75 plate Karoq SE 1.5 tsi

Petrol

8266 mileage

PCP

I was getting some intermittent funky sounds from the car recently and long story short the front drivers brake disc was found to be 30% worn. As we’re about to go on a two week driving-heavy holiday I had it replaced so am now £450 lighter and absolutely fuming about the whole thing!!!! I’ve only had the car since September! Am I being totally unreasonable to think this is effing ridiculous at this point in ownership??

This is my 3rd karoq:

1st one no disc issues;

2nd one both front discs replaced at 3.5yrs.

Some people on here have really decent mileage and are STILL on their original discs so what the heck is going on with my current car? And just the one disc which is so weird to me. I’m still living on the same house, doing the same commute etc as I was with the other cars so I just don’t understand what’s caused this? I cannot afford to be forking out for discs left right and centre! Argh!

“30% worn” is not a valid reason to replace brake discs. It also does not mean braking efficiency has fallen by 30%. Disc thickness has relatively little effect on the braking torque available in an ordinary stop. That is determined mainly by hydraulic pressure, caliper clamping force, pad friction, disc radius and tyre grip. A disc can therefore continue to produce normal braking force while substantially worn.

Manufacturers specify an absolute minimum thickness. For example:

new disc: 25.0 mm

minimum thickness: 23.0 mm

measured thickness: 24.4 mm

Such a disc has lost only 0.6 mm, but it has used 30% of its permitted wear allowance. It still has 70% of its usable wear remaining. Replacing it solely on that basis would be premature.

In such a case I would ask the garage to provide three figures:

the original nominal thickness;

the manufacturer’s minimum thickness;

the actual measured thickness of each disc.

Edited Tuesday at 19:071 day by mumpsim
typo

Generally one disc wearing excessively compared to the other side suggests that the pads could be sticking.

EDIT: I forgot to add that there was obvious corrosion to the disc

8 hours ago, thamestrader said:

Generally one disc wearing excessively compared to the other side suggests that the pads could be sticking.

What sort of things would be causing pads to stick? Is that something I’m doing?

Low mileage and gentle braking parked near the sea could cause this.

6 hours ago, U32ng said:

What sort of things would be causing pads to stick? Is that something I’m doing?

If there is corrosion on the pistons pushing the pads out then they will go out with pedal pressure but can be reluctant to return. A previous car I had used sliding calipers (doubt the Karoq has these but) and one side wasn’t sliding hence the majority of braking effort, pad wear and disc wear was on one side of the disc.

7 hours ago, U32ng said:

EDIT: I forgot to add that there was obvious corrosion to the disc

This is the cause surely, but your annual mileage seems pretty average, and usually it's the rear discs that corrode before the front as they don't generally contribute so much to the braking effort. So for one of the front discs to corrode more than the rest suggests that either the brakes are unbalanced due to sticking pads etc as discussed above, or a manufacturing defect in the disc.

Re discs. Location location location. I sèe Scotland. Is the car parked kerb side. Many a rusty disc or sticky caliper is from wet/ salty rain water hitting drivers side. More than passengers when parked up. Maybe more an issue some regions / weather conditions.

20 hours ago, U32ng said:

And just the one disc which is so weird to me.

Did you touch the wheels? Is there any difference in temperature? Are discs the same colour. Dont you feel puling force to the left when braking? Maybe left wheel doesnt brake. All the job goes to the right wheel. Go to garage with gauges and compare braking force.

I take it you have had it since new or low mileage and at 8k I would not expect corrosion or wear that would warrant a disc change unless the caliper is either defective or pads are sticking in carrier. I assume it was a dealer if its under warranty that did the work plus you mention one disc was replaced. Its normal and safe practice to replace in pairs.

If it is a defective seized caliper it should be covered by warranty and because it caused damage to disc maybe disc should also be covered. If the pads had seized in carrier I doubt it would be covered

Alasdair