Machining Break Disks

[M3 SHAM]

Hmm.. I shall check to see if it is crud, just assummed the disks were getting worn

 

[jaymanek]

Oh yes... I remember those....

BTW, I also remember when they use to have wheel balancing machines that balance the wheel while on the car.

Some of the trade magazines we get advertise some quite complex machines... they work with lasers and prices start at £3K. Very popular in the supercar scene...

 

[corned]

My personal opinion (FWIW) is that there is nothing inherently wrong with dressing a lip with a file (or an angle grinder) if otherwise the disc is serviceable.

If the disc is getting thin, and there is quite a lot of surface scoring, then I wouldn't hesitate in replacing the whole lot. It's not worth it!

However, if there is still plenty of 'meat' on the disc, and the active surface is still smooth and even, then there is no reason not to consider skimming/dressing/etc.

I have taken lips off discs myself (Spike method) and not had a moment's concern as a result. But there were no other signs (warping/scoring/min thickness) to worry about.

 

[balge]

Hmm.. I shall check to see if it is crud, just assummed the disks were getting worn

Natural enough, it does look like they're worn, but the edges pick up lots of stuff, pad, disk and just road muck can build up, and even if the pad is slightly worn, as long as it's flat and straight, why replace them when you can easily make good?
A decent file will do it easily, if you don't have power tools, as long as you don't mind getting your hand's dirty..and beware of brake dust, obviously !

cheers

 

[John]

I think it is different to just take off a lip to ultimately stop it scoring your caliper and buy more time than trying to rectify score lines or warping - which is a nonsense.

As already said, you are not using that part of the disc anyway which is why the lip is there.

 

[Doodle]

How would it score the caliper? The lip isn't growing with wear.

 

[flango]

Disc Skimming is part of the standard Service schedule for both Porsche and Ferrari but with discs around £3K a time you can understand why you would want to maximise them. On anything other than a supercar it's probably false economy around £20 a disc to skim a normal metal disc is the going rate so for most cars not much more to replace and have full thickness.

 

[NOMONEYBUTAMERC]

^ +1

 

[clever dicky]

Any time I ever had a lip on a wheel brake disc it was also rusty, which meant a light tap with a small rounded hammer and the lip just falls away.

 

[John]

How would it score the caliper? The lip isn't growing with wear.

On the contrary, it does grow as the disc gets thinner as a result of wear.

Eventually it gets to the point where it wears a groove in the caliper.

Might not affect modern cars but I've seen it on older cars.

 

[balge]

I'd be more worried about it jamming the pads to be honest, but whatever, it's good practise to clear it off!

cheers

 

[Doodle]

On the contrary, it does grow as the disc gets thinner as a result of wear.

Eventually it gets to the point where it wears a groove in the caliper.

Might not affect modern cars but I've seen it on older cars.

I can only assume you are referring to the brake disc suffering physical deformation and changing the position of the edge then, as the lip is merely unworn material and cannot "grow" in itself (notwithstanding the expansion and flaking caused by corrosion)

I would postulate that if there is sufficient deformation to cause disc and caliper to contact, then there is something seriously wrong. I've seen it a couple of times with sub-standard materials or poorly designed brake conversions, but never on a properly sorted system.

 

[Dieselman]

My front and back brake discs are starting to show a littlt bit of a lip maybe 2-3mm and I was looking into getting them replaced.

If the lip is 2-3 mm then the disk is well below the minimum thickness. Normally the lip can be 1mm each side and the disk is at minimum.

 

[DRBC43AMG]

That is a quick way to check and good to know

 

[Dieselman]

^ That info is for cars with high performance brake systems. Lesser models are normally 1.5mm per side.

 

[Sp!ke]

If the lip is 2-3 mm then the disk is well below the minimum thickness. Normally the lip can be 1mm each side and the disk is at minimum.

I disagree, I've had cars with disks that had over 5mm of wear before they hit minimum thickness.

Best way is to read the minimum thickness and then measure with a vernier guage.

My W124CE did 200,000 miles on original front disks.. still within minimum tolerances. changing disks because of a bit of a lip seems crazy to me.

 

[camerafodder]

I disagree, I've had cars with disks that had over 5mm of wear before they hit minimum thickness.

Best way is to read the minimum thickness and then measure with a vernier guage.

My W124CE did 200,000 miles on original front disks.. still within minimum tolerances. changing disks because of a bit of a lip seems crazy to me.

A lip of 2 -3mm represents 4 -6mm of wear overall.

 

[balge]

...unless the lip is mainly just rust and muck?

cheers

 

[Dieselman]

I disagree, I've had cars with disks that had over 5mm of wear before they hit minimum thickness.

Not on a Mercedes.

Here are the spec for the O/p car.

Diameter...288
Thickness...25
Min Thickness...22
Height...47
Bore Diameter...67
Studs...5
Solid/Vented...vented



Just checked the ones for your old C124.

Diameter...284
Thickness...12
Min Thickness...10
Height...44
Bore Diameter...67
Studs...5
Solid/Vented...solid


Looks like proper brakes might have been a cost option...

 

[rf065]

Any time I ever had a lip on a wheel brake disc it was also rusty, which meant a light tap with a small rounded hammer and the lip just falls away.

The same method I've used for years, takes 5 minutes per disk and never had any problems, best to wear goggles though.

Russ