What Are The Chances ...

is200 Newbie · August 2, 2014

I changed my front discs approx. 6000 miles ago which is a little over a years worth of driving. I do a lot of stop start and I don't run up a lot of miles through the year.

Both front calipers and carriers have recently been replaced with new ones.

I am experiencing a slight judder when braking - feel it more when braking from speed.. What's the chances that the discs could have warped in this short time? I did replace one of the calipers, passenger side a while ago, as it was a bit sticky and also the rubber boots on the caliper (piston and slide boots) had torn. I am thinking that if the caliper had been slightly sticking then it could have been heating up that side of the disc and possible caused a slight warp in it.

Is there anything else that I could check that would cause this when braking other than the discs ?

johnatg · August 2, 2014

Did you check the run out of the discs? Absolutely critical - any run out greater than 0.1mm will lead to uneven disc wear, which then causes judder. It's unlikely that the discs have warped - lots of people try to claim under warranty for this and it's almost invariably rejected as the cause is diagnosed as incorrect fitting (ie uneven wear due to too much run out)

The run out is measured at the disc edge (preferably with a dial gauge) - it's important to clean the hub face before fitting as even a tiny spec of dirt there will cause an ampified effect at the edge.

is200 Newbie · August 2, 2014

Hi John

The faces of hub to disc to wheel are all clean. The disc has not been off since they were replaced and they have been fine up to now.

I cant remember what make the discs were - they were either Mintex or brembo. I cant myself see it being the discs.

The rear calipers have been done but I have not done the disc yet - if that was on its way out how would you tell. Would you feel any shudder at all?

johnatg · August 3, 2014

I think it's not likely that the judder comes from the rear. You could check the rear discs - swing the calipers out of the way and look carefully at both sides of the disc (take the disc off) or use a mirror to check the 'hidden' side.

As long as there's no rust on the friction faces and the discs are within minimum thickness spec (8.5mm for solid ones - I don't have the figure for vented) they should be OK.

If you can lay your hands on a 50mm micrometer and a dial gauge, it's worth checking the front discs for runout and thickness. (Your standard micrometer is measures to 25mm and the discs are 28mm thick so you need a bigger than usual one).

It is possible that it's the pads causing the judder - sometimes they'll wear to a point where they judder for no obvious reason. Maybe try filing the surfaces to remove a layer - it's a bit clutching at straws but it might work!

Or live with the judder, but it's irritating to say the least!

Good luck!

is200 Newbie · August 3, 2014

Stripped down the front caliper and disc today just to see if its clean - done the rear caliper to re-grease the pins also.

The front discs were tight on the hub and I had to use two bolts to ease them off. After cleaning they went back on a hell of lot easier with no issue with them being tight when fitted - they could be pulled of easily enough after re-fitting.

I have not taken it out for a run yet, will do that tomorrow but maybe due to them being tight was the issue as a bit of rust had formed around the centre of the hub and could have pushed them out a bit when the wheel was last off?. Just a guess as I cant see any thing else it can be.

Will see tomorrow.

is200 Newbie · August 13, 2014

Judder is still there but not as bad as before - the rear discs need doing anyway so I will get them done first - if no change then its the front discs. That's after replacing the sensor that's gone !