form.

I have the future classic f8x hub conversion for the front axle of my track e90, it's a great upgrade! Good job IND!

[r4dr]

F8X bearings would be stronger I'd imagine? Might also solve screw-in wheel stud snapping issues by running M14 studs instead. I don't really notice F8X owners posting about their M14 studs snapping, but seems like a lot of E9X people experience that.

[r4dr]

Core 4 now offers F8X hubs with 14mm press-in studs for E9X cars:

https://www.facebook.com/core4motorsports/posts/2623156598000148

Probably as bulletproof as you can get...

[tdott]

The F80 front hubs save a little weight also, they are a good looking piece.

I wouldn't say a lot of people experience stud failure, the failures were on heavily tracked cars, so it is a good upgrade for those type. The rears are harder change, so unless you do all 4 corners, you'll be running M14 on front and M12 on the rear. You'll have to babysit every shop that has to take your wheels off, otherwise there is a pretty good chance they mess it up.