Hi,

I have two symptoms, which might be connected or not...:

1)
Driving my XJ8 faster than 80miles/h ( 130km/h), I can hear a deep noise which seems to correlate with the rotation of my wheels.
As I accellerate up to full speed, the frequency and the amplitude increases.
Changing from sommer wheels to winter wheels makes no change.
The amplitude (very) slightly increases the more throttle I give.

2)
Braking the jag at highspeed brings strong vibrations.
The brake disks seem to be in perfect condition, the bad pads are genuine jaguar.

My request for help/questions:

A)
How can I locate the source of vibration to front/rear or left/right ?

B)
Are 1) and 2) independent effects or caused by each other ?

 

How many miles (or kms), on the car ? Could be the wheel bearings, they don't last forever.

Sometimes the rear discs can cause this vibration. On my own car, I had vibration on braking, and it went when the rear discs were replaced. Its now back slightly after about 25k miles, but this could be the fronts now.

 

88000 km.

I had failing wheel bearings on my former car. It was correlated with a rough noise that changed amplitude when turning left/right.
Do jag bearings fail/wear different ? Should it be detectable when lifting the car and measuring tolerances ?

The rear disks...I must admit, that I only inspected my front disks.
All disks/pads seem to be less than 8000km on the car.. I can hardly believe they must be changed again ...

 

Do you drive fast and brake heavily?

Can you feel pulsing of the pedal when braking? That is a symptom of warped discs,it may be that warped discs on the rear are not so obvious.You may not see warping just by looking at the disc.

The image shows how to measure run out.

I would jack up each wheel in turn and spin it by hand and listen for bearing noise.

The other possibility to my mind is CV joints on the rear drive shaft but you do not have many miles on your Jag.

 

The rear discs and pads wear out quicker than the fronts because the traction control uses the brakes, there being no limited-slip differential. So as well as you using the brakes, the car does too !

Check disc thicknesses at rear as well as front.

 

I just recently had to deal with this. I had what I thought was an exceptional amount of "road noise" while driving. Especially for a jag. Sure enough it was one of my rear wheel bearings. Had it switched out and its night and day the difference. For parts and labor it cost me just under $290.

I also have vibrations in my braking. I haven't resolved that problem yet but agree that its probably your rear disc brakes. Because of my wheels(sepang) I can see where the most brake dust is accumulating. Definitely more in the back breaks than the front. I didn't think about traction control being the cause of them to wear quicker. However I believe it based on my driving.....(who doesn't love to stomp the gas on an xjr?)