Bike Stem Buying Guide

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Bike Stem Buying Guide

For many people, part of the fun of cycling is working on the bicycle. Trading out one part for one of a different size or quality is a way to customise a bike for the rider's specific needs and a way to enjoy exploring the complexity of the machine. One such part is the bicycle stem. All bikes come with a stem, but many riders decide to replace the stock stem with something else in order to improve comfort or handling or both. For those who are new to bicycle mechanics and are considering getting a new stem, an overview of this aspect of bicycle anatomy, plus a discussion of how bicycle stems vary, may help. What kinds of stems are used for what kinds of riding and how to choose among different construction materials and sizes are also useful to know. Ultimately, however, which bike stem to get depends on how the rider wants the bike to function and how he or she wants to feel while riding.

What is a Bike Stem?

Before discussing how to choose a bicycle stem, it is important to know what a bicycle stem is, where it is located, and what types of bicycle stems there are. The stem connects the handlebars to the steerer, the steerer being an extension of the fork, which in turn holds the front wheel. The shape and size of the stem dictates the height of the handlebars and their horizontal distance from the seat and therefore the posture of the rider. Posture has a big influence of the efficiency, control, and comfort of the rider. What postures riders prefer depends on the type of riding they do and also on their body type. Riders who want a different posture can adjust their bicycle stem, if it is adjustable, add a stem extender, or switch to a different stem.

Types of Bike Stems

There are three main types of bicycle stems: quill stems, threadless stems, and direct mount stems. Each type offers its own advantages, but the stem has to match the steerer and the headset both in terms of type and size. A rider who wants to install a new stem must choose among those stems that match the type of both the steerer and the headset.

Quill Stems

Quill stems fit inside the steerer. An expander or wedge holds the stem inside the steerer tube. Quill stems are shaped like an upside down letter L and their height can be adjusted by changing how much of the stem is inside the steerer.

Threadless Stems

Threadless stems, in contrast, are straight and clamp to the top of the steerer. They can be adjusted by adding spacers, but this is not as simple as adjusting the height of a quill stem and does not change their height very much. But, unlike quill stems, threadless stems can be flipped upside down. Because stems are angled, flipping one effectively changes the height of the handlebars. Most older bikes have quill stems, although threadless stems have become dominant more recently.

Direct Mount Stems

Downhill racing mountain bikes often have a third type of stem. Direct mount stems are similar to threadless stems except they are shorter and clamp to the crown of the fork rather than to the top of the steerer. Direct fork stems offer a lot of strength and control right where it is really needed.

Bike Stem Sizing

There are two parts of bicycle stem sizing. The first has to do with the way the stem connects with other parts of the bike. Unless the rider is rebuilding the entire front-end assembly, the diameter of the steerer and the size of the handlebars are both givens that the stem has to be able to fit or it cannot be installed. Quill stems have to fit inside the steerer, so they have to match the steerer's inside diameter. Threadless stems have to match the steerer's outside diameter. For both types of steerer, one or two sizes are popular and account for the majority of steerers. Handlebar clamps come in a greater variety of sizes. The second aspect of bicycle stem sizing is the rider's choice. The shape and function of a stem depends on its length, its rise, and the stack height, which together dictate the posture of the rider.

Bike Stem Rise

The rise is the angle of the arm portion of the stem with respect to an imaginary line drawn perpendicular to the steerer. If the steerer were perfectly vertical, than a stem with no rise would be perfectly horizontal, but steerers are not vertical. The actual angle of the stem to the ground is the stem rise subtracted from the angle of the steerer. Bikes designed for road racing typically have a rise of seven degrees or less. Some have no rise at all, meaning that they actually angle down toward the ground. On the other end of the spectrum, comfort bikes can have stem rises of up to 30 degrees.

Bike Stem Length

Bicycle stem length is measured along the stem from the steerer, or from where the stem bends, in the case of quill stems, out to the junction with the handlebars. Because the stem has some angle, however, the measured length of the stem is somewhat different from the horizontal distance between the steerer and the handlebars.

Stack Height

Stack height is the height of the vertical part of the stem, or the height at which the stem clamps onto the steerer, in the case of threadless and direct mount stems. Stack height is adjustable to some degree, depending on the type of stem, or it can be increased by buying a new fork or by installing a stem extender.

Choosing Bike Stems

Choosing a bike stem involves several different considerations. The new stem must fit the bike and must work for the type of riding the cyclist wants to do. Which of several construction materials to choose and how to spot good overall quality are important as well.

Finding a Bike Stem that Fits

The first thing to look for in a new bike stem is whether it fits the existing steerer and handlebars. The stem must match the steerer and headset type as well. Only a quill stem can work with a threaded steerer and headset, and only a threadless stem can work with a threadless steerer and matching headset. Within these limits, the buyers are free to customise their bikes by getting new stems with a different height, length, and rise.

Bike Stem Rise, Length, and Height

The appropriate shape and size of a bicycle stem depends on the kind of biking the rider wants to do and the rider's body type. The higher the handlebars are and the closer they are to the seat, the more upright the rider can sit. Lower, farther away handlebars give a lower, more stretched-out posture that is good for road racing but uncomfortable otherwise. A rider whose bicycle frame is too small could simply get a larger stem rather than a larger bike, at least on a trial basis. The new stem would move the handlebars both farther up and farther out. If the seat is raised higher also, the overall effect is equivalent to a larger bike. A rider who is comfortable with the distance from seat to handlebars could adjust the stack height alone or flip the stem, if it is threadless, upside down, so as to make the rise negative.

Buying a new quill stem with a longer quill, or installing an extender, is another way to change the stack height. Cyclists who use road bikes for touring not racing often need to increase stack height because stock stems on quality road bikes are often designed for racing. Mountain bikers often raise or lower stack height in order to customise the handling of their bikes on hills. As a general rule, lower handlebars provide more control downhill while higher handlebars provide more power uphill.

Bike Stem Materials

Most bicycle stems are made of one grade or another of aluminium, but carbon, steel, and titanium stems are not uncommon. The performance differences among them are minor, since any bike stem of decent quality is safe and workable, regardless of material, yet serious cyclists can tell the difference and do have preferences. Note that while carbon stems are strong enough, they are vulnerable to damage. An accident, or even the use of a star nut rather than an expander plug to anchor a quill stem, can cause all but invisible damage to the stem leading to very dangerous equipment failure later. The following table summarises the advantages and disadvantages of common bicycle stem materials.





Lightweight, strong, low price

Can transmit a lot of road vibration


Very strong for its diameter, low price

Relatively heavy

Carbon Fibre

Very lightweight, strong, reduces road vibrations

Expensive and vulnerable to damage


Similar to aluminium in weight and strength

Expensive, too flexible

The above list is not exhaustive. Importantly, construction material alone does not dictate performance or price; material grade and the design of the stem both play a role as well. As a result, there is some overlap in terms of strength, weight, and other characteristics among the different materials.

Bike Stem Quality

There are several indications of overall quality of a bike stem. A steel threadless stem is often poor quality, not because there is anything wrong with steel, but because there is no special advantage to using steel for a threadless stem, except to cut costs. A manufacturer interested in cutting costs may also have used poor quality work in order to further cut costs. A steel quill stem, in contrast, is stronger than aluminium and so its use in that context is not a bad sign. But although aluminium is less expensive than carbon fibre or titanium, the use of aluminium does not indicate poorer quality than these other materials. Aluminium is the most popular material and so the use of aluminium is something of a default option and does not indicate anything about quality. The use of fewer bolts or the use of pinch clamps to attach the stem to the handlebar are also indications of cost savings that may suggest poor quality.

Buying a Bike Stem on eBay

Buying through eBay has a number of advantages. The selection and prices are both good and the buying process is convenient and secure. Many bicycle mechanics are happy to install a piece the customer brings in, or the buyer can install the new stem personally.

Finding a Bike Stem on eBay

Begin the search for a new bicycle stem by typing 'bicycle stem' into the search box. Then use the menu options to narrow the results and to specify brand, construction materials, and other variables. To go directly to a particular type of bicycle stem, use the Advanced Search option.

Buying a Bike Stem on eBay with Confidence

The purchase process through eBay is straightforward. If there are any questions about a particular item, just ask the seller. The seller's profile page includes a contact link as well as his or her feedback score and return policy details. Finally, make a point of rereading the listing before finalising a purchase, as people occasionally misread the listings and buy the wrong thing by mistake.


Buying a new bicycle stem begins with deciding the old stem that came with the bike is not doing a good enough job. Perhaps it cannot be adjusted far enough or is forcing the rider into an uncomfortable posture. No matter what the reason for switching, once the buyer has a good, general idea of what to look for, the next step is to determine the type and size that the new stem has to be in order to fit with the rest of the bike. Of course, if the buyer is also replacing the rest of the front end assembly, then matching size and style is a simpler matter because all the components can be bought together to make sure that they match.

Next, there are detailed questions to consider, such as construction material, rise, length, and height. These details are what dictate both the performance and the price of the bicycle with its new stem. A stem can have a huge effect on the posture of the rider and the balance and handling of the bike, so it is not surprising that the stem is one of the most important pieces to consider replacing if something about the bike is not working out as well as it could. Fortunately, a convenient way to find a new stem is through eBay.

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