(Excluding off-road cycling, touring, and bikepacking where it’s common to need one)
Just out of curiosity. Have you ever needed tools for anything beyond a flat on the road?
I stopped carrying one years ago and sometimes I get the feeling that I’m taking a chance by not carrying one. However, in most cases it’s either something that can wait until I get home or bad enough that I can’t do it on the side of road.
Of course, posting this means I’m gonna need one in the next ride…
Saddle/seatpost slipping is a common one.
Yup, off the top of my head:
Sure plenty more times, for the light weight of a tool I’d generally take one.
Yes, for the chain breaker function and some adjustments via Allen keys (my own and others bikes) for the weight I would never leave it a home. (Topeak pro 20)
Hell yeah. I’ve tightened plenty of fasteners over the years.
Mostly just fit adjustments for me.
I always carry one though since I ride with a small saddle pack anyway.
I swapped my fork before a ride yesterday and I didn’t remember to center and tighten down the front brake caliper until I got outside. Luckily, I did remember, but that would have been a really good opportunity to use a tool out on the road. 
Yep. Mostly random bolts that don’t get a torque wrench (i.e. water bottle cage bolts, SPD cleat bolts, lots of others) manage to vibrate themselves loose over time.
As a general, the bolts that come loose probably won’t be ride-ruining, but they will very likely end up bugging the shit out of you. Best to be prepared.
Yeah, I was wondering about this one. In my case, I intentionally avoid making fit adjustments in the middle of a ride. I think it gets into my head and then I overthink it and probably overcorrect any perceived issue.
The exception is if I’m riding to test a fit change or something new.
Are you kidding? Yes! A few examples:
Not taking one with me on rides seems very risky to me. I have a saddle bag with essentials:
It isn’t just fit adjustments. Sometimes bolts come loose and you need to re-tighten them.
I totally agree. I’ll force myself to wait around an hour to make any adjustments to warm up otherwise it’s a never-ending process. 
I carry one religiously offroad/ on gravel, but admittedly don’t always have one on me on the road. I probably should, because a short list of things that have come loose/needed to be removed over the years that I can think of for me include:
-Cleat bolt loosens and cleat moves
-Pedal tension needs adjustment
-Seatpost slips or I want to change position
-Hit a bump and saddle angle changes
-Crash and brake lever moves
-Handlebars slip in stem and angle is odd
-Through Axle skewer with no lever
-Bottle cage loosens and rattles
-Never happened to me, but I’ve seen someone’s crankarm fall off mid ride.
You convinced me with this one.
Oh definitely. I guess I’ve been lucky that in those cases I’ve been able to finish the ride. Although, in one case I had to put a bottle in my jersey pocket because the cage was loose but nothing major.
I didn’t carry one for years and never needed it. Bought one of the Cannondale ones that has a Dyna plug in it and a week later needed the dynaplug. But in all my years of riding I’ve never needed any of the Allen keys. I think I’m going to go back to just a 5mm hex for the thru axle and a small dynaplug tool. Maybe put this one in my gravel bike saddle bag.
Does anyone else only carry small allen wrenches in the sizes for their bike? It’s a minor weight savings, and can be easier to use a single than one attached to a multi-tool.
Absolutely. Many times.
FWIW, the best way I know of to guarantee something breaks on a ride is to forget my multi-tool.
never used one, however I posted this on Strava two days ago:
would have been nice to have an 8mm hex wrench on the ride.
I’ve packed a multi-tool a couple times, but only for epic adventures in the middle of nowhere.
you win
I only carry allen wrenches … Park Tool AWS-10.
Yes, though never for my own bike. It always seems that someone else needs a tool. So I guess I carry it for others? Maybe time to stop 
This is what I do on my road bike; just a single loose 6mm for my through axles, bundled with my spare tube and co2.
