Polo 6R braking thread (Mainly GTI/Diesel)

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Originally Posted by gavs

Generally, I would agree with you (like i do on a good 90% of things), but when you see this kind of weight saving, per corner at the front.... (courtesy of APR)
http://www.vwwatercooled.com.au/forums/

VS

http://www.vwwatercooled.com.au/forums/

That is a 4 piston, 323mm alcon setup (shown in one of the previous images) vs the stock, single piston, sliding caliper setup with 288mm rotor.

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That's bloody impressive but I imagine most of that weight saving is in the calipers (machined aircraft aluminum billett vs gravity cast T356 or similar aluminum) so it's non-rotating mass. It would be interesting to know the rotational moments of inertia of the rotors (anyone else remember the effect of the big brake upgrade on the Top Gear Renualt Aventine's lap time? OK, they had to 'upgrade' the wheels to fit over the bigger brakes which also hurt the time but this is another thing people do here a lot)

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Originally Posted by gavs

Some cars are just under braked (VX-VE Commodore SS for example) from the factory. Is the 6R GTI one of them?.....

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That's the point - an old Falcadore is quite likely to be underbraked but Polo GTis and the like are very well spec'd in this manner and pads and fluid are limiting on road factors (unless maybe towing but who hoons while towing a trailer??).
Braking really, really late on every corner going down a mountain just isn't smart - if you only do it every now and then because you are being caught out, the brakes will recover (and you need to adjust your braking points).

All you are saying is quite pertinent but I think you are simplifying things unnecessarily - I'd rather you give the full blown tech picture with justification for why the things you are saying are the best choices instead of dumbing it down

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Originally Posted by kaanage

And I still don't believe that a car like a Polo Gti should be fading brakes on the road if driven properly. Being "king of the late brakers" on public roads is not responsible behaviour and is totally unnecessary, even for showing off

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i agree with this - whenever i drive spiritedly, i am always ''relatively'' easy on brakes, and i always trail brake early before a corner as i never take for granted that the cumulative effect on brakes of corners "may" catch me out if im not careful.

to illustrate a clearer picture as to what happened on the day when i decided that the stock brakes were simply not enough:

i was very much driving conservatively - this was my first ever cruise. troy was there, way back when, when he'd just bought his polo and it still had just apr stg 1, fmic, and the former owner's cut springs.

i was not pushing the brakes at all - put simply, i was a complete newbie to twisty road driving (stock suspension at the time, and the remap only as a result of finding out that these torque gains were possible for such a low price and with no hardware changes).
to put it into perspective: on the 2-3 times that we stopped off and then left off again, it only took troy (second last, i was at the very back) around 2 corners to completely leave me for dead - after coming down from baw baw and meeting the boys, colin told me that they'd been waiting for me for roughly 15 mins.

so with that in mind, and the fact that my stock brakes had never before had me feeling doubtful, it was after only a half dozen corners on the way down from baw baw parking lot, that my brakes started fading BAD, loss of pedal feel, hugely decreased braking ability etc etc. another half dozen corners later, as i approached the group at the first T intersection/ turn off down the hill from baw baw, even others saw my brakes smoking bad.

no, one should not be a late braking hero on every corner on the road, but it was at that point, with that shtty feeling, wondering whether my brakes will be able to keep me safe if there are multiple corners involved (even braking at legal speeds after a straight), that i decided that the stock setup on my particular car was just plain fuggin unsafe, and unsatisfactory.

this decision was made after 6 corners of a downhill run on which i was slow enough such that all the other cars were out of sight after the second corner, the gap eventually growing to 15 minutes over 30km's or so. never again will i allow myself to feel that unsafe with just myself in the car again, let alone with other people or a car full of cargo.

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Originally Posted by gavs

I agree, it is quite stupid, but on the odd occasion when someone might like to drive a bit more spirited, either down mount buller or on a track, there is the possibility of the brakes fading. I personally, would prefer the possibility of the brakes fading to be a slim one, not a certainty, but hey, that is just me. As Scott said, 6 corners and his brakes were shot and I know that Scott can be a bit more brave than others when driving, but I also know he isn't an idiot. Some cars are just under braked (VX-VE Commodore SS for example) from the factory. Is the 6R GTI one of them?.....

