Will having two different TPI tires make a difference? For instance, rear tire is 120 TPI and front tire is 60 TPI. I just bought a Vittoria Pro Slick 23mm - 120 TPI to replace my stock tire, Hutchinson Equinox II 23mm - 60 TPI. I have the Vittoria on the rear and the stock tire on the front. I haven't had a chance to ride the bike yet..

Is it better to have both tire TPI the same or should I just stick to this combo until my front tire wears out? Will there be a noticeable difference between a 60 and 120 TPI vs both tires being 120 TPI?

Thanks!

Makes no difference to safety or handling. Ride quality won't be as good as both tires being high TPI, but the difference is small.

Thanks for the quick reply!

higher TPI = better ride quality
lower TPI = better sidewall protection/puncture resistance

As I understand it.

No reason you can't run two different tires on a bicycle.

Higher tpi allows for a thinner, more supple casing which improves ride quality at the possible expense of lower puncture resistance.