New Brakes!

[dave_r]

Aren't all 6R Polo's MY11 or only ones built post June/July?

that and the gear knob is much better then before.

LOL yep that'd be it. Updated DSG shifter improves the car 17.3%*

*Estimated

[Hail22]

Who wants to drive a car with a shifter that looks like a dinosaur bone haha.

[gavs]

Dredging up an old thread due to current relevence:

i'll chip in here. i know i've just got a 9n polo, but here was my experience: prior to getting my brakes done, i had the tune, and having a ''spirited'' drive every now and then wasnt a problem - squirting up the eastern, up mtn hwy, etc etc.

hooked up with some watercoolers for a baw baw cruise, with some people who ACTUALLY drove spiritedly (much more than i was used to), and it completely transformed the way i viewed my brakes - i got heavy brake fade after around 6 corners on the way down from the baw baw car park, and stopping at a T intersection, my brakes were visibly smoking like blackening toast in a toaster (seriously - plumes of dark smoke coming from both wheel arches).

got the front slotted rotors, A1RM pads front and HPX pads rear, plus GSL Rallysport's TRW race brake fluid...

now, i have full confidence. dont know if you guys have had this experience in your polos, but it's pretty bad when your brakes give way on a road like baw baw or reefton - very unsettling. now, however, my tyres will give way before my brakes.

put it this way - since doing the brake upgrade, im convinced that this has to be the first mod on any car i buy from now on. I've been over reefton spur (40kms of twisties into Marysville) almost a dozen times since having the brakes done, and I'm on it hard the whole way - my brakes have never once let me down, even when you're on it so hard that ABS is engaging every other corner.

So the general concenscous is that the A1RM pads over the HPX is probably the better deal. So, these I will get and maintain my OE rotors (when the car gets here of course!) and look at changing brake fluid, probably for the QFM stuff too.

[gavs]

Ok, so I've spoken with Greg at GSL Performance regarding brakes and this is what he had to say:

Hi Gavin,

The A1RM is completely streetable, it's just going to have higher than normal rotor wear. If A1RM was a bench mark 10, then HPX would be 7 and Remsa would be 8. Neither of those two a track type pad, but the later would go bloody close on a car as light as the Polo. Just wouldn't have the friction and subsequent speed retardation of the A1RM.

Regards,
Greg

He also mentioned that the QFM products need you to retro fit your brake pad wear sensors to the pads as they don''t come with them, the Remsa on the other hand have pre-installed. A1RM are fair dusty too from all reports.

Sooooo, based on that, I will be probably going Remsa pads all round with stock rotors and TWR GP600 fluid (1L for $60)

[Frostee]

Thanks Gav's, this is interesting but i have to admit I know nothing about brake mode's. A few quesitons come to mind;

How much would you expect to pay for the Remsa pads fitted?
How much life would you expect to get out of a set?
What performance benefit would you expect using this configuration versus stock pads?
What performance benefit comes from the TWR GP600 Fluid?
Is it complicated to change the fluid? i.e. is there much involved to purge the system of existing fluid and replace?

Cheers

Frostee

[gavs]

Thanks Gav's, this is interesting but i have to admit I know nothing about brake mode's. A few quesitons come to mind;

How much would you expect to pay for the Remsa pads fitted?
How much life would you expect to get out of a set?
What performance benefit would you expect using this configuration versus stock pads?
What performance benefit comes from the TWR GP600 Fluid?
Is it complicated to change the fluid? i.e. is there much involved to purge the system of existing fluid and replace?

Cheers

Frostee

Damn Frostee, that's a lot of questions! I'll try to cover off as much as I can with my (limited) knowledge! I also made a boo boo, $65 for a 1L bottle of TWR GP600....

