What usually causes a knock over bumps?
A knock over bumps or potholes is almost always a worn or loose part in the suspension or steering — a bush, a link, a ball joint or a mounting that has developed play. It's very rarely the engine. The only reliable way to find the exact part is to get underneath the car and check each joint for movement; the sound alone doesn't tell you which one has worn.
Does it matter which side the knock comes from?
It can help narrow things down, but it isn't conclusive on its own. A knock that only happens on one side, or that also happens when turning, points toward a specific corner of the car. Several parts sit close together in that area though, so a full check is still the only way to be sure which one is actually causing it. If your noise is specifically on turning rather than over bumps, our guide on knocking when turning covers that separately.
Is it safe to keep driving with a knocking noise?
A knock over bumps means a part has more movement than it's designed to have, and that tends to get worse rather than better on its own. It isn't usually an emergency, but it isn't something to put off indefinitely either. If the noise is new, sudden, or getting louder, it's worth getting checked sooner rather than later.
Will a knocking noise show up on an MOT?
Worn suspension and steering parts are exactly the kind of thing an MOT test is designed to pick up, so it's often worth sorting before your test is due rather than waiting to find out at the test itself. If you want to check whether a vehicle already has an advisory recorded against it, that's free to do on the government's own MOT history service.
What should I check myself before booking?
You don't need any tools for this. Note whether the knock happens on smooth bumps, potholes, or both; whether it happens when turning as well as driving straight; and roughly where it seems to come from — front, back, left or right. That information doesn't replace a proper check, but it helps whoever looks at the car get to the answer faster.
What if there are other signs as well as the knock?
A knock combined with the car pulling to one side, a vibration through the steering wheel, or uneven wear on one edge of a tyre usually points to the same area of the car rather than two separate problems. It's worth mentioning any of these when you book, for the same reason as above.
What will ONEFIX actually do about it?
Every check at ONEFIX includes a written digital vehicle health check with photographs, so you can see exactly which part has worn and why, rather than just being told. We quote any work in writing before it starts, and nothing is carried out without that quote being approved first.
How much does it cost to fix a knock over bumps?
There isn't one number for this — it depends entirely on which part has worn and how many need replacing, and that's only known once the car has actually been checked. Once it has, you'll get a written quote for that specific job before any work starts.
What should I do next?
Book a suspension and steering check at ONEFIX, Plas Acton Garage, Chester Road, Wrexham. A noise like this is usually easier, and cheaper, to put right before it wears the parts around it as well.