Excessive tyre wear on both edges, causing the tyre tread to look rounded rather than flat, can indicate underinflation. When the tyre is insufficiently inflated, the load in the contact patch on the road surface is not even. The central part of the contact patch is not correctly supported and the load is transfered more to the outside edges (also called shoulders). More load in the shoulders leads to more rapid outside edges tyre wear.
An underinflated tyre tends to over flex and run warmer than normal. This accelerates rubber wear rate and increases rolling resistance, which in turn increases vehicle fuel consumption.
How to avoid excessive outsides edge tyre wear?
To prevent this abnormal wear from occurring, your tyre should be inflated to the recommended pressure, using a reliable pressure gauge and the pressure should be checked at least once a month when the tyres are at ambient temperature.
To find the recommended pressure, check your vehicle owner's manual or the sticker on the driver's door pillar.