1) pads alone $99 fronts $89 rears, will fit them myself as it is a dead easy job, easier than changing the oil and filter in my opinion (we can do it together if you like, a polo GTI brake-fit-love-in )
2) Not sure, depends on how hard you use them I guess but as a high performance street pad, probably less than standard pads (for reference, I've had the same pads in my golf for nearly 2 years now!)
3) The pads are rated at 650 Celsius which is generally higher than OE, which means that they can withstand higher temps before the compounds start to break down and generally catch fire (see Buller_Scott's post about the alpine run he did with stock pads!). It also means that there is generally along with this, less off-gassing of the pads on hard stops (I'll get to that later)
4) The GP600 fluid, being a race fluid, has a much higher boiling temperature, which in turn means it's less susceptible to producing brake fade (again, will get to that too )
5) No, changing fluid is easy as pie, just don't get it on the paint as it loves dissolving it! It generally consists of using a bleeder and pumping the pedal to push all the old fluid out. Would be interesting to know if the fluid the cars leave the factory with is the same as when we pick them up....

Ok, now to try and explain the principles of braking using my simpelton knowledge

Brakes are heat generators. They do this to turn your kinetic (moving) energy into heat energy which gets dissipated into the atmosphere. How? Your pads creating friction against your rotors.

That's the simple answer. The biggest enemy of your brakes is heat. Because they are heat generators, the hotter they are initially, the less heat that they can dissipate, therefore it takes you longer to stop. This in turn affects your pads. If the pads have a heat limit of say, 300 degrees C, then after that temperature, you start getting a longer stopping distance because they are starting to break down and are no longer in their operating range, therefore you go to a higher temperature level in your pads. How does different brake fluid help? Well, there are 2 reasons:

1) Brake fluid, like any liquid, has a boiling point. Due to the heat generated by using your brakes, this heat in turn gets transmitted through your calipers, back into the fluid. Again using 350C as an example, if water boils at 100C, this example fluid boils at 360C and your pads are no longer in their optimum range at 350C. This means that they are hotter than this when you go to stop, elevating their temperature to 370C. Remember, the brake fluid boils at 360C, so it is now boiling and turning to vapour in your brake lines. The pressure which is generated in the system when you put your foot on the pedal is sufficient to pressurise the fluid which squeezes your calipers onto the rotors, but it is not enough to compress the gas (vapourised brake fluid) in your lines as gasses need much more pressure to be compressed. This results in a "long pedal" which you might have heard of before. After being boiled, your brake fluid is never the same again and will have a constantly decreasing boiling point.

2) Again, with the temperature, but from a different perspective. Brake fluid is hygroscopic, meaning it absorbs water and eventually as it reacts with air (it takes a fair while!) but it can break down into water. This is bad because as shown in the example above, if you have any water in the system (and it can seep in over time) it boils long before the fluid, but because water has gotten into the system, your brake fluid itself is breaking down into water, so just 1 drop in a sealed container can destroy the fluid. So, if you standard fluid boils at (again) 360C, yet a Race fluid boils at 800C, the amount of water that renders your 360C fluid useless wont render your 800C fluid useless for a longer period of time. Race fluid is also engineered to withstand more extreme heat loading and cycling so it is far less likely to break down as readily, hence the $30 price difference to standard Castrol Dot 4 stuff.

[gavs]

That as far as I know is the fundamentals behind braking regarding disc brakes anyway, don't ask about drums because I have no idea! What about cross drilled and slotted rotors, cross drilled rotors, slotted rotors etc? Well, there are 3 fundamental thoughts behind this.

1) Cross drilled. The thought is that under braking, your pads produce gasses due to friction against the rotor, which they do, but to the levels that adversely affect your performance, you are really going to struggle to get to that point..... The drilled holes supposedly let this gas escape into the ventilated part of the rotor, yet remove surface area and weaken the rotor (have a close look at an old drilled rotor and notice the cracks around the holes...)
Slotted. Again, same principle to remove gasses from between pad and rotor, yet vent to the outsides of the rotor. Again, material is removed resulting in less surface area, but the rotor is not weakened as these slots are generally cast into the rotor.
Combo of both. Honestly, these rotors do both? Give me a break....

