Originally Posted by MRT2

Yes, helmets should be replaced eventually. How often is often debated. I doubt you need to replace your helmet every 2 to 3 years but if you ride a lot, and if the helmet is exposed to the elements, and sweat, etc...you might. That said, I am in the habit of buying a new helmet every couple of years, and rotating the new helmet in with the previous helmet, so at any given point, I have a new helmet that splits time with a helmet about 2 or 3 years old, and a 5 to 7 year old helmet relegated to use as a loaner in case a friend from out of town shows up and wants to go for a ride.

As to what else you need, I would break it down this way. If cycling becomes a regular activity, you will eventually get all the accessories and tools you need, if not at once, as you come to need them. So where to start?

The absolute necessities.
Pedals - Cheap platforms might work, but if you think you might go with clipless pedals eventually, a pedal like the SPD M324, with SPD on one side, platform on the other (or a similar model from Wellgo) might be a good idea. Just remember to save the cleats that come with the pedals to mount on the shoes you get down the road. These pedals are well made. I have a set of these and 2 sets of similar Wellgo pedals and they all work fine, even after 7 to 10 years of use.

Helmet - I know some don't use them, but I always do, for the last 20 plus years. Modern helmets are light, with most weighing less than 300 gms, and well ventilated. And while I am fortunate not to have sustained any blows to the head while riding, I was riding a couple of years ago with a guy who did. Slow speed crash, broke the guy's helmet, and he went to the hospital, but the helmet might have saved his life.

Eyewear - You don't need cycling specific eye protection, but some kind of eye protection is good to keep dirt, dust, bugs, and debris out of your eyes, as well as to protect from the sun. After going years with whatever cheap sunglasses I had around, I eventually bought some photochromatic sunglasses from Tifosi, which, IMO are very good and more reasonable than some high end cycling sunglasses. That said, my son prefers either cheap sunglasses or alternately, some cheap clear lenses on cloudy or rainy days. My wife just uses her prescription glasses, which are already photochromatic.

Bottle cage/water bottle - If you ride, you need to drink water. you can always fill up before and after a ride but on longer rides, you need to stay hydrated or you could get heat stroke, which is miserable and potentially dangerous. That said, I have a friend who stubbornly refuses to take water with him on rides.

Gloves - I like gloves. Short fingered in spring and summer, long fingered in fall and winter. They keep my hands on the handlebars even in the heat, when sweaty hands might otherwise cause my hands to slip. Modest amount of padding reduces hand fatigue from road buzz. How much padding you need in a glove is a matter of personal preference. And if you go crash, gloves may save the skin on your palms.

Lock - If you leave the bike unattended for any length of time, you will need a lock. How strong a lock depends on factors such as your tolerance for risk, and the prevalence of bike theft where you ride. I have a cable lock that I use just for minimal deterrence when I ride in rural and suburban areas, and a U lock that I use when I park my bike in urban areas.

Spare tube, patches, tire levers, mini pump - And know how to change a flat. critical for flat repair on the road, unless you plan to call for help every time you get a flat. Flat tires are a funny thing. You can go a year or two with no flats, then get 2 in the same week, or day. Best to be prepared.

Floor pump - Bike tires lose air quickly. You will need to be able to inflate your tires at least once a week, if not before every ride. A floor pump is better suited to this task than is a mini pump that you carry with you.

Mini tool/allen wrenches. - Carry this with you always. Sometimes things come loose, and one of these handy tools should be all you need to adjust a seatpost, or something similar.

THINGS YOU MAY EVENTUALLY WANT TO GET

Cycling shoes - once you start riding a lot, you might like having a retention system. I like SPD. It is inexpensive, and the cleats are recessed so you can walk on them a bit. Which brand of shoes is a matter of personal preference.

Shorts - I like them. Makes my rides more comfortable. Jeans are a no go for me. Even riding in technical underwear like Under Armor and running shorts is not as comfortable as decent cycling shorts. I can ride for about an hour in running shorts, but 2 to 3 hours in cycling shorts. I currently rotate between Specialized, Gore, Pace, and Craft shorts. YMMV.

Jersey - Yes, I know you can get away with a regular technical T shirt from Nike, Adidas, Under Armor, or Champion, but a cycling jersey, with zipper, back pockets, and somewhat longer back is something you may come to appreciate over time. I usually keep my cell phone, house key, ID and some money in the back pockets when I go out for a ride.

Socks - Lightweight, wicking socks are nice for hot days over cheaper thick socks for general use. Alternately, on cool or cold days, Merino wool socks are lightweight and warm at the same time.

Wind/rain jacket - doesn't need to be cycling specific, but necessary if you ride in the rain. A wind proof layer is nice on cool, windy days, say for temps between 50 and 65 degrees F.

Lights - necessary if you ride at night. Not so much you you don't.