Bremsentuning? | Posts 64+

'So, I find the whole thing about the Zimmermann brakes really shocking. I was actually planning to buy them this year to treat myself to something 'good'.' I probably won't do that after all.


So far, I have had excellent experiences with Brembo MAX rotors combined with ATE brake pads. Does anyone share this experience with me?

The large sport brake system from the Ibiza Cupra should also fit the Polo 9N, Ulf... However, things get pretty tight when it comes to choosing the right wheels... especially in the winter, because as far as I know, you can only fit 17-inch wheels.

Best regards, Alex.

Bertil wrote:

ulf wrote: ... What were your concerns about the old brake pads and rotors on the rear? Nothing! That's it, then. I have experienced several times that a brake that was not working properly started working correctly again after replacing the rear brake components.

Hello,

I can fully confirm what Bertil wrote, based on my own experience. My rear brake pads still had about 4 mm of material left when I replaced them. The handbrake had no noticeable free play, but the braking force was very uneven, and the lever "rattled" when pulled. However, one of the brake pad guides was completely seized and was repaired, and new brake pads (original VW) were installed. With these new pads, not only does the handbrake work smoothly again, but the responsiveness of the regular brake is also much more immediate. Even at high speeds, the delay becomes noticeable quickly, and under heavy load, it doesn't decrease as much as one might expect.

I would only recommend paying close attention to the rear brake pads when there are complaints about braking performance. If necessary, replace them; they don't cost a fortune. If I had been able to foresee the effect, they would have been eliminated much earlier.

Roger wrote:

My rear brake pads still had about 4 mm of material left when I replaced them. The handbrake had no noticeable free play, but the braking force was very uneven, and the lever "rattled" when pulled. However, one of the brake pad guides was completely seized and was restored, and new brake pads (original VW) were installed. With these new brake pads, not only does the handbrake work smoothly again, but the responsiveness of the service brake has also become much more immediate. And even at high speed, the delay quickly becomes noticeable, and under heavy load, it doesn't decrease as much as you might expect.. . .

Hi Roger,

My problem mainly lies with the maximum possible braking force on the front axle, because I never reach the active ABS range. That is, with "ABS OFF" at a high speed, even with (initially) cold brakes, a complete brake lock-up would not even be possible.

Did you experience similar problems with the old brake pads, and after the change, what was the maximum...? The braking performance is clearly better in the sense that the ABS system started to engage again during full braking on dry pavement.
If not, then your experience would at least partially be irrelevant to my problem .

My main problem is with the maximum possible braking force on the front axle, because I never reach the active ABS range, meaning that with 'ABS OFF' at a high speed, even with (initially) cold brakes, a complete brake lock-up would not even be possible.

Hello,

What was that about the maximum transferable moment of the tires again?
AFAIK, this is speed-dependent, meaning that at higher wheel speeds, more torque can be transferred to the road.

If this is the case, Ulf is currently struggling with the compromise between high braking performance at high speeds and not excessively high braking force at low speeds, which would correspondingly improve braking performance in normal use.

You might have encountered one of the 'drawbacks' of your vehicle configuration here, as the 'basic' Polo is designed for lower speeds rather than high ones.
The corresponding sports models are, for example, equipped with a larger braking system.

The fact that brakes that are too large can lead to 'problems' in smaller vehicles was demonstrated, for example, by the old Seat Ibiza CUPRA, which was delivered with brakes optimized for the rally series of that time. He had the 280 x 20 brakes from the Golf GTIs, which gave it very aggressive braking performance, and this, in turn, led to criticism regarding its usability on the road.

As long as Ulf's brakes don't tend to fade, he will probably have to accept that his brakes provide sufficient deceleration for normal driving.

Excuse me, with dimensions of 257x20, and with 130 horsepower, and an average curb weight of 1200 to 1300 kg, it is really not suitable for 'racing.'

So far, I have had excellent experiences with Brembo MAX rotors combined with ATE brake pads. Does anyone share this experience with me?

I've read this many times before, and I'm going to install it in my colleagues' Polos.
Considering the friction coefficients, I expect nothing different regarding the braking performance. The disadvantage of driving alone is that the (standard) ATE brake pad achieves this high friction coefficient with a relatively soft compound, which leads to higher wear and more pronounced contamination of the rims (fine dust alarm ).

Best regards, Jochen.

