Rear Brake Wear: VW Golf IV Variant AXR

Hi everyone,

Since the search function [discs, wear, brake discs, rear] didn't provide any helpful results, here's a brief description of my problem:

Habe am WE Sommerreifen draufgemacht. Dabei ist mir aufgefallen, dass die hinteren Scheiben (Original VW ab Werk) nach ca. 10Tkm symmetrisch (also sowohl beide Seiten einer Scheibe, als auch die rechte und die linke Scheibe) schon ca. 0,75mm verschlissen sind. Die Scheibenoberfläche sieht "vernarbt aus", überall sind kleine Einschlüsse zu sehen. BeThe values are okay.
"The rear brakes have been making a scratching noise since the very first kilometer. The dealer told me to wait until around 1000 km, as the brakes need to be properly bedded in. My objection was dismissed with his claim of having years of experience."

The front windows are only about half as dirty and have no scratches.
The car is driven daily (and the brakes are used). Occasionally, slightly bulky items are transported (2 meters long, 5 kg heavy). I haven't noticed any signs of rust on the windows so far.

If I were constantly driving around with a full trunk, I would understand the cracked windows, but it seems strange to me in this situation.
The brake caliper and pads are moving smoothly because I applied a small amount of copper grease to them after the 1000km service.

I would appreciate any helpful information regarding the source of the error.

Regards,
Sure, here is the translation of the text from German to English:

"Micha"

Hi again,

What is the brake force distribution between the front and rear axles in the Golf IV Variant? How is it regulated?

Regards,
Sure, here is the translation of the text from German to English:

"Micha"

Quote:

How is the brake force distribution between the front and rear axles in the Golf IV Variant? How is it regulated?

The G IV no longer has a brake force limiter. This function is now handled by the ABS system with EBV (Electronic Brake Force Distribution).
In an unloaded state, the braking force is likely to be distributed approximately according to the axle loads. Roughly estimated, this is about 2/3 at the front and 1/3 at the rear, with a dynamic shift towards the front during heavy braking.

I've gotten into the habit of using the handbrake for the last few meters when reversing out of the garage, due to the well-known issue with the G IV where the car can sometimes get stuck. My rear brake discs are nice and clean.

Hi Roger,

"Yeah, I usually do it that way too. Since the road drops about 50 meters right in front of my parking spot, the brakes are warm when I park the car."
My initial thought was also that it must be due to rust, but even when I didn't use the car for 3 days a few weeks ago, there was no sign of rust.

I'll check with the workshop tomorrow and see what they have to say about it.

How does the Electronic Stability Program (ESP) know how to distribute the braking force? Are there any sensors for axle load, or are there simply two fixed values specified (e.g., 67% for the front axle, 33% for the rear axle)?

Regards,
Sure, here is the translation of the text from German to English:

"Micha"

There are no sensors.

Unfortunately, I can only speculate about the underlying rules. Specifically, I suspect that basic values, such as the ones you mentioned, exist and are then adjusted by the ABS during the braking process, based on the tendency to lock up.

Mephisto wrote:

I installed summer tires this weekend. While doing so, I noticed that the rear brake rotors (original VW from the factory) have already worn down by about 0.75mm after approximately 10,000 km, and this wear is symmetrical (meaning both sides of each rotor, as well as the right and left rotors, have worn down equally). The surface of the rotors looks "scarred," and there are small imperfections visible everywhere. The brake pads are okay.

Hi,

"On my Polo, the brake cable was set too tight from the factory, so that even when the handbrake was released, the lever on the brake caliper was still a few millimeters away from its stop."

While the brakes weren't noticeably worn, I still adjusted the settings.

Perhaps your car is experiencing the same problem, but to a greater extent.
Do your rear windows also get warm (or warmer than the front windows) when you've barely braked during the last few kilometers?

I now also regularly(!) use the handbrake for light braking in clear traffic situations because the rear brake discs on my G3 rust away faster than the pads wear out .

Both brake cables caused a slight, constant braking effect. I had previously cleaned the brake pad guides because I thought the problem might be coming from there. When that didn't improve things, I checked again and discovered the brake cables. The inspection is quite straightforward.
Engage parking brake, then release.
Place the tool under the car and pull the levers by hand (where the brake cables are attached). If the levers can still be pulled back a bit, it usually helps to lubricate or replace the brake cables.

Hi,

Thanks for the tips. I'll check the handbrake cables next time I have the opportunity.

Regards,
Sure, here is the translation of the text from German to English:

"Micha"

In addition to Roger's information on brake force distribution, I also found the following.
The braking force is distributed via the ABS (EBV) system, as correctly suspected. During cornering, the braking force to the rear wheels is reduced. The system detects that the car is cornering through the ABS sensors, which detect the different wheel speeds.
The EBV (Electronic Brake Force Distribution) is designed to operate faster and with greater sensitivity than a mechanical brake force distribution system.
Unfortunately, I couldn't find any information about the basic front-to-rear brake force distribution scheme. Generally, it is said that the rear wheels are fully engaged in braking, but if the wheels lock up or experience slippage, the braking force is reduced.

Here are a few facts I know about the basic distribution:
My vehicle is equipped with a mechanical brake force distribution system. In the unloaded state, it distributes the braking pressure in a 2:1 ratio between the front and rear axles. The piston diameter is 60mm at the front and 38mm at the rear.
Roughly speaking, this results in a braking force distribution of approximately 71% at the front and 28% at the rear (assuming the same friction coefficients for the brake pads on the front and rear axles).
However, during strong braking, the rear of the vehicle lifts, which causes an even greater shift of the braking force towards the front.