Brake judder could be bent wheel hubs?

[jonbarrett]

Following on from my previous brake judder post, my shiny new magnetic dial gauge has been put to work.

Firstly, I measured the runout on the outer face of the offside disc. As the images show, the runout is 0.13mm or 130um.


Disc min


Disc min

Then I decided to measure the front face of the disc hub to see if the runout was limited to the braking surface. Unfortunately, as the images show, the runout on the front face of the disc hub shows a runout of 0.05mm or 50um.


Disc hub max


Disc hub min

Then I decided to measure the front face of the wheel hub itself to see if the runout was a manufacturing fault with the disc. I had already cleaned the wheel and disc hubs to ensure the surfaces were smooth. Unfortunately, the wheel hub showed the same readings as the disc hub.


Wheel hub max


Wheel hub min

I'm guessing these runout readings are way out compared with what they should be. Does anyone have max runout figures for a wheel hub.

The only conclusion I can come to is that the wheel hub is bent.

Any other thoughts?

I'll measure the other one tomorrow.

[Brummmie]

I had a bent hub on my Chimeara, it wasnt really noticeable on the standard discs, but when i grafted Ford Focus RS discs on to it, the extra diameter magnified the runout. Replaced the hub and all was good.

[Peppe]

Rotate the disc to get it in another position compared to the hub and measure again. If you are unlucky when you put two parts togehter like the hub and the disc you might add their tolerances. When you have tried all five possible positions choose the one with the smallest measured values and try the car again.
I think I measured values betwen 50-80 µm at the edge of the disc on my car and it works fine. I am not sure though since it is two years ago. I also measured the thicknes of the disc all around it, and had a diff of thickness that was less then 20µm.

Edited by Peppe on Saturday 26th July 22:19

Edited by Peppe on Saturday 26th July 22:26

Edited by Peppe on Sunday 27th July 07:13

[Ireland]

I've still got a set of half-knackered discs on mine and they are still slightly warped but my judder problem has almost been cured entirely by fitting new bushings and new bolts to the front suspension.

I still have a little bit of pedal-bounce but nothing like the judder I had.

It's certainly worth checking this thoroughly as it may be something as simple as a slightly bent bolt or even a loose bolt.

Also check the pads as mine had bowed slightly with age.

I'd done the whole skimming the discs bit, etc and spent a lot of time looking for the cause.

I'd definitely say to look beyond the obvious.

I still plan to fit new discs to mine now as I skimmed the originals which were reading out about the same amount as yours are.

Worth a look .....