On the subject of discs.

I changed my warped front discs (and pads) around 2 years ago - it was very noticeable when braking, with a shaking, and pumping through the pedal. All new parts sorted this.

Now, 2 years on, I am starting to get a bit of a judder again. Discs look virtually new, 20,000 mixed miles, pads still have loads of life.

So, they are starting to warp again.

I dont keep my foot on the brake when stopped, I never do sharp braking etc, so am at a loss as to how this is occuring.

Any ideas?

Thanks Alan.

Reply to
A.Lee
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There's a somewhat controversial theory that transfer of microscopic particles of friction materiel from the pad to the disc can build up unevenly, causing judder. This is said to be more likely when non-OEM materials are used.

If the discs are 'scoured' with a Scotchbrite pad, the material can be removed, and smooth braking returns.

It appeared to work for me on the one vehicle I tried it on, although I'm also willing to accept that removing/replacing the pads as part of the process might also have done the trick.

Either way, it's a virtually cost-free thing to try first.

Chris

Reply to
Chris Whelan

If the discs do not run exactly 'true' when new the pedal will feel fine at first and they will stop properly, but over time they will develop disc thickness variations (DTV) The only real cure is new discs and when you fit them do a run out check and fix the problem (sometimes by replacing the hub. A common cause of excess run out is insufficient cleaning when fitting new discs, another is when a wheel is removed some dirt falls between disc and hub (common on things with loose discs, unlikely on vehicles where the disc is secured)

a good write up here:

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ebc have a good page too:

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Reply to
Mrcheerful

I can't help feeling that if I'm trusting you to make my brake discs then I'd want you to turn them more accurately than I could manage with something bolted to the caliper. But the biggest cause of repeated judder, IME, is the ARB bushes going soft and exaggerating any slight issues.

Reply to
Duncan Wood

On car rotor machining is something the yanks have done for years, nearly as common as getting a four wheel alignment done over there. But here it has definitely been rare. If the disc is well bolted on, then machining from the caliper mounting points should be very accurate , they are pretty solid. But it is another thing like on vehicle wheel balancing, not done very much in this country.

Reply to
Mrcheerful

My thoughts!

Some of the common problems - some have already mentioned in this thread.

On long descents the rotors will heat and hot spots will occur. (This is somewhat prevalent when a trailer is attached.)

Heated rotors will distort. (hard pad material)

Dirt on the rotor mating surfaces when the pads are replaced the rotors become loose dirt can drop between.

On VW's recommendations over tightening of the wheel nuts/studs will cause the judder.

I have found that it has become more critical for the pads and rotor materials to be compatible. Such, genuine rotors and pads are optimal. One of the reasons they get changed together.

Just a question have the callipers been serviced as they could be sticking causing the pads to rub on the rotor creating heat, is there one rotor giving off more heat than the other after a drive?

Reply to
Rob

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