Hi folks. I have checked out the runout on the brand new brake discs installed on the front axle of my V6 Superb. The max runout came out as 0.003", which is about 0.075mm. I cannot find the specification. I have tried reducing the runout - the discs are perfect, the hub itself is deformed a tiny bit. Tried cleaning it thoroughly, but that's yielded in limited success - it was very clean already, just took some sandpaper to it to remove some minor rust from the high spots and that improved the situation a bit. I also notice that while the wheel was off, and the disc was bolted down with two wheel bolts, the pads were chafing against the disc at the high points on the disc (very minor - but audible), but when the wheel was installed and the bolts torqued to 120Nm, the chafing noise reduced significantly in intensity. This would indicate that the clamping of the disc by the wheel and spreading the clamping load uniformly across the disc area has reduced the runout - but obviously I cannot measure it now as the wheel is in place.

It was exactly the same story on the other side. 3 thou' runout, reduced when wheel installed.

What I can recommend from this:

1. when fitting the disc, clean area thoroughly on the hub, and install disc using all the 5 bolts (with a thick washer) and torque to 120Nm

2. check runout against the spec.

3. then remove the bolts and now fit the wheel

4. torque bolts to 120Nm

5. Drive for a few days, then check torque of wheel bolts again

Does anyone know the r/o spec?

Reading on the internet, some large cars specify 0.1mm in the middle of the disc contact area.

For those wondering why on earth I am writing about this, basically discs last much longer when running "true". Any runout out of spec is likely to cause disc judder after only a few thousand miles.

Edited 19 April, 201115 yr by oh_superb

I tend to use M16 or so nuts to stop the wheel bolts from bottoming as the wheels are quite "deep".

Probably too late for you, but when I buy a new car, I tend to whip the discs off and clean up and apply some copperease to prevent any corrosion forming as I know that while I own the car, I will probably need to replace the discs - also at this time apply some copperease to the outer surface to prevent the wheels sticking to the hubs/discs. Learned this lesson from owning a Fiesta (wife's car) and needing to smash the discs off when they ran out of life - first the swept area broke off then I had to crack the remaining "top hat" so that it could be removed.

Edited 29 April, 201115 yr by rum4mo

Hi folks. I have checked out the runout on the brand new brake discs installed on the front axle of my V6 Superb. The max runout came out as 0.003", which is about 0.075mm. I cannot find the specification. I have tried reducing the runout - the discs are perfect, the hub itself is deformed a tiny bit.

I think you have answered your own question really, hub at fault and nothing to do with new discs.

Sort hub out doing whatever it takes, and avoid botching discs to make them not run out.

Question:- are both front hubs each side giving these run-out figures.??

Identical runout on both sides. EBS discs perfect, no runout, hubs have a slight runout. On a Ford Scorpio the specification is 0.1mm total runout at mid friction contact point, the scorpio is similar in size to the superb so specification will not be far off, so within spec.

Identical runout on both sides. EBS discs perfect, no runout, hubs have a slight runout. On a Ford Scorpio the specification is 0.1mm total runout at mid friction contact point, the scorpio is similar in size to the superb so specification will not be far off, so within spec.

So it's all a storm in tea-cup, glad your happy with the situation.