Need a little help with Tires for my VXL rustler

Ok so I picked up a set of Anaconda's for the rustler (rears only) they work great by the way. But I want to pick of a set for the fronts. At first it looks like they would be the same as the rears but when I put the rears on the front there is some play (kind of like the wheele wiggles). Does anyone know if that is a diff hex on the front then the back??
Thanks guys