Why Is My Car Pulling to One Side (or My Steering Wheel Crooked)?

If your car drifts off line on a straight road, or you have to hold the steering wheel slightly turned to keep it straight, don't assume it needs an alignment. Manufacturer diagnostic procedures, including Nissan's and Toyota's, rule out the road and check the tires before anyone measures the alignment, because a tire can cause a pull that looks like an alignment problem.

Pull, drift or crooked steering wheel?

Toyota's service bulletin separates two complaints that often get lumped together: with a pull (a gentle one is often called a drift), the vehicle doesn't go straight. With an off-centre steering wheel, the vehicle goes straight but the wheel sits at an angle. You can have one, the other or both, and they're corrected differently.

The timing tells a technician where to look first:

Rule out the road first

Roads aren't level from side to side. They're built with a crown, a slight slope down from the centre toward the edges, so rain runs off. BC's design standard for subdivision roads calls for a centreline crown with a normal cross slope of 2% on paved roads, and the province's highway cross-section standard uses the same 2% normal cross-fall.

Nissan's bulletin on pull diagnosis explains what that does to a car: vehicles naturally drift toward the low side of the crown, and the steeper the slope, the faster the drift. Tires and vehicles are designed to counteract a typical crown, but may not fully cancel out a steeply crowned road. On a highway that slopes both ways from the middle, a car may drift slightly left in the left lane and slightly right in the right lane. A slightly off-centre steering wheel on a crowned road can be normal for the same reason, and Nissan treats it as a road effect, not a vehicle fault.

On a two-lane road with a centre crown, the low side of your lane is the right-hand shoulder, so a gentle drift to the right that you correct without thinking is the classic road-crown pattern. A pull to the left in that same lane runs against the crown, so the road doesn't explain it. It's more likely the car if:

• It pulls the same way on every road and in every lane.
• You're holding steady pressure on the wheel, not just a light touch.
• It started suddenly, or it's getting stronger.

Crosswinds can feel like a pull too. Nissan's procedure says a pull can't be diagnosed when the wind is strong enough to push the car off a straight line. Keep both hands on the wheel while you pay attention to any of this; you don't need to let go to notice a pull.

Why tires get checked before alignment

Toyota's bulletin explains the risk: a pull is frequently blamed on alignment, and aligning a car to cancel a pull that's really coming from the tires can leave the settings outside specification, which then causes uneven tire wear. It's also why a car can get an alignment and still pull: if a tire is the cause, setting the angles to specification may not remove it.

Pressure

A low tire on one side is the simplest cause to rule out, and it's the one check worth doing yourself.

Those points come from Transport Canada's tire guide. If one tire keeps losing pressure, it needs to be checked for a leak or damage, not just topped up.

A tire that pulls on its own

A tire at the right pressure can still push the car sideways. Toyota's bulletin describes two forces built into radial tires. Ply-steer comes from the angle of the belts inside the tread. Conicity is a sideways force from slight unevenness between the tire's two sides, and it pushes the same direction whichever way the tire rolls. When a pull comes from the tires, conicity has the biggest effect.

In Toyota's figures, a car at 100 km/h can drift as much as 1.5 m over 100 m from conicity, compared with about 0.5 m from side-to-side camber and caster differences within Toyota's limit.

Because conicity is fixed to the tire, swapping the left and right front tires reverses it. That's the test both manufacturers use: if the pull changes direction or disappears after the swap, a tire is the cause. If nothing changes, Toyota's procedure points to front alignment. A tire that's causing a pull may be moved to the rear, where it usually has less effect, or replaced.

Leave the swap test to a technician rather than trying it at home. Wheel nuts have to be tightened to the manufacturer's torque specification, directional tires can't simply be moved to the other side, and some vehicles need the tire pressure monitoring system reset afterward. Nissan's bulletin, which describes the test, is written for qualified technicians with the right tools, not do-it-yourselfers.

Pull that started after new tires or a changeover

If the pull began right after new tires, a rotation or the fall switch to winter tires, the tires move to the top of the list. A new tire can have enough conicity to pull. Pressures may not have been set to the tire information label after the swap. And tires that differ in size or wear have to be sorted out before a pull can be diagnosed at all, according to Nissan's procedure. Transport Canada's guide recommends the same type of tire in every wheel position, which is also why winter tires go on all four wheels. When the pull follows tire work, have the Wheels & Tires counter look at the tires first.

How a technician narrows it down

The details vary by manufacturer, but the Nissan and Toyota pull procedures follow the same general order. An inspection typically goes like this:

1. Tires, brakes and stance first. Tire sizes, wear, damage and cold pressures are checked and corrected, and mismatched or damaged tires are dealt with before any testing. Toyota's procedure also checks for a dragging brake, and for a vehicle tilted noticeably to one side or one end, which changes the alignment angles from side to side.
2. Confirm the complaint. A road test on a straight, flat road in calm conditions separates a pull from a crooked wheel and from road crown. Nissan's procedure uses a gauge that measures the road's slope and a marker on the steering wheel that shows how far off-centre it sits.
3. The swap test. Tires are swapped side to side and the car is driven again. A pull that reverses or disappears points to a tire.
4. Measure the alignment. A computerized wheel alignment measures each wheel's angles against the manufacturer's specifications. If they're out, the procedure calls for a suspension and steering inspection, and any damage is repaired before anything is adjusted.
5. Adjust and re-test. Nissan's procedure adjusts the rear first on vehicles where it's adjustable, then sets front toe with the steering wheel held straight, recalibrates the steering angle sensor where the service manual calls for it, and road tests again.

If a car both pulls and has a crooked steering wheel, the pull gets fixed first. Nissan's bulletin notes that correcting the pull may straighten the wheel on its own.

The alignment angles behind a pull

MOTOR's alignment primer and the Nissan bulletin describe four angles, and each one shows up differently:

Steering wheel crooked, but the car goes straight

If the car tracks straight and only the steering wheel sits tilted, Nissan's bulletin points to three causes:

• Road crown. On a steeply crowned road, the wheel may be turned slightly to hold a straight line. That's why the road test for this is done on a flat road.
• Front toe set unevenly. When the tie rods on each side are adjusted to different lengths, the wheels point straight while the steering wheel doesn't.
• Thrust angle. If the rear wheels aren't lined up with the vehicle's centreline, the steering wheel can end up off-centre when the car is going straight.

Pulls only when you brake

A pull that shows up only under braking often means one side is braking harder than the other. Brake & Front End's guide to finding the cause of brake pulls lists the brake-side causes:

• A caliper piston stuck and not applying. The car pulls toward the side whose brake is still working.
• A collapsed brake hose. It can restrict fluid, giving a strong pull when you first press the pedal that fades after a second or two. Or it can trap pressure so that brake doesn't fully release, which acts like a stuck caliper.
• Loose caliper hardware, which makes one brake apply unevenly, or seized hardware that stops it releasing fully.
• Mismatched pad material from side to side, for example when pads have been replaced on one side only.
• Pads contaminated with grease, oil or brake fluid, which need replacing once the leak is found and fixed.

A dragging brake can cause a pull even when you're not braking. And some causes outside the brakes show up under braking too: incorrect tire pressure or mismatched tire sizes, worn or loose steering and suspension parts, and a worn wheel bearing. Worn upper strut mounts can cause a related complaint, memory steer, where the steering drifts back toward the direction you last turned.

Which brake is at fault, and what state it's in, only becomes clear with the wheels off, so a pull under braking is a reason to book a brake inspection now rather than waiting for it to get worse. If the pull is strong or the pedal feels different, call the shop before driving the car in; a tow may be the safer choice. If the brakes are squealing or grinding as well, what each brake noise means explains which sounds mean stop driving.

Pulls only when you accelerate

A tug on the steering wheel under hard acceleration is often torque steer. Continental's guide to torque steer describes it as mainly a front-wheel-drive trait, strongest when a lot of power goes to the wheels at low speed or pulling away, and much reduced in modern designs. Uneven tire pressure or tread wear, damaged tire sidewalls, worn suspension parts, worn engine mounts and a worn CV joint can make it worse, and the unequal-length driveshafts many front-wheel-drive cars use are a common built-in contributor. A slight tug that's always been there can be normal torque steer for that car. A tug that's new or getting stronger should be checked.

What to tell the shop

A pull is easier to track down when the technician knows exactly what you've noticed. Before you call or book, note:

• Which way it goes, and whether the car pulls, the steering wheel sits crooked, or both.
• When it happens: all the time, only when braking, only when accelerating, only at certain speeds, or only on certain roads or lanes.
• When it started, and what happened around then: new tires, a rotation or seasonal changeover, a pothole or curb hit, or recent brake, steering or suspension work.
• Whether it came on suddenly or has been building.
• Anything else new: noises, clunks, vibration, a warning light, or a tire wearing on one edge.
• Your cold tire pressures in kPa, next to the pressures on the tire information label.
• Whether all four tires are the same size and type, with similar wear.

At West Yale, the automotive line is 604-793-9310, and the Wheels & Tires counter is 604-391-1766 if the pull started after tire work.