OEM brake upgrade

[hf delta]

Hi,
first of all - this is my first forum thread ever! Been using the audizine forum alot but never posted anything..

Have upgraded front brakes to the 312x25 from the V6 model. (Black Diamond grooved and drilled rotors, Redstuff C pads and OEM v6 carriers)
Car is 2003 A4 B6 Avant 1.8TQ, rear brakes is still stock with stock pads.
Now I am looking to upgrade my rear brakes as well. The idea from the beginning was to use the V6 brakes (255mm) also here.
But I have some thaughts..

After the 312 front upgrade the braking felt slightly stronger on summer tires. The braking bias is pushed a bit towards
the front and gives the front wheels more weight under hard braking.
On winter tires, and especially when its wet, the total stopping power feels weaker than before the upgrade.
The front wheels "locks up" too fast and therefore I think the new brake distribution gives a longer braking distanse because the rears does a smaller part of the job.
(The braking does not give the front enough extra "weight")
In the winter I drive a lot on snow and my braking power will be even weaker compared to stock.

255 mm is not a big upgrade compared to stock 245, and definitely a weaker upgrade than going fron 288 to 312 in front.
So I did some approximate calculations:


Re = Effective radius (rotor radius minus the "average" of the brake pad area, wich I assume is 30mm on both because I dont have pads available)


Stock: Re front / Re rear = ((288/2)-30) / ((245/2)-30) = 1,23

V6: Re front / Re rear = ((312/2)-30) / ((255/2)-30) = 1,29

I looked at this relation because torque at center is linear in relation to radius.
Caliper pressure is kept out because the models use same caliper.

To keep the stock brake bias I would need a rear brake rotor with 265mm in diameter,
but the next OEM a4 rear upgrade is 288mm from A4 B7. Have anybody done this rear upgrade? (I guess the B7 have different caliper)
Is my calculations way out and what is normal to do with the rear brakes after bigger brake upgrade in front?

Thanks!

[A4twin]

alright i would do at least B5 s4 brakes up front(321mm or 322mm cant remember), which are really cheap and get the b7 a4 rears(which are solid) or get the b6/b7 s4 rears which are vented(which are much better). I have cayenne turbo calipers upfront and b6 s4 rears. my bias is fine. before that i had b5 s4 fronts and b6 s4 rears and my bias was fine. car stops on a dime, also i recommend you get some nice soft tires. which i help out alot...

[hf delta]

Thanks for quick reply! Forgot to mension what my needs really are. I am very happy with my tires, but my winter tires have 16" rims and therefore I am limited to A4 B7 in front (320mm). Also I do not use the car at the track and dont want to add lot of unsprung weight I dont "use".. My concern with the 288 rear upgrade is the danger of rear wheels locks up first

[diagnosticator]

Thanks for quick reply! Forgot to mension what my needs really are. I am very happy with my tires, but my winter tires have 16" rims and therefore I am limited to A4 B7 in front (320mm). Also I do not use the car at the track and dont want to add lot of unsprung weight I dont "use".. My concern with the 288 rear upgrade is the danger of rear wheels locks up first

The ABS controller must be coded according to the front brake specification fitted. For 312mm rotors, the spec is 1LT/1LF, the coding value is:

L00,Brake Electronics (J104/Bosch 5.7) Login
L01,0?xxx: Chassis
L02,9 = Audi A4
L03,0x?xx: Brakes
L04,2 = Brembo 17" (PR-1LJ)
L05,3 = FN3 16" (PR-1LT/1LF)
L06,4 = HP2 16" (PR-1LX)
L07,4 = FNR 16" (PR-1LA/1LG)
L08,5 = FN3 15" (PR-1LB/1LE)
L09,6 = C54 (PR-1LZ)
L10,0xx?x: Engine
L11,5 = 4/6 Cyl. Diesel
L12,7 = 4/5 Cyl. Gasoline
L13,9 = 6/8 Cyl. Gasoline
L14,0xxx?: Transmission
L15,5 = Manual
L16,7 = Automatic (09L)
L17,9 = Multitronic (01J)
L18,
L19,Note #1: After Login/Coding-II has been carried out you need to recode the Control Module.
L20,Note #2: Special Login/Coding-II 09399 is used for BFB Engine with 1LT Brakes and Multitronic.
L21,
L22,40168 = Basic Settings Enabling (i.e. mandatory prior to Steering Angle Sensor Alignment)
;
;

