cabin noise

[Peter667]

Hi guys,
I'm brand new to XK8s but have rebuilt several Triumphs in the past and still have a couple. Yesterday I acquired a '98 coupe in very nice condition but I'm puzzled by some cabin noise - didn't really notice it on the short test drive before purchase. It has a very low-frequency sort of 'woofle' in the cabin between about 15 and 50 mph - a bit like the sound you get when you part-open a window at speed. There's no obvious vibration, just a sort of pressure in the ears. Anyone had anything similar. I think it could be a natural frequency of some body panels perhaps due to wheel wobble. I'm getting all the wheels balanced and tracked this week. It's not related to engine speed as I've run it in neutral with no change.
Any comments welcome, other than on my mental state over imagined noises.!

[mike020150]

It's obviously a puzzler with no apparent answer from fellow owners. Did you get anywhere with the wheel balancing exercise? Mike.

[Peter667]

So I'm now answering my own question on cabin noise! It was a combination of problems including the fact that the XK8 does seem to be more susceptible to road noise than my previous cars, probably linked to the relatively large wheels & tyres (18" on mine).

I had the car checked by Protyre (Slough) who I can recommend as knowledgeable and efficient. Before they had all the wheels off to check and balance they sent me back out to warm them up - at least as much as feasible on a wintry day. They found all the wheels out of balance (these with recent new tyres). Also the tracking was out both front and back, thereby making the tyres scrub at all speeds, and this was corrected.

Another thing was that the tyres fitted were a cheap brand. When bought the car I'd seen new tyres with lots of tyre blacking and the number "x000" prominant. I'd assumed they were Pirelli 6000s or Dunlop 9000s. In fact they are Nexen N3000, a brand I'd never heard of and at about £86 each online price, about half the quality brand equivalent. As Protyre advised, 'yer gets what yer pays for' and they will have less grip, more wear and more noise than others.
The car is much better now although I'll plan an early change of tyres and check reviews for a low-noise brand. I still think there is an issue of some body panel vibration at certain speeds and will look for accessible places where I can fit sound sound deadening pads.

[mike020150]

Hi Peter,
It sounds like sensible advice from your tyre man. Don't bother with the sound deadening if you intend to fit one of the tyres that Jaguar uses. The factory went to great lengths to tune out resonances and produce an exceptionally quiet car. A non standard tyre undoes all that hard work. Equally, for safety's sake, make sure that whatever tyres the car wears, they have the correct speed and load ratings. XK8s are heavy cars which can generate high tyre loads even without utilising the car's high speed potential. Being a law abiding citizen you may not use the car's full speed capabilities but it's all too easy to overstress wrongly rated tyres through cornering and acceleration. If you search the bulletin board you will find some members' views on tyre brands that they've tried. Mike.