How Do You Know When Your Brake Disks Are Worn??

[Sarnie]

Ok, slightly embarrassing question given all the cars I've had over the years!!

 

So, how exactly do you tell when the disks are worn??

 

Porsche are telling me that I need new front disks and pads as they are "95%" worn.............and want £980 to supply and fit them.

 

I've read of numerous other people getting well over 70k out of theirs but my car has barely done half that mileage!!

 

I can see that the pads are probably shot but the disks as well?

 

Visually they look fine to me but I don't know what they would look like when they are shot!?!?

[370Ad]

Big old lip on them will tell you.

 

There will be a minimum and maximum thickenss that Porsche supply if they are OEM. You then measure them and see if its getting close.

 

As Porsche have said 95% worn I imagine they have done this but always best to double check.

[Sarnie]

So is it the lip on them or the thickness?

 

Or is the lips only created as the pads wear away at the disks causing them to get thinner creating the outer lip???

[350zedd]

If there's a lip on the outer edge of the disc or scoring, this can usually be ground off in situ.

If they look ok visually then maybe check the thickness of the disc with a micrometer or vernier caliper against the manufacturers minimum thickness spec.

[gsexr]

the lip is created as the disc is worn away but there is always a manufacturers minimum thickness that the disc can be.

Ask what this is and what yours measures

[Paddy78]

The thickness and or any warping, as you can always have the discs skimmed if there is enough meat on them.

 

I know my discs need replacing as they are starting to rust, but quality discs should last years unless you are tracking loads.

[Watshot]

The lip is created as the pad eats away the disc, as the pad doesn't extend right to the edge of the disc, that material is left behind. However, if the disc seems otherwise okay, i.e. no grooving, run out variation etc., then as 370Ad says, measure the remaining disc thickness. If it's within spec then you consider whether there is enough meat left on it to warrant fitting another set of pads. No point if they won't outlast the remaining disc life. Porsche seem to be suggesting this.

 

I find increasingly nowadays that I am changing discs and pads on the front of modern cars at a ratio of one to one, whereas in the past you could expect maybe two or three sets of pads before renewing discs.

[Sarnie]

The lip is created as the pad eats away the disc, as the pad doesn't extend right to the edge of the disc, that material is left behind.

 

Wow, I did not know that.

 

Every days a school day

[glrnet]

Some garages (from personal experience) will try it on and tell you you need discs as a matter of course whrn they are actaully not required.

[Sam Mcgoo]

It's all pretty much been covered above.

Worth measuring them to ensure they are indeed worn.

You can take a file or grinder to them to get rid of the lip, but be cautious as you don't want to throw them out of balance.

 

You can remove them and get them on a lathe.

 

Or you can contact Marcus@discskimmers (trader on here) and he can do a professional job on them while still fitted on your car.

[Ekona]

You need to measure them. Porsche don't often lie with stuff like that, as it's very easy to catch them out if they were. Which OPC?

 

Porsche discs rarely last beyond 40k. Mine were 60% worn at 45k miles, but I'm a VERY light braker.

 

£980 from OPC is a bit much, I'd be looking elsewhere I think. Even if you stick with OEM for the warranty, anyone can fit them for you, it's not a difficult job.

[davedutch]

I believe the pads are now made out of a harder compound so the pads tend to last longer but the discs wear faster.

 

I've just had rear discs and pads on my work Volvo both o.e. and covered 85,000 miles how's that for gentle braking, Z front discs blue after one weekend in Wales - clearly not so gentle braking !!!