Big Brake Kit for the Octavia? (Fits GTI MK5/6 and others)

[Martin]

Each caliper has three pistons on each side of the rotor disc
2 * 28mm & 2 * 31mm & 2 * 35mm (approximately)
In total this will be a lot more surface area than stock for sure
Normally with bigger pistons you would get a longer peddle, better feel and need to use less force
I'm guessing the smaller pistons are trying to reduce this effect - they should kick in fairly quickly

[Martin]

I found this very useful post regarding piston size on a UK forum:

In a single piston sliding caliper, you need to work out the area of the single piston, then double it, because on a sliding caliper, the opposite fixed pad in the caliper applies an equal and opposite force to counter the force from the single piston, this is why the disc isn't 'pushed' over to one side by the single pot.

If you DO decide to look at other calipers, just to the maths on the piston sizes and you can get an idea of how it'll effect the pedal feel.

So, the S3 has a 54mm piston as standard, which has an area of 2290mm², which doubled, gives 4580mm². This is what you need to match to retain an OEM pedal feel.

On a fixed 4 pot caliper, you consider each piston just once, as they work in opposite pairs.

The porsche 996 front calipers, and LCR Brembos, both have 36 and 40mm pistons. each 36mm piston has an area of 1018mm², and each 40mm piston has an area of 1256mm².

2 of each gives you a total of 4549mm², surprisingly similar to the 4580 of the standard setup. it's only 0.7% different infact, so a very good match indeed. This is why the pedal feel still remains good. You also get much less flex with the 4 pot calipers compared to a nasty sliding iron caliper.

[Weekend-Warrior]

In total this will be a lot more surface area than stock for sure

More than double.

I'm guessing the smaller pistons are trying to reduce this effect - they should kick in fairly quickly

To my knowlegde the reason for the dissimilar piston sizes is for even wear across the pad.

You may find that the rears actually come on faster and under hard braking may even trigger the ABS on the rear.

If you have high temp pads you may find it a bit interesting when they are cold pulling up at the first set of lights.

IMO a BBK is great on a track hack if set up correctly with the right master cylinder and bias valve. Not so great simply bolted onto your road car.

[Martin]

The kit comes with ceramic pads intended for (heavy) street usage but can handle (limited lap) track work
They are Corvette pads - huge area on them
Should be fine even when cold...

[Martin]

I've been measuring these HPA brakes and my wheels to see if the installation is likely to be successful
I'm only concerned about calliper clearance to the wheel spokes - all other mechanical aspects are fine

I can see why these will fit under stock wheels - it's because of the large rotor diameter - that pushes the calliper further away from the hub and wheel centre - there is more clearance to the wheels spokes out there

I also discovered that my Audi RS4 wheels have much more clearance than the Skoda Neptunes (which are sold) and the Golf R wheels - they are my backup plan if things to get too tight (need 3mm clearance)

I also placed a rotor inside a bare 18" wheel to see what it looks like - our 18" wheels do tend to dwarf our stock 312mm brakes, but it's completely different with these 355mm rotors which fill 80% of the interior wheel diameter

Our VRS rotors are 25~26mm thick - these HPA rotors are 32mm thick
Now on paper that does not sound like much - although mathematically it's 23% thicker
However, holding these big HPA rotors is quite intimidating - they are a massive lump of very thick steel

I may have to see if I can weight stuff - the stock brake parts and the HPA components
The HPA callipers are clearly very light, despite being physically massive they are not at all heavy
The rotors weight a ton, I would expect tears if I dropped one on my foot

I'm very tempted to throw some DS2500 pads in the rear
(can't find the Ferodo DS2500 part number for the 1Z4)

Any suggestions as to what brake fluid to use?

[Martin]

To my knowlegde the reason for the dissimilar piston sizes is for even wear across the pad.

Now I understand - the leading edge may bite harder than the trailing edge - thanks

IMO a BBK is great on a track hack if set up correctly with the right master cylinder and bias valve. Not so great simply bolted onto your road car.

I agree in principle
The VRS has a bigger master cylinder than the normal models - that's why its brakes currently feel over powered around town
There are numerous big brake kits designed for the Audi/Golf/Skoda platform - people that do purchase them are very happy with the performance and feel

[rc_vRS]

Then I found the HPA big brake kit which fits numerous VAG vehicles
HPA Motorsports Inc. - Big Brake Kits
355mm rotors - hur hur hur - 6 pot calipers - hur hur hur
The rotors are 32mm thick, two piece hat, slotted rotor face
But they are designed to fit under stock 18" wheels without a spacer - we have a winner!
(You have to remove the factory rotor dust shield however - I'm fine with that)
Apparently these save 14.5kg of unsprung weight

So stay tuned for installation and road test reports!!!

They are big brakes. I'd be very skeptical about a claimed 14.5kg weight saving though. I'd be impressed if they weigh less than the stock set up at all given the size increase.

What are the weights of the HPA caliper/disk?

[Martin]

They are big brakes. I'd be very skeptical about a claimed 14.5kg weight saving though. I'd be impressed if they weigh less than the stock set up at all given the size increase.

Yes, have to agree, I guess the question is what was the claimed weight saving compared to?
If they were comparing to R32 brakes - maybe...

What are the weights of the HPA caliper/disk?

The calipers, brake pads, mounting plate and bolts weight 4.2kg (heavier than it feels)
The rotors weight 9.2kg (lighter than they look/feel)
That seems like a good weight for the rotors considering their diameter and thickness

[rc_vRS]

Yes, have to agree, I guess the question is what was the claimed weight saving compared to?
If they were comparing to R32 brakes - maybe...

could be right there, so they are not quoting that saving based on a mk VI / octavia?

The calipers, brake pads, mounting plate and bolts weight 4.2kg (heavier than it feels)
The rotors weight 9.2kg (lighter than they look/feel)
That seems like a good weight for the rotors considering their diameter and thickness

The calipers and mounting hardware are pretty light for what they are, I'd guess that stock calipers would be more than 4.2kg each.

[Martin]

could be right there, so they are not quoting that saving based on a mk VI / octavia?

I think I'm the only nutter to install these brakes into an Octavia
The target audience for these brakes is people running Audi TT and R32 with HPA StageIII engine or HPA Twin Turbo gear

The calipers and mounting hardware are pretty light for what they are, I'd guess that stock calipers would be more than 4.2kg each.

I will report back...