Disclaimer: UBI is neither a tool manufacturer nor retailer of tools. The following discussion is not in any way intended to promote any one type or brand of tool over another. All designs have some strengths and weaknesses. The purpose of this discussion is to help identify those when considering if a given tool is right for you or not.
Tools (Multi-tools vs. Dedicated/shop tools):
A “shop” tool typically lives in the shop and is a dedicated tool with one (or maybe two) functions. Shop tools are optimized for leverage, comfort, and access angle. Rarely is there a concern to make them light weight, and in fact many mechanics feel that the heavier a tool the better. Multi-tools however, are optimized to take on rides and have as many tools in a compact, lightweight package as possible. Generally multi-tools do not work great as shop tools and conversely, shops tools are too bulky and heavy to take along on rides. For the rest of the tool portion of this article we will focus on multi-tools.
“Compromises are made to leverage, reach, and ergonomics in order to make them as light and compact as possible.”
Multi-tool types:
Most multi-tools fall into a few basic styles with each type having inherent pros and cons. The three main styles are mono-structure, folding, and bit-type.
Mono-structure multi-tools usually have a forged or cast main body that has many tool protrusions with a few articulating pieces added (e.g. Ritchey Logic CPR, Cool Tool). These tool types can be light and strong and intuitive to use, but usually don’t offer the best leverage and often have very limiting reach/ergonomics.
Folding multi-tools most resemble a Swiss Army knife. Where instead of blades and scissors that fold out, there are hex and Torx keys as well as various other common bicycle tool types that fold out (e.g. Topeak Alien, Crank Brothers tools). These tools are reliable, inexpensive, very intuitive to use, and can offer very good tool reach. These qualities make this the most common type of bicycle multi-tool. However, their compact nature does much to limit their leverage and usually the chain tool requires a lot of hand strength to use.
Bit-type multi-tools often have a compact ratchet handle and take standardized ¼” hex bits (e.g. Topeak Pocket Rocket, PrestaCycle Mini-Ratchet). The ratchet is handy for ergonomics and the bits are easily sourced from a normal hardware store. The great thing about interchangeable bits are that it makes the tool very customizable (maybe you need a Torx T-20 for your bike but no other multi-tools offer that) and the bits are replaceable when worn, damaged, or lost. Unfortunately these are often limited in leverage to the length of the ratchet handle, and the bits are often short (limiting reach into some deeper fasteners). Also most of these require a separate chain tool and tire lever.
Storage/Care:
Multi-tools can be as compact as to store in a road rider’s jersey pocket, or seat bag. For mountain bike riders, they are often stored in a hydration pack worn on the rider. Or sometimes a small frame pack attached to the frame. Increasingly there are ever more clever designs where the multi tool is stored somehow within the bike’s componentry. Industry nine has a tool called “Matchstix” that is actually the front axle of the fork. One-Up has a tool called “EDC” which stores inside the fork’s steerer tube (modification of the steerer tube, or a special stem, is required to run this tool design). Specialized has a tool that attaches to the underside of their water bottle cage.
“No matter how the tool is stored it may be susceptible to damage.”
Tools that are allowed to roam free in a pack can be damaged by other tools or can damage other necessities like a spare tube (by rubbing a hole in it). Also loose parts of the tool can become lost. While most quality multi-tools have some kind of weather resistant plating, if they are left in a wet container they may still become corroded. Periodically checking your stored multi-tool to confirm its condition, can pay dividends the next time you actually need it trailside. Folding multi-tools can also loosen up at the pivot points over time. This doesn’t usually prevent them from working (unless they’re falling apart) but it certainly doesn’t improve their performance.
Ergonomics and tool reach:
Multi-tools offer an incredibly convenient assortment of tools in a compact package. However, there are many instances where the tool you need is not actually useable on your bike either because of inadequate reach and/or leverage. If the tool you need is not long enough (or is too wide) it may not reach all the way to a deep set fastener. Some examples of this are; 8mm hex keys that are too short to reach into crank arms or suspension pivots, Torx T-25 wrenches that are not long/slim enough to reach brake mounting hardware, and 5mm hex keys that cannot reach into rear derailleur mounting bolts. The other consideration is leverage. Many multi-tools offer only a small amount of leverage and may not be able to adequately tighten/loosen a stubborn fastener. See the following paragraph for more on fastener tension.
What about torque specifications on the road or trail?
