tyre wear

We've just crossed the 28k mi mark with our i3 REx and the rear set of tyres are very close to the tread wear marker now. First service is due next month (according to the dashboard info), so will probably get them swapped then.

Front tyres have at least another 5k miles in them, I'd say, maybe even 10k miles.

We're planning a trip to Arizona so I used the BMW tire checker on our tires with 10,000 miles (16,000 km) service and found they were 5 mm with one at 6 mm. Using this table: http://mdcommerce.bg/wp-content/uploads/2013/12/Tire-tread-depth-conversion.pdf

• 4.7 mm -> 6/32"
• 5.56 mm -> 7/32"
• 6.35 mm -> 8/32"

Now the BMW tire report calls them "MARGINAL" and indicates the stopping distance has increased by 30%. Personally, I would rather get down to 4/32" (3.18 mm). My understand the legal limit is 2/32" (1.59 mm).

Did I get anything wrong?

Bob Wilson

Tread depth is crucial for stopping with moisture on the road. Otherwise, a slick will actually give you pretty good friction. If there's anything on the road, the sipes can allow it to be channeled away while keeping the tread in contact with the road.

One thing probably not yet an issue on your tires is the natural hardening that occurs with age. Industry standards suggest discarding any tire older than 5-years for that reason, regardless of the tread depth. That's the plan on my other car for next year as I changeover with the seasons...new summer tires, then next fall, new winter ones.