The engine on mine is unreliable as hell. Always crapping out. I should probably take it to the shop or something.

It depends. The vast majority of time my roadside "repairs" are usually just "adjustments." Saddle height adjustments, tightening the bolts on the handlebar clamp, etc.

The last time I actually BROKE something while on my bike (actually, the last two times, funnily enough) was me snapping a derailleur hanger off my old road bike because the chain was one link too short, and snapping the derailleur in half/derailleur hanger in half as well because a stick got jammed in the mechanism.

Both times I hobbled home because no tool in the world would make either bike workable again. We had an entire backpack full of tools on my mountain bike and I just ended up coasting/pushing/running the bike home because it was mostly downhill. (Harder than you'd think.) Yes, we attempted to make it into a single speed. No, it did not work. The chain was too loose and would just pop off with any bump that I hit. I did the same on my road bike although it was less downhill, so I did a lot of one legged bike pushes with my foot on the ground. I'm sure it looked hilarious.

I'm with you. I broke a chain on my mountain bike and discovered my Park mini chain tool was missing it's replaceable pin. I lowered my seat so that I could Flintstone 4 miles back to my truck.

I'm flat-prone but it seems to be my own fault.

I suppose the obstruction in my ticker counts as a mechanical problem.

Derailleur adjustment is my most common problem. I'm not very good at it. Brakes, no problem. Taking a bike apart, cleaning everything and putting it back together, not much of a problem. But derailleurs are just not my bag.

Other than flats...dropped chain. This usually happens when I haven't been a good girl and done my basic maintenance (wipe down chain, test shifting) before (or better, after) a ride. Inevitably, the black grease winds up on my face. Sometimes, also due to a lack of proper maintenance, I need to adjust the brakes - but that happens less frequently.

I honestly don't remember the last time I used my bike tool while out riding around. I figure that if I stop carrying it around, that will be the day that I'll end up needing it.

Sometimes I get nervous when I forget to switch the saddle bag over to the bike I'm riding for the day, despite the fact that I've had no mechanical breakdowns/flats on any of my road bikes for last... 3 years?

I had my rear derailleur come apart, and was able to ride loose chain for the few km toy immediate destination, then throw it on the front of the bus to get home. I now have a multi tool with a chain tool to shorten the chain. It would shift if I leaned the bike slightly.

I assume that the derailleur got bent in the bike rack at work (I was just a couple hundred m away.)

Flat tires are a given, sometimes can go months without them, largely depends on the tire and road conditions.

Most annoying though are creaks, clicks, squeaks or other odd noises that don't show up until mid way through your ride.

Far less likely with a new bike (or an older bike with mostly new parts) that is in good working order.

Not much here, my bikes get complete overhauls during the winter. Haven't had a flat in at least 3 years (that's about 5K of riding). Only real problem is lack of power on the hills. KB

1) Flats
2) Spokes /wheel trueing
3) Derailer cable - likely bad luck, but seems to go out every 2000 miles for me.
4) On my old triple campy, dropped chains - but that really doesn't need tools to put back on.

Thanks everyone. I'm going to go with a Lezyne SV-5 because it fits all the bolts and derailleur screws on my bikes--except the cranks. I'll lose the chainbreaker, but it doesn't sound like that is ever much of an issue.

I excluded flats from my original question because I've had so many. I ride in Detroit, and there is a never-ending supply of broken glass and other metal annoyances. Two tubes and a patch kit are always with me.

Yup. My shorts always have been and always will be black.

I bring all the hex wrenches that bike needs. Sometimes a spoke wrench. My fix gears get a 6" crescent, PB wrench or Pedros Trixie. A Leatherman is my pocket to country rides, a much smaller and fabric friendly Gerber for city rides.

Ben

It's ME.

Adjust your limit screws?

Brakes. Brake pads wearing out or making loud noises. I've also stretched out 2 chains (on 2 different bikes) that had to be replaced.

Once a bike is set up? No, not on the road. Maybe a re-adjust from scratch rarely if something gets bashed out of alignment...

Leave the multi tool at home. Then see if you would ever have occasion to use one. (Sarcasm)*
Personally I have and I've loaned it to a few fellow riders. They lived by the above statement.

Shouldn't be getting chain suck if set up properly. YRMV

I haven't had much happen while out riding, and other than the usual adjustments while I was still messing with fit, I've only needed to tighten up the threadless adapter once. I had a spoke start pinging one ride, but I took the wheel to the shop for that.

Me too, went out with friends a couple of days ago and was terribly embarrassed any time we had to climb a hill. Still trying to figure out where I can take myself for a tuneup.

Flats due to urban commuting.
Derailleur cables - I've gone to replacing them every winter so it's an infrequent issue now.
on my road commuter the fenders are a tight fit and they get banged around and need to get adjusted when rubbing.

The occasional flat and that is about it. I take meticulously good care of my bikes and I think that prevents any would-be mechanicals.

-Shin

It used to be flats, but I've had none since switching to puncture resistant tires. (No goat heads in my locale). Next most frequent is attachments coming loose -- rack, fenders, etc. So I just go around all of the bikes in the family fleet, whenever I remember, and tighten everything.

I'm a marine mechanic and can fix about anything. I interface well with all things mechanical, likely better than I socialize. I am easy on all my equipment from cars, motorcycles, power boats and sailboats. I rarely have any problems with my bikes and rode the same one for 30 years until recently. My 1985 Performance Superbe is still a nice ride and I still ride it on occasion. In 30 years, I had to replace two front derailleurs due to a weak point in the lever where the cable attaches. I had to relace the rear wheel and replace the rim, but if it were properly tensioned initially, it likely would have never needed replacement. That wheel tolerated up to 210 lbs, now about 190. Chainwheels and cogs minimal wear, I wipe down and lube chain nearly every ride. Likely only 2 or 3 chain replacements in 30 years. I ride 10 to 20 miles at least 3 times a week likely about 8-9 months a year. Shift cables and brake cables are original.

Original brake pads that look nearly as new after 30 years of riding. I keep my rims clean and only use brakes minimally. I never wear out brakes on motorized equipment either. Bought a Toyota Celica new and when I sold it with 175K miles, it had original pads front and rear. Wife's 2001 Accord is now driven by my son and has 300K miles on rear brake shoes. Yes, they work.