Break Disc Rust

[mm888]

Hi

My first post - have a E85 3.0Si. After reading numerous posts regarding wheels and tyres I've replaced my alloys and now run normal tyres ... what a massive difference!!! I was so fed up with the car prior to the change that I was on the verge of dumping the car. During the replacement I had to change the front bushes and did a full alignment. The car is super now - got the car washed, switched to Sports mode and had a excellent run with the roof down.

So the "bad news" are the brakes ...



My rear.



My fronts.

So I've had two garages "look" at them - one said change all discs and pads; the other said its fine.

I have no experience with cars so am lost as to what to do.

Any advice on how to proceed?

Note the brakes seem to work quite well

 

[PerryGunn]

Fairly normal - the rotors and calipers rust, as long as the rotors aren't warped or cracked and are still within wear limits you'll be fine

You can paint the calipers and hubs, plenty of threads on here, you can treat the rusty edge of the rotors with something like Kurust if it bothers you

 

[mm888]

Thanks for the advice. Another 101 question, is there a way for me to measure wear and what is the limit?

 

[Bing]

Thanks for the advice. Another 101 question, is there a way for me to measure wear and what is the limit?

Wear on pads and discs are easily measured by a garage - you need to find a trusted independent BMW specialist so you don't end up with conflicting advice as above. If you give an idea of location there may be someone in the general area on the forum who can recommend one. I don't know how to measure discs, but (from the photos anyway) the fronts look ok, not too much lip. The rears, harder to tell. As for pads, there are wear sensors on the front right and rear left pads if I recall correctly - if a garage doesn't spot that they need changed then eventually a light will come on in the instrument cluster.

I'd be interested in the limits if anyone knows what they are...

As for the rust, get in there with a couple of different sized wire brushes and some silver high temp/hammerite paint - takes a bit of effort, but can be done without taking the caliper off - bonus of satisfaction of a DIY job well done, and they will look ace. Looks like they have been painted before tbh. Mine looked worse than yours on my last car and cleaned up really well.

Before :

After :

Wheels back on :

 

[mm888]

Thanks for all the responses so far ..... currently reading up on Kurust; so it gets rid of the rust and leaves the material black? Would that not look weird on the brake disc? Also reading up on how to paint the calipers .... brush or spray?

I am based in Welwyn in Hertfordshire - so any recommendation is very much welcome. Also am happy to meet up with any local members for catch ups, etc :driving:

 

[markeg]

You could try Fast Etch, although you may want to remove the worst of the rust first.

 

[srhutch]

There is no reason to change the discs unless they are below limit, even then change them next time the pads need changing. Just paint them to make them look presentable.

To measure the discs you need a micrometer or vernier will do. Doesn't mean they are not worn if there is no lip, just means the pads are touching right to the edge of the discs. Disc thickness (minimum) are stamped on them so easily checked.

 

[Bing]

I brushed mine on. Spraying needs a lot of masking, and as Jonny kind of says, you'll paint the pads too. Use different sized brushes to get in the crannies. I didn't remove my pads and only got a little paint on them, not noticeable unless you looked for it.

Jonny - you can't get the pads off without taking the calipers off too mate, a real PITA unless you have time and skills...

 

[mm888]

Thanks for all the help. So I think this is my shopping list:

- Wire brushes
- Hammerite paint
- Mircometer
- Trolley jack
- Axle Stands

When the time comes, I guess I will consider changing the discs and pads to EBC USR and Red Stuff respectively - thoughts ???

 

[swanicyouth]

This rear disc has to be too thin and should be replaced. The lip is huge. The lip will give you an idea of the original rotor thickness.

 

[srhutch]

Providing the thickness was checked last time the pads were changed then the disc should not need replacing. Just paint them and replace when the pads need replacing.

 

[Bing]

I had Textar ePads on my last car - great performance and much, much less dust than OEM. £119 for the full set IIRC. Never used Red Stuff though, so I can't give you a comparison.

Maybe the rear discs need replaced, but I'd still paint them. If you look at my pics above, the front discs on mine were pretty new but the bare metal was hard to keep clean. Once painted the dust and grime washed off really easily - maybe because it was a smoother surface, or the brake dust couldn't adhere to it so easily.

I understand where Jonny's coming from, but as the current parts work fine it comes down to whether you want to spend £300 on new discs and pads all round... Or £100 quid max on the kit required to tart them up, 80% of which is the jack and stands that you'd have to buy anyway if you were changing everything yourself. And if you're not changing them yourself, add £150-£200 labour onto the parts bill.

 

[mr nurburgring]

Those discs and pads may work ok but they look s**t, for what they cost get some new ones, spray them with zinc primer, then clean up the caliper with wire brush and zinc primer that too.
It will look oem fresh and the zinc primer will last years

 

[mm888]

Correction is required as you all have stated and partly the reason I posted as clearly the car has been neglected .... Will update with pic once finished.

 

[mm888]

A few more questions:
- are the pads meant to be the same size as the disc?
- if I was to take an extra step and get new calipers, which ones should I get?

 

[mm888]

Front: New disc, pads and painted calipers ....


Results not as good as other pictures I've seen on the forum. Also stock calipers look "small" .... BBK is what I really want.

Will sort out the rears later.

 

[Wildfire]

For the £100 or so I would replace the rears, that lip does look massive.

Bizarrely I replaced bothe front discs and pads, on one side the pads go to the edge of the discs, the other the normal ridge.