I'd guess that very few people know the size of their tires offhand, so their first experience will be experimentation. Add a list of the "Most Popular" 5 tire

I'd guess that very few people know the size of their tires offhand, so their first experience will be experimentation. Add a list of the "Most Popular" 5 tires sizes so that these first-time users can still use the site and understand what it does. Then when they actually need to shop, hopefully they'll give you another go.