Juddering whilst braking?

Warped discs. A DIY job on most cars

Yes, almost definatly warped discs.

Do you sit with your foot on the brake when in standing traffic? Thats the cause. Heat that has been built up while driving/braking cannot dissipate from the area where the pads are touching the discs as quick as the rest of the disc surface. This causes the metal of the disc to cool slower than the rest and so over time, warp.

Some discs will be better than others, go to a motor factor (not halfords) and see if any offer a anti warp warranty (i bought some a few years back that had). Other wise buy the best you can afford.

Steve

Its an automatic, so, yes !!!!

I've got a warranty with it but it doesnt cover 'normal wear and tear' or 'brake friction' materials. Obviously, they mean pads but could this cover disks as well?

I'm assuming new disks means new pads as well (bummer since they're only two weeks old !!!).

If the disks are covered under warranty wonder if they'll shell out for pads too (since the warped disks would have wrecked them!)

the pads will still be OK, just fit new disks

I doubt if you'll get discs under warranty, but it depends on the policy. Given that the pads are only 2 weeks old, I'd re-use them, but I'd give them a bit buff up with some course sandpaper on a flat surface to break the glaze and level them off.

However, if they've been roasted due to the judder issue, I'd replace them.

I never came to terms with this theory on the cause of brake judder. It doesn't stack up. Even if you release the brakes when you stop, there's bugger-all clearance between the pads and the disk. Certainly not enough to allow any significant airflow. If the disks really are warped, then I don't believe it had anything to do with sitting on the brakes whilst stationary.

I read a much more plausible theory on the web a while ago. Sitting with you foot on hot, stationary brakes actually causes some of the pad material to transfer to the disk, leaving a raised print on them and it's this that causes the judder. Instructions were given on how to remove the print whilst driving by violently braking in some carefully described manner.

I tried it on the brakes of my Saab 9-3, which had newish, OE pads and disks, and was juddering annoyingly. It worked a treat and I haven't needed to repeat it. I wonder how many disks have been junked over the years just because they had pad-prints on them.

Cheers,

Colin.

Now that's an interesting theory. I will be interested to know how it works out if "paulfoel " gives it a try. I put my warped discs down to high speed / violent braking. However I also drive an automatic and keep the brakes on when stationary.

Please give feedback on the "Violent braking" remedy. Hope your airbags are working ))

Everyone does, judging by their brake lights.

You get the brakes that hot in traffic?

Do they come to rest at the same place every time?

Warped discs or worn lower track control arm bushes.

But there is clearance which means that heat isn't being transferred back from the pads and caliper as much as it would be with the brakes on.

Also ... the position of the "hot spots" from different brakings would be randomly distributed around the disk, so I'd have thought any effect would balance out over time.

Ian

I dug up the original article:-

Prior to this, I'd changed the disks and pads because the disks were below minimum thickness. The new set started juddering a few hundred miles later. Thinking the disks had warped, I returned them for a refund and got another new set. When the judder started again, I tried the method in the article.

Cheers,

Colin.

It happens that Colin Stamp formulated :

It works, I have just tried it!

My car suffered alarmingly from judder on the steering when the brakes were applied at around 50mph, when I first got the car. I eliminated almost all of it by changing the wish bone rear bushes some months ago, but the juddering gradually came back - not as bad as before, none the less I wanted it sorted. I was on the point of ordering some new disks, when I read the above URL.

Based on that information, I took the car out today to test out the theory. I got the speed upto 70mph and applied the brakes hard, on a dry road I could feel the ABS cutting in. I repeated the process several times over, with a minimum amount of time lost between the braking sessions, but never actually coming to a stop.

My brakes are now almost completely judder free again. There is just the slightest trace of judder when the brakes are first applied, which disappears as the brakes come into operation.

So far as the rest of the theory goes -

I never leave my brakes on after stopping, I use the handbrake. I normally make little use of the brakes and that is fairly light use.

In my experience it's *always* been bushes and many people pay out unnecessarily for new discs. If the brake pedal itself doesn't judder up and down then I'd say it's more likely to be suspension related.

Not necessarily. Put some new discs on the wifes' Mundano the other week. No pumping through the pedal there. I know for a fact it wasn't the bushes because I replaced the lower arms 6 months ago.

brake its not

No brake pedal doesnt judder....