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i agree with you as well, gavs - from now on, whenever i buy a car, any upgrades i do will be done (to my best effort) in stock sizes, but one thing i WILL be doing at the very least, even when seemingly unnecessary, is replacing the fluid with top shelf stuff - going from the feeling that i had when my brakes were fading and i was running wide on subsequent corners at low speeds, pumping the brake pedal and shtting my pants, i cannot emphasise what huge peace of mind i have had since replacing my fluid (and pads and rotors at the same time), and never getting brake fade/ faded, spongy pedal feel, ever again.

regardless of how hard i drive in the hills (and it's getting more and more sedate - in and around town, im often reaching for 5th gear at 60kmh these days), i know that the bare minimum that my brakes are now capable of, is keeping me and friends safe whilst coming down from buller/ falls creek. i honestly believe that my stock setup would NOT have lasted at even slow speeds, coming down from falls, with 3 in the car, a boot full of crap, and a roof wide load of boards/ skis.

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Originally Posted by kaanage

All you are saying is quite pertinent but I think you are simplifying things unnecessarily - I'd rather you give the full blown tech picture with justification for why the things you are saying are the best choices instead of dumbing it down

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not trying to smooch up or anything, greg, but in my honest opinion, you are one of the people on here with the most technical, broad-based, intricate knowledge that i can think of. petrol or diesel, subwoofers or suspension geometry, your knowledge is huge, to the point that i reckon you are one of the very few people on here who could go toe to toe with some of the guru's on tdiclub, and anyone who's read through even moderately technical threads there, knows that this is saying something.

i think gav's hit the nail on the head with regard to technicality - sure, it will be up to the more knowledgable to question and respond, as you are doing, but i also think that this thread services a solid member base with its explanations that are thorough, yet not beyond the grasp of anyone who's new to car modding - the 6R section generally seems to be pretty good so far, but the 9n3 section is seeing a new wave of peeps coming into the second hand gti market who are asking lots of questions about what they can do to improve their cars.

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Originally Posted by gavs

Ok, so why are certain things irrelevent on a 6R? Simple. Control module 03, 10 Adaptation, 09: 0, 1, 2

This code alone is what controls your braking. In the 6R, your braking system is 90% identical to any hydraulic braking system except for one thing, the brake pedal itself. It is not connected to the braking system, it is connected to a box full of 1's and 0's that sends coded signals to another box that controls the brake master cylinder.

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I changed the value to "2" on my GTI and the braking seems to be more immediate...

What I noticed is that when I changed the value (computer connected, ignition key in "on" position and "Do it" command done on VAG software), I heard a "clack" on the right side of the car coming from engine room... Don't know exactly what can be, I guess it's just a different setting for vacuum brake helper, like a valve that change position and get more decompression from the engine to help braking...
It's only my assumption...

As I said braking didn't change so much, just the pedal seems to be more immediate, that is just IMO the largest lack in GTI's braking...

If I can get some time on cad to do the exact value calculations using a common hole pattern for drilled rotors, then I'm more than happy to show the loss of surface area by using the holes, but I can also show how the weight also changes for the better, based on a 312 mm rotor. I can also show the surface area loss by going to cross drilled and slotted.

The next thing I was going to talk about is bedding in and how it can benefit your braking performance if done correctly.
The following is taken directly from the stoptech website:

Stock Brake System Bed-in

This is based on standard style rotors and is sufficient for our purposes. At the end of this I will put some links to the stop tech website which is where I have learned much of my knowledge from along with the guys I work with and yes, they do discuss drilling of rotors, but I won't spoil it.

The fundamental reason behind the correct bedding in of your brake pads is to 'bake' on pad material to the rotor. This forms an adhesive layer for the pads to adhere to. This layer is more sticky than the cast steel of the rotor, so the pad can grip onto it better, hence providing a stronger handle moment, providing greater torque to the rotor, slowing the rotor down quicker, theoretically allowing you to stop quicker. There is a fundamental problem with this though and that is that most of the braking we do is light pedal application braking, which doesn't occur at the higher temperatures required for adhesion braking. In this case, abrasive braking occurs, which means that the pad and rotor both wear. This type of braking removes the layers of adhered pad compound. When adhesion kbraking occurs, the rotor will actually grow in thickness and the pad shrinks, with abrasive braking both wear. With the lighter pedal applications in day to day life, you remove any semblance of the bedding in. BUT. If you're going to do a track day etc, then you can still perform the bedding in procedure and you will once again, have adhesive braking abilities:)


Have a read of the following, while not the be all and end all of the technicalities of braking, it does cover off a sizable amount of technical info.

Technical White Papers

Hi gavs
Firstly, thx for all the info, it was great
secondly, i was wondering if the mk6 golf gti brake kit will fit in my 1.2tsi polo, and is there any cheap alternative options to do a upgrade on my polo ( i dont have money for brembo or alcon those kind of stuff), my polo has only done 20000kms and the discs have already wrapped.
lastly, on my brake reservoir it says dot 4 only, can i still use dot 5 brake fluid.
cheers

Has anyone actually fitted one of these bbk's as of yet?

