Bremsentuning? | Posts 32+

brezelmann01 wrote:

... because these systems, due to the amount of power required, certainly operate relatively slowly. ...

<0.5 seconds for full braking force.
I would call that anything but slow (at least for a manual braking system).

Hello!

I've also never heard that the mechanical simulation is supposed to serve the purpose of replicating the operation of the service brake. How does it work, for example, at Porsche? In those systems, the service brake acts on a disc, while the parking brake acts on a drum.
Six months ago, I replaced the brake pads on the rear of a Volvo 850. It has the same system as a Porsche. There's absolutely no chance of it being a copy.

...
The information that the follow-up mechanism on the rear brake is for the service brake is incorrect; it functions exactly the same as on the front brake, using the hole in the master cylinder through which fluid flows from the reservoir. The adjustment is only for the handbrake and saves you the trouble of adjusting the brake cable.
...

Then explain why some cars have handbrakes that affect the front wheels (e.g., The Alfasud had an automatic adjustment feature for the rear brakes.
Or why vehicles with electrically operated parking brakes (where there are no cables and the distance is irrelevant... the system always applies the pads with a defined force) also have automatic rear axle adjustment. Some of them even have all-wheel-drive parking brakes. A follow-up mechanism would therefore be pointless in this case.
I won't explain that because I don't know the systems well enough. Besides, what you're constantly doing is like comparing apples and oranges. Why don't you try explaining it the other way around: explain why the service brake needs the adjustment, but please do it thoroughly and clearly, and ideally cover all the different scenarios. Then we have a foundation to start from; I'm happy to change my mind.

Forenheini wrote:

... Explain why the service brake needs to be readjusted. ...

I already did that above.
That's how it was explained to me, and if that's not correct, I have no problem with it.
My observation aligns with the described problem, where the rear brake often plays a significant role in the overall performance of a braking system.

P.S. By the way, the idea about the brake hoses isn't bad either. It works wonders. Unfortunately, the approved stainless steel flexible hoses are quite expensive.

Hello,

The automatic brake adjustment is only intended to reduce maintenance costs. I remember my early days of car ownership. Back then, a visit to the workshop every 3,000 km was normal. During that visit, the oil would be changed, and the brakes would be adjusted. My son, in addition to his Corrado, also owns a VW Sülzer from 1979. With this car, the brake shoes also need to be adjusted after approximately 3,000 km. However, there is no actual improvement in the poor braking performance, even if one subjectively feels that there is.

Benno.

Ulf mentioned brake tuning at the beginning. Okay, so let's assume that the brakes are in good working order and that the adjustment is functioning correctly.

Theoretically, one can...
1. increase the coefficient of friction between the brake pad and the disc.
2. increase the contact pressure of the pads.
3. increase the effective diameter (of the disc or drum).

1. Parts from motorsports can be used, provided they are street legal. My experience is that the really potent stuff (which is, of course, not allowed) is significantly worse than the regular product when it's cold.

Here are some possibilities for option 2:
- Larger pistons in the wheel brake cylinders.
- smaller pistons in the main brake cylinders.
- Change the pedal ratio.
- Modify the brake booster (increase vacuum or install a larger one).
where the latter is not associated with a longer pedal stroke as the only measure.

Regarding point 3, there are also parts from the sports sector, or often from more powerful models within the same group of companies.

I've already mentioned the difference between our two vehicles. Others have reported similar observations in the opposite direction. I suspect that this might be related to the effect of the power brake booster. If anyone knows whether the vacuum pumps fit interchangeably between the AFN and ALE models, I might try it out this weekend. (If not, I'll still give it a shot.)

That leaves the brake booster itself. Does anyone know from the parts specialists what differences VW/Audi uses here?

Best regards, Rudi.

I already did that above. If you're referring to: The fact that the mentioned article glosses over certain things is just a minor detail.

If the brake pads are slightly worn, the foot brake will automatically adjust the handbrake.

Unfortunately, this also initially adjusts the engagement point of the service brake. The simultaneous shortening of the handbrake travel is a nice side effect and is mentioned here as the main reason for the adjustment. That's not entirely correct. Then, take a closer look at the matter, especially from the other side; that's the only way to understand it. Due to the play in the thread of the adjustment mechanism, the brake piston can move independently up to the adjustment limit, which is also essential because otherwise there would be no clearance for bleeding! The issue of the engagement point is not an argument; it would still be ensured by the follow-up hole in the master cylinder without mechanical adjustment. Only by combining the adjustment of the handbrake mechanism within the brake caliper does the adjustment effectively define an 'engagement point,' but this only works if it's done correctly, in which case the engagement point will be located where it should be within the hydraulic system.

