Uneven Front Tyre Wear Question

[SageBrush]

I noticed today that both front tyres have excessive outside tyre wear. Some googling and reading gave me a list of possibilities but I would like to try to narrow them down with some help. The car has 30k miles and has not been in any accidents although my wife is attracted to potholes and I tend to pump up the tyres to max sidewall rated psi.

Does the wear on both front tyres point to the cause ?
I'm inclined to seek a mechanic review of the suspension, and if no bent parts are found to get an alignment. Is this a reasonable approach ?
Something better ?

[GerryAZ]

If you keep the tires up to at least 42 psi and have outside edge wear on both tires, I would check for excessive toe-in. Of course, aggressive cornering will tend to wear the outside edges of the front tires even with proper alignment and adequate inflation. That is why I rotate my Leaf's tires every 5,000 miles or so and cross the ones from the front when moving them to the back.

[LeftieBiker]

It does sound like an alignment issue. Low pressure can cause that, but not too high - that causes center wear.

[SageBrush]

I'll be delighted to find out that all that is needed is an alignment. Does it surprise anybody that both tyres show the same wear pattern ? I have it stuck in my head that each tyre has its own independent alignment, even though pictures tend to show tyre wear patterns in pairs. Why is that so ?

[johnlocke]

Toe in causes the tires to wear on the edges and because the caster forces the the contact point to trail the axles slightly, tires will usually wear either on the inside edges if the toe in is too high or on the outside edges if the toe in is too low. One of the symptoms is drift to one side and another is misalignment of the steering wheel to the right or left of center. Wear on both edges of a tire either indicates too low a tire pressure or excessive hard cornering (scrubbing). Wear in the center of the tire is almost always too high a tire pressure. Nissan sets the tire pressure too low to improve the ride quality. Tires should be set to 40-44 PSI for best tire wear.

[GerryAZ]

Excessive toe-in will cause the outside edges to wear. Insufficient toe-in (or actual toe-out) will cause inside edges to wear. Incorrect caster and/or camber can cause one front tire to wear differently from the other.

The toe-in was slightly higher than recommended when I had the alignment checked after replacing the original tires on my 2011, but all other settings were within specifications. I have not yet checked front wheel alignment on my 2015, but tire wear is fairly even.

[derkraut]

Toe in causes the tires to wear on the edges and because the caster forces the the contact point to trail the axles slightly, tires will usually wear either on the inside edges if the toe in is too high or on the outside edges if the toe in is too low. One of the symptoms is drift to one side and another is misalignment of the steering wheel to the right or left of center. Wear on both edges of a tire either indicates too low a tire pressure or excessive hard cornering (scrubbing). Wear in the center of the tire is almost always too high a tire pressure. Nissan sets the tire pressure too low to improve the ride quality. Tires should be set to 40-44 PSI for best tire wear.

Excellent, accurate comment, Johnlocke.

[Titanium48]

I'll be delighted to find out that all that is needed is an alignment. Does it surprise anybody that both tyres show the same wear pattern ? I have it stuck in my head that each tyre has its own independent alignment, even though pictures tend to show tyre wear patterns in pairs. Why is that so ?

Caster and camber settings are independent for each wheel (if they are adjustable at all), but toe-in is a relative setting across an axle. To drive in a straight line, any deviation of the wheel's rotation axis from perpendicular to the direction of travel needs to be equal in magnitude and opposite direction across an axle. If it isn't, the vehicle will not continue in a straight line. Thus, too much toe in wears both tires outside edges equally.

[LeftieBiker]

Does it surprise anybody that both tyres show the same wear pattern ? I have it stuck in my head that each tyre has its own independent alignment, even though pictures tend to show tyre wear patterns in pairs.

I used to buy and resell Ford Mavericks, and one of the things I liked about them was the very easy Toe-in adjustment. Just a bolt for each upper arm with an eccentric cam on it. Back in those days tires often did develop issues just one wheel at a time. Most Mavericks I gave the Quick & Dirty Alignment just needed it on one wheel.

[GerryAZ]

I used to buy and resell Ford Mavericks, and one of the things I liked about them was the very easy Toe-in adjustment. Just a bolt for each upper arm with an eccentric cam on it. Back in those days tires often did develop issues just one wheel at a time. Most Mavericks I gave the Quick & Dirty Alignment just needed it on one wheel.

Leftie,
That was caster or camber adjustment (much easier than installing offset shims or bushings on many modern vehicles). Toe-in is changed by adjusting the length of the steering tie rods. As noted previously, too much toe-in causes excessive wear on the outside edges of both tires. On the Leaf, excessive toe-in also makes the car more prone to sway on grooved pavement or bridge decks (depends upon tire characteristics).