Currently we look like we are about to purchase a MY12 Polo Comfortline 77TSI but one of the things we are quite unsure about is the brakes. In fairness, my wife and I are used to my car (which happens to have a Brembo GT BBK) so I never expect the braking quality to be quite that good, however if there is a way to get a slight improvement I would definitely be interested. If i could get R32 style braking I would be more than happy. From what I understand my MK5 GTI calipers wont fit, but MK4 ones will?

Basically I just want to know about clearance etc. Had a lot of trouble finding wheels to fit the brembo's and this time around i dont want to move away from OEM rims. As such, i figure im likely looking at OEM single piston.

Also, whilst I have no scientific basis for what im about to say (and you obviously do) I really do feel that saying better brakes wont stop you faster seems incorrect. Perhaps its all in my head (and a placebo) but fitting the Brembo's to my car has made it feel like a completely different car. So much so that I find myself in dangerous situations now when i decide to brake in any other car i drive (including my dad's R32) as i brake way too late (see above question). You could be 100% right, i might just be trying to justify $5k worth of brakes, but apart from my bi-xenon's, they are my favourite part of the car...

I'm sure I posted a reply to this the other day but obviously I didn't....

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Hi gavs
Firstly, thx for all the info, it was great
secondly, i was wondering if the mk6 golf gti brake kit will fit in my 1.2tsi polo, and is there any cheap alternative options to do a upgrade on my polo ( i dont have money for brembo or alcon those kind of stuff), my polo has only done 20000kms and the discs have already wrapped.
lastly, on my brake reservoir it says dot 4 only, can i still use dot 5 brake fluid.
cheers

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First off unless your discs were red hot and you drove though a massive puddle, your discs aren't warped. It is nigh impossible to warp a brake disc in regular use. What you will be experiencing is uneven pad material deposition due to incorrect bedding in.
Secondly, no it wont because you will need to, well, buy an entirely different car. The Golf and Polo GTI share the same front brake caliper, but that is it. You could retrofit the GTI brake package but for the cost involved, you might as well have just bought a GTI to start with, unless of course you can find a cheap wreck. You are far better off getting the discs machined or new discs altogether and fit better pads and upgrade your brake fluid to something like TRW, Martini and even the top spec Castrol stuff. If you aren't paying ~$20 a bottle for the brake fluid, it's going to be pretty standard stuff. Regarding the DOT ratings, your better guide will be to follow the VW spec (can't remember off the top of my head, 541 or something from memory...) and get fluid that matches that.

Please maraach, if you are going to quote me, ensure you are quoting correctly. "Also, whilst I have no scientific basis for what im about to say (and you obviously do) I really do feel that saying better brakes wont stop you faster seems incorrect. " I never, ever said BETTER brakes won't stop you faster, i said BIGGER brakes will not make you stop faster.

For the 1.2TSI, you will really be wasting your money. I believe that yes, on your R32 that $5k is going to need a pretty big placebo hit because I am sure that when fitted, there would have been fresh rotors installed along with new pads, which would have been bedded to those rotors. New fluid as well of a better grade than factory and you don't have th einherent slop of a sliding caliper with a machined alloy caliper. The unsprung mass is probably considerably less also which all contribute to the feeling but what you are describing is comparing apples with lemons.

Unless you put the same fluid, same pad and rotor compound combination on the car before fitting the brembo's and do a GPS based brake stopping distance test, then repeat the test with the new brakes, you will never know. You also mentioned wheels, so if the wheels too are different then the tyres would be newer and possibly better as well.

Pads and fluid guys, pads and fluid. If you want a multi-piston caliper setup, try and stick to the existing rotor size or an increase that is as small as possible. On both of your 1.2 77TSI polos, it isn't worth the expense. New hubs, hub spindles, tie rods, fluid, pads, rotors, calipers, caliper carriers, hardware, wheel bearings, wheel bearing tool, brake lines etc.

As a final note, there is nothing wrong with sliding calipers. A BMW M3 CSL does quite well with supposedly crappy sliding calipers.......

Is it possible to change the brake assist via VCDS in the 77TSI? Perhaps that can get the harder stopping feel you desire.

http://www.vwwatercooled.com.au/foru...tml#post785181

The XDS setting won't be there of course

I am starting to wonder whether the brake issues some people are having might also be influenced by the XDL and agressive cornering and not necessarily from late and agressive braking.
I also wonder if people are lazy with appropriate gear selection.
Anyway this is a great thread, and am seriously considering these options depending on how I think when I get the car

I don't know what brake issues you are talking about melon head because the people that have been complaining about the rotors on their cars all have 77TSI polos and the 77TSI doesn't have the XDL.

Readerr0r, the brake assist channel will be the same so try and see of its available....