Originally Posted by
Yo Spiff
I replaced the standard Zaffiro on my rear wheel when it acquired a squared off profile.
The profile on a tire will square off, long before the useful life of the tire is up. The squared off profile isn't a problem, particularly on a rear tire.
If you're particularly risk adverse, you can take squared off tires off the front and put them on the back.
Personally, I run tires until the cord shows.