Aside from your mind, hands, and possibly a bottle opener, there’s nothing more useful in a bike shop than a hex wrench (aka hex wrench, hex wrench). So why do so many of us invest in other bike tools rather than cheap L-Allen wrenches, or worse, multi-tools?
Take a peek into a well-equipped workshop or a professional mechanic’s toolbox and you’ll see that experts often disagree on which hex wrench is best, and more importantly, they rarely stick to just one style. Also, you can almost always find a torque wrench or two.
Where most hex wrenches will do the job, the right tool for the job will be more efficient and likely to give you better results.
Of course, the debate over different types of hex wrenches is minor at best, perhaps on par with bicycle saddles – what works for one person doesn’t mean it works for you. But what does less time for repairs and more time for driving sound like? Everything is fine?
Below I will explain the different styles of Allen keys and when to use them. If you’re a home mechanic and have never thought about these tools, read on (and if you buy a lot of IKEA furniture, read on). This article applies equally to Torx wrenches, as torx tools are fast becoming commonplace on high-end bikes.
Old Faithful. This is a standard hex wrench that can be easily and cheaply obtained wherever you live. The L-shape flexes in tight spaces while providing leverage.
If you could only own one set, that’s the style. However, it is not heavy enough to easily turn the wrench for fast tapping, and is uncomfortable to hold in your hand for long periods of time.
With hundreds of options, the Bondhus 1.5-10mm long wrench set is always worth the money.
Popular in motorsports, the T-handle acts as a counterbalance to help you turn the key quickly while still providing enough torque for everyday use. There are some areas of the bike that are not suitable for T-bars (such as adjusting most seatposts), and the bars and pedals are often too tight for regular T-bars.
The exception is the Beta 951 wrench, which allows the T-handle to slide into place to form an L-shaped tool. They’re fast becoming the choice of many professional road and mountain bike mechanics (and this member!), but at over $20 a key, they’re best for those who are financially rewarded from their tools.
This hex wrench is popularized by Pedros, Park Tool and others, and I often see it in professional workshops. It’s actually a large L-wrench with a comfortable curved handle that offers the same benefits as a T-handle.
I have used them for all my miserable years – they are a good choice, and only in rare cases, like seat clips, do they require a different style.
Park Tool created this style, in which the three most common sizes are combined in one tool, as is known… and is still used naturally by mechanics all over the world. Many brands now offer tees in two or three different sizes, but standard 4, 5, and 6mm tees remain the gold standard. With this single tool, most bicycle parts can be made.
Unfortunately, however, the limited length and triangular shape mean it’s not the best choice when working in tight spaces. Installing bottle cages, adjusting saddles, and even just adjusting disc brake calipers can be slow, if not impossible.
In fact, the basics of a multitool is that you get a whole set of hex keys as a collapsible set with double the storage space as a handle. This “Swiss Army Knife” for bicycle keys is popular with some mechanics because they rarely have to reach for other tools.
Of course, there are many downsides, including a general lack of leverage and licensing. Of all the styles mentioned, this one is the only one I don’t use in the workshop, but I keep one in the car.
There are several different types of hex ratchet wrenches. The best bikes use replacement bits instead of real sockets, keeping the tool’s profile shallow. Ratchets provide significant speed advantages, but require changing bits of different sizes.
While most work on the bike can be done efficiently with ratchet straps, I only carry PrestaCycle ratchet straps for awkward things like saddle clamps.
Also, these ratchet bits can be used with a drill. This, of course, can do more harm than good if used incorrectly, but it’s a popular choice when working with rotor bolts (usually a T25 bit) and other repetitive tasks.
Far from being necessary, the screwdriver type is handy when low torque and tight clearances are key. I prefer this style for the bottle cages and adjustment knobs on some of the disc brake levers – otherwise they are of little use. I use a Bondhus 1.5-5mm kit.
A torque wrench is an essential part of the workshop, especially if you’re working on any fragile components, but it can’t replace a hex wrench, especially when it comes to loosening bolts. (Actually, torque wrenches really deserve an entirely different article—thankfully, we have a complete guide.)
Stop by your local hardware store and you’ll find plenty of options, including as low as a dime. When it comes to tools, you usually get your money’s worth, although you might get lucky and find a decent set for the cheap.
Less expensive tools lack the durability of their more expensive counterparts, but more importantly, they often lack the tolerances and tight fit on the bolt head.
The application of torque on bicycles is usually small, but the tolerances are also usually small. If you use sloppy tools, you will most likely dislodge the (cam) bolt.
This is certainly an unpleasant experience, and in some cases can prove to be a costly mistake. In most cases, a decent set of hex wrenches is a lot cheaper than replacing a proprietary pivot bolt stuck in a freshly removed rear shock.
Since the original publication of this post, I have written in detail why you should not buy cheap bike tools. The code snippet below shows various 5mm hex keys measured with a micrometer. This is a testament to how much tolerance there is between brands.
For a 5mm hex wrench, you want it as close to 5mm as possible since the bolt size is too large to fit. As you can see, the cheaper Chinese options are clearly outperformed, while the American and European made instruments usually come out on top.
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0.06mm is just a small difference, but use each of the two extreme examples in the same bolt and you’ll feel a noticeable change in grip and movement, and you can see the smaller version bump into before you start . The edge of the bolt turns.
Because most of the force is on the six smaller edges, it’s easy to cause wear.
If you frequently use a hex wrench, keep a close eye on its condition. You need sharp edges – rounded or tapered edges are a sign that the tool is not as good as it should be, and you risk rounding brittle bolts.
The disadvantage of ball joints is that the bolts have less surface area, which means they are more prone to stripping at high torque. Ball screwdrivers are great for pinching and turning things, but use the square end of a wrench for initial loosening or final tightening.
In some cases, such as loosening tight pedals or cranks, leverage will be key. Looking at a set of hex wrenches, you’ll notice that the larger the size, the longer the tool – simply because a larger bolt can handle more torque.
If you only have a set of short hex wrenches, consider purchasing longer sizes of at least 8mm and 10mm.
Remember to be careful with the levers when tightening the bolts. Torque results vary greatly depending on where your hand is on the tool. It is unlikely that you will need all the leverage available on this 5mm wrench.
Another factor is the length to the handle or knee, some deeply recessed bolts can be difficult to access with a normal hex wrench. An example of this is the Campagnolo Ultra-torque crank, which requires a 10mm drill to reach the middle of the hollow crank spindle.
Ultimately, the best tool is the one you’re most comfortable with and can trust. If you’re an occasional mechanic, a good set of L-wrenches will do just fine. But if you’re serious about your job, think about how you can improve your productivity – each type of hex wrench has real benefits under certain circumstances.
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Post time: May-08-2023