I commute about 7 miles to work and average around 15-20 miles a day between work and errands, I currently do it with a backpack.
I live in Phoenix so luckily weather is easy.
Are frame bags as amazing as they look? Do they come big enough for my office clothes and a lunch?
What cool products do I need to be a cool kid?
Getting the bag off your back and onto your bike is always best. You'll be more comfortable, and if you have bulky groceries they won't dig into your spine.
For awhile I went with the topeak trunk bag and rack. Now I just have a milk crate strapped to my rack. If I'm riding to work, I just throw my bag into the milk crate. If I'm going to the grocery store, my normal shopping bags fit securely in the crate as well.
A frame bag can be big enough for your clothes and lunch depending on how you pack it and how much room your frame has. Panier racks will make it easier to haul a lot of stuff.
One tip I would suggest if you wear clipless shoes is to just leave your work shoes there and not bring them back and forth. Saves weight and space.
I take commuting a bit to the extreme....about 30 miles each direction and live in the southeast where the weather is unpredictable. I utilize frame bags for essentials that I may need quick access to. Wallet, office keys, phone, and a few other necessities but I like riding with a backpack for work clothes and food. The frame bag helps keep my backpack from getting too full, especially in the winter with so many layers, and allows me to run errands on the way home. I use an older version of the deuter trail pack that has a built in rain cover for unexpected wet rides. The bag has a rigid mesh panel that sits against my back and sits away from the main comparment for exceptional air flow.
With all this being said you can definitely find some frame bags that will fill the space inside your frame's triangle and can hold a lot of items. I'd recommend something waterproof and possibly invest in a handlebar bag for the items you need to get to quickly.
Oh, my goodness. All your stuff in a backpack. A whole new world is waiting for you out there. I love backpacks - a lot - but not on my bike! On my bike, I can't do without my bicycle panniers.
You'll need a bicycle rack. There's a lot of variety out there, but often the simple ones are just fine. If you have disc breaks, you'll need a slightly different type.
And then you'll need the really important part - the pannier(s). I started with inexpensive ones, and eventually got a really nice commuter bag. My current one is from Arkel. It's big enough to carry my laptop (in a padded sleeve), my bulky lunch, and a few other things. I splurged on the Arkel because I've had the cheaper bags pop off my rack when I go over big bumps. I wasn't willing to subject my laptop to that. The top of the Arkel clamps to my rack so that won't ever happen. It's also pretty waterproof. It felt really expensive when I got it, but it's one of those things that I use, and use, and use, and use.
On the other side, I use pannier I got at Goodwill - a very simple one - to carry my lock, my repair tools, and cold weather gear, so I always have those things.
And then your back will be a lot cooler - and you'll feel "cool" too!
I live in Phoenix as well and have commuted a lot over the years. Saddle bags are the way to go if you can. I have a set of Ortlieb. In one bag I can fit all my work stuff and climbing gym gear if needed.
Weight is off of you. Your back can breath so its cooler. Bages are massive.
They suck to carry around. You need to secure all the straps every time you ride. Getting a strap stuck in your rear tire is a pain.
Having said all of this, this for pure commuting. I'm a mountain biker at heart with trials tendencies. More often than not I'm riding with a backpack because I link some trail riding in. Also I can't hope a bike with saddles bags. But... when I do have my commuter bike with saddle bags it feels like I'm playing on easy mode.
You've already gotten a lot of great advice-- but I think a few more questions are necessary to give you the best/focused solution:
This is probably more than you bargained for in a response, but hey!... you asked 🙂 Good luck with the commuting-- I think it's amazing how many miles we can cover in a week just not driving (not to mention the base fitness that come with it). Feel free to DM me for any explanation on what I said above if it didn't make sense.
Yeah I used to race road bikes and have ridden almost my whole life as primary transportation... Messenger bags do not work well when sprinting or hoping over things in the road. I commute on a fixie, its technically dedicated to commuting but I still don't want to turn it into a barge. It is a beautiful bike and I have spent a lot of time building it.
I commute in phoenix... it would be hilarious to wear my work clothes on my commute...
For me, the primary goal is to get the gear off your back. While I once used panniers over the back wheel, during a recent visit in San Francisco I noticed quite a few bikes with front racks on. They look like they can handle a nice load, on a wide platform. Done!
I ride year-round in the Denver area. Leave what can at work; like shoes, toiletries, lock. Completely agree with @nealos comments