Quote:
Originally Posted by graaja 1. Has anyone faced such a problem? What things did you do to fix this? Did something simple as brake bleeding or changing to a better brake fluid solve the issue? |
I have faced this problem multiple times and effectively resulted in replacement of discs before their service life (i.e. before minimum thicknes was reached). Our GT TDI has clocked close to 1.1 lakh KMs now.
In my opinion it is due to the inferior quality of the brake discs being supplied by TVS-Brakes India to VW. I suspect the rotor to be a bigger problem than the pads themeselves. The disc rotors act as
heat sinks. Larger the braking force/energy demanded by driver, larger the heating and the rotors should be able to dissipate the same (within definite time limits). I believe the rotors supplied by TVS-Brakes India don't do this properly. After replacement with a new OE set of pads/rotors, problems always used to start with a high speed brake application (higher braking demand effectively,
heat soaked, starts shuddering, warping etc).
When you change
only the brake pads to better ones (here Brembo), you are still
limited by the heat sink (rotor). For the same braking pressure (at the pedals), a
better pad will generate
greater braking force and thereby
more heat. However the OE TVS rotors are still not up to the job of dissipating this heat (let alone the lesser heat with OE pads).
I had switched to OE Brembo replacement discs (regular disc) and OE Brembo replacement pads (red ones). The problems of heat soaking / brake discs shuddering early into service life etc has been solved and braking has improved. Is it still sufficient for the power/torque on tap - nope.
VW should have provided the 288m front discs (and discs at rear) for the GT cars, as is the case in other markets which use the powertrain. We get the lesser 256mm front rotors and drums at the rear.
Quote:
2. Is the brake fluid used in the GT dot3 or dot4? If it is dot3, would changing to dot4 improve braking?
|
It is DOT4.
While DOT4 has superior boiling points (both wet and dry) over DOT3, the problems of poor braking in OE setup of Polo is not a due to limitations of the brake fluid. Going to superior DOT 5.1 won't solve the problem either as it not a case of brake fluid boiling temp limits being exceeded. Periodic brake fluid replacement (first at 3 years and then every 2 years) is sufficient.
Quote:
3. Has anyone tried Brembo drilled or slotted rotors? How is the performance and life?
|
I haven't used them. However, the life of both performance pads and rotors will be lesser. Using a
slotted rotor ('Brembo Max') or a
drilled rotor ('Brembo Xtra') will reduce the life of OE pads more than regular rotors. I would say that the Brembo Xtra are more for aesthetics. Here in EU, as I have sampled, Brembo Max (slotted) rotors along with performance pads (black ones) have better braking than stock units. In India I have heard mixed stories, some claims of fake products etc. I would suggest you to first start with regular OE Brembo replacement rotors and pads (red ones). Do keep in mind that most of the performance pads / rotors are often less effective than OE replacements at colder temperatures / normal driving conditions.
Quote:
Originally Posted by adi_petrolhead May be changing to PS3 will make a heck of a lot of difference. |
Michelin PS3s are not available in 205/55 R15 or 205/50 R16 sizes. Actually
none of the top spec performance tyres (PS3s, Conti SC3 or SC5, Yoko Advan Sports, Hankook V12/S1 evo2 etc) are available in that size in India.
Quote:
I won't suggest changing rotors, try the EBC yellowstuff pads.
|
Using any of the performance pads in conjunction with OE TVS rotors won't produce the desired increase in braking performance. In fact they will just result in the OE rotors going bad earlier.
Quote:
Originally Posted by graaja The tires are 205/55/R15 Conti MC5s. They have run just 11000 kilometers. The tires offer very good grip. Braking while the brake system is cold is very good. Only when the brakes get hot from a few repeated braking, the fade happens. ......
The EBC yellow stuff pads are my choice as well. Unfortunately, VW has changed the brake pad size and shape (it is called type 2 in Brembo dealer site) and EBC yellow stuff is not yet available for type 2. I heard that they may be available in August. |
Yup Conti MC5 is pretty much the best tyre we can get for Polo in that size. I had run two sets of Yoko S-drives prior to MC5. Yoko grip levels (both wet and dry) are good, but quite noisy. I also downsized from 205/50 R16 to 205/55 R15 and finds it a better setup.
It is true that they changed pad shape (type 2 as the Brembo distributors calls it). Brembo has a very user friendly catalogue, you should check it if you haven't already.
Brembo Catalagoue -Europe/EN.
For VAG CKD cars, part numbers match perfectly. However for models like the GT with parts sourced in India, there is limitation in finding part numbers for pads (not properly updated in the catalogue). For example type 2 pads is essentially Brembo# P 85121. This is listed against Polo Saloon and not the hatchback (make sense, same inventory for Polo n Vento). Rotor part numbers (whether for regular, UV coated, slotted, drilled etc) match perfectly with EU catalogue. However the distributor in Goa do ask for VIN confirmation before shipping.
As I said above, your problems of brake fade after repeated application is the same faced by me too. I can only attribute it to a heat soaked rotor (whether due to material choices or manufacturing process, we will never know).
Quote:
Originally Posted by graaja If my understanding is correct, black pads provide better braking, but result in quicker brake wear, right? |
Yes blacks pads are the performance variants, they bite better when hot but wears out faster.
Quote:
Originally Posted by graaja Not sure how the performance would be with stock pads and Tarox rotors. Pads are the most important components in braking. You may not get the best results for the money you are spending on the Tarox rotors with stock pads. |
Pads are rotors are equally important. Having a pad with stronger bite won't yield better braking if the rotor can't dissipate the extra heat. Converse also holds true. If both are not matched properly you are effectively creating a bottleneck and never achieving the maximum capabilities of either component.