Juddering under braking
 

Last May (2018), my 2007 XKR (135k miles) started juddering whenever I braked. It got worse of the course of a month and the guy who looks after my car said it was probably due to rusty disks and suggested I try to clean them by breaking harder. After a week there was no change so he put new front disks and pads pass on and the issue went away.

Great, problem solved, except that it started happening again 5 months later. In the 11 years I've owned this car I've never experienced this problem before. I don't drive it hard and use a combination of engine braking and the foot brake on my daily 50 mile round trip to work, which is on country roads, averaging 60mph.

I took the car back to the garage and he replaced the disks and pads under warranty saying the disks were warped. This would explain the juddering. He assured me it wouldn't happen again, but I'm not so sure. It seems like too much of a coincidence that this has now happened twice and I can't help thinking there may be another issue causing this to happen. I assume I'll find out for sure in another 5 months!

Any thoughts on what might be going on here?

Sounds like warped rotors but it would have been better if the specialist put a gauge and checked the rotor run out. That would have verified warped rotors. Also when replacing the pads do you know if he checked to see if the caliper pistons were free with no binding. The lubrication of the caliper/pad slides to make sure that the pads were free to move. Do you know if it was 1 wheel or 2 and was it front or back. If this happens again I would suggest that the calipers be checked out.

Did the garage fit OE Jaguar discs or similar looking Chinese ones? There's a reason the far eastern discs are cheap.

Graham

Warped rotors is often a claim made by shops wanting to sell you parts and service. The reality is that most serious rotor manufactures debunked this decades ago. Rotors simply do not warp unless seriously mistreated (or are cheap Chinese junk as Grahm points out). 95+% of the time it is found to be uneven pad material transfer.

Have your shop (or yourself) take sandpaper to both sides of the rotors and clear off any old pad material, then re-bed the pads again.

:icon_twocents:
Vince

Another cause of brake judder is a sticking caliper piston.

Some people will tell you that your rotors are warped and need to be replaced. Although extreme heat can cause rotors to warp, in most cases vibration is more likely to be caused by an uneven build-up of brake pad material on the rotor that causes the pad and caliper to move up and down as they grip the uneven disk surface, which you feel in the steering wheel as vibration, shimmy, or judder.

I suggest that you have your rotors checked for build-up and run-out (wobble in and out while spinning) and determine if they need to be resurfaced. Even if your rotors have sufficient thickness remaining to be machined (also called "turned"), my experience is that you're better off to buy brand new rotors as resurfacing leaves them thinner and less effective.

I don't understand why some people buy cheap aftermarket brake pads and rotors. There's a reason why they're cheap. Brakes are critical to safety. Don't skimp out and risk your life and the lives of others. Top quality aftermarket brakes are usually OK, but I trust Jaguar engineers and prefer using OEM brake parts.

Thanks for all your comments.

Just to clarify, it's the front rotors (disks) and pads that have been replaced and they were replaced free of charge under warranty, which suggests there was a fault with the original disks and pads that were fitted in May (possibly!).

As far as I'm aware the shop only use OEM equipment and this is certainly what I'm playing for!

No mention of the front callipers being stiff. I had wondered this myself as one of the rear callipers was replaced earlier this year.

I guess I'll see if the issue returns in 5 months and if it does this will be the third time so would suggest there is an underlying problem, possibly the callipers.

What are your driving habits? Is it daily driven, or does it sit a long time (weeks and weeks) before being driven again?

Not so much pad amterial transfere but rotors rust when it rains and is sitting. Normally not a issue. But if it get enough rust buildup on the rotors this will yes be cleaned off when brakeing the first few times. Except that the rotors dont rust where the pads were siting so when that rust is cleaned off the rotors are now slightly thinned except where the pads sat. Those areas are now high spots and you will feel it when it is enough of a differance. The other thing to check is the front lower curved control arm bushings. Or torsion arms. These help to control suspension movement when brakeing and the fluid in them is no minimise feedback into the pedal when braking. Obviously when they leak or are cracked they dont do this as well. Another reason i dont recommend the cheaper aftermarket bushings that are solid

The sad part here is that you have already discovered 2 things:
One is you have been lied to, (see below), and two you are actually uncertain of the parts used, in which case please go back and revisit discovery number one.

I cannot reiterate enough, that if an actual 'shop' claims your 'rotors are warped', then you should really consider just how knowledgeable the mechanic or shop really is.
If this tern was indeed used in your dealing with them, then you need to know that you have flat out been lied to in your face, or at best, dealing with an uneducated grease monkey that will cost you dearly in the long run. I have little patience for incompetent mechanics feeding off an uninformed customer for profit.

Vince

Could you please advice the OEM names for the brake parts ? Also are britishparts.co.uk a reliable source ? I inquired with them for brake pads, rotors and piston kits (all available on their website), I was apprehensive for the piston kit because the part number did not look like a jaguar part number. They replied that jaguar does not manufacture piston kits. If you can advice the good names of OEM that will help going ahead and purchase the parts.