Can you measure camber with your phone? Yes, if you fix these four errors.

Quick answer: Yes. Camber is the tilt of a wheel from true vertical, and your phone measures its own tilt from gravity, so the sensor is doing the right job. What ruins the reading is not the phone, it is four setup errors: a garage floor that is not level, a small zero offset in the phone or the way it sits, holding it against the wrong part of the wheel, and a suspension that has not settled. Fix those and a phone is a reasonable way to check a road car. For the setup errors you cannot fix, there is a cross check at the end that tells you when to stop trusting the number.

People go back and forth on this question on car forums, and the answers are mostly opinions. One person is happy with a phone app, another swears by a dedicated magnetic gauge. Almost nobody says why a phone reading is good in one garage and wrong in the next. That reason is almost always one of the four errors below, so it is worth understanding them before you trust any number.

Why a phone can do this at all

A phone has an accelerometer and gyroscope, and the operating system fuses them into a direction for gravity. Camber is the angle between the wheel’s vertical plane and true vertical. If the phone sits flat against the wheel, the angle it reports against gravity is the camber, once you tell it which way is zero.

That is the whole principle. Everything that goes wrong is some reason the phone’s idea of “against the wheel” or “vertical” is not what you think it is.

Error 1: the floor is not level

Camber is measured against gravity, not against the ground. If the car is sitting on a floor that slopes sideways, the whole car leans with it, and so does every wheel.

How much does it matter? Half a degree of slope is about 9 mm of drop for every meter of width. Across a typical track width of around 1.5 meters, that is roughly 13 mm of difference between the left and right tire contact patches. You would not see that by eye, and it is enough to move a camber reading by half a degree.

Here is the useful part. A sideways slope pushes the two wheels in opposite directions. The side where the car leans outward reads more positive camber, and the other side reads more negative by the same amount. So:

• The average of the left and right readings on one axle cancels the floor. If you care about the axle as a whole, average the two sides.
• The difference between left and right does not cancel. It doubles. If you care whether the two sides match, you need a level surface, or you need to know your floor’s slope.

To find your floor’s slope, lay the phone on the floor under each tire with its long edge pointing across the car, and read the tilt. Then turn it end for end and read again (the next error explains why).

Error 2: the phone’s zero is not zero

Every sensor and every mounting has a small offset. The phone case is not perfectly flat, the back of the phone is not perfectly parallel to the screen’s reference, the surface under it has a tiny bump. A phone laid on a perfectly flat, level surface will often read a fraction of a degree instead of zero.

You can remove this offset without any special equipment, using a flip.

1. Place the phone against the wheel (or the straight bar you are using) and note the reading.
2. Turn it 180 degrees, so it is end for end and facing the same way, and place it in exactly the same spot. Note that reading.
3. The offset is the average of the two readings. The real angle is half the difference between them.

The reason it works: the real tilt flips sign when you turn the phone around, but the offset does not. Averaging cancels the part that did not flip. If the two readings are, for example, minus 1.4 and plus 0.8, the offset is minus 0.3 and the true camber is minus 1.1.

Do this once for each wheel, or at least once for the phone and the setup you are using. If you are using an app that has a zero button, zero it against a reference you trust (a known vertical like a plumb line, or a flat block on a surface you flipped) and not against the wheel itself.

Error 3: measuring the wrong part of the wheel

The phone has to sit on something that represents the wheel’s plane. A lot of bad readings come from using something that does not.

• Do not measure against the tire sidewall. It bulges, it is soft, and its profile changes with pressure and brand.
• Use the flat of the rim face, or lay a straight, rigid bar across the rim lip and rest the phone on the bar. The bar spans the whole wheel, so one dent or one low spot cannot fool it.
• Keep the phone square. The phone’s reference edge has to be aligned with the vertical of the wheel, not rotated. If you rotate the phone away from vertical by a lot, you start reading something other than camber.

The simplest way to catch a bad spot is to roll the car forward a quarter turn of the wheel and measure again. If the reading changes by more than a little, the wheel face is not flat at the spot you measured. That can be a bent lip, a curb scar, or a wheel with runout, and a reading taken at one spot is not a reliable one.

Error 4: the suspension has not settled

The weight of the car loads the suspension, and it does not always settle to its true resting position by itself. Springs, bushings and tires all have a little stiction. If you jacked the car, rolled it onto the floor or just parked it, it may sit a few millimeters off where it settles after a short drive.

Before measuring:

• Roll the car back and forth a few meters, then stop without braking hard, so it rests where it naturally rests.
• Point the steering straight. A turned wheel changes camber because of caster.
• Check tire pressures. A soft tire sits lower and changes the reading.
• Measure with the car loaded the way you normally drive it, and the fuel level in mind. A road car with a full trunk sits differently than an empty one.

A cross check that tells you when to stop trusting it

Take each reading twice, with a flip and a quarter turn of the wheel in between, and compare. For a check that needs only a string and a ruler, see what one degree of camber looks like in millimeters. A good measurement repeats. If the same wheel gives you three different numbers, the problem is your setup, not the car, and no amount of averaging will fix it.

Then compare the two sides. Front left and front right should usually be within about half a degree of each other on a healthy road car. A big difference is either a real alignment issue, which is worth a shop visit, or a floor slope, which you can check with the lay flat test above.

What a phone cannot measure

Camber is one of three angles. A phone sitting on the wheel face cannot tell you toe, which is whether the wheels point in or out, or caster, which is the tilt of the steering axis. Toe in particular matters a lot for tire wear and is easy to get wrong with a phone. For anything beyond checking camber against a spec, or watching how it changes after you adjust something, a shop with a proper alignment rack is still the right tool. Compare your result with the vehicle’s published alignment specification before you change anything.

Making the process easier

Camber Gauge, one of the apps we make, is built around exactly this routine on iPhone and iPad. You zero it against a reference, hold the phone still until the reading is marked stable, and save each wheel. It handles all four wheels in one session, so you can compare the left and right sides on the same axle and keep a history for each vehicle. The flip method above still applies, since it is about the way the phone sits, and no software can cancel what it cannot see. Treat the reading as a good estimate and confirm against the factory specification before you make adjustments.

Frequently asked questions

Can a phone measure camber?

Yes. A phone’s accelerometer and gyroscope give a direction for gravity, and camber is the angle between the wheel’s vertical plane and true vertical. A reading is only as good as your setup.

Why is my phone camber reading wrong?

Almost always one of four setup errors: a sloped floor, a phone zero offset, measuring the wrong part of the wheel, or a suspension that has not settled.

How do I remove the phone’s zero offset?

Use the flip. Take a reading, turn the phone 180 degrees in the same spot and read again. The offset is the average of the two readings and the true angle is half their difference. For example, readings of minus 1.4 and plus 0.8 give an offset of minus 0.3 and a true camber of minus 1.1.

Does the floor matter?

Yes. A half degree of slope is about 13 mm of height difference across a typical 1.5 meter track width, enough to move a reading by half a degree. Averaging the left and right readings on one axle cancels it.

Where should I place the phone on the wheel?

On the flat of the rim face, or on a straight rigid bar laid across the rim lip. Not on the tire sidewall, which bulges and changes with pressure.

What can a phone not measure?

Toe and caster. Toe matters a lot for tire wear, so for more than checking camber against a spec, use a shop with an alignment rack.