Bearings – Test the smoothness of the bearings in your bike’s headset, bottom bracket, hubs, and pedals. Are they crunchy or do they have excess play during normal use? If so, they are in need of service or replacement. Some bearings can be opened up and cleaned/repacked, but other fully sealed designs will require replacement. Headsets and threaded bottom brackets have the most user-friendly replacements for the DIY-inclined. If the bearings require a special removal or installation tool, like press-fit bottom brackets or hubs, head to your local shop, which will be happy to help you with these services.
Tires and Sealant – Even sealant that was fresh a few months ago can crust up and become a rubbery latex pancake if left to sit too long. Give the tire a shake and listen for a sloshing noise. If there’s not one, there’s a good chance the sealant has gelled up. To visually inspect, pop one tire bead off the rim and orient the opening at six o'clock. If no liquid sealant flows to the bottom, remove the tire, scoop out the old sealant, and replace it with fresh liquid.
Examine tires for wear or significant damage. If the rubber looks cracked or excessively worn, consider replacing your tires for the start of the season. If the casing is visible through any slashes in the tread or sidewall, it’s time to consider new tires as well.