In my opinion, a compensation mechanism for hydraulic brakes is only necessary when the maximum piston stroke is less than the wear allowance of the pads, but even in this case, the compensation hole ensures that the piston's travel always remains the same. The problem is that the piston will eventually fall out of the cylinder , which is not ideal. The integrated handbrake mechanism on the rear disc brake, as commonly used by VW for several years, only serves the purpose of the handbrake. Certain consequences that arise from this are merely a result, not a necessity.

My observation aligns with the described problem, where the rear brakes are often the limiting factor for the overall effectiveness of a braking system. I agree. Often, the argument is made that the significantly higher braking power at the front means the rear brakes are not important. However, this is unfortunately not the case, because maximum braking force is only achieved when both axles brake at their maximum. Therefore, the proper functioning of the rear brakes is also important. The lack of function is only compensated by the fact that the rear brakes simply have to brake harder, which is usually not the problem, because in general, the deceleration is so weak that it doesn't become noticeable. That's also the reason why the rear disc brakes tend to get clogged, because they don't receive enough stress to verschandeln themselves properly.

P.S. By the way, the idea about the brake hoses isn't bad either. It works wonders. Unfortunately, the approved stainless steel braided hoses are quite expensive. 100-150 Euros or so, I don't find that too expensive... You can either install/bleed them yourself, or have it done cheaply during the inspection if the brake fluid is being changed anyway. No worries.

@Ulf

What about the Polo? Does it have a brake assist system? In my Golf, there's definitely a noticeable difference whether the ABS engages during hard braking or not.

Forenheini wrote:

... The issue with the engagement point is not a valid argument, as it could still be ensured through the bleed hole in the master cylinder, even without mechanical adjustment. Only by combining the adjustment of the handbrake mechanism within the brake caliper does the adjustment effectively define an "engagement point," but this only works if it's done correctly, in which case the engagement point will be located where it should be within the hydraulic system.

What's the point of automatically adjusting the rear brakes without a handbrake being engaged, especially if the handbrake is only on the rear axle?
Then this construction can only be used for the point of application.
I'm planning to work on my car this spring. It belongs to a friend of mine who's into motorsports. By the way, there are even brake discs on the transmission.

Quote:

A bleed for hydraulic brakes is, in my opinion, only necessary when the maximum... The piston stroke is shorter than the wear allowance of the pads, but even in this case, the bore hole ensures that the piston's travel remains constant.

The piston definitely can't be that short.

Quote:

The (weak brakes) are also the reason why the (disc) brakes on the rear tend to get corroded, because they simply don't get enough use to verschandeln themselves properly.

I already wrote that above. I don't have a strong opinion about using self-billing invoices (although I don't have any major problems with them).
Even in my rally car, I have drum brakes in the rear.

Quote:

... 100-150 Oirohs or so, I don't find that very expensive right now...

So, for a working brake, that wouldn't be too expensive for me, but many people start complaining when the price reaches 150 euros...

joegolf wrote:

What about the Polo with a brake assist system? Does it have one? In my Golf 4, there's definitely a noticeable difference whether the

system engages during full braking or not. The manual doesn't mention anything about a brake assist system, and I haven't noticed any "phenomena" so far that might suggest such a system is present.
According to that, the 9N model probably doesn't have a brake assist system.

ulf wrote:

Therefore, the 9N probably does not have a brake assist system.

Only in Germany, with ESP.

Hi,
I also experienced that effect with the Golf 3, where the brake pads looked good but had poor braking performance due to being hardened.
In my opinion, the primary change is in the braking performance, specifically how it responds during moderate braking. Depending on the type of brake force distribution system, the pressure on the rear brakes is reduced during full braking to prevent the rear wheels from locking up and causing a loss of control. My G1 performed well on the track. At the same time, the overall stability of the system is increased under moderate, sustained loads, such as a downhill section with insufficient engine braking, because the rear axle can provide more effective braking force compared to a system with a rigid distribution.

Are we always talking about the same thing? Of course, drum brakes require mechanical adjustment, whether it's manual or automatic. With disc brakes, this process essentially happens automatically.
However, I don't understand how excessive clearance in the brake system could affect braking performance. Aside from friction coefficients, no braking force can be generated at the front axle as long as the rear brake pads are not engaged. Or are there EBV (Electronic Braking Force Distribution) or mechanical brake force limiters that might be causing the issue?

Do stainless steel braided hoses actually last longer, or do we just not see the fine cracks inside?

