Overhaul front brake caliper

Hi,
The vehicle has been pulling slightly to the right for some time, and the brake pad on the front right side has also shown signs of increased wear. Adjustments to the rear alignment and camber adjustments on the front within the acceptable range did not resolve the issue, and a wheel bearing defect and replacement also failed to fix the problem. The caliper guide pins are in good condition, and the brake pad guides are cleaned and lubricated once a year.
I have now disassembled the brake caliper on the front right side (a single-piston caliper from Girling). The piston and the wall inside the caliper housing show no signs of corrosion. The cylinder wall shows clear signs of friction at approximately the 7 o'clock position (if looking inside, 3 o'clock is the direction of travel), and the piston exhibits corresponding wear marks (dull) on the chrome-plated surface.
The piston can be inserted by hand without the seal, and it just fits, making a slight squeaking noise.
Do I have a slightly sticking piston?
hg
Herbert.

Quote:

Do I have a slightly sticking piston there?

I don't think so. It's not new anymore.

The main problem is usually rust behind the dust seals on the cylinder wall and in the groove where the seal is fixed. Everything must be clean.

But, if the vehicle pulls to the right due to a sticking brake,
You should be able to see a stuck wheel and a discolored brake disc.

Strictly speaking, it should actually pull slightly to the "left" if the vehicle is in its standard configuration. Why ---> negative steering radius.

Is spread and... Afterflow is okay, are the tires the same?

Hi,
The car has been pulling slightly to the right for some time now .

Generally, there are many misdiagnoses when it comes to vehicles pulling to the right, mainly because of the right-hand traffic in conjunction with road surfaces that slope downwards to the right.


and occasionally showed higher tread wear on the front right side.

Occasionally?

If both brake pads on the right side are more worn than those on the left, a sticking caliper piston could be the cause.


I have now disassembled the brake caliper on the front right side (a single-piston caliper from Girling). The piston and the wall inside the caliper housing show no signs of corrosion. The cylinder wall shows clear signs of friction at approximately the 7 o'clock position (when looking inside, 3 o'clock is the direction of travel), and the piston accordingly has corresponding sliding marks (dull) on the chrome-plated surface.

As long as the measurement tool cannot detect any wear and there are no noticeable scratches or similar imperfections, then it is acceptable.


The piston can be inserted by hand without the seal, and it just fits, making a slight squeaking noise.
Do I have a slightly sticking piston there?

It's hard to say without experiencing it. Does 'gerade so' (meaning 'just barely') indicate that there is excessive friction, and is the piston sticking in certain areas?

If it's (too) difficult to move, the piston and/or the cylinder would be deformed, which could be measured.

If a brake is affected by a slightly sticking piston, you can...
'A stuck wheel' can only be detected when the piston is actually stuck.

A discolored brake disc is not necessarily an indication of a problem, as various color changes can occur on brake discs that are not easily noticeable. Even a clearly visible blue discoloration will quickly disappear with normal braking.

If the right front brake is stuck, the vehicle will pull to the right, not to the left. The braking action of the right front wheel creates a torque that causes the car to pull to the right. The force transmitted through the negative... The radius of the swivel rollers and the forces applied are negligible in this case.

'If spread and...' If the toe-out angle is incorrect, the values for tracking angle and camber would also be incorrect in practice.

If the tracking and camber are correct, but the toe and rear alignment are not, the question is what is wrong with the car in the area of the front suspension. Wheel suspensions that have been modified, rebuilt, or (accidentally) damaged.

Tires can definitely cause a vehicle to pull to the right or left, and this can be checked using a process of elimination with the other wheels.

Ultimately, when dealing with persistent straight-line driving issues, the rear axle should not be overlooked.

Quote:

A discolored brake disc is also not necessarily an indication of a problem; various shades of discoloration are not visible on brake discs, and even the clearly visible blue discoloration fades away very quickly.

Who is talking about the friction surface?


Herbert is well aware that many other factors need to be considered.

Let him answer first, so we can see how much effort he's willing to put in.

Who is talking about the friction surface?


What is this supposed to mean?

What other area of a brake disc would visibly change color due to temperature if not the friction surface?

Hello.
First of all, thank you for your information.
As mentioned before, there is no corrosion present, except for some traces in the groove of the dust seal. I removed these traces with a fine file and a nylon brush on the Proxxon grinder, leaving only some scratches. There was definitely nothing stuck or raised there. I polished the inner wall of the cylinder with a fine brass brush and red-white polishing compound. The piston now runs a bit smoother and more freely, and it rotates fully (although it did before as well).
Let me finish preparing the brake caliper and reinstall it first.
hg
Herbert.

Is the brake hose also okay?

Klaro is 4 years old. The "expiration date" for this model is 7 years.
Sure, here's the translation:

"Best regards."
Herbert.

Hello.
The brake caliper has been reassembled, installed, bled, and is now functioning correctly.
It was an attempt, but the actual problem hasn't gone away.
Before we continue this discussion, I'm going to have a new, up-to-date measurement taken after the previous repairs. Before that, I want to replace the HA (rear axle) control arm bearings, even though they are supposedly okay according to the TÜV (German technical inspection), but they are 400,000 km old.
Thank you.
Herbert.