Faint Thump Noise on Smooth Roads

[eric19371]

I have an issue with my recently acquired V50 that I would like a little advice on diagnosing. When driving on very smooth roads I can hear a faint speed related 'thump' sound that sounds like a flat spot on a tyre or a dodgy bearing, or something... If I am accelerating it is very hard to hear due to the engine noise but it is still there with the throttle just maintaining speed, or lifted to slow down.

I took it to a local reputable tyre garage near me (Falkham Tyres, Longfield, Kent) who checked all four tyres (one front badly worn on inside so replaced with a new Falken, another rear needed balancing) and checked the tracking/camber (all ok), etc. They also gave a basic check while each wheel was jacked up to look for play in the bearings (none).

Following this it was definitely a lot better but there is still something there. I feel safe as I have had it checked professionally but I still want to get this sorted so I am looking to the forum for any suggestions.

I am thinking that maybe it is a very slight flat spot on one of the tyres (it feels like it could be coming from the rear). The three original tyres while appearing in good condition and quality (Avon) are a few years old and the car has done less than a 1k miles each year since 2015 (but was still serviced every 12 months at a main dealer!!) so maybe there is a flat spot and I should get the old tyres replaced?

[Bungo]

Depends if it's a regular thump or random.
Did they check front struts and springs.
Springs are prone on these and it's not always easy to see one is broken at the ends.

[andyv40turbo]

A friend of mine swapped the drop links on his after have issues with an odd noise over bumps, taking them out they looked identical to the ones we swapped in but he could notice the difference straight away.

[eric19371]

Originally Posted by Bungo

Depends if it's a regular thump or random.

It is a regular thump, sounds like once per revolution of the wheels.

[PNM]

I would try swapping the wheels from front to back, if it sounds like the noise has moved to a different place, you'll know it's a tyre or wheel issue.

[Welton]

I've had this on a second hand car I bought years ago, the car had been sat on a flat tyre for a while and damaged the carcass.

In this case I would put the spare wheel onto each corner in turn until the noise stops...then you will either find the culprit or rule out a tyre issue.

[eric19371]

It was the rear tyres. Two brand new Falken tyres put on the rear last Saturday and it is quiet at last.