how do you know when to change brake discs

[IATM]

Hi guys.

Just want to expands my knowledge on general braking system. One key thing I would like to learn is how do you know when your brake discs need changed. What are the visual signs and braking symtpons.

Thanks

[Eighteeteewhy]

The manufacturer will give a minimum thickness.


ETA...which you check with one of these...

Edited by Eighteeteewhy on Sunday 26th February 21:39

[Eggman]

You measure their thickness with a micrometer and compare it to the manufacturer's recommended minimum.

[Defcon5]

When the inner face has holes burned into it

[drophead]

Normally a good sign...

[Bat Fastard]

When you crash at very high speed

[mybrainhurts]

Visual...lip round the outside of the disc or bad scoring or grooves on the face of the disc.

Warped discs can produce a wobble under braking.

[iva cosworth]

Also when rust on them won't come off after a drive.

And when they vibrate WAY too much under braking ,assuming it's not something else

wrong with bushes/joints.

Or when the surface is all ripply and shiny/glazed.

[mybrainhurts]

iva cosworth said:

Or when the surface is all ripply and shiny/glazed.

I have it on good authority that's an accurate description of your good self, sir...

[IATM]

iva cosworth said:

Also when rust on them won't come off after a drive.

And when they vibrate WAY too much under braking ,assuming it's not something else

wrong with bushes/joints.

Or when the surface is all ripply and shiny/glazed.

Sorry can I confirm what a glazed disc would look like. Any example pics?

[Andyjc86]

When the edge if the disc starts falling off, or a crack appears anywhere (everything I can think of has been covered already)

[iva cosworth]

mybrainhurts said:

iva cosworth said:

Or when the surface is all ripply and shiny/glazed.

I have it on good authority that's an accurate description of your good self, sir...

[iva cosworth]

IATM said:

iva cosworth said:

Also when rust on them won't come off after a drive.

And when they vibrate WAY too much under braking ,assuming it's not something else

wrong with bushes/joints.

Or when the surface is all ripply and shiny/glazed.

Sorry can I confirm what a glazed disc would look like. Any example pics?

I used to be a mechanic so could spot one but not able to describe it over the net.

[IATM]

How bad do these look then . Sorry I know its not the best pics

[iva cosworth]

Bit of a ridge/line of something on top pic but otherwise not too bad.

[disclaimer] not responsible if brakes fail [disclaimer end]

[freecar]

They look a bit lipped but without knowing the original thickness we can't easily tell you.

Personally I'd change them, the lip could be 1.5mm deep both sides which has stripped 3mm from the original thickness, barring any other data I'd change them now.

However, some manufacturers give more meat to begin with so I'd check what the minimum thickness would be in case you've got another 12 months on those.

NEVER run under minimum thickness, your pads may actually fall out! Other issues include increased brake fade due to less heat dissipation and jammed pistons as they slightly fall out and can't return squarely.

You must find out the manufacturers minimum thickness though, anything else is just guesswork, from a photo, over the internet, hardly gospel!

[IATM]

Haha I like the disclaimer. Well I am going to the garage to have it checked out however I certainly get a juddering under braking especially when brakes are cold. And it's 100% from the rear. I can feel it quite very obviously

I like to gain knowledge and understand things before I go to garage so I know the right work is being done.

Any more info would be most helpful.

[Eggman]

They look pretty new to me, but you would need to whip the wheels off to have a proper look. The top one looks like it may have some kind of brown deposit on it - probably nothing, but I'd give it a prod and a sniff to see what it is,

[Efbe]

in my experience, there have always been far far more likely things to cause shudder or juddering under braking.

tyres, wheels, brake disks, bushes, ball joints, arms, even bits of plastic coming off from around the arch (actually quite common!) even duff springs thinking about it, and probably some other suspension related issues I haven't thought of.

I have never actually needed the disks needing changing on any car I have ever owned, and i've had a lot of old interesting and powerful stuff!

[iva cosworth]

IATM said:

Haha I like the disclaimer. Well I am going to the garage to have it checked out however I certainly get a juddering under braking especially when brakes are cold. And it's 100% from the rear. I can feel it quite very obviously

I like to gain knowledge and understand things before I go to garage so I know the right work is being done.

Any more info would be most helpful.

If you go ahead and have discs replaced ask for the old parts to be returned to you

in a bag,including brake pads.This is your right,they are your property off your car.

Post more pics on this thread for the PH perusal