The obvious difference between stems is the point at which the bars are connected. The two main types (excluding some variations over the years) are respectively top-loading, where the bar is loaded from the top of the stem and the plate is clamped down on the base of the stem. On the other hand, front-load stems are loaded from the front edge of the stem and the bolts screwed into the front of the stem body. While both types of stems promote strength and durability the look is a big consideration when buying a new stem. Top load or front load, if the stem is working correctly and has been fitted correctly by your local bike shop both types should clamp the bar with even pressure and therefore neither one holds the bar better then another.
The reach of the stem is the distance from the center of the steerer tube to the center of the handlebar channel. This distance has an effect on the way your bike will feel as it essentially is lengthening the top tube of your bike. By lengthening the distance to where you hold the handlebars your bike will feel longer. The average reach on most stems is 50mm, with shorter stems 48mm and longer stems 58mm This is an important consideration given the importance of choosing the right length frame. Combined with the stem to make your bike feel perfect for you.
The rise of the stem is just what it sounds like, how high it holds your bars. This is where you would think the difference would be between the front and top load stems. However top load stems can have a lower rise then a front load, and consequently truly turns the purchasing process into more of a brand and aesthetic decision. The average rise for stems ranges between 27mm-32mm, the difference in rise and reach and the combination you choose for your bike ultimately is a personal choice but should be taken into consideration when choosing the perfect bike for you.
The vast majority of BMX stems are made from strong, lightweight aluminium alloy, with 6061 and 7075 being the two most common types. 7075 is regarded as having a higher strength to weight ratio. Most higher-end BMX stems will feature extensive CNC machining to shed weight without compromising strength. The machining process maximizes strength as it is cut from one block of material so no joins will be needed. This process is very common for most stems that range in the $90-$150 range.
Cold forged BMX stems undergo a different process where a bar stock is inserted into a die and squeezed with a second closed die. The deformation starts at room temperature and changes the shape and size of the initial part until it has assumed the shape of the die. Forged stems can start as low as $39.99 and will stand the test of time.
Due to the many processes and material combinations BMX companies have access to, BMX stems range in price from $39.95 to over $200.00 Understanding the processes and materials of how the stems are made can help to understand the difference in price point, like most things, the more you pay the better the quality of the product your buying.
Although your stem might not seem like the biggest deal on your bike, it’s a part that needs to be considered. A different stem can change the feeling of your bike so make sure you know what you like before making the jump.