Strange braking behaviour

[jonbarrett]

When I bought my 4.5 the front discs and pads were badly worn and juddering. New Mintex pads and AP discs fitted. Excellent braking for a while (1,000 miles) then the judder started again. Had the discs surface ground at an automotive engineering shop and they are perfectly flat. Still they judder.

The amount of judder varies according to speed, disc temperature, pressure and steering angle. For example at Brands Hatch, at the end of Brabham Straight the vibration was violent yet at Druids (slower speed, harder breaking, steering lock on) I could break through the vibration.

On the road, medium braking sets the judder off and when I slowly roll to a standstill I can feel the brakes pulsing. Then from time-to-time I have a period where the brakes seem perfect.

I've checked the pads are free and springs inplace. I've pumped the cylinders out and cleaned their surfaces. General condition of calipers and disks have been checked. Surfaces look smooth and even.

What is going on? Could it be a 'bad' set of pads, suspension fault or something else? While running the checks I did notice the cooling vanes between the discs are spinning in opposite directions. Is this right or should the discs be handed?

Any ideas as this is driving me mad and spoiling every drive out.?

[ridds]

People have had problems with lower wishbone bushes causing this. Might be worth looking at.

[saranigel]

This is quite interesting, I can take my Cerb out three or so times with no judder at all then the fourth time it will do it some of the time- comes and goes?

[jonbarrett]

Wishbones, interesting?. If I put a crowbar in the front lower wishbone bush I can move the lower wishbone backwards and forwards a few millimeters and the whole wheel hub moves with it. Looks like this is the next job then?

Thanks for the help. I'll report back with my findings.

[Old Geezer]

Jon I have the same symptoms, having had new disks and pads fitted when I got the car I don't see it can be the disks.

Do you get any high speed vibration??
Sort of resonates at 80/90.
Thought someone has told be it could be due to worn bushes??

Steve

[Roy Batty]

Juddering can indeed come from other places rather than the obvious brakes.

Play in suspension or steering components can result in vibrations, as I had this with my Rangie due to play in steering (steering box and drag links), but worn suspension bushes are also a common cause as had already been sugested.

[jonbarrett]

I'll take a look at the suspension play this weekend and report back.

[jbvipercerb]

Have you checked the brake disc mounting flange for rust or dirt? if the flange is rusty it will make the disc run out of true?

[jonbarrett]

Disc flange itself is flat and smooth because it was checked before the surface grinding. Hub looks OK but I'll double check the surface.