Then explain why cars whose handbrake acts on the front axle (e.g., Alfasud) had an automatic adjustment of the rear brakes.
Or why vehicles with an electrically operated parking brake (where there are no cables and the distance doesn't matter... the system always applies the pads with a defined force) also have automatic rear brake adjustment. Some even have all-wheel drive parking brakes. Therefore, an adjustment mechanism would be pointless in this case. As I said before... I don't know the systems well enough to speculate about them. Google didn't help me much with the Alfa Sud brake either, other than confirming what we already know: the parking brake acts on the front wheels, and the brake is located on the inside of the front. It would definitely be important to know more about the construction.

Do stainless steel braided hoses actually last longer, or do you just not see the fine cracks inside? Of course, stainless steel braided hoses don't last indefinitely either, but they usually last for the entire lifespan of a car. There are no cracks in the outer rubber, as you might find in regular hoses.

hiho

Without having read much about it, I've also often had problems with braking on my 6n (approximately 1 ton, ~110 horsepower, 256x20, 14-inch brakes) (wow, what's that glowing in the rim ). Well, I first installed slotted Zimmermann discs and Ferodo DS Performance brake pads, which already helped, and the responsiveness was excellent. After 20,000 km, one of the front brake discs cracked (fortunately at 20 km/h). According to Zimmermann, I somehow caused them to rust too much. Then I used the heat-treated, slotted ones from Sandtler, and those were great too.

And what helped the most with the excessively high temperature was the rims.

Sure, here's the translation:

'Here are some pictures of the Zimmermann brake rotor after 2 years or 20,000 km.'

I am sorry, but I cannot access external websites or specific files online, including the one you provided. Therefore, I am unable to translate the text from the image.
I am sorry, but I am unable to access external websites or specific files online, including the one you provided. Therefore, I cannot translate the text from the image.
I am sorry, but I am unable to access external websites or specific files online, including the one you provided. Therefore, I cannot translate the text from the image.

Oh dear, that's quite unpleasant. Lucky in misfortune.

So, my all-around tires are still looking great, and they've now been driven for about 35,000 km.

How exactly should one understand the issue of rust? What influence do I have on it, other than leaving the vehicle in the mud for a year? And even then, it's highly questionable. "In everyday situations, something like that should never fail."

It's a shame, I thought Zimmermann was competent.

hiho

Well, don't ask me.

Sure, here's the translation:

'Here are two emails from Zimmermann.'

Hello Mr. Keil,

... how can this possibly happen???

With only 30,000 kilometers on the odometer, the brake surfaces are, frankly, in a rather 'worn' condition. The brake surfaces are heavily pitted, which indicates that they have been repeatedly subjected to sudden cooling or quenching while in a hot state. This can lead to cracks and changes in the material's structure, which can impair its mechanical strength.

The triggering moment for the catastrophic failure was evidently a brake caliper that was blocked on one side. This meant that the caliper was subjected to a lateral force acting on only one side. This type of tension-compression stress is extremely unfavorable for the brittle cast material and subsequently leads to what is known as a brittle or stress-induced fracture! Unfortunately, your photos do not show the inner braking surface, which should show significantly fewer signs of pad contact.

Best regards,

Achim Kerstan.
Head of Quality Assurance. B.Eng. (Bachelor of Engineering)

and number 2:

Hello Mr. Keil,

Your uninformed comments have prompted me to respond once again.

A caliper failure is always the result of a one-sided tensile-compressive stress (see my first answer); if the caliper was still functioning two days prior, then, for whatever reason, it doesn't necessarily have to be the case at the time of the failure! ... Or are you yourself sitting as an involved observer while driving, inside or on the brake caliper, and did you personally verify the functionality of all components just at the moment of the failure?

The combination of heat and moisture, coupled with drastic cyclical stress, leads to complete corrosion of cast iron with flake graphite, also known as gray cast iron. This is especially true when it occurs repeatedly, as appears to be the case in your situation (to put it mildly, the BS components look like they were mounted on an amphibious vehicle!).
Cast iron, even in its alloyed forms, consists almost entirely of iron. Therefore, from a purely chemical perspective, it is logical that cast iron will corrode if exposed to the appropriate weather conditions and operating environments. The manufacturer is likely not responsible for these conditions.

Original equipment manufacturers' coatings often provide a certain level of corrosion protection, which may delay or minimize rusting, but it can never completely prevent it! However, the price is double, if not even triple, compared to ZIMMERMANN products.

Since you haven't specified which product you're referring to, I can't tell you what material your BS is made of.

Best regards,
Achim Kerstan.
Head of Quality Assurance. B.Eng. (Bachelor of Engineering)


and the saddles definitely weren't installed properly because I was able to push them back in by simply pulling them outwards.