I'm a newbie to the world of cycling and need some help. I've recently purchased a used Trek 7500FX bicycle that has 700x35 tires. The tire I'd like to move to is the Specialized Nimbus Armadillo. Unforunately, it comes in 700x28 and 700x38 not 700x35. Do I have to buy the exact same size or can I go with 700x38 or something else? Any help will be appreciated. Thanks and take care.