A 255/70/15 will be taller than the 215/70/15, in addition to being wider. The 215/70/15 will be approximately 26.9" tall, the 255/70/15 comes in at around 29.1". Those diameters will vary depending on brand and inflation pressure. You may also need to get wider wheels, depending on what you currently have. The 255 will work best on a 7-8 inch wide wheel.
