215/70 is not narrow and short, it is the same 8.5" wide(sidewall) but taller than a 215/60. 70 or 75 series tires will be even taller due to the aspect ratio. A 60, 70, or 75 series tire in 215 width is still 215mm wide, only the height is different.
When going to 15" in place of 14" you are already gaining an inch in diameter just from the wheel, so the aspect ratio has to be smaller to maintain the same overall diameter as the 14" tire was so it will fit in the wheel opening designed around the 14" tire. This is why short tires like 195/65R15(25.98" tall, not really short enough though), 205/60R15(24.68"), and 215/55R15(24.31") have been suggested.
The 215/60R14 is nominally 24.15" tall, real close to the 215/55R15(24.31") is.
Last edited by ericnova72; 05-24-2010 at 10:16 PM.