Little Darwin

I always carry a spare tube and a patch kit. The patch kit is small enough that it will be nice to have if I ever get a second flat... but also, the people I ride with don't seem to carry anything, and we ride in places where help isn't close by, and cell coverage is minimal or non-existent, so whatever size tire they have, I can help with a patch. I also carry 2 or 3 CO2 cartridges, and a road morph pump.

I have several thousand miles over 10 years since I started riding again, and I have had a total of 4 flats. All either before or after the rides, but I still ride prepared. On the road, I have given a small patch kit to another rider, and this past weekend was the second time I have used a CO2 cartridge, and it was to inflate a flat tire someone had on their rental bike, which seemed to be from a leak so slow it would have been hard to find it to do a proper fix.

And like others above, I carry extra... I have a schraeder adapter in case it is needed. I carry the sleeve that allows you to use presta tubes in schraeder drilled rims in case anyone needs them. A SRAM master link that matches my chain. On longer rides, I have been known to carry a second spare tube, and I have also carried a crescent wrench, vice grips, and a few times even carried a couple of spare cables... and of course a multi-tool, tire irons.

I also carry a first aid kit (including my epi-pen if the weather is cool), and other assorted emergency gear, including a couple of ponchos if there is any chance of rain.

I obviously ride with more than one of those little under the saddle packs, I have a rear rack with a large trunk bag.

I am obviously not a weight weenie, and I figure that the extra weight I carry makes the ride a bit more challenging, and adds to the workout.

ancientbikegeek

I have only been back to riding for about two months, but I already learned to carry an extra tube, pump, tire levers, and a multitool. I had a flat (thorn) in the first couple of weeks while using my daughter's old mountain bike with old tires. No mishaps since I got my Specialized Expedition Sport with puncture resistant tires.

JerrySTL

Both. And I've had to use both a couple of times.

Sunsanvil

I keep meaning to put a tube in my seat pack but, then I'm reminded that its next to pointless unless I have inflation equipment, which isn't cheap if you want nice compact light stuff....

camjr

I carry this pump (less than $20 and it weighs 85g or just over 3oz): Spin Doctor RXP Mini Pump - Mini Pumps. You could also go with CO2 cartridges.

Nylon tire levers don't weigh anything and are less than $5. A small patch kit is less than $10 and weighs nothing. A tube probably weighs more than anything else but are less than $10. You can always go without carrying a tube and just carry the patch kit.

All of those things are cheap and much lighter than the bike you'll be carrying if you get a flat.

Frogbutt

I carry a small frame pump, spare tube, patch kit, tire tool, small first aid kit, and an epipen for my serious allergy to bee stings. If the weather looks crappy I'll also carry a poncho. Most of the time I'll carry it all in one of the pockets of a courier bag. I've simply walked too many bikes too many damned miles.

Hauptmann6

Get a Road/Mountain morph pump for $35 on amazon (I ordered one yesterday) they come with mounting brackets. A patch kit from Meijer or Walmart is $3 and you should be able to get a cheap (shwinn) bag for under $10 the bag won't be great, but it will get you by. Tire levers are also under $5. You can skip the bag if you wear a fanny pack or something with pockets.

Little Darwin

This is true in general. Even though it has never happened to me while on a ride, I have had to replace 2 tubes in the last 10 years because of valve troubles (once at home, and once at the trail head while preparing for a ride). So I always suggest that if someone has room that they carry a spare tube.

And Sunsanvil... carry what you have. I help people with patches or inflation if I encounter them, but I am happier to help if the person is somewhat prepared.

camjr

I carry one tube and a patch kit