@jochen145:

Yes, that's right about the soft materials; you could verschandeln the rims every other day... As a small 'consolation,' the coating is gentler on the glass...

Best regards, Alex.

Hi,

Quote:

The fact that brakes that are too large can lead to "problems" in smaller vehicles was demonstrated, for example, by the old Seat Ibiza CUPRA, which was delivered with brakes optimized for the rally series of that time. He had the 280 x 20 brakes from the Golf GTIs, which gave it very aggressive braking performance, and this, in turn, led to criticism regarding its usability on the road.

Are you sure about that data? I actually have the same brake (280x22, with a wear limit of 20) in my ASV-Ibi (as standard equipment). It brakes really well, especially in conjunction with the high front axle load, but it can become a bit unstable at high speeds, precisely for that reason. During the only emergency braking situation I've experienced so far, going from almost 200 km/h to 120 km/h, I believe the ABS engaged somewhere around 140 km/h (at least in the front, as you don't really feel it in the rear).

The Cupra R is listed in the data I have access to as having a 305x28 brake system from Brembo. Are you perhaps referring to the previous model, i.e., the second-to-last Cupra model up to 1999? Indeed, the 280x22 brake is the largest size listed.

It's really surprising that VW equips the 130-horsepower Polo with smaller brakes than its budget-friendly subsidiary, Seat, used on the 110-horsepower Ibiza a few years prior.

Best regards,

Jan.

ulf wrote:

Did you experience similar problems with the old HA linings, and after the change, was the maximum... The braking performance is clearly better in the sense that the ABS system started to engage again during full braking on dry pavement. If not, then your experience would at least partially be irrelevant to my problem

.
Hello Ulf,

I had this exact problem for quite some time - actually, since taking delivery of the new car - despite having ESP with BAS. The BAS, after all, is supposed to provide a much more aggressive braking force in emergency braking situations, and therefore the ABS should, in principle, bring the braking force back into the regulated range much earlier should. It worked so far with the old pads, but only at city speeds.

It's significantly better now, although the ABS system has only engaged once, and briefly, at highway speeds so far. It happened around 140 km/h when an idiot in the left lane slammed on the brakes for no reason, two cars in front of me. The Vectra C in front of me swerved left and right during the necessary braking, but thankfully, I avoided that. The effect of my system was so unusually strong that a 45kg lead battery, which was being transported lengthwise in the trunk near the back seat, hit the seat back quite forcefully and left a permanent impression there .

Jan6K wrote:

Are you sure about that data? I actually have the exact same brake (280x22, 20 is the wear thickness) in my ASV-Ibi (as standard). It brakes really well, especially in conjunction with the high front axle load, but at high speeds, it can become a bit unstable for that very reason. During the only emergency braking situation I've experienced so far, going from almost 200 km/h to 120 km/h, I believe the ABS engaged somewhere around 140 km/h (at least in the front, as you don't really feel it in the rear). The Cupra R is listed in the data I have access to as having a 305x28 brake system from Brembo. Are you perhaps referring to the previous model, i.e., the second-to-last Cupra model up to 1999? Indeed, the 280x22 brake is the largest size listed. It's really surprising that VW equips the 130-horsepower Polo with smaller brakes than its budget-friendly subsidiary, Seat, used on the 110-horsepower Ibiza a few years prior. Best regards, Jan

Hello Jan,

Ulf already wrote about his records:

ulf wrote:

My vo. According to the documents, the panes are 288 * 25 mm in size, which is slightly larger than those in the G4 Kombi.

Roger wrote:

ulf wrote: Did you experience similar problems with the old HA linings, and after the change, was the maximum... The braking performance is clearly better in the sense that the ABS system started to engage again during full braking on dry pavement? I had this exact problem for quite some time - actually, since taking delivery of the new car - despite having ESP with BAS. The BAS, after all, is supposed to provide a much more aggressive braking force in emergency braking situations, and therefore the ABS should, in principle, bring the braking force back into the regulated range much earlier should. It worked so far with the old pads, but only at city speeds. It has gotten significantly better now.

Surprisingly, I will also try my hand at my HA brakes.

What I just can't wrap my head around is:
With a functioning brake system and the same full brake pedal force applied, the hydraulic system will always generate the same pressure. This modulation of pressure only occurs when the ABS system is active.
As long as the ABS is not activated, I always have the same pressure in the wheel cylinders, and therefore the same clamping force of the brake pads.
Where (the heck) does the increased braking power on the front axle come from, if only the rear brake pads were replaced or adjusted?