2)
This, is a brembo F1 brake disc, see any slots or holes?....... Brakes (as mentioned above) are to dissipate energy through heat. The greater swept area of the rotor in contact with the pad during braking, the greater amount of energy can be removed as heat. This is also another reason to go to a bigger diameter, they won't decrease your stopping distance, however they are able to dissipate more heat over a broader area, therefore you are less likely to generate heat-induced brake fade.

3) Now, as a designer, I have spoken with a few engineers and fellow designers in the automotive field in my time. The reason they give me for cross drilling/slotting rotors? It's a simple one, looks. Cross drilled rotors and slotted rotors look cool, it's as simple as that. One designer who works for the VW group said that when he was working on the 977 lineup of Porsche GT series 911s, the engineers designed the carbon ceramic brakes for them, but they looked hideous, so the decision was made to cross drill them, so they looked cool, like they were actually worth the $25,000 premium.

So, on that note,I will be sticking with the standard rotors, just upgrading the pads and fluid

I hope that helps you guys in making some decisions

Gav

[Frostee]

Fantastic Gav's, you've significantly enhanced my knowledge here. I like the sound of a brake fitting love in. How long do you estimate it would take to change pads and fluid per vehicle?

[gavs]

Maybe an hour, hour and a half.... since they're new cars, they should be pretty quick and easy winding back the piston on the rear calipers and remove/refit of the wheels would take the longest amount of time...

[Frostee]

Would love to get together and do them together. I'll be totally in your hands as I have no experience with this. WHere are you planning to purchase the pads and fluid from?

[kaanage]

1) Cross drilled. ......weaken the rotor (have a close look at an old drilled rotor and notice the cracks around the holes...)

There is a simple way to prevent this - you put a large ball bearing in the hole, with solid backing for the rotor, and belt it with a hammer to peen the edges of the hole (repeat for each hole and on both sides). The compression of the material greatly reduces the tendency to crack from the thermal expansion and compression cycles. Obviously, you can't to this to the interior of a ventilated rotor but the heat is greatest at the pad surfaces.

I never had cracks with my racing disc rotors when prepped this way.

tech info about crack propagation and the peening technique from Engineer To Win - Carrol Smith (RIP)

3) Now, as a designer, I have spoken with a few engineers and fellow designers in the automotive field in my time. The reason they give me for cross drilling/slotting rotors? It's a simple one, looks. Cross drilled rotors and slotted rotors look cool, it's as simple as that. One designer who works for the VW group said that when he was working on the 977 lineup of Porsche GT series 911s, the engineers designed the carbon ceramic brakes for them, but they looked hideous, so the decision was made to cross drill them, so they looked cool, like they were actually worth the $25,000 premium.

Maybe that's true now and if you can afford carbon ceramic brakes (and put up with the poor cold performance and noise) but for cast iron rotors, slotting and crossdrilling not only reduce the "trapped air" effect (which I agree is negligible) and help cooling but also helps the pad dust clear while braking. All this is really only relevent at racing speeds.

[gavs]

I'll be ordering through Greg, he is a forum sponser too. Will wait for GTI JOE and see if he also wants in...

[kaanage]

Also note that larger rotors => greater rotating and unsprung mass (unless going for a carbon/ceramic setup which is $$$$).

This is why the Top Gear experiment with bigger brakes on the people mover made it lap slower.

[GTI JOE]

I'll be ordering through Greg, he is a forum sponser too. Will wait for GTI JOE and see if he also wants in...

Thanks Gav, I've sent you a PM. Great posts, lots of useful information as usual man.

[gavs]

Also note that larger rotors => greater rotating and unsprung mass (unless going for a carbon/ceramic setup which is $$$$).

This is why the Top Gear experiment with bigger brakes on the people mover made it lap slower.

Exactly, another good point kaanage What you posted by Carrol Smith is right too, but how many people can afford the rotors that are of the correct steel grade for this to work, I can see so many people going out to their cars now, fitted with the cheap DBA drilled discs and shattereing the discs doing this!