From Ross-Tech VCDS lable file,

"C00,Brake Electronics (J104/Bosch 5.7) Coding
C01,0?xxx: Chassis
C02,4 = Audi A4
C03,0x?xx: Brakes
C04,1 = C54 (PR-1LZ)
C05,2 = FN3 15" (PR-1LB/1LE)
C06,3 = HP2 16" (PR-1LX)
C07,3 = FNR 16" (PR-1LG)
C08,4 = FN3 16" (PR-1LT/1LF)
C09,5 = Brembo 17" (PR-1LJ)
C10,0xx?x: Engine
C11,5 = 4/6 Cyl. Diesel
C12,7 = 4/5 Cyl. Gasoline
C13,9 = 6/8 Cyl. Gasoline
C14,0xxx?: Transmission
C15,5 = Manual
C16,7 = Automatic (09L)
C17,9 = Multitronic (01J)
C18,Note #1: Coding is accepted after a specific Login has been carried out.
C19,Note #2: Special Coding 04499 is used for BFB Engine with 1LT Brakes and Multitronic.
C20,Note #3: After successful Coding the Steering Angle Sensor Alignment needs to be carried out.
;
;"

From the above, for the 312 mm brake rotors, the coding is 04577. (the old coding should be 04277)

Before coding, the Coding II login must be entered,

From Ross-Tech Label file; 8E0 614 517.lbl

"

[hf delta]

Thanks, never thougt of the coding! But do you refer to the 312 front and 245 rear or 255 rear? (May upgrade to 255 rear later...)
Where can I find more information about the coding alternatives? The code 04577 is C09,5 = Brembo 17" (PR-1LJ)?

What is the login/code steps? Have never coded in vag com...

[DiertyEuroSpec]

Went digging into some older threads as the rear caliper carrier bolts are a PITA on my 03 A4(Letting them soak overnight ) Just noticed this post about recoding the ABS controller for larger brakes. I am going to B6 S4 all the way around, what coding should I use here? Much thanks

[drjonez]

If anyone can actually get their ABS unit to take a different brake size coding, please post up! I've tried and failed...multiple times.

[Charles.waite]

If anyone can actually get their ABS unit to take a different brake size coding, please post up! I've tried and failed...multiple times.

Yea I'm interested in this as well. I've never had to recode yet, but I'm doing the B6S4 upgrade soon and will probably try to recode. Not sure if it'll work or not.

[drjonez]

I've made a few posts on the topic....and my inability to recode the ABS module to anything other than what it came with stock.

[Charles.waite]

I've made a few posts on the topic....and my inability to recode the ABS module to anything other than what it came with stock.

Yea I've read some of those. The process sounds like it should be so easy, yet I'm not sure anyone has ever managed to do it...

[dewey527]

Yea I've read some of those. The process sounds like it should be so easy, yet I'm not sure anyone has ever managed to do it...

I'm installing the B6S4 brakes too so how about we meet up and then meet diagnosticator to recode it? Sounds like a plan to me since he is the master jedi of audis!

[Charles.waite]

I'm installing the B6S4 brakes too so how about we meet up and then meet diagnosticator to recode it? Sounds like a plan to me since he is the master jedi of audis!

Haha. Maybe if we placate him with some booze. That is if he really exists (I have my doubts!).

Either way its probably a few weeks off for me. Still need to source some parts. Well actually all I have are B7A4 rears, haha, but soon enough I'll finally pull the trigger.

[dewey527]

I was going to just stick with stockers but I am really debating switching to the B7A4 of S4 rears...since I am experiencing some issues with my ebrake now sticking anytime - cold or warm. Hell I might have to get a loan out for all the PM stuff coming to the surface.

[walky_talky20]

but my winter tires have 16" rims and therefore I am limited to A4 B7 in front (320mm).

I know this is an old comment, but I wanted to add that the B5 S4 HP2 calipers do indeed fit under 16" rims. They came this way on the earlier C5 A6 2.7T's. There are only a few styles which will allow this fitment, but it is possible.

These speedlines are one example:


And I believe these tapered 5-spokes are another:

[vhstejskal]

I've made a few posts on the topic....and my inability to recode the ABS module to anything other than what it came with stock.

*1000000 I've read your posts on this topic, followed the direction trying countless combinations of logins procedures but nothing stays...

[Pitzury]

*1000000 I've read your posts on this topic, followed the direction trying countless combinations of logins procedures but nothing stays...

I have just done the ABS recoding on my 2004 Passat and it is a different car. I had the ABS disabled because the stopping was so bad after a Porsche/Audi 80 S2 front calipers on 321x30mm Audi discs upgrade. Now it is recoded for 321mm diameter brakes and it works wonderful. I wish i have thought about this before last year's accident where I couldn't stop as fast as the car in front of me and I had a somewhat slight bumper to bumper. We both were going about 130kmph before the sudden braking.
I plan to replace the rear brakes too and I will probably play with different coding to see which one works best. Interesting that coding only takes the front brakes size into consideration and not the rears too.

You have to login with the code that matches the new coding you are trying to set and then change the coding. Makes sense?