Hello Ulf,

As mentioned earlier, there have been several explanations offered. I also noticed a somewhat stepped response with the old brake pads, where you had to overcome a kind of intermediate stage before a firmer engagement was felt. It's possible that the stuck brake pad guide caused the pad to initially bind, before sufficient force could be transferred to the remaining rear pads. Consequently, full pressure wasn't being applied at the front. Part of the braking force was being absorbed by the elastic deformation of the brake pad guide. That's my humble theory on the matter, as far as it goes.

The way the coating was applied suggested that it wasn't properly lubricated from the factory. Therefore, premature wear is definitely a possibility. It's a well-known problem.

ulf wrote:

... My problem mainly lies with the maximum possible braking force on the front axle, because I never reach the active ABS range, meaning that at "ABS OFF" from a high speed, even with (initially) cold brakes, a complete brake lock-up would not even be possible. ...

The fact that you are not engaging the ABS system has (primarily) nothing to do with the VA (front) brakes!

How does the ABS control strategy work? When does the ABS (Anti-lock Braking System) activate?
The answer to that is very simple:
The ABS system only activates when the brake pressure exceeds a minimum value 'f' within a time period 't'. In this case, the ABS (anti-lock braking system) is (more or less) deactivated.

Let's assume, for whatever reason, your brake pads are too far away from the brake rotors. This increases the hydraulic travel, which in turn extends the time it takes for pressure to build up in the braking system. In the worst-case scenario, this could even prevent the ABS control threshold from being reached.
What reasons can cause an extended hydraulic travel? Well, one reason could be a warped brake disc. This pushes the brake pad back too far, thus extending the travel. You should be able to feel this, especially on the rear axle. A second reason could be the automatic adjustment of the rear brake pads. Rusted discs (which are common on many TDIs at the rear) can also push the pads back further than necessary after braking. Same error message as above.
These are just two of many other reasons that could explain the error messages you reported.


By the way, I just demonstrated a trick to bypass the ABS. If you gradually increase the brake pressure, it's possible for the wheels to lock up even with the ABS engaged. More recent ABS systems regulate this through a brake assist function.

Okay, so with ABS, you need to initially "slam" on the brakes quickly, and then gradually modulate the braking force. Here's how to maximize the system's full potential.

Are you sure about these data? I actually have the same brake (280x22, with a 20mm thickness for wear) in my ASV-Ibi (as standard equipment).


Hi Jan, yes, quite! However, the first Cupra model would have had to be built before 1999 (with a 2.0L 150hp naturally aspirated engine from the Golf GTI), so it would be your predecessor model.

According to the data available to me, the Cupra R is listed with a 305x28 brake system from Brembo - or are you referring to the previous model, i.e., the second-to-last Cupra up to 1999? Indeed, the 280x22 brake is the largest size listed.

Yes, that's correct. I just meant the predecessor .

It really surprises me that VW equips the 130-horsepower Polo with smaller brakes than the budget-friendly subsidiary Seat equipped the 110-horsepower Ibiza a few years prior.

My vo. According to the documents, the glass panes are 288 * 25 mm in size, which is slightly larger than those in the G4 Kombi.

Sorry, I somehow missed that..
Best regards, Jochen.

Bertil wrote:

The ABS system only activates when the brake pressure exceeds a minimum value of 'f' within a time period 't'. Here, the ABS (more or less) is inactive.

Therefore, the ABS reacts to a sensor value of "pressure increase rate in the hydraulic circuit"?

Quote:

Let's assume, for the sake of argument, that your brake pads are (for whatever reason) too far away from the brake discs. This increases the hydraulic path, and consequently, the time it takes to build up pressure in the braking system is extended. In the worst-case scenario, it could even be so extreme that the ABS intervention threshold is no longer reached.

Okay, let's say I were to perform a full-force emergency braking ("BAB" - Autobahnbremsung) with "ABS OFF": Why, despite maximum pedal force, can't I get the tires to lock up, or at least make them squeal a little?
The pedal is still quite a distance from the floorboard, the brake booster seems to be working normally (IMO), and I don't think my legs are weak enough that I can't apply the usual amount of force needed for a full brake application.

Quote:

What reasons can cause an extended hydraulic travel? Well, one reason could be a "warped" brake disc. This pushes the pad back too far, thus extending the travel. You should (at least on the front) be able to feel this. A second reason could be the adjustment of the rear brake pads. Rusted discs (which are often found on the rear of TDIs) can also push the pads back further than necessary after braking. Same error pattern as above.

But if you've overcome the potentially extended pedal travel and are applying full force to the pedal (still well above the floorboard), shouldn't the full hydraulic brake pressure still be reaching the calipers?

And so, my question remains: Why does the full hydraulic pressure of the emergency braking system in my Polo, even on a dry highway, not cause the tires to squeal, nor activate the ABS?
Or does applying the same amount of pedal force generate less hydraulic pressure "lower down" (but still above the floorboard)? If so, why?

I have also tried experiments with sudden, full braking, so that the pressure increase was definitely faster than with a retiree's full stop and a brand new braking system, even with a longer hydraulic travel: the result was always the same: no squealing, no ABS activation .

Hi,

Quote:

Sorry, I somehow missed that.. icon_redface.gif

It doesn't matter... I could have also checked Ulf's post. So, the world is right again...

@Bertil:

Quote:

By the way, I just showed someone a trick to bypass the ABS. If the brake pressure is increased very slowly, the wheels can still lock up.

But only for a short time, right? Once they're really stopped, shouldn't the ABS release the brakes again in a situation like that? Or am I missing something? I think that the control system can differentiate between the "car is stopped" state and this case (even if all four wheels stop simultaneously) by analyzing the rate of change of the wheel speeds.

Of course, it's undeniable that it works more effectively during sudden braking.

Best regards,

Jan.

Quote:

The fact that you are not entering the ABS control range has (primarily) nothing to do with the VA brake! How does the ABS control strategy work? When does the ABS (Anti-lock Braking System) activate? The answer to that is quite simple: The ABS system only activates when the brake pressure exceeds a minimum value 'f' within a time period 't'. Below, the ABS (is more or less) inactive.

I would say that the ABS engages when there is a certain amount of slippage between the road surface and the tires. If it activates too early, it only unnecessarily increases the braking distance.

If the braking performance of the rear axle of a vehicle is weakened for any reason, a portion of the total braking force is lost, which then, theoretically, must be compensated for by the front brakes.

Due to the further increased dynamic axle load shift towards the front axle, the forces transmitted between the road surface and the tires increase, which reduces overall wheel slip and, consequently, the ABS may intervene later or, depending on the grip level, not at all.

ulf wrote:

...Therefore, the ABS reacts to a sensor value representing the "rate of pressure increase in the hydraulic circuit"?

Yes, also.

Quote:

OK, so, let's say I were to perform a full-stop braking maneuver with "ABS OFF": Why, despite applying maximum pedal force, do the tires not lock up, or at least make a little squealing noise?

... So, eventually, it should start squeaking. That sounds quite strange.

Quote:

... But, if you've overcome the potentially extended pedal travel and are applying full force to the pedal (still well above the floorboard), shouldn't the full hydraulic pressure of the emergency braking system still be reaching the calipers?

Yes, that's how it should be.

Quote:

And so, my question remains: Why does the full hydraulic pressure of the emergency braking system in my Polo, even on a dry highway, not cause the tires to squeal, nor activate the ABS?

On any road surface? So, does that also include wet conditions or snow/ice?

Quote:

Or does applying the same amount of pedal force generate less hydraulic pressure "lower down" (but still above the floorboard)?

No... the pressure should also be able to be generated "lower down" on the pedal stroke.

Quote:

I have also tried experiments with sudden, full braking, so that the pressure increase was definitely faster than with a retiree's full stop and a brand new braking system, even with a longer hydraulic stroke: the result was always the same: no squealing, no ABS activation

.
Well, that sounds a bit strange. The brake really has a problem.

Jan6K wrote:

But only for a short time, right? As soon as they are truly stopped, shouldn't the ABS release the brakes again in a situation like that...?

Yes, but until then, the car has already traveled a certain distance without ABS intervention (even if it's only a few meters).

Quote:

I think that the control system can distinguish this case (even if all 4 wheels stop at the same time) from the "car is stopped" case by analyzing the rate of change of the wheel speeds...

Yes, that's right. The ABS only reduces speed by 5 or 10 km/h anyway. It completely disables it.