6R Brake Master Cylinder Upgrade

[Jay-Jay]

Don't worry, iichel!
I've just ordered the 23,81mm brake master cylinder.
I'll update this topic as soon as it arrives to me.

[Jay-Jay]

Well, I've just installed the Ø23,81mm brake master cylinder and all I can say is wow!
The pedal is much stiffer and more reactive and pedal travel is much shorter: I would say 50% shorter.
It gives me the confidence I always wanted after having upgraded the front brakes to 288/312 setup.

Here are some side by side comparison photos I've taken during the installation:

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As you can see both master cylinders look almost identical: the fitting to the servo, to the clutch line and to the brake lines are in the same positions.
Also the brake liquid reservoir is totally exchangable between the two master cylinders.
The only relevant difference is the outer diameter, which is obviously larger on the Ø23,81mm one, but it doesn't cause any fitting/interference problems with closer components in the engine bay.

So, in the end, if you have ABS unit Bosch ESP 8.2i and you upgraded or you want to upgrade from 256mm front brakes to 288/312 front brakes, I highly reccomend upgrading your master cylinder too, as the bigger one makes your brake pedal stiff and reactive again, maybe even stiffer and more reactive than it was with the old 256mm front brakes.

[iichel]

Thank you jay jay. Was it an easy fit?

[Jay-Jay]

Yes, it was. At least on my engine bay.
Firstly, I removed the airbox and the intake hoses to give me more space.
Then, to avoid brake liquid dripping on other components during the removal of the old master cylinder, I did as follows:
- I removed all the brake liquid inside the reservoir with the help of a siringe;
- I put few rags and a little plastic tray under the master cylinder;
- I removed the brake liquid reservoir by extracting the little plastic pin from the left side of the master cylinder and by pulling the reservoir upward;
- I unplugged the clutch plastic line (be carefull to remove also the rubber seal and to put it back inside the plastic clutch line, as it will make it easier to replug it to the reservoir later);
- at this point, I slowly unscrewed the two brake lines's nuts, allowing the remaining brake liquid to drip into the trail underneath;
- in the end, I unscrewed the two nuts on the servo and pulled off the master cylinder (be carefull to check if the metallic/magnetic rod inside the brake servo doesn't move from its position, because it could happen that it detaches from the servo. It happened to me, but luckily I noticed it and I immediately putted it back in its position. It is extremely important it stays in its position, otherwise it could not properly touch the brake maste cylinder's rod, causing fatal braking issues).

Then, I installed the new master cylinder in the reversed order and I bled the entire system with a pressure bleeder pressurized at 2,4bar. I checked the pressure after each caliper bleeding to ensure it didn't go under 2bar.

And that's it!

[iichel]

Great, thanks for sharing and enjoy your upgrade!

[amer6R]

Brake feel is bad on stock setup and soft suspension doesnt help at all.

[Jay-Jay]

My brake pedal felt pretty good with stock brakes (256mm front, 232mm rear), but I already had sport suspensions (Bilstein B12 at that time) and HEL Performance stainless steel braided lines.
It became softer and less reactive (with a longer travel) only after I upgraded to 288/312mm front calipers.
I bled the circuit so many times that I lost the count.
I got close to the original feeling, but it still was softer and less reactive.
So, I gave up for a few years, because I was 100% sure there was no air in the system.

Now, with the bigger Ø23,81mm brake master cylinder, brake pedal feel has become even better than with stock brakes and you can't imagine how happy I am!
For me, this is the confirmation that the Ø22,22mm master cylinder combined with ABS unit Bosch 8.2i isn't enough for the 288/312 front calipers.

Two of my friends did my same front brake upgrade, but their Polo 6R have Ø22,22mm brake master cylinder combined with ABS unit Bosch 9.0i and their brake pedal feel almost didn't change at all (especially the TDI one, which has a separate vacuum pump for the brake servo).
I guess the ABS Unit Bosch 9.0i has a better internal hydraulic circuit than the Bosch 8.2i.

So, my suggestion is to upgrade to Ø23,81mm brake master cylinder only if you have ABS unit Bosch 8.2i and you upgraded or you want to upgrade to 288/312 front brakes.

Great, thanks for sharing and enjoy your upgrade!

It's a pleasure to share and help others.

[CNK]

Thanks for the great info and photos! I already have a 9.0 pump, but many of my friends complain about poor brakes in their 6R

[Jay-Jay]

You're welcome!

It seems like ABS Bosch 8.2i of the first production years is the main culprit of bad brake pedal feeling.

I once test drove a friend's Polo 6R GTI MY2010 with 288mm front brakes and Ø22,22mm MC combined with ABS Bosch 8.2i: the brake pedal was very spongy, with poor reactivity and long travel.
Then, I test drove another friend's Polo 6R GTI MY2012 with same 288mm front brakes and Ø22,22mm MC/ABS Bosch 8.2i: the brake pedal feeling was very good.
A week later another friend of mine bought a Polo 6R GTI MY2013 with 310mm front brakes and Ø23,81mm MC combined with ABS unit Bosch 9.0i: the brake pedal was rock solid and extremely reactive.
Then, my mum bought an Audi A1 produced in late 2011, which has 256mm front brakes and Ø22,22mm MC/ABS Bosch 8.2i: the brake pedal feel is extremely stiffer and more reactive than any older Polo with the same brake setup I test drove.

So, I arrived to these conclusions:
- the ABS Bosch 8.2i unit of the first years (MY2009, MY2010 and maybe MY2011) has an internal circuit which gives a bad brake pedal feeling (spongy, not reactive and with long travel), especially with 288/312mm front brakes.
- starting from MY2011 or MY2012 (I still need to discover it), ABS Bosch 8.2i unit has been updated and the brake pedal feeling got much better (infact my mum's A1 still has an 8.2i unit, but it has a newer hardware and software revisions than my Polo's MY2010 ABS 8.2i unit).
- starting from MY2013 ABS Bosch 9.0i unit has been introduced, maybe to completely fix this problem and to implement new functions.

So, in the end, I think the solutions are 2: upgrade your MC (like I did) or upgrade your ABS unit to a later 8.2i revision or to the newer 9.0i unit.

[amer6R]

I dont like the part, soft, soft -> than bites hard and softish springs front dives too much. On lowering springs it became better, btw. Stock setup pretty good for heel and toe, but for me the gas pedal is >1 cm too far to the right

I think that your upgrade was smart braided hoses than conversion. These cars would be awesome if they came all stock 288 front.

Also the throttle response is bad, but remap solves this.

[ORiOn]

Hey everyone

Can anyone tell me if the master cylinder from the Scirocco R which is also 23.81 will fit on the Polo 6R. Some people have done it on the Ibiza, I'm pretty sure they are the same as the ones from the WRC. Because I can't find anywhere one from the WRC, and I don't want to buy it at VW...

Polo 6R:
6R1 611 019, 6R1 611 019 A


Scirocco R:
1K1 614 019 A, 1K1 614 019 E, 1K1 614 019 L


Thanks

[amer6R]

Hey everyone

Can anyone tell me if the master cylinder from the Scirocco R which is also 23.81 will fit on the Polo 6R. Some people have done it on the Ibiza, I'm pretty sure they are the same as the ones from the WRC. Because I can't find anywhere one from the WRC, and I don't want to buy it at VW...

Polo 6R:
6R1 611 019, 6R1 611 019 A


Scirocco R:
1K1 614 019 A, 1K1 614 019 E, 1K1 614 019 L


Thanks

what about bolting holes to the brake booster are they in the same location?