Being the only contact between the bike and the road, choosing the right tire can be quite a worthwhile investment. But there are a few things to consider when buying a tire.
Clinchers vs. tubulars vs. tubeless: <more information to come> <may be a link to a video from GCN?>
Weight: <more information to come>
“TPI”: <more information to come>
Width: The current trend in tire selection for road bikes is towards using wider tires. In the past, the standard for road bikes had been 23mm (700x23c) tires, but the professional peloton has since moved to riding on slightly wider 25mm (700x25c) tires. During “spring classic” races over the cobble stones in Europe, teams will even ride tires as wide as 28mm. This trend is based on the latest research which suggests that at a given tire pressure, wider tires generally deform less, and thus has a lower rolling resistance (i.e. faster tire). Wider tires also allow riders to ride with slightly lower tire pressure for added comfort. Again, latest research appear to show that tire pressure has as much influence on comfort as the stiffness of the frame, which is important when you may be buying a frame that you have little knowledge on. When choosing your tire width find out from the frame manufacturer what is the maximum tire clearance that the frame allows. Also, note that taking full advantage of wider tires without aerodynamic penalties will require using a slightly wider rim too.
Go cheap: Years ago when I was a penny-pinching graduate student, I used to run Nashbar Prima 2 Plus tires from (obviously) Bike Nashbar. The tires are made in Taiwan by Chin Sheng, which is a huge tire manufacturer in Asia. When Nashbar has a sale (20-25% off), you can get them for as little as ~$13 USD per tire. The tires had reasonably-low rolling resistance (admittedly based solely on anecdotal experience), reasonable traction on most conditions—I’ve never felt like losing grip when cornering—the tires last reasonable long (3000-4000km), and they were reasonably easy to mount onto my wheel. Nothing that stands out about the Prima 2 Plus, except that it performed as well as some tires that cost 3 times as much.
Go bombproof: After I have a bit more income, I started using Continental Gatorskin tires. I became a huge fan of its durability, and puncture resistance quality. I recently put a set on a friend’s build (not a carbon bike; it was built up from a pristine 1988 Bianchi steel frame that was ridiculously comfortable and quick) and they just rolled and rolled and rolled. It’s always a pain to install Continental tires, as I’m usually okay with it because they won’t need to come off for a long time.) I have friends who get more than 10,000km out of their Gatorskins, but I haven’t worn out my tires yet, because….
Go High performance: …I switched to using the Continental GrandPrix 4000S II when I signed up for a charity bike ride in 2015 from Toronto to Montreal, and I needed a high-performance tire. The 4000S II has a reputation for being the fastest clincher tires that are still affordable, and it does not disappoint. I’m currently riding a 28mm width (despite my wheels not really designed for it), and the comfort and the speed is quite noticeable compared to the Gatorskin and the Prima 2 Plus. The 4000S II won’t last as long, but for about $50 CAD per tire (from Chain Reaction Cycle), it’s well worth the money. That said, the 4000S II, like most Continental tires, tend to be (on average) more difficult to install onto wheels.
Where to Buy Them: If you live in the US, Bike Nashbar is a great online store to buy, particularly if you buy their reasonably priced store brand tires, and if you make a purchase over $49 USD, they will ship for free to the continental US. Otherwise, Wiggle, Chain Reaction and Merlin (all UK-based companies) also very aggressively price the tires that they sell, and sometimes, you can also get some bundle deals with inner tubes as well.
Of course, there are many options for tire selection, and there are many brands out there with great products. This is just my personal experience, but if you know what tire you want, go with that.