Intermittent knocking noise

[fungus]

Hi there, I wonder if anyone can shed any light or offer any suggestions. I have a 2001 C70 coupe which has developed an intermittent knocking noise. I am not mechanically minded and the only other info I can provide is:
1. it seems to happen when I am on the motorway
2. the car starts to handle as if I am driving on rumble strips
3. if I put the car into neutral (on the motorway) the knocking noise continues but only when the car is moving. If I stop and the car is running idle the noise stops.
4. there is a burning smell when it happens (a rubber or plastic smell) but the engine temp is fine.
5. it has never happened on small journies around town.
to summarise, it feels like the tracking is out in how the car handles but the knocking noise is concerning. Performance appears unaffected and if I am doing 90 and it starts to knock and I slow down to 60, or even 30, the knocking continues.
I would really appreciate any opinions or suggestions. The main issue is that it is intermittant and very annoying!
Thanks in advance
Simon.

[RPM]

Wheel bearings?
Drive Shafts?

[fungus]

Thanks, i spoke to a friend on the phone earlier who said it might be the drive shaft. If so, could thid be intermittent, would it explain the burning smell and if i take it to a garage for repair any idea how much i would be looking at?

[Liddo]

Is it worse when turning??? Do you get the knocknig then??? It could be a CV Joint thats gone VERY VERY dry. Put the wheel on full lock, and look behind the wheel, you should see a rubber/ribbed sleeve that runs along to drive shaft to the center of the back of the wheel. This should be attached by a large clip. If this is flapping around, your CV will have gone dry. I had mine done a kwik fit, and it was £110 fitted.

Cheers

Paul

[fungus]

Thanks for the feedback, I took the car to an independent garage that I use today and they said that they were unable to find anything wrong but that my brakes were in need of replacement and were so bare that this would be what was causing the burning smell as there was some discolouration on the discs which suggests that the brakes have been getting very hot. I have arranged to have the front brakes done in the morning but am not sure why this might cause a knocking noise and am obv concerned that this isn't actually the cause of the problem!!!!