What is torque?! It’s the measure of how much force (usually measured in inch pounds in•lbs or Newton Meters N•m) we are using to tighten a threaded fastener. Why do you care? We’ve all stripped out a fastener or broken a component when working on it but it is especially frustrating when you’re away from home and relying on your now broken bike to get you back. Most manufacturers are now supplying us with how much force (or torque) is appropriate when tightening up your stem bolt or derailleur mounting bolt as examples.
“Applying proper torque to fasteners is becoming even more critical as bike parts become lighter weight and more expensive.”
Most multi-tools do not allow us to properly gauge a specific torque spec for a given fastener. However, there are some neat solutions for this problem. One is Topeak’s Nano-Torque-Box which is a small fitting that attaches to your current multi-tool’s 6mm hex with the other end taking a ¼’’ hex bit. Depending on which one is in use they break free (like a car gas cap) at 4Nm, 5Nm, or 6Nm of tightening force. This is great if you want to convert your existing multi-tool into a limited torque wrench.
Another great option is Feedback Sport’s Range hex bit based ratcheting multi-tool. This tool is lightweight, very compact, and is used as a ratcheting multi-tool to tighten or loosen fasteners. However, if a specific torque spec is required you hold onto the small plastic ball protruding from the end and watch the Nm reading as you tighten the fastener. When you see the correct torque spec highlighted you must stop applying force. The wrench has a 2-10Nm range which is very useful for many of the specs you might need on the road or trail.
Usability (strength)/Test at home before needed in field:
It’s all well and good to think you are totally prepared with the right tools until you find out that you can’t actually use them for critical jobs out on the trail. It’s highly recommended that you test your tool at home before you need to use it in case of a roadside problem. Try to use the chain tool on an extra section of chain similar to what is on your bike (maybe the remnant from your last new chain). Do you have enough leverage to push the chain pin out? If your hands are cold and wet can you still break the chain? Do all the hex and Torx keys reach all the fasteners on your bike? Can you remove/install your tire with your tire lever?
Other considerations:
Flat tires; Tubeless, tube type
As good as wheel and tire designs are these days flat tire are still probably the most common mechanical problem we run into on a regular basis. Tube, Tubeless, and Tubular are all susceptible to flats (some more than others). If you get a flat are you able to get the tire off to fix it? Tube type is easiest but many Tubeless tires have a very tight fit to the rim and Tubulars are glued to the rim. 
For tube-type carry spare tubes and a patch kit (periodically check the patch kit to make sure the glue hasn’t dried out and that you haven’t used up all the patches). For Tubeless there are a number of tubeless repair plugs that can make for a quick trailside fix (e.g. Dynaplug, Genuine Innovations). However, these don’t always work and in that case the fix is the same thing as for tube-type tires—Remove valve and install a new tube. Tubular—Good luck.
“For all of the above make sure you practice the fix at home before you are counting on it in the field.”
Once you’ve got the tire fixed it’s time to air–up. Whether your primary inflation device is a pump or a CO2 inflator it is a good idea to test the function at home before you’re relying on it. Does the head work with your valve type? If not can it be converted? Do you understand how to use your CO2 inflator? Burn up a couple of cartridges next time you are replacing a tire just to make sure it works. I usually carry a CO2 as a quick air up for rides but then also carry a mini pump in case I get more than one flat in a ride or if I need to top off a tire out on the trail.
Spare parts:
For shorter rides (my 1 hour lunch mountain bike ride – yes, those are a thing at our Ashland campus, see the article that Rich wrote…) I have a small pack with a quick link to fix my chain, multi-tool, tube, and inflation device. For longer rides I have a larger pack with all those same things plus; Spare derailleur hanger, cable, spare cleat and bolts, spare fasteners common to my bike, patch kit, tubeless valve, small first-aid kit, thin rubber gloves, paper shop rags, space blanket, small flashlight and fire-starting stuff. None of this stuff takes up a whole lot of space or is very heavy but can be very useful or even lifesaving. For really big bike rides (like bikepacking for instance) I’d take all the above things plus; A spare tire, more spare tubes, spare spokes, nipples, & 1’’ wide gorilla tape, extra brake pads, chain lube, and any unique tools needed for that specific bike.
“A little bag of spare parts can go a long way in emergencies.”
It can’t be said enough that the most important aspect to all of the above is to practice the skills with your tools at home before you need them outside. Maybe the next time you need to change a tire, chain, or cable & housing on your derailleur use your multi-tool at home to see how it goes? You will learn a lot guaranteed and no matter what it will help you be better prepared for your next roadside repair.