6R Brake Master Cylinder Upgrade

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Jay-Jay
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6R Brake Master Cylinder Upgrade

Post by Jay-Jay »

My Polo 6R 1.2 TSI has a 22,2mm master cylinder.
I've always found the brake pedal feel a bit soft in the initial part of the pedal travel (even after many proper bleeds and ABS bleeds).
Car stops very well, but brake pedal doesn't give me the confidence I want.

After having tested few Polo 6R GTI and 6C GTI with a 23,81mm brake maste cylinder, I really liked the pedal feel: it is tougher, more reactive and with shorter travel. Exactly what I'm looking for! :D
Looking in the engine bay of a friend's 6R GTI with a 23,81mm master cylinder, it looks like it is identical to the 22,2mm one.
I don't notice any difference in dimensions and in the way it links to the servo.

Do you think it might be a plug&play upgrade?

Part number has been updated few times:
  • Polo 6R
    • untill 3.11.2013
      6R1611019B
    • since 4.11.2013
      6R1611019E --> 6R1611019G
  • Polo 6C
    • 6C1611019 --> 6C1611019B
What part number should I order?
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iichel
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Re: 6R Brake Master Cylinder Upgrade

Post by iichel »

Remember you need to re-bleed the entire system again and there are no guarantees it will be perfect this time around
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Jay-Jay
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Re: 6R Brake Master Cylinder Upgrade

Post by Jay-Jay »

I'm honestly not worried about that anymore. :)
Some time ago, after previous bad experiences with normal bleed procedure and cheap pressure bleeders, I bought a good pressure bleeder able to pressurize the brake circuit up to 4,8 bar.

As you know, ElsaWin says it is mandatory to bleed the circuit with a pressure of at least 2 bar, otherwise the internal ABS valves don't open and it is impossible to fully bleed the circuit.
Well, thanks to my new tool, I bled the system at 2,5 bar and I've been able to remove all the air trapped within the ABS Unit.
You can't imagine how many air bubbles came out of the clear hose I used. :shock:
After that, my brake pedal became a lot stiffer and more reactive: much more than I remember it was from factory.

Recently, I replaced brake fluid once again, because it was 1 year old and I wanted to go from Motul RBF660 to the new RBF700.
I bled the brake circuit in the same manner at 2,5bar and brake pedal feel didn't change at all.
So, I have no doubts this pressure bleeder can perform brake bleed procedure succesfully. :)

Now I just need to understand if the 23,81mm brake master cylinder is plug&play on my servo. :P
The question could be extended also to the 25,4mm brake master cylinder (6C1611019A --> 6C1611019C).
My Audi S1 has a 25,4mm master cylinder and pedal feel is AWESOME!
If someone could confirm that I can install the same master cylinder on my Polo, it would be immediately Christmas! :lol:
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Re: 6R Brake Master Cylinder Upgrade

Post by RUM4MO »

That is interesting about the suggested higher pressure for bleeding brakes, I have not seen that written in my official workshop manual for either of my cars which has been sourced from ErWin which is the same source as ElsaWin, maybe I need to read it again, I'd think that the part that limits the bleeding pressure will be the fluid reservoir and I'd surprised that it has not tried to split at the welded seams at pressures around 2.0Bar.
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Re: 6R Brake Master Cylinder Upgrade

Post by iichel »

yes you can fit the 25mm master cylinder on your 6R as well. it is often done in conversions to WRC/S1 brakes in countries where the rules are strict like Germany and Switzerland.
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Re: 6R Brake Master Cylinder Upgrade

Post by amer6R »

I think it's because the Dealer uses diagnostic procedure to bleed the system.
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Jay-Jay
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Re: 6R Brake Master Cylinder Upgrade

Post by Jay-Jay »

iichel wrote: Sat Nov 28, 2020 7:04 pm yes you can fit the 25mm master cylinder on your 6R as well. it is often done in conversions to WRC/S1 brakes in countries where the rules are strict like Germany and Switzerland.
Do I have to change the servo as well? Or can I install the bigger master cylinder on my servo?
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Re: 6R Brake Master Cylinder Upgrade

Post by iichel »

just the master cylinder is fine
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Re: 6R Brake Master Cylinder Upgrade

Post by Jay-Jay »

Thank you so much iichel! :)
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Re: 6R Brake Master Cylinder Upgrade

Post by Jay-Jay »

Today I opened the hood of my S1 and took a look at the brake master cylinder.
Unfortunately it is very different respect to the 22,2mm and 23,8mm master cylinders.
Image
Image
As you can see, the second hard line is connected from the top of it.
Instead on the 22,2mm and 23,8mm master cylinders, the two hard lines connect from the left side of it.
So, if I want to install 25,4mm master cylinder I should re-route the second hard line...
I just need to understand how much of a hassle it would be to do it and if it's worth it.
Plus to that, there could be the risk the 25,4mm brake master cylinder is also different from behind, where it connects to the brake servo.

Installing a 23,8mm master cylinder, instead, is 100% plug&play and a bit cheaper.
I can't take the risk that I buy the 25,4mm master cylinder and only then I discover it is impossible to adapt and install it on my car...
So I think I'll go for the 23,8mm one.
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iichel
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Re: 6R Brake Master Cylinder Upgrade

Post by iichel »

Yes, but you'll find the complete brake setup of the S1 quattro is different, it has the 8J1611021E master brake cylinder and the ESP block on the driver side.
The 6R WRC has the ESP block on the passenger side and it has the 6R1/6C1 master brake cylinder.
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Jay-Jay
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Re: 6R Brake Master Cylinder Upgrade

Post by Jay-Jay »

In reality, my Audi S1 doesn't have the 8J1611021E master cylinder, but the 6C1611019A or C one.
8J1611021E master cylinder is from Audi TTRS/RS3 and it has both hard lines connected from its left side, but at a different angle than on 22,2/23,81mm master cylinder:
Image
Plus to that, there's no assurance it is compatible with my brake servo.

It seems like 23,81mm master cylinder (6R1611019B) from Polo R WRC and 6R GTI MY2013 is the one to go.
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iichel
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Re: 6R Brake Master Cylinder Upgrade

Post by iichel »

isn't the WRC also 25mm? if not, i stand corrected.
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Re: 6R Brake Master Cylinder Upgrade

Post by Jay-Jay »

Nope. The R WRC has the 23,81mm master cylinder like the 6R GTI MY2013 and the 6C GTI. :)
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Re: 6R Brake Master Cylinder Upgrade

Post by iichel »

I think that's where I f****d up, sorry for my misinformation. Then go for the 23.8mm!
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