Buying a BMX Frame in 2020

Author: Tim   Date Posted:28 January 2020 


Frame Buyers Guide. 

Top Tube Length

As the name suggests, the top tube length relates to exactly that. Bmx frames range all the way from 12” bikes through to 24” BMX bikes so the length of this tube can change a lot. 

Top tube length is relevant to wheel size which helps when choosing a bike for yourself. However, there is much more to it than just choosing the correct top tube length. Too long the bike could feel harder to manual, too short and the bike will be too small for the rider. Most BMX frames come in 20”-21” with some slightly more or less. To put it simply, you need to fit the bike to the rider.  

 

Headtube Angle

Next up is something that you might not have considered yet, but is equally as important. The head tube angle refers to the angle in which the head tube rests. (90 degrees being vertical)  Most BMX frames range between 74-76 degrees headtube angle. The higher the number the steeper the front end will feel, similar to fork offset, the steeper the more responsive it becomes. The more mellow the angle, the less responsive and more stable at higher speeds it will become. It’s important when building your bike that you choose angles that fit with other parts of your bike.  

Chain Stay Length 

Chainstay length is the distance from the center of the bottom bracket to the center of the rear axle. This length is important to consider when choosing a frame because it changes the way your bike will react in different situations. The standard chainstay length on BMX bikes is between 12.8-14 inches. In 2020 popular street and park frames are leaning towards a short more “snappy” back end. The shorter the back end the closer the bike is together allowing the rider to spin, hop and manual easier. Longer back ends aim to give more clearance for the rider missing their back peg, however, the longer the chainstay length the more resistance the rider will feel when trying to manual. Basically, if you want to have a more responsive frame the shorter the geometry the more responsive it will be, but this can impede if the frame is too small for the rider.      

Under is a list of the approximate frame size for height.  

Height 

Bike Size

Under 100cm 

12” or balance bike 

99cm-122cm

12”-16”

122cm-137cm

16”-18”

137cm-147cm

18”-20”

142cm-177cm

19.5”-20.4”

162cm-178cm

20.25”21”

172cm-180cm

20.5-21.5”

180cm+

21”-22” 


 

Standover/ Seat Tube Angle  

The final piece of the puzzle is the stand over and seat tube angle. The stand over refers to the height of the tube that holds the seat pole. This height determines the height of the top tube and therefore can have implications on certain tricks given the height of the top tube. Some frames over the years have had very low standover (6.5”), where most bikes have a more standard standover height ranging between 8.5 and 9.5 inches. Stand over is more of a personal preference as the height of the tube doesn’t impact the feel of the bike. Where taller standover can be viewed as easier to pinch the seat for barspins and shorter can be seen as an advantage for doing tailwhips these heights have minimal impact on the feel of the bike. The angle of the seat tube does change the feel of the bike. This is why it is important to take note of both the height of the tube with the angle of the tube. Most frames have a common angle of 71 where some lean a little lower with a 69-70 degree seat tube angle.   

 

Materials/ Heat Treating

Most BMX Frames are made from heat-treated 4130 Chromoly, however, the thicknesses, lengths and the machining process are always vastly different, resulting in very different shapes and weights. Like all BMX parts, it’s important to consider the durability of materials when choosing the right frame for you. 4130 Chromoly has become the trusted material for many freestyle BMX parts. What does 4130 Chromoly actually mean though?  4130 Chromoly is an alloy steel that is made up of two parts, combining two or more metallic elements, that allow greater strength. 

With some brands boasting heat treating it’s another aspect to consider. Heat treating refers to the process of how the Frames are made. Heat-treating is applied and the properties in the alloy are changed which can align different parts creating a stronger bond which then makes the material stronger throughout and able to withstand higher tolerances from impacts and stress put on it from riding. Heat-treated frames have had an extra step added to the manufacturing process and subsequently have an added cost, however, the added strength is well worth the extra cost.


 

Pricing

The talking point of every BMX riders bike should be their frame. For that very reason, the frame can also be quite a big expense. Most 20” BMX frames range between $350- $550 with an exception for American made frames that can go up to $800. Similar to forks, frames use a variety of methods during the manufacturing process that can impact on the cost of the frame. American made parts are more expensive and promote a higher quality product.


Choosing a frame is usually where people start when building up their dream bike and makes a huge difference in how their bike will feel. So what does all this mean? It means that it’s important to do your research before making your purchase. Ask your local bike stores, or inquire online, getting your bike set up correctly for you will not only feel better but learning tricks becomes easier.  Hopefully, this guide has given you something to think about before choosing your next set of forks.

 


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