[johnung]

Originally Posted by Onizukachan

johnung

My understanding is that it is when you go to dual piston 345 rears that you need to recode as those would require different bias, ergo 340/330 to 370/345 requires the recode, but a 312/300 to 340/330 still with single piston rears doesn't. That why the direction from bmw are to add S2NH to VO on the 335i/340i as well.

I was told that it's the front Brembo's that change the brake bias. So that anytime you upgrade to front 370 or 340 from a front 312 or 330, the bias needs to be re-coded.

One of my brake upgrades was F340/R330 to F340/R345. It was done by an experienced dealer mechanic who said that no coding was necessary since the factory coding with my car was already set for either one.

[Onizukachan]

Puzzle for another day the I reckon.

[Ennoch]

Originally Posted by johnung

I was told that it's the front Brembo's that change the brake bias. So that anytime you upgrade to front 370 or 340 from a front 312 or 330, the bias needs to be re-coded.

One of my brake upgrades was F340/R330 to F340/R345. It was done by an experienced dealer mechanic who said that no coding was necessary since the factory coding with my car was already set for either one.

My guess is that the bias isn't changed because of the power balance changes caused by disc sizes but rather the varying piston sizes which changes the ratio of power at the caliper front to back. That would account for the change in bias in the coding. Have you any idea what the piston size is on the stock single piston sliders out back? A quick bit of maths suggests that to equal the 40mm 2 pots it would be about 57mm if the hydraulic ratio was to stay the same. If it's away from that by a noticeable amount then it would change the pedal length etc which would then throw out EBD sensors etc.

Have you tried driving the car in anger before/after coding, or have you always done it at the same time as fitting? I'm just curious as I wonder whether it's actually doing anything other than preventing the driver aid sensors becoming confused.

[Onizukachan]

That’s my guess as well that it has something to do with tc engagement or another e driver system like abs as the mechanical proportioning ratio couldn’t possibly be changed by coding.

[sqwinny]

I went from front 330mm single piston to 370mm with no issues. Then again this was a limited "m sport" n20 exclusive for around 2-3 years. No issues driving around town and braking is nice compared to stocks. Brakes felt the same when I did the initial swap with factory pads, but EBC reds woke it up. It's also possible I got a pair of glazed pads onto new rotors so they didn't bed properly or something.

I'll dig out the stock calipers and show mounting points for front vs rear over the weekend.

Otherwise depending on the year of your f30, you can get caliper adapters on your car to run 380mm all around with the f80/f82 calipers just like an M car. The fronts will work 100%, the rears depend on the parking brake size you have in the rear.

[sqwinny]

As promised, this is why the front calipers can't mount to the rear. The bigger bracket + sizing is the front. The rears are mini. I suppose you could create a bracket to make it work if you really wanted to, but the next question to ask is will the front rotors hat accommodate the parking brake from inside the rotor hat? I'm not sure nor have tried but it's a good question to investigate.

[Ennoch]

Going back to the aforementioned point, the piston sizes are totally wrong which means that even if you could bolt them up, they're still not going to work unless you want the back brakes to lock any time you try to slow down as it'll be akin to yanking on a hydraulic handbrake.

[liveevil]

Originally Posted by johnung

Hope this helps!

I have the hawks 5.0 with 370 at the front. It stops great but the first few braking in the morning has very little bite. It is squeaking quite loudly after a few months though.

[johnung]

Originally Posted by liveevil

I have the hawks 5.0 with 370 at the front. It stops great but the first few braking in the morning has very little bite. It is squeaking quite loudly after a few months though.

Sounds strange. My Hawk 5.0 pads warm up when I touch them for the first time. Maybe they weren't quite bedded in properly and have some build up on them.

Squeaking usually means that brake paste wasn't applied properly or some of it has been removed. That often happens if wheels were pressure washed and paste was washed away. See diagram.