I had to replace my rear pads/discs at 25k miles when the 'low pads' warning light came on. The dealer also said my front discs were grooved/lipped but I'll only replace them when the pads wear down. However I've never noticed any juddering and certainly no clunking noises; I would expect that from a Trabant not a Jaguar! My previous car (a Chrysler) had the same juddering/warping you describe but, like you, my dealer would only 'skim' (ie. sand down!) the discs when under warranty. As you're out of warranty maybe get a second opinion from a non-franchised Jag specialist or another dealer?

 

Pads and disc don't last long, how long depends on driving style. My rear pads went at 38k so I replaced pads and disc on that axle. However at 51k, the fronts are still orginal and not worn out.
There may be another cause, What are your tyres like? Reason I ask is I had sone judder noise and the periellis had run out of true at just 23k. Maybe get these rebalances first? I fitted contis at 23/28k and they are still fine, no judder anywhere.

 

The tyres are the Dunlop as they came with the car, however i had one tyre replaced at the front. I don't think it is the balance of the tyres, as there is no vibration at high speeds, it is very stable even at 95 mph, but under braking judder a lot.
I'm typically very gentle with the brakes, no excessive braking, most of the miles are on the motorway. I have always manage to get at least 50k miles on brakes on all my previous cars.
I think there is underlay problem somewhere but not fully convinced that this is entirely down to the discs.

 

As I said in your other thread, break judder is not an unknown problem and this is the subject you should bring forward to your dealer / Jaguar. Pads and disc can easily wear out on or before 30k miles although following your story in your case that might be due to the judder which does warp them

 

Brake disc "warping" doesn't actually occur. The "run out" effects are caused by uneven pad material deposition often through hot pad imprinting.

Brake judder can result from this imprinting or from sticking caliper guides.

I continue to be amazed by the incompetence of mechanics who repeat these myths about brake disc "warping". They don't warp.

The problem comes from the measurement of run out, which reflects the pad imprinting. Then they skim the rotors to remove the warping which works so "proves" the warping is real. But, really folks how does a vented rotor actually warp?

 

I must admit that, I would rarely use the brakes as you suggest. But I find it quite interesting, it make sense what you say, so I will take the car out for a drive to see if this would improve the issues I have.

 

I went for 30 mins drive around the bends and back on the motorway, using the brakes more in the manner you have suggested. It seems like there was a slight improvement but overall the vibrations are still there. How much braking is necessary in order to clear any deposit of the pads ?
Any advice how often this should be performed ?

Thanks

 

http://www.stoptech.com/technical-support/technical-white-papers/-warped-brake-disc-and-other-myths

http://www.stoptech.com/technical-s...port/technical-white-papers/bed-in-theory-definitions-and-procedures/bed-in-faq


http://www.stoptech.com/technical-s...echnical-white-papers/bed-in-theory-definitions-and-procedures/brake-pad-bed-in

http://www.stoptech.com/technical-s...white-papers/bed-in-theory-definitions-and-procedures/stock-brake-system-bed-in

Other interweb sites give similar information.

CAUTION: street pads are soft and designed to heat up to maximum usable friction temperature very quickly. This is why they are prone to what feels like fade when they overheat, but is mainly just slight degradation in peak friction.

When bedding in standard street pads, or trying to rebed them if necessary, the key is to get them up to proper temperature but not to overheat them.

For "used" brakes that have been regularly heat cycled but not used in anger one should probably not do ten stops as recommended for "street performance" new, green pads. However, one needs to do more than just tickle the brake pedal a couple of times.

Find clear and preferably straight road. Achieve around 60 mph and brake hard enough to engage ABS if feasible. Do not bring the car to a stop but speed up again allowing the brakes to cool a little. Repeat this until you feel the brake irregularities improve. If the uneven pad deposition or rotor wear or uneven caliper movement (caliper seizing) do not improve fairly quickly them it is too late and you need new rotors or skimmed rotors to clean them up, or the pads need sanding physically or the calipers need lubricating or, in worst case, rebuilding or replacing.

It is always worth trying the road test method of re bedding your brakes. It can't make it worse and might clean up the problem.

Now, you may make it "worse" if the problem can't be fixed this way but that doesn't matter since you've simply "diagnosed" that your brakes must be serviced. Some conditions require that the rotors be skimmed or replaced because the uneven pad deposition can't be removed by braking. These are still not warped rotors but a surface dial gauge will show run out as if the metal itself is warped due to pad material embedded unevenly in the rotor surface.