Thumping noise from a tire: the three causes

A thump that keeps time with the wheels, getting faster as you speed up, is one of three things: a flat spot from the car standing still, something lodged in the tread, or a broken belt inside the tire. The first goes away by itself, the second is a five-minute check, and the third means the tire is failing. Two questions sort them out in the first mile.

Question one: did it start after the car sat still?

If the thump is there when you set off after the car has been parked for days or weeks, especially in cold weather, and it fades within the first few miles, it is a standing flat spot.

The contact patch takes a set while the weight of the car presses on it, and the rubber returns to shape as it warms and flexes. This is normal, it is not damage, and nobody should sell you a tire for it. If it is still there after fifteen miles, something else is going on.

Question two: is the thump constant, or intermittent?

There all the time, at every speed, scaling directly with road speed: that points at the tire itself. Go to the inspection below.

Comes and goes, or only at one particular speed: more likely a balance problem showing up as a vibration you feel as much as hear. That belongs with a shop, because we do not do balancing as a standalone job, though we balance any wheel we fit or repair.

Changes with engine load rather than road speed: not tire or wheel related at all. A mechanic.

The five-minute inspection

Park somewhere flat and safe. Work round all four tires.

Look for something lodged in the tread. A stone wedged between blocks, a bolt, a piece of metal. Anything hard that hits the road once per revolution makes a clean, sharp thump, and a stone usually levers out with a screwdriver. If it is a nail or a screw, leave it in place and book: it is partly plugging the hole. Nail in a tire: can it be repaired covers what happens next.

Run your palm slowly over the tread, right round each tire, rolling the car a few inches at a time. You are feeling for a raised dome. That is a separated belt, the serious answer, and bubble or lump in the tread covers it fully.

Look at the sidewalls for a bulge. Same failure, different place, same answer. See bulge in a tire sidewall.

Check the pressures against the door placard. A tire well below pressure thumps and drags.

The broken belt case

If you find a raised area in the tread, stop driving the car.

The steel belts under the tread have separated. The tire has gone out of round in that spot, which is what you are hearing, and the separation grows on every rotation until the tread lifts off at speed. It is not repairable: the US Tire Manufacturers Association standards cover punctures in the tread up to a quarter of an inch, fixed with a plug and a patch after an internal inspection, and none of that applies to a structure coming apart.

Nobody can tell you how many miles it has left, because nothing about a propagating tear is predictable.

What is not a tire problem

• A thump once per engine revolution rather than once per wheel revolution is a drivetrain or engine mount issue. A mechanic, not us.
• A knock over bumps only, gone on smooth road, is suspension. A mechanic.
• A thump with a grinding that changes when you steer left and right is usually a wheel bearing. A mechanic. Humming or roaring that changes with speed has the test that separates bearings from tires.
• A thump from a loose plastic wheel arch liner catching the tire is a body clip, not a tire.

We do not do suspension, bearings, brakes or alignment, and a page that sold you a tire for one of those would deserve to be ignored.

What we do

We come to the car at home or at work. If it is a repairable puncture in the tread area, we take the tire off the wheel, inspect the liner, and fit a plug and a patch. If it is a broken belt or a bulge, we supply and fit a tire matched to the door placard, balanced and torqued. Repair versus replace a tire sets out which is which, and find your tire size tells us what to bring.

Questions people ask

• What causes a thumping noise from a tire? Three things, usually: a temporary flat spot from the car sitting still, an object lodged in the tread, or a separated belt inside the tire. Only the last one is dangerous.
• Will a flat spot from parking go away? Usually yes, within the first few miles as the tire warms and flexes back into shape. If it is still there after fifteen miles of driving, it is not a temporary flat spot.
• Is a thumping tire dangerous? It can be. If the cause is a separated belt, the tread can come off at speed. Feel the tread with your palm before deciding, and stop driving if you find a raised dome.
• Should I pull a screw out of my tire if it is thumping? No. Leave it in. It is partly sealing the hole, and the decision about repair is made after the tire comes off the wheel and is inspected from the inside.
• Could the thumping be the wheel bearing instead? A bearing usually hums or growls and changes as you steer gently left and right, rather than thumping in time with the wheels. If it changes when you swerve, that is a bearing and a mechanic's job, not ours.
• Can you fix a thumping tire at my house? If it is a puncture or a replacement, yes, at your home or workplace. If it turns out to be suspension, bearings or brakes, we tell you and you will need a mechanic, because we do not do that work.