![]() Spanish Bottom Brackets – Spanish bottom brackets also use bearings that press directly into the frame. ![]() This style of bottom bracket is the most common. Because the bearings are the same size as an American bottom bracket, there is no difference in strength between the two styles. The bearings are pressed directly into the frame, allowing for a less complicated setup and a reduced weight. Mid Bottom Brackets – Mid bottom brackets use the same bearings that American bottom brackets use, however the cups are completely removed from the equation. They are often found on bikes with one-piece cranks. They also take a considerable amount of force to press the cups into the frame. The downside to American bottom brackets is that they are large and contain unnecessary weight. They use a bearing set that rests inside cups that are then pressed into the frame. These can be broken down into four groups: American, Mid, Spanish, and Euro.Īmerican Bottom Brackets – American bottom brackets were more common in the early days of BMX. There are several variations of bottom brackets that use different bearing styles. This portion of the frame is called a bottom bracket shell, and it’s size determines the type of bottom bracket the frame will use. The bottom bracket, commonly referred to as the “BB,” is located inside the portion of a frame that the crankset’s spindle passes through. This head tube uses bearing cups that are pressed into the top and bottom of the frame, and the bearings rest outside of the headtube.įor more information on head tubes and headsets, see our Headset Buyer’s Guide Article. Standard Head Tubes – Standard head tubes are found in older frames and complete bikes. The difference is that internal headset bearings do not rest directly inside the frame, but instead use an additional shim or bearing cup inside the headtube to position the bearings. Internal Head Tubes – Internal head tubes, also sometimes referred to as “semi-integrated head tubes,” use a press-fit system that functions similar to an integrated headset design. This system is the most widely used style of headset in aftermarket BMX frames. Integrated Head Tubes – Integrated head tubes use sealed cartridge bearings that are pressed directly into the headtube of the frame without the need for additional bearing cups or shims. They can be broken down into three categories depending on the bearing systems they use. There are several variations of head tubes available in BMX frames today. The head tube is the portion of a frame that the fork’s steerer tube passes through. Frames are made with seat tube angles ranging from 69-71.5 degrees, with 69 degrees being the shallower option. A shallower angle means the seat tube sits further back and the top tube’s length increases. This angle affects the position of your seat and the length of the frame’s top tube. Seat Tube Angle – This is the angle that the frame’s seat tube sweeps back, away from the back end of the bike. Bikes with steep head angles also have shorter wheelbases.Ī “shallower” head tube angle (lower numbers those in the 74-74.5 degree range) make the frame feel more stable at speed and in turns, which is why trails and dirt jumping frames generally have a shallower head tube angles. ![]() This makes tech tricks and nose manuals easier. See the diagram below to get a grasp of how it is measured.Ī “steeper” head tube angle (higher numbers those in the 75-75.5 degree range) generally positions a rider over the front end of their bike, while also sweeping the bottom of the fork inward towards the frame. Head Tube Angle – The angle of a frame’s head tube affects how the bike responds in terms of both steering and the rider’s position over the bike. The diagram below outlines the main geometries and frame components. It is important to understand the different geometries and styles of a frame before making a purchase.
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