What should I carry on day trips for emergencies?
In my opinion, minimal set of what to carry:

Bare Minimum: (able to call a taxi and pay them to get you to a bike shop or to home)

Cell phone.
ID (I prefer both a photo ID such as driver's license and something useful to emergency personnel like a Crash Tag/Road ID. So I can buy a beer at the halfway point and have something useful in case there's an accident and I'm unconscious)
Some form of payment (cash, atm card, credit card, whatever)
Water (bottle in a bottle cage)


Optional, but I'd never leave home without these: (because a flat tire is your most common problem)

Pump, or CO2 valve and a couple CO2 cartridges, or a pump with the CO2 valve and 1 CO2 cartridge. CO2 is faster and smaller, but you can basically only handle as many flats as you have cartridges.
tire levers (2 is easier, 1 might be sufficient)
1 spare tube
patch kit (pre-glued patches or patches and glue)
Any tool needed for wheel removal (not needed for quick-release hub)


Optional, but I always have for a ride longer than half an hour: (dealing with most problems)

Energy bar or some other sort of small portable food item (low blood sugar when you need to pedal for another hour sucks).
Small multitool that can adjust brakes, derailers, and at least temporarily deal with saddle issues. Also good to include chain tool, spoke wrenches...


Really optional, but I usually have these: (and they're all quite tiny)

A couple nitrile gloves, so you can deal with drivetrain repairs more cleanly. Especially if you have handlebar tape/grips in any color but black.   Useful when doing any chain repairs, but also comes in handy if you encounter a medical incident along your route.
A masterlink for your chain (if chain breaks, use chain breaker in multitool to remove broken link, masterlink to put chain back together and avoid your big ring until you replace the chain)
Medications. I usually have a few Ibuprofen and a couple Benadryl. Ibuprofen for aches and Benadryl in case I get stung by something I'm allergic to. (not allergic enough to need epipen)



Basically, the most likely problem on the road is getting a single flat.  The next most likely is getting two flats (running through some glass that gets both tires or not getting the first flat quite fixed right).  So you need to be able to handle a flat and preferably two.  If you have a few small bills (or an energy bar wrapper) you can use one to temporarily patch the tire if there's a big hole in the tire itself.
I like having 1 tube and a patch kit because swapping a tube is faster (especially with slow leaks) and it's possible to get a flat you can't really patch (too big, valve stem sheared off while pumping, etc).
After that everything else is much less likely to go wrong.  Brakes having an issue or the saddle sliding back are possible.  Running out of energy is possible. But those other non-flat things are unlikely enough that being able to call a friend or taxi or something like that is a sufficient backup plan.
That's a small enough set of things you can carry it in a jersey pocket or saddle bag. Pump can mount next to the water bottle cage or might fit in the bag.