Front rotors.

[Lukes3]

I no its another brake thread but i have run out of idea's so need some advice lol,
I have had some new rotors made to fit the oem bell/hat, i had them made at 380x34 and had the spacers made for the caliper with new ebc yellow stuff pads,
Now every time i press the brake there is terrible vibration, only when press the brake an can feel it in the pedle.
I have cleaned all the faces an cheacked run out on all faces, In total i am getting a run out of 0.003" on both front rotors but its still bad.
I have only done 50 mile so far so do i just run with it to bed them in or...???
Any help would be great cheers.

[Bogyoch]

Hello Luke

That's a pain that you've got vibration. I know that you've checked the run-out of the discs and at 0.003", and this is about the maximum tolerance, but shouldn't cause "terrible" vibration as you describe. However, it won't be smooth.

There are so many things that can brake vibration, but the next measurement to check would be disc thickness variation. Even the teeniest difference can make some awful vibrations. For example, if you have 0.001" thickness variation, the car will probably be undrivable.

Can I ask who made the discs for you?

[Lukes3]

Hello Luke

That's a pain that you've got vibration. I know that you've checked the run-out of the discs and at 0.003", and this is about the maximum tolerance, but shouldn't cause "terrible" vibration as you describe. However, it won't be smooth.

There are so many things that can brake vibration, but the next measurement to check would be disc thickness variation. Even the teeniest difference can make some awful vibrations. For example, if you have 0.001" thickness variation, the car will probably be undrivable.

Can I ask who made the discs for you?

Hi thanks for the reply,
Normal driving around isnt to bad up to 50-60 mph then once pressing the brake pedel u can feel it pulsing then onwards from that is just terrible,

I didnt realise thinkness veriation that little could be so bad, maybe i should ad at this point they was also zink coated so it could be that.

Company was wp pro brake, tbh not the best company i have used.

[Bogyoch]

Zinc plating usually comes off the disc surface fairly quickly. Do you have a nice even looking surface just now? If not, give the brakes some decent bedding in. A few firm 60-20mph stops will help. If the surface still doesn't look right, take a pad out and see if it's got the zinc on it. If so, you'll need to take the pads out and with a piece of 150 or 200 grit emery paper on a perfectly flat surface, rub the pads to remove the zinc. Doing this will mean you'll have to rebed the brakes.

Still check the disc thickness. Take various measurements around the outside diameter: you'll need a decent micrometer for this.

Have you checked the caliper to bracket bolts?

I take it you didn't have this vibration before the "upgrade"?

[audi_do_dat_den]

As Bogyoch stated, a thickness variation at any point around the disc surface could easily cause it.
The zinc coating/plating could also be acting as a lubricant, despite that sounding altogether wrong.

Its kind of going backwards, but getting them skimmed by a few hundredths of a mm might bring them back to perfectly true.

When you run a dial around the face, are you doing that on the car or in a lathe?

[Lukes3]

By just looking at them they seem ok but feeling them im sure i can feel difrances across the rotor. I was thinking about getting them skimed anyway as ebc seem to think this is good thing to do to get them running true to the car.
Ill take a pad out an check see if the zink is on the pad.
Ill also check the thickness of the rotor tomorrow at work,
I was running a dti gauge on the car with every thing tight (like the wheel is on)
An i have checked the caliper surfaces an the brackets and had the spacers between calipers skimed so they are are 7mm an bang on true.
No didnt have the problem before this upgrade but the old rotors were uneven an 2mm under the spec (30mm thick) min is 32mm so dont know if that was why didnt feel it?
Cheers for the help lads

[Rick_RS4]

why are you skimming new disks?

ebc are <beep>

did you fit the disk to the bell? sure its all flush, who made the disks

[Lukes3]

why are you skimming new disks?

ebc are <beep>

did you fit the disk to the bell? sure its all flush, who made the disks

Just to have them made true to the car an remove any high spots.
Wp pro brakes made them.

[Rick_RS4]

why are you skimming new disks?

ebc are <beep>

did you fit the disk to the bell? sure its all flush, who made the disks

Just to have them made true to the car an remove any high spots.
Wp pro brakes made them.

why would they make new disks that are not flat, more likely that the disk is not sat flush to the hub or the bell or the caliper is missing aligned

Can the calipers be moved/twisted when finger tight. I mean so they are not square on to the disk? Or centralised? I'd say it's possibly that

Use a steel rule over the edges and see if there are any high or low parts

not ideal but loosen the caliper bolts slightly then get someone to press the brake pedal then tighten up whilst they are still pushing on the pedal

[Lukes3]

I will try the calliper alignement first but there is not much play in that anyway

[Lukes3]

Just a little up date. The car is booked in to see if they can find the problem. Could be the ebc pads i have been told so... Think the plan is to put oem pads in an the garage might just give the discs a little skim just to bring it true again due to any high spots from the yellow stuff pads.

[Lukes3]

Excuse the mess!

[Lukes3]

Update on this.
Got the rs back today from having the rotors skimed on the car. all sorted now the rotors were skimed by 0.004" each. Terrible that the company let these go out. Now beding in the pads again an sww how we go.

[Surrey Sam]

Can't say I told you so. As I refrained from being negative about a small company in that brake disc thread, where you mentioned about getting some made up.

When it come to brake discs, there really is only three choices:

OEM = ££££'s
AP Racing = £££££'s
Ceramics = £££££££££££££££££'s

[Lukes3]

Can't say I told you so. As I refrained from being negative about a small company in that brake disc thread, where you mentioned about getting some made up.

When it come to brake discs, there really is only three choices:

OEM = ££££'s
AP Racing = £££££'s
Ceramics = £££££££££££££££££'s

Yep live an learn. Ap racing i think next.