The rule of thumb I've always heard was that you could go one size wider if you went down a size in aspect ratio which is what you have done. I went from 215/65/17 to 225/60/17 on our 2001 and the speedometer was perfect when I checked it over a 10 miles stretch of interstate.
2001 GC ES, 203K miles, Chrysler 2000,000 mile club license plate holder
1988 GC LE, 208K miles(RIP)
2012 Camry hybrid
1970 Camaro, original owner