Originally Posted by
+fireamx
I drove on two different "Name Brand" tires for several years with no ill effects. Just make sure one set isn't summer only, and the other set is 4 seasons rated. You may have some precarious moments during sudden temperature changes.
The other factor to consider when using different tire sets is to use the same tread configuration. Mixing Asymmetric & Symmetric tread patterns is something most tire shops won't recommend. And if the set you're keeping is a directional tread design, then the new set needs to be that design also.
Attached documents cover the possibilities. (Note: Keep in mind, the attached documents from TireRack.com are documentation from a vendor that sells tires. But the overall philosophy is sound.)