How much tread do my tyres need to pass a WOF?

How much tread do you need to pass a WOF in New Zealand? At least 1.5 mm of tread depth in the main grooves, all the way round the tyre. That's the legal minimum set by NZTA, and it applies to every tyre on the car, not just the one you looked at.

1.5 mm is not a lot. It's about the thickness of two bank cards stacked together. So it's worth knowing how to check, and what else the inspector looks at.

What does "1.5 mm in the main grooves, all the way round" mean?

The main grooves are the wide channels that run around the tyre. They're there to move water out from under the tyre so it keeps its grip on a wet road. The smaller cuts in the tread blocks don't count.

"All the way round" matters. Tyres often wear unevenly, especially if the wheel alignment is out or a tyre has been run low on air. The middle can look fine while the inside edge, the bit you can't see without crouching down, is nearly bald. The inspector checks the whole tyre, so you should too.

Source: NZTA Vehicle Inspection Requirements Manual, tyre tread depth.

How do I check my tyre tread at home?

It takes about a minute per tyre.

1. Find the tread wear indicators. Most tyres have small raised bars moulded into the bottom of the main grooves. Look on the sidewall for a small triangle or "TWI" mark, which shows where they are. When the tread is worn down level with these bars, the tyre is at or near the legal limit.
2. Use a tread depth gauge. They're sold at most parts stores and service stations, and they give you an actual number. Push the pin into a main groove and read the scale.
3. Check in several places. Measure the inside, the middle and the outside of each tyre, at a few points around it. Roll the car forward half a turn to see the part that was on the ground.
4. Don't forget the inside edge. Turn the steering wheel to full lock and you can see the inside of the front tyres without lying on the driveway.

If the wear is very uneven, for example worn on one edge only, that usually points to wheel alignment or suspension wear. Worth a look before you buy new tyres, or the new ones will wear the same way.

What else about my tyres can fail a WOF?

Tread depth is the one most people know about, but it's not the only tyre check.

• Cuts, bulges or lumps in the tread or sidewall.
• Exposed cords showing through the rubber.
• Mismatched tyres on the same axle, such as different sizes or construction types.
• Tyres that rub on the body or suspension.
• Damaged wheels, or missing or loose wheel nuts.

Tread depth is one of many items on the list. Our article on what a WOF checks in New Zealand goes through the rest.

Is 1.5 mm enough tread for Auckland roads?

It's enough to pass a WOF. It isn't a lot for a wet Auckland winter. As the tread wears down, there's less room for water to escape, so the tyre takes longer to stop on a wet road and is more likely to aquaplane. And 1.5 mm is the legal minimum every day the car is on the road, not just on WOF day, so a tyre sitting just above it may need replacing well before your next WOF.

Our advice: if your tyres are getting close to the limit, plan for new ones before winter rather than the week of your WOF. You'll get to choose, rather than have to.

Getting your tyres checked in Albany

We check tyre condition, tread and pressures (spare included) as part of our full service, and tyres are on the list at every WOF, $79.99. We're an NZTA-authorised WOF site. If a tyre fails, you get the reason and the price before we replace anything.

If your car failed on tyres somewhere else, you can have them replaced by any mechanic you choose, and you'll still get your free recheck where you had your WOF if you go back within 28 days. Our article on what to do after a failed WOF explains how that works.

Midas Albany, 3C Saturn Place, Albany. Family owned since 2004, MTA Assured. Call Robin on 09 415 6595, Book online, or Request a callback. Open Mon-Fri 7:30am-4:30pm and Sat 8am-12pm.

FAQ

Written by the Midas Albany team.