When to change brakes

[freenote]

I know it's foolish to skimp too much on brakes but I'm also aware that garages often recommend changing them way before needed. My front discs have substantial lips and my rears have developed some rust and clearly aren't working to their full potential.

How do you know when discs actually NEED changing??

[DAVEVO9]

freenote said:

I know it's foolish to skimp too much on brakes but I'm also aware that garages often recommend changing them way before needed. My front discs have substantial lips and my rears have developed some rust and clearly aren't working to their full potential.

How do you know when discs actually NEED changing??

New discs all round from what you describe.

[freenote]

DAVEVO9 said:

New discs all round from what you describe.

Would you replace discs as soon as they get a lip??

[Ricky_M]

I wouldn't bother, they just slow you down.............


On a serious note, I go on visual condition. When the pads are low and when the discs have a noticeable lip or are looking on the thin side.

I probably change mine way to early though!

[stabbed rat]

I believe there is usually some form of wear indicator on them.

When i swapped my MINI discs, the new ones clearly had wear indicators on them and I now know what i would be looking for as a wear indicator. Perhaps ring up a dealer/ look online to see if you can find where or what the wear indicator is?

[DAVEVO9]

freenote said:

Would you replace discs as soon as they get a lip??

Yes going by what you said a "substantial" lip.

[Ricky_M]

You could just buy a cheap Vernier Caliper and check their width against the minimum recommended by the manufacturer.

[WhoseGeneration]

freenote said:

I know it's foolish to skimp too much on brakes but I'm also aware that garages often recommend changing them way before needed. My front discs have substantial lips and my rears have developed some rust and clearly aren't working to their full potential.

How do you know when discs actually NEED changing??

You measure the thickness of the discs and refer to the manufacturer's specifications.
Regarding your rear discs and rust, it may be that your driving situation and or style means your rear brakes are rarely used or that the brake proportioning valve is faulty.

[stabbed rat]

Ricky_M said:

You could just buy a cheap Vernier Caliper and check their width against the minimum recommended by the manufacturer.

Wont work if there is a lip you could do it with a micrometer, bit of an investment though just to check your discs. How about getting a second opinion from another garage?

[GTR Cook]

I would say they need checking when performance starts to drop off. It does become noticeable when this happens. Also regular checks on pad thickness can give an indication.

[freenote]

stabbed rat said:

Wont work if there is a lip you could do it with a micrometer, bit of an investment though just to check your discs. How about getting a second opinion from another garage?

It's more that I just want to know when a disc is past it's safe usage.

[Ricky_M]

stabbed rat said:

Wont work if there is a lip you could do it with a micrometer, bit of an investment though just to check your discs. How about getting a second opinion from another garage?

Thats the one I meant, they can be had pretty cheap on Ebay.

[GTR Cook]

freenote said:

It's more that I just want to know when a disc is past it's safe usage.

I would think the pad would wear out first before the disk- large lips and small cracks are indications of wear on the disks.

[WhoseGeneration]

freenote said:

It's more that I just want to know when a disc is past it's safe usage.

You've been given the answer, when it's at the minimum thickness as specified by the car's manufacturer.
Unless, prior to that the disc is exhibiting other potential failure modes, which are very rare on a normally driven road car.

[Eggman]

Micrometers can be had pretty cheaply; you don't anything super-accurate for measuring discs. I routinely make a note of the thickness of my discs and pads at service time so I can see how they're wearing, then if at any point I suspect there might be something funny going on I can check my measurements against the last lot.

Having said that, it doesn't do any harm to pop the calipers off periodically so you can have a proper look at the pads, check the sliders haven't seized and so on. Garages very frequently try to stiff you by recommending they replace bits with tens of thousands of miles left in them; this is one of the many reasons why (providing you're not totally inept) doing your own work saves a fortune.

[parapaul]

The last discs I fitted were Pagid, OE equivalent on a Mondeo. The new discs had a minimum thickness of 2mm less than the new thickness. I didn't measure, but I'm pretty sure the lip on the old discs was more than 1mm each side.

[psychoR1]

The stealer recommended new discs on my car. They were "allmost 75% worn" at 110k miles. I said leave them - they have another 15k in them at least.

[XG332]

When they look like this.

[MX7]

stabbed rat said:

Wont work if there is a lip

You put a magnet each side of the disk, and then measure how thick the magnets are.

[eldar]

If they look like this, change them...