how do rotors get warped when they are only 6 months old? that is what i found out on my 2001 XJR R1 spec ...i ordered new rotors from the UK and when i asked my mechanic to check them he confirmed they are warped...i am surprised they warped so quick and am wondering what happened for them to warp...i haven't even done a full stop at all?

 

Incorrect torque can distort a rotor. Rust between the hub and rotor can make a true rotor feel warped.

Also, friction material transfer onto the rotor can give the same symptom as a warped rotor.

Did your guy actually measure the rotors for run-out?

Cheers
DD

 

yes he measured them for run out...any ideas? did i get bad rotors you think? or could bad pads cause it?

 

The vast majority of 'warped rotors' issues are actually pad material as stated above.

 

"pulsation's" in the brake system are often rust formations and you can get pad transfer -- but most of the time this will go away. The serious stuff is warped rotors. One of the brake pad companies likes to put out a lot of information to support the use of their pads -- but rotors warp ... and cheap rotors more so.

Sorry to hear about the rotors -- what brand are they?

Making sure all the attachments and the wheels are properly torqued is important.

 

I had the same experience with some grooved discs and Redstuff pads. 4000 miles later, it was terrible to touch the brake. The seller claims that my wheel bearings were not in order, and skimmed my discs for free. Why they don't specify this on the producer site(only for perfect cars) ?

 

The main reason I use solid discs and proven pads. I've been down the rather expensive route of running Brembos' - not worth the extra till. The performance is marginal over the standard ATE system. They also decay over in the UK, mine where pitting badly on the rear side.
Disc skimming isn't an answer on these either as even a mild couple of thou puts them out of spec'.
FWIW - try and find a pad that suits you and your car.

 

what about two piece rotors will they ever warp? what are your best suggestions for two piece rotors for a R1 spec XJR?

 

It is a known problem on R1.

See TBS 206-11 http://www.jagrepair.com/images/TSB/...0vibration.pdf

and this background information:


DETAILS:
We have identified a potential concern on XJ and XK vehicles equipped with Brembo Brakes. The nature of the design of the hub-disc interface is the root cause of this issue.
The hub outer face and disc inner face are of different diameters, the hub face being much smaller diameter than the disc/hub contact surface area of the disc. This has the effect of forcing a distortion of the disc if the disc and wheel is fitted incorrectly. The issue is compounded by the fact that, both the disc and the hub are concave, so incorrect wheel nut tightening can again lead to distortion of the disc.
Having a disc distorted like this may or may not create brake judder immediately, however if brake judder is not immediately apparent, it will occur at some stage in time due to the repeated wearing of one part of the disc causing Disc Thickness Variation. The phenomenon WILL ultimately lead to brake judder.
Brake disc runout is the initial determining factor as to whether there will be a brake judder issue. The method for measuring runout in JTIS is not applicable in this context. In order to get a useful disc runout measurement, the measurement must be taken on the inside of the disc with the disc and wheels mounted to the hub, the wheels nuts correctly tightened to the correct torques having followed the correct procedure detailed below. The runout measurement needs to be less than 40 microns and needs to be measured to an accuracy of +/- 5 microns. It is worth emphasising that the runout which matters is the installed runout and therefore a hub with high runout mated correctly with a disc with high runout MAY create a situation where there is virtually no total installed runout. When the installed runout is less than 40 microns, a car will be very unlikely to return with brake judder.

A new hub is currently being developed by Jaguar Special Vehicle Operations in conjunction with Brembo which will be the solution to this issue. In the meantime however, the following points are useful to bear in mind when carrying out work where a customer complains of brake judder. When handling vehicles fitted with Brembo Brakes, special care must be taken. Cleanliness of hub, disc and wheel is essential. Power tools are not to be used for the fitting of brake components or wheels. The wheels must be mounted and tightened using the correct procedures.

**When fitting new components it is essential to ensure that runout is minimised. For example, when fitting a new disc or hub, the disc must be optimised to the hub using the normal procedures.

**Wheel nuts must all be fitted and tightened gradually moving from one to another which is not next to the original one (see diagram below). The nuts must be eventually tightened to the correct torque.

**Wherever practicable, steps must be taken to minimise creation of adverse runout.

**As a final check, the total installed runout should be measured on the inside of the disc when the vehicle is ready for customer collection. The runout must be less than 40 microns.

Failure to carry out the above points will increase the risk of brake judder on Brembo equipped vehicles

 

wow luc...thanks so much ...my mysteries have been solved...and i am going to get rid of this brake judder once and for all!

 

You're welcome
You need some new rotors, best price ($212 for the pair, free shipping) is from the link below.
If the link don't work go to europartsdirect.com and look for part # 40526027613
They are the british eurospare brand.
Beside Jaguar/brembo, they